Will We Get Tropical Or Subtropical Storm Bonnie?

I started discussing the possibility of a subtropical or tropical system developing somewhere off the Southeast U.S. coast towards the end of this month into early June, and as the majority of you know by now, there is an area of low pressure that is currently being monitored. What we try to do at Firsthand Weather is look at the upcoming pattern and determine what implications that has later down the road. Often this time of year when a mid and upper-level ridge builds into the northeastern U.S. with a trough underneath that extends into the open waters of the western Atlantic, it’s usually time to watch for home-brew subtropical or tropical development. However, these systems generally stay on the weaker side, even if they technically do meet the criteria to be named. So, could we have tropical or subtropical Bonnie by this weekend?

Brief Discussion:

As mentioned above, an upper-level trough extends down from the eastern Gulf of Mexico up along the Southeast coast. On the east side of this trough where the dynamics are favorable, convection (stormy conditions) have developed over the open waters off the Southeast coast. Due to the favorable environment, an area of low pressure has developed in the region of interest. Everything that I just explained has been expected for a while now given the pattern.

Now, the forecast begins to get tricky when we actually get that region of interest like we have. The upper-level trough is primarily responsible for the development of the low pressure system; however, the trough itself actually creates a sheared environment (strong winds aloft). . .a condition unfavorable for the development of a fully tropical storm. Generally, convection needs to wrap fully around the center of circulation (around the low pressure system), but a sheared environment doesn’t often allow that to happen. In this case, storm activity is developing to the north and northeast of the center of circulation. Recently however, convection has begun to fire just to the west/northwest of the center also.

To give you a visual of all of this, this is the last satellite image as of 1:45 ET. The “I” designates the center of circulation, but actually that’s a little off. It’s a little northwest of that point now.

satellite image bonnie

Over time, the area of low pressure will continue to drift northwestward towards the Southeast coast into a less sheared environment. It will be steered in this direction by a Bermuda ridge that extends all the way to the East Coast. So, I generally agree with the consensus of this system moving into the Carolinas.

bonnie projected path

Some Other Obstacles For This System:

I know the map below is in Celsius, so please bear with me. A tropical system needs greater than 26°C (79°F waters) to maintain its strength or strengthen further. As you can see, temperatures are still cool off the Southeast coast, with the exception being that tongue of warm water (which is actually the Gulf Stream). Subtropical systems do not need waters quite that warm, but keep in mind that the winds are typically weaker and more spread out from the center of circulation for subtropical systems.

sea surface temperatures

Assuming that other factors become more favorable for this system to develop into a subtropical or tropical system, this system will likely strengthen most over the Gulf Stream waters. However, before we make that assumption, we need to consider yet another obstacle. See all of that orange in the water vapor image below along and just off the Southeast coast? That’s dry air. When these systems start wrapping around/ingesting dry air, they can weaken if they’ve previously strengthened or remain weak overall.

water vapor imagine showing dry air along southeast coast

So as you can see, there are a few obstacles ahead for this system (along with a couple others I didn’t mention), but that doesn’t mean we won’t get a weak tropical or subtropical system out of this.

What You Should Expect From This:

Finally, I want to give you an overall idea on what should be expected. There will likely be a window this weekend that this system could strengthen. As mentioned, wind shear should decrease farther west, but it will take some time before this system moves into an area with substantially less shear. Even if this system gets a name later tonight or tomorrow, convection still may have a tendency to not wrap fully around the core of the system.

The timeframe to watch this most closely will be once it moves over the warm Gulf Stream, especially since this system is a slow-mover. If there is a period of some quick strengthening, it would occur then, but still, I expect this to remain a relatively weak (under hurricane strength). If we do get the Gulf Stream strengthening, the system will likely weaken as it moves over the cooler shelf waters along the coast, especially if this becomes purely tropical. Again, dry air could also hinder this system’s development.

The regions that should watch this most closely are those along the Carolina coast and the very northern Georgia coastal regions. Heavy rainfall with possible flooding will be the biggest issue this weekend, along with breezy/windy conditions and rip currents. Precipitation could eventually spread farther northward along the East Coast once this system pulls north. There are some uncertainties on overall timing, but Firsthand Weather will keep you updated on all of that.

Below is a 5-day rainfall forecast that I pulled off the WPC website:

5 day rainfall forecast

Of course, stay up to date with Firsthand Weather. The National Hurricane Center currently gives this system a 90% chance of becoming a tropical or subtropical system storm within the next 48 hours, which I agree with. If anything changes, I’ll keep you up to date!

As an aside, keep an eye on the western Gulf of Mexico/western Caribbean in early June. There could be something to watch there around that time period, but it’s much too soon to give any details.

Severe Weather Update

Severe thunderstorms are expected this afternoon with the primary risk over Texas.

severe outlook

Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 20,860 199,864 Del Rio, TX…Uvalde, TX…Pleasanton, TX…Hondo, TX…
SLIGHT 39,819 3,629,577 San Antonio, TX…Laredo, TX…Mission, TX…Pharr, TX…Edinburg, TX…
MARGINAL 109,236 25,822,516 Houston, TX…Jacksonville, FL…Austin, TX…New Orleans, LA…Tampa, FL…

Summary

Clusters of strong to severe thunderstorms with large hail to locally very large hail,and locally damaging winds in excess of 60 miles per hour are expected across Southwest and South Central Texas.  There is potential for a few Tornadoes in this area.

tornado outlook

Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 21,049 202,528 Del Rio, TX..Eagle Pass, TX..Uvalde, TX…Hondo, TX…
2 % 84,937 19,833,286 San Antonio, TX..Jacksonville, FL..New Orleans, LA..Tampa, FL…Laredo, TX…

Currently, A severe thunderstorm watch has been issued from just eats of Marfa down to Hondo and just west of Cotulla.  This watch includes Midland, Del Rio, San  Angelo and Junction Texas.

severe watch

This watch is in effect until 10  PM Central Daylight time.  Additional watches are possible East and Southeast of the current watch box.  Hail up to 2.5 inches in diameter and winds up to 70 mph are possible in this region as additional storms form when coverage increases later this afternoon.

Severe Weather Analysis

 

A few storms are forming over the Lower Pecos Valley and they should strengthen this afternoon along a slow moving cold front.  The air mass within this area and the Concho Valley is moderately unstable at this time with substantial wind shear.  The risk will spread downstream later this evening towards the Edwards Plateau.

The surface ridge over the Southern Plains exhibits maturing thunderstorms on the latest visible satellite imagery across Big Bend and Northern Mexico.  Strong boundary layer heating is noted in this region.  Convective temperatures will be breached later this evening West of the Rio Grande and supercell activity is expected to move east into Texas.

Robert Millette

Staff Meteorologist

Firsthand Weather

Forecast and Severe Outlook: Wednesday, May 11th

Additional severe weather is in the forecast as the last several days have brought 67 tornadoes from Colorado to Kentucky.  Strong low pressure moving into Canada will continue to move a strong warm front North ahead of a weaker cold front.   This clash of frontal boundaries is responsible for the weather the Plains and river valleys have been dealing with.

The current Surface Analysis

Surface map us

Today’s National Forecast

Weather Forecast map

The main weather feature across the nation will be a strong low pressure system over the north-central U.S. that will have a trailing cold front extending southward to Texas and the Desert Southwest. An occluded surface low over North Dakota will slowly lift northeastward to southern Canada, with rainy weather over eastern Montana and western North Dakota for the first half of Wednesday. Farther to the south, another surface low along the trailing cold front will also produce widespread showers and thunderstorms extending from Texas to the Ohio Valley. Some of these storms could be severe at times, and also produce localized flash flooding.

Temperatures are expected to be below normal across much of the Intermountain West with an upper level trough in place, and also for the Northeast U.S. which will be under the influence of a Canadian surface high. It will continue to be warm and humid south of a stationary frontal boundary, which will extend from the Ohio Valley eastward to the Mid-Atlantic coast. Highs in the 80s to near 90 along with noticeable humidity will be commonplace across the Deep South and the Southeast states.

West of the Rocky Mountains, a quiet weather pattern should prevail through the end of the week with no Pacific storm systems imminent. Inland temperatures should slowly return closer to average after the recent cool weather.

Current Severe Weather Outlook

Fire Weather Update

Fire Weather

No critical Fire areas to report.

Severe Weather Analysis

Summary

Scattered severe storms are forecast from parts of North Texas into Oklahoma and the Missouri and Mississippi River Valleys. Large hail and damaging winds will be the main concern by late in the day but a brief tornado or 2 are possible for this region.  For the Ohio Valley into the Mid-Atlantic, isolated severe hail or wind is possible during the day.

Severe Outlook

Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 47,289 2,762,058 Norman, OK…Wichita Falls, TX…Lawton, OK…Broken Arrow, OK…Muskogee, OK…
SLIGHT 218,024 19,885,612 Dallas, TX…Fort Worth, TX…Oklahoma City, OK…Kansas City, MO…Tulsa, OK…
MARGINAL 378,142 52,006,921 Chicago, IL…Indianapolis, IN…Columbus, OH…Charlotte, NC…Milwaukee, WI…

Analysis

Low pressure will move across Iowa during the day today and bring a warm front across Missouri into Central Illinois and across the remainder of the Ohio Valley. A very moist air mass exists behind this front supporting scattered storms during the day from Iowa into the Ohio Valley.  Warm advection will allow for development of storms across Virginia and North Carolina under the influence of the disturbance currently causing thunderstorms in Kentucky.

Moderate to strong mid-level flow will spread into the Oklahoma and Far Northern Texas area as a weak cold front extends from Missouri down into Northwestern Texas by late this afternoon. A very warm and moist air mass is already in place though current storms in the area will play a pivotal role in destabilization during the day.  Strong instability will lead to intense clusters of thunderstorms with the primary threats of wind and large hail across the enhanced risk area.  A couple of tornadoes cannot be ruled out for this region.

Substantial moisture and instability is currently developing over Eastern Kansas and Western Missouri causing cluster of thunderstorms to form during the overnight hours. This activity is expected to continue during the morning hours with a threat of large hail.  Further development of stronger storms during the early afternoon will present a risk of damaging winds as a mesoscale convective system develops.

Dewpoints in the 60s across Iowa are forecast to result in a small corridor of supercell activity. Some heating is expected during the day as shear profiles are locally enhanced by the presence of the low pressure system.  Hail will be the primary threat with these storms but there is a risk of tornadoes later in the afternoon.

This Week’s Flood Risk

Flood Risk

Yesterday’s Storm Reports

storm reports 2

Robert Millette

Staff Meteorologist

Firsthand Weather

Forecast and Severe Outlook: Monday, May 9th

Southerly winds ahead of an upper system moving out of the central Rockies into the Great Plains are forecast to draw warm, moist air from the Gulf of Mexico supporting widespread showers and thunderstorms across the lower and central Great Plains into the lower and mid Mississippi valley Monday into Monday night. Some of these storms may be strong to severe, particularly from northeast Texas, southeast Oklahoma into Arkansas and northwest Louisiana, where the air mass is expected to become highly unstable as well.

The current Surface Analysis

Surface map us

Today’s National Forecast

Weather Forecast map

Moisture spreading further to the north is likely to focus along a slow moving frontal band supporting widespread moderate to locally heavy rainfall accumulations across portions of the lower Missouri and mid Mississippi valleys.

On Tuesday into early Wednesday, the previously noted upper system is forecast to weaken as it continues to track to the east. Organized showers and thunderstorms are expected to focus along the frontal boundary that will continue to extend from the mid Mississippi into the Ohio valley and Mid-Atlantic states.

Back to the west, a well-defined cold front is forecast to drop through the western U.S. this period, with below-average temperatures spreading south and east from the northern Rockies and High Plains. Moderate to heavy precipitation is likely to develop west of an organizing area of low pressure over the northern High Plains. Heavy rain accumulations are expected to center over eastern Montana, with heavy mountain snows over the ranges of southwestern Montana and northwestern Wyoming.

Current Severe Weather Outlook

Fire Weather Update

Fire Weather

Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
Critical 35,626 780,783 Las Cruces, NM…Roswell, NM…Hobbs, NM…Carlsbad, NM…Artesia, NM…

Critical Fire Weather area for portions of Eastern New Mexico and Far West Texas.

Severe Weather Analysis

Summary

Severe storms are forecast Monday into Monday night from parts of the Southern and Central Plains eastward into the Lower to Mid Missouri Valley, the Ozarks, and ArkLaTex region. Tornadoes and very large hail are possible across the region under the enhanced risk from Eastern Oklahoma and Northeastern Texas into Central Arkansas and Northern Louisiana.

Severe Outlook

Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 67,531 4,070,056 Shreveport, LA…Little Rock, AR…Tyler, TX…Fort Smith, AR…Longview, TX…
SLIGHT 228,723 20,439,696 Dallas, TX…Oklahoma City, OK…Kansas City, MO…Omaha, NE…Tulsa, OK…
MARGINAL 203,583 16,544,671 Houston, TX…Memphis, TN…Fort Worth, TX…Arlington, TX…Pasadena, TX…

 

tornado risk

Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
10 % 45,082 2,815,545 Shreveport, LA…Little Rock, AR…Tyler, TX…Fort Smith, AR…Longview, TX…
5 % 56,517 4,200,601 Tulsa, OK…Mesquite, TX…Broken Arrow, OK…Fayetteville, AR…Springdale, AR…
2 % 135,312 14,700,662 Dallas, TX…Fort Worth, TX…Oklahoma City, OK…Arlington, TX…Wichita, KS…

hail risk

Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SIG SEVERE 73,480 8,648,809 Dallas, TX…Tulsa, OK…Plano, TX…Garland, TX…Shreveport, LA…
30 % 67,798 4,097,285 Shreveport, LA…Little Rock, AR…Tyler, TX…Fort Smith, AR…Longview, TX…
15 % 229,629 20,571,862 Dallas, TX…Oklahoma City, OK…Kansas City, MO…Omaha, NE…Tulsa, OK…
5 % 202,489 16,100,321 Houston, TX…Memphis, TN…Fort Worth, TX…Arlington, TX…Pasadena, TX…

Analysis

Strong heating over much of the region will combine with steep lapse rates aloft to result in strong instability from Eastern Texas into Eastern Oklahoma and Kansas as well as Western Arkansas. Southerly low-level flow will continue to bring moisture into the region as it did with yesterdays storms.  Dewpoints are forecast to reach the mid to upper 60s across the region.  Thunderstorms currently near the Red River will shift into Arkansas by this afternoon.  There is a risk of damaging winds and hail with these storms.

The outflow from the aforementioned storms should help to focus the areas of severe weather development later this afternoon when instability reaches its maximum. Wind Shear profiles will clearly favor the development of discrete supercells and support conditions for tornadoes.  The most likely area for tornadic development will be Eastern Oklahoma into West Central Arkansas southward across the ArkLaTex region.  Supercells may also develop farther south within the moist regions near Shreveport.  Convergence in this area will be weak but rapid moistening and weakening outflow boundaries may be enough to initiate discrete storms.

Further west, from Central Oklahoma into Central Kansas, severe storm chances are more conditional along the Dryline but some storms should develop in this area and large hail is the primary risk.

Further north along the weakening warm front, strong warm advection pushing north will result in destabilization from Missouri into Western Illinois. A few severe storms capable of large hail and possibly a tornado or 2 cannot be ruled out.

This Week’s Flood Risk

Flood Risk

Yesterday’s Storm Reports

storm reports 2

Robert Millette

Staff Meteorologist

Firsthand Weather

Severe Weather Update

Severe weather is forecast from South Central Texas up through Central Nebraska, Southwest Iowa and Western Missouri.  Very large hail and a few strong tornadoes are anticipated in the primary threat area from Central Kansas into Western Oklahoma beginning late this afternoon.

SEVERE

Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 54,976 1,283,928 Topeka, KS…Enid, OK…Salina, KS…Manhattan, KS…Hutchinson, KS…
SLIGHT 116,764 6,492,921 Oklahoma City, OK…Kansas City, MO…Omaha, NE…Wichita, KS…Lincoln, NE…
MARGINAL 135,470 7,240,517 Fort Worth, TX…Tulsa, OK…Arlington, TX…Des Moines, IA…Grand Prairie, TX…

TORNADO

Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SIG SEVERE 28,279 270,045 Hays, KS…Great Bend, KS…Woodward, OK…Weatherford, OK…Clinton, OK…
10 % 36,238 441,164 Salina, KS…Hutchinson, KS…Dodge City, KS…Hays, KS…Great Bend, KS…
5 % 44,315 2,041,268 Wichita, KS…Topeka, KS…Olathe, KS…Lawrence, KS…Shawnee, KS…
2 % 56,703 3,837,823 Oklahoma City, OK…Kansas City, MO…Lincoln, NE…Overland Park, KS…Kansas City, KS…

HAIL

Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SIG SEVERE 54,953 1,221,772 Topeka, KS…Enid, OK…Salina, KS…Manhattan, KS…Hutchinson, KS…
30 % 55,091 1,222,413 Topeka, KS…Enid, OK…Salina, KS…Manhattan, KS…Hutchinson, KS…
15 % 117,251 6,638,156 Oklahoma City, OK…Kansas City, MO…Omaha, NE…Wichita, KS…Lincoln, NE…
5 % 135,114 7,194,400 Fort Worth, TX…Tulsa, OK…Arlington, TX…Killeen, TX…Norman, OK…

— SEVERE WEATHER DISCUSSION —

Scattered severe thunderstorms are expected today forming along and in front of the dryline and low pressure system moving across the Central and Southern Plains.  Additional thunderstorms may form near a developing warm front over Kansas up into Nebraska and along the dryline in Western Texas

Large hail, Severe wind gusts and a few tornadoes are all possible.  A couple of these tornadoes may be strong especially during the later part of the afternoon and early evening as moisture advection increases.

Surface dewpoints are climbing into the 60s near the Red River.  Moisture advection ahead of the dryline and behind the warm front will continue throughout the day.  This advection, along with day time heating, will contribute to high CAPE values across much of the area.  The strongest shear seems confined to Western Oklahoma and Central Kansas.  Supercellular activity should be favored in this area.  Development should begin near the dryline but will shift east as outflow boundaries and cold pools begin to form.  This will allow activity in Northern Kansas and Southern Nebraska to last longer into the overnight hours after convection associated with the dryline diminishes.

Further south, scattered severe thunderstorms are expected to form along the dryline across portions of West Central Texas after the dryline begins to retreat.  Strong day time heating combined with an influx of moisture will help these storms develop very rapidly.  This activity will shift towards Northwest Texas during the overnight hours.  Large hail and isolated damaging wind gusts are the primary threats in this region.

 

Forecast and Severe Outlook: Sunday, May 8th

After yesterday’s tornadoes in Colorado, Severe weather is forecast to continue on the Plains today.  A few tornadoes, very large hail and damaging winds will be the primary threats.

The current Surface Analysis

Surface map us

Today’s National Forecast

Weather Forecast map

A broad upper low currently centered over the Great Basin and southwestern U.S. is expected to slowly lift northeastward this period. Scattered showers and thunderstorms are forecast to continue today from the Sierra eastward to the central and southern Rockies, with precipitation expected to end by early Monday across California and much of the Great Basin as the aforementioned low reaches the central Great Plains.

Further to the east, southerly winds are expected to draw moist, unstable air from the Gulf of Mexico northward increasing the threat for strong to severe thunderstorms across portions of the southern and central Great Plains. On Monday, the threat is forecast to shift further east, extending into portions of the lower and mid Mississippi valley.

The greatest potential for heavy rainfall accumulations is expected center across the lower Missouri and mid Mississippi valleys. Moisture advecting from the south is forecast to focus along a slow moving frontal boundary, supporting heavy rains across the region.

Across the Northeast, a strong low moving across southeastern Canada is expected to usher in cooler temperatures and another chance for showers and thunderstorms early Sunday. Further to the south, scattered showers and thunderstorms are forecast to focus near a frontal boundary dropping into the region. Meanwhile, high pressure and dry conditions are likely to prevail across the Southeast.

Current Severe Weather Outlook

Fire Weather Update

Fire Weather

Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
Critical 50,750 896,717 Las Cruces, NM…Roswell, NM…Clovis, NM…Carlsbad, NM…Portales, NM…

A Critical Fire Weather area has been issued for portions of Eastern New Mexico and Far West Texas.

Severe Weather Analysis

Summary

Severe Outlook

Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 51,455 1,370,679 Wichita, KS…Enid, OK…Salina, KS…Hutchinson, KS…Dodge City, KS…
SLIGHT 163,105 8,307,061 Oklahoma City, OK…Kansas City, MO…Omaha, NE…Tulsa, OK…Lincoln, NE…
MARGINAL 109,930 5,511,073 Fort Worth, TX…Arlington, TX…Des Moines, IA…Grand Prairie, TX…Denton, TX…

Severe thunderstorms are forecast across much of the Central and Southern Plains Sunday afternoon into evening. Very large hail and a few tornadoes are anticipated with the primary threat area from Central Kansas into Northwestern Oklahoma beginning in the late afternoon.

Tornado Risk

tornado risk

Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SIG SEVERE 38,306 907,149 Wichita, KS…Enid, OK…Hutchinson, KS…Dodge City, KS…Hays, KS…
10 % 37,880 807,808 Wichita, KS…Enid, OK…Hutchinson, KS…Dodge City, KS…Hays, KS…
5 % 57,931 1,772,470 Edmond, OK…Salina, KS…Manhattan, KS…Stillwater, OK…Kearney, NE…
2 % 35,823 1,715,349 Oklahoma City, OK…Lincoln, NE…Topeka, KS…Norman, OK…Lawton, OK…

Hail Risk

hail risk

Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SIG SEVERE 50,943 1,364,854 Wichita, KS…Enid, OK…Salina, KS…Hutchinson, KS…Dodge City, KS…
30 % 51,776 1,381,121 Wichita, KS…Enid, OK…Salina, KS…Hutchinson, KS…Dodge City, KS…
15 % 163,586 8,317,521 Oklahoma City, OK…Kansas City, MO…Omaha, NE…Tulsa, OK…Lincoln, NE…
5 % 112,522 5,439,040 Fort Worth, TX…Arlington, TX…Killeen, TX…Denton, TX…Lewisville, TX…

Analysis

Low pressure will quickly deepen across Southwest Kansas today as strong moisture advection takes place across the Southern Plains. A well-developed Dryline should be in place by this afternoon from Southwest Kansas into Western Oklahoma and Northwest Texas with Dewpoints at the surface getting into the 60s.  Widely spaced thunderstorms are expected to develop along and east of the Dryline during the mid to late afternoon.

The model forecast soundings for the day are impressive with high levels of CAPE and shear. These conditions are very favorable to supercell development.  Tornadoes, very large hail and wind damage are likely with any cell that develops east of the Dryline.  The Storm Prediction Center has removed the moderate risk they issued yesterday for this region due to some uncertainty in the levels of moisture available to the storms, but a wider area of enhanced risk has been created overnight and I will not be surprised if an area of moderate risk is reintroduced as observations create more certainty for moisture levels.

Further south along the Dryline, from Northwest Texas down to the Rio Grande, moderate instability will form when daytime heating combines with a retreating Dryline and the arrival of moisture advection this afternoon. Widely spaced thunderstorms should form along the Dryline.  This activity will move eastward into an area of increasing low level flow.  Supercells with large hail and damaging wind will be likely.

This Week’s Flood Risk

Flood Risk

Yesterday’s Storm Reports

storm reports 2

Robert Millette

Staff Meteorologist

Firsthand Weather

Forecast and Severe Outlook: Friday, May 7th

As severe weather returns to the Plains, Fire Weather remains Critical in Eastern New Mexico after yesterday’s dry thunderstorms.  Today’s forecast and severe weather analysis follows below.

The current Surface Analysis

Surface map us

Today’s National Forecast

Weather Forecast map

An omega block pattern aloft at the beginning of the period is forecast to slowly break down over the weekend. Well defined upper level lows are evident over the Desert Southwest and near the Mid-Atlantic coast Saturday morning, and a weakening upper level ridge over the Plains.  By Sunday afternoon, the pattern should not be quite as amplified with the upper low lifting northward towards Canada and the ridge becoming more suppressed to the south.

In terms of sensible weather, temperatures are expected to begin moderating across the eastern U.S. after several days of unseasonably cool weather and persistent cloudy skies. The same also holds true across much of the Intermountain West region with below normal temperatures likely to continue through the weekend, along with numerous showers and high elevation snow.  The heaviest snow is expected for the highest mountains of Wyoming, Utah, and Colorado.

Across the south-central U.S., it will become increasingly warm and humid as moisture returns northward from the Gulf of Mexico ahead of the upper low near the Rockies. Strong to severe thunderstorms will be possible from Texas to Nebraska on Sunday, and general thunderstorm activity is possible along a frontal boundary that will extend eastward to the Southeast U.S. coast.

Current Severe Weather Outlook

Fire Weather Update

Fire Weather

Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
Critical 36,742 239,972 Roswell, NM…Clovis, NM…Carlsbad, NM…Portales, NM…Artesia, NM…

Critical Fire Weather area for portions of Eastern New Mexico and Far West Texas.

Severe Weather Analysis

Summary

Severe Thunderstorms are forecast to occur this afternoon and evening across the Central and Southern High Plains and the Ohio River Valley.

Severe Outlook

Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 95,499 9,079,542 Denver, CO…Cincinnati, OH…Aurora, CO…Lexington-Fayette, KY…Louisville, KY…
MARGINAL 347,529 20,467,273 Indianapolis, IN…Columbus, OH…St. Louis, MO…Pittsburgh, PA…Lincoln, NE…

Analysis

A southeastward moving trough over the Great Lakes will impact the high amplitude pattern in place and allow the closed low over Southern California to finally begin to move east. Surface cyclogenesis will occur over Northeast Colorado and the adjacent Central Plains as a southward moving front extends across the Middle and Lower Missouri Valley into the Ohio River Valley.

In the High Plains, Moist Southeasterly upslope flow will establish itself this afternoon and evening along the Front Range in Northern Colorado and Southern Wyoming. Storms are expected to develop and steadily increase by mid-day over the higher terrain and then move into the foothills and then over the High Plains.  Severe hail is expected and a coup-le of Tornadoes could occur particularly over Northeastern Colorado.

Further east, a cold front associated with a deepening low near the Great Lakes will amplify over the Ohio Valley. Persistent strong west southwesterly winds will feed moisture just above the surface and raise surface Dewpoints into the 60’s by late afternoon.  With near surface based storms expected to form this afternoon and evening, severe hail and winds should be the primary hazards.

This Week’s Flood Risk

Flood Risk

Yesterday’s Storm Reports

storm reports 2

Robert Millette

Staff Meteorologist

Firsthand Weather

Forecast and Severe Outlook: Monday, May 2nd

Severe Weather is forecast in the Piedmont of the Carolina’s to the Mid-Atlantic as the system that brought a few tornadoes to Indiana yesterday moves east.  Meanwhile in Texas, showers and thunderstorms will continue to exacerbate the flooding problems across that region.

The current Surface Analysis

Surface map us

Today’s National Forecast

Weather Forecast map

A quasi-stationary front extending from the Mid-Atlantic and Central Appalachians southwestward to the Lower Mississippi Valley will slowly sag south and eastward to the Southern Mid-Atlantic to the Southeast and parts of the Eastern Gulf Coast by Tuesday evening. Showers and thunderstorms will develop along and ahead of the boundary from the Mid-Atlantic to the Southern Plains that will extend from the Northern Mid-Atlantic Coast to the Central Gulf Coast by Tuesday.  Rain will also develop over parts of the Great Lakes to the Northeast that will slowly move into Southeastern Canada by Tuesday afternoon.

Meanwhile, upper-level energy over Southern California will move slowly eastward to the Southern Plains by Tuesday. The energy will produce rain with embedded thunderstorms that will have a diurnal component to the areal coverage over parts of Central California to the Central and Southern Rockies that will end over the Region by Tuesday morning.  Another area of upper-level energy will move southward from the Northern Plains to the Southern Plains by Tuesday evening.  The energy will trigger rain over parts of the Northern Plains on Monday morning that will move southward to the Central High Plains by Tuesday morning.

Furthermore, a front moving southward out of Central Canada on Tuesday morning will move to parts of the Upper Great Lakes and Upper Mississippi Valley and Northern Plains by Tuesday evening.

Current Model Analysis

6 hour model

On Monday, one batch of rain moves out of the Northeast as another prepares to move in. Rain should stop for a time in New York and New England as the second batch comes through the Ohio Valley.  This system did produce a couple of Tornadoes on Sunday and brought several instances of severe weather across the Ohio Valley.  This risk will continue from Virginia down through the Gulf Coast along the cold front.

Showers and storms will continue to exacerbate the flooding issues down in Texas throughout the day though conditions will begin to dry out later in the forecast period.

High pressure will dominate the western half of the country but a couple of weak disturbances will be enough to generate some rain  and snow showers from the Pacific Coast into the 4 Corners region.

18 hour model

 

Monday afternoon, the rain shifts east and is now impacting the East coast from Florida to Maine within this broad circulation and along the cold front.  Areas near Dallas should begin to dry out as the front pulls east toward the coastline.  Rain and thunderstorms should be expected along the entire Gulf Coast and Eastern Seaboard at some point during the day.

High pressure will completely dominate the western half of the ountry Monday afternoon with only a few spot showers and a small batch of rain showers in the Dakotas associated with a weak low in Canada.

36 hour model

By early Tuesday, High pressure dominates the West with only the remnants of a cold front draped across the Country from Massachusetts to Coastal Louisiana. Low pressure in the Mid-Atlantic will continue to bring rain to nearly the entire East Coast.

Current Severe Weather Outlook

Fire Weather Update

Fire Weather

No critical fire weather expected

Severe Weather Analysis

Summary

A few severe storms are forecast today across the Appalachian Mountains and Piedmont of the Carolinas into the Mid-Atlantic region.

Severe Outlook

Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 70,267 19,724,039 Baltimore, MD…Charlotte, NC…Washington, DC…Greensboro, NC…Durham, NC…
MARGINAL 155,209 27,778,806 Philadelphia, PA…New Orleans, LA…Virginia Beach, VA…Atlanta, GA…Raleigh, NC…

Analysis

Weak to moderate boundary layer destabilization is expected by this afternoon near and east of the lee surface trough from the Piedmont region of the Carolinas to the Mid-Atlantic. Moderate instability and strong southwesterly low and mid tropospheric winds are forecast to be sufficient for convective development.  These thunderstorms will be capable of producing damaging wind gusts and some hail.  Storm coverage east of the Appalachians is expected to become more widespread this afternoon with the approach of a upper level disturbance emerging from the west.

This Week’s Flood Risk

Flood Risk

Yesterday’s Storm Reports

storm reports 2

Robert Millette

Staff Meteorologist

Firsthand Weather

Forecast and Severe Outlook: Sunday, May 1st

Today’s forecast brings rain to the East Coast and another risk of severe weather to the Gulf Coast.  Heavy rain will bring several Texas waterways back into moderate to major flood stage for a short time with the risk for flooding now spreading into Louisiana.

The current Surface Analysis

Surface map us

 

Today’s National Forecast

Weather Forecast map

A front extending from the Lower Great Lakes to the Western Gulf Coast will become quasi-stationary with the boundary inching to New England Coast southwestward to the Lower Mississippi Valley by Monday evening. The system will develop showers and thunderstorms from the Ohio Valley to the Lower Mississippi Valley that will move to the Northern Mid-Atlantic Coast to the Lower Mississippi Valley and Western Gulf Coast by Monday evening.  Rain will develop over parts of the Central Plains eastward to the Great Lakes and parts of the Northeast as well as parts of the Northern Mid-Atlantic.  The rain will come to an end over the Central Plains and Middle Mississippi Valley by Monday morning and over the Great Lakes by Monday evening.  The rain will move into Northern New England by Sunday evening.

 

Current Model Analysis

6 hour model

On Sunday, thunderstorms will continue across the Appalachian region. Storms will not be as severe as they have been over the past several days but severe weather will continue to be a threat.  The low bringing this risk to the mountains is very broad, and continues to have rain and snow across Nebraska, Wyoming and Colorado this morning.

Dual disturbances in the Southeast continue to bring showers and some storms to the 4 corners region.

While rain won’t be a big factor in the Northeast early this morning, it will be by this afternoon and most of the East Coast, from Northern Florida up through Pennsylvania and New Jersey will begin to see rain by this morning.

18 hour model

Sunday afternoon, the rain shifts east and is now impacting the East coast from Florida to Maine within this broad circulation.

Rain and snow will begin to let up during the afternoon over the Rockies of Colorado, Wyoming and Nebraska.

A low over Arizona will begin to bring rain and snow to the 4 Corners region as a weak and moisture starved low moves into California with nothin to show for it.

36 hour model

By early Monday, High pressure dominates the West with only the remnants of a cold front draped across the Country from Massachusetts to Texas. A weakening low pressure system will set the stage for what looks to be a very wet week along the East coast.

 

Current Severe Weather Outlook

Fire Weather Update

Fire Weather

No Critical Fire Weather areas

Severe Weather Analysis

Summary

Scattered Strong to severe thunderstorms are possible across Southern and Central Texas and the Central Gulf Coast Region as well as in the Ohio Valley and Central Appalachians.

Severe Outlook

Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MARGINAL 309,811 43,672,165 Houston, TX…San Antonio, TX…Indianapolis, IN…Columbus, OH…Austin, TX…

Analysis

With moderate destabilization forecast from the Ohio Valley to the Central Appalachians, strengthening mid to upper level wind fields will allow for marginally conducive conditions for severe storms.  Deep layer sheer will be strong and supportive of supercells, but lower level wind shear is forecast to me weak.  This will minimize tornadic potential in this area but severe hail and strong surface gusts are forecast in the strongest storms.  These storms are expected to be widely scattered this afternoon and evening.

Along the Gulf Coast, Upper level flow is forecast to be moderately strong between the divergent jet streams. Instability will be high ahead of the advancing frontal boundary which could lead to severe weather development.  While some storms are forecast near Upper Texas and Louisiana Coastal areas, most storms will develop near the higher terrain of the Rio Grande River late this afternoon and evening.

This Week’s Flood Risk

Flood Risk

Yesterday’s Storm Reports

storm reports 2

Robert Millette

Staff Meteorologist

Firsthand Weather