Flash Flooding Risk Will Expand Into Southeast and Mid-Atlantic This Weekend

Over the last several days, a longwave trough has remained in place across the western U.S., while a ridge has dominated the pattern across the eastern third of the U.S. Between these two larger-scale features, smaller shortwave impulses have generated favorable conditions for excessive rainfall amounts across parts of the Southern Plains and mid-south.

Rainfall amounts over the last 3 days

Over the weekend, a northern stream shortwave trough will dig into the Northern Plains and move into the Great Lakes by late weekend. This feature will usher in a pattern change and begin breaking down the ridge that has been placed across the Southeast and Mid-Atlantic. Before the cold front associated with the northern system pushes through the Gulf Coast and East Coast states early next week, a period of widespread moderate to heavy rain will fall across a large region of the southern U.S. and extend into parts of the Mid-Atlantic.

Projected 3-day rainfall amounts

Since the northern stream system will begin flattening and weakening the ridge, there will be an eastward expansion of the rainfall and potential flooding risk. Deep, tropical moisture will advect northward and northeastward throughout the weekend; thus, any rain that falls could be heavy and tropical in nature. The next three graphics outline the flash flooding risk for today (Friday), Saturday, and Sunday. Notice how the flash flooding risk will begin shifting eastward with time.

Flash flooding risk for Friday, May 10, 2019
Flash flooding risk for Saturday, May 11, 2019
Flash flooding risk for Sunday, May 12, 2019

Any additional rainfall that occurs across southeast Texas and southern Louisiana today will become problematic given recent heavy rain over the last 24 hours. This includes the Houston and Baton Rouge areas. States east and north of Alabama have remained relatively dry compared to the region just west. Even though soils are quite a bit drier east of the mid-south, high rainfall rates will still result in localized flash flooding farther east. By Sunday, lower rainfall rates will be necessary to cause flash flooding concerns, due to prior rainfall today and Saturday.

Even though I didn’t explicitly mention all regions under a flash flooding risk, please refer to any maps included in this article and future maps we post on social media. The purpose of this article is mainly to give you a heads up on this wet and stormy pattern, especially with Mother’s Day being this Sunday.

Southern Plains Storms

As expected this time of the year, it has been hot and oppressive across the Southern Plains this week. Luckily, changes are in store beginning tomorrow (Friday). An approaching upper-level trough will push a cool front into northern Oklahoma late tonight into Friday. This cool front will provide adequate lift to generate scattered thunderstorm activity along and north of I-40 in Oklahoma, southern Kansas, and parts of the Texas Panhandle. Any thunderstorm that develops tomorrow has the chance to become severe. The main threats are damaging winds and large hail.
Slide02
SPC Thunderstorm Forecast (Friday)

Heavy rainfall is possible with the thunderstorm activity on Friday, too, and the rain chances will continue through Sunday. These rain chances will continue throughout the weekend due to a couple upper-level disturbances moving across the area. 1-2″ is possible north of I-40, and for parts of the Texas Panhandle; with isolated higher amounts.
Slide03
NAM Rainfall Forecast Through The Weekend

While most of southern Oklahoma and northern Texas wont see widespread rain chances. A few thunderstorms are possible for these areas; however, the more widespread activity will remain further north. Areas that do not see rainfall/cloud-cover can expect temperatures and humidity levels to remain uncomfortably high.

Southern Plains Storms

Shower and thunderstorm chances will continue across much of Kansas, northern Oklahoma, and the Texas Panhandle over the next few days. Isolated thunderstorms are ongoing across parts of the Southern Plains this evening, but more widespread activity is expected to develop in eastern Colorado/western Kansas and propagate towards northern Oklahoma tonight into early Thursday.

By Thursday evening a weak cool front will advance into Kansas and north of I-40 (in Oklahoma) by Friday morning. This boundary will be the focus for several rounds of showers and storms for Kansas as well as northern and central Oklahoma. Heavy rainfall is likely during this setup; most areas north of I-40 will see 1-2″ with isolated 3-6″ possible. This could create flash flooding for localized areas during the day on Friday. Isolated damaging winds and large hail is possible with any storm over the next few days, and lightning will be a major concern for those who have outdoor plans.
Slide02
Potential Rainfall Totals (Next 5 Days)

It is important to note that the area will see a northerly flow aloft, so some of the thunderstorms that develop in northern/central Oklahoma may move further south than the models indicate. This will keep scattered rain chances in the forecast for southern Oklahoma as well as northern Texas, but the greatest coverage will be north of I-40.

Rain chances will subside for northern Texas and much of Oklahoma on Saturday, but appear to return later in the weekend. These rain chances will be bumped up a few notches on Sunday into Monday due to the upper-level ridge weakening. Temperatures will top out in the 80’s and 90’s the rest of this week so make sure you’re staying hydrated! I’ll have more details on the Monday (4th of July) forecast in the next day or two.

Flood Outlook and Forecast: Tuesday, April 19th

Flood risks remain for the Texas area which has been hard hit already.  Additional rain can be expected in this area over the next couple of days.

The current Surface Analysis

Surface map us

Today’s National Forecast

Weather Forecast map

A cutoff upper-level low with an associated quasi-stationary front from the Midwest to the southern plains will continue to generate numerous showers and thunderstorms over the next couple of days. Excessive rainfall has already caused significant flooding issues in Texas – the threat will slowly decrease through the day as the area of higher precipitation expands eastward into the Lower and Middle Mississippi Valleys. Flash flooding concerns will be elevated for east Texas to southern Illinois/Indiana. The model output for total rainfall through Wednesday night can be seen here.

total qpf

Additionally, the mountain snow in Colorado and Wyoming will taper off as the area as the position of the upper low and surface front shifts eastward. The system is forecast to begin a slow eastward movement by Wednesday afternoon and evening, when showers and thunderstorms will begin to spread into portions of the Ohio and Tennessee valleys.

Much of the Northeast and Mid-Atlantic states will continue to have pleasantly warm and dry conditions through midweek. Afternoon high temperatures are forecast to be near or above average for mid-April. A vast portion of the West will also remain relatively dry with well-above normal temperatures. Many locations will have afternoon highs ranging 15 to 25 degrees above average through Wednesday.

Current Model Analysis

6 hour model

The chance for flooding continues to increase on top of the flooding already in place as the rain continues to fall along a slow moving boundary in the Plains. The Houston area has already seen an incredible amount of rainfall with this system and several local rivers are in major flood stage at this time.  While the rain does taper off slightly in this region, reducing itself to showers, another inch or two should be expected through Thursday.

In the Rockies, areas of heavy snow continue from Northern New Mexico up into Wyoming in the mountains, which can expect several more inches throughout the day before things begin to taper off. While the snow does continue its total coverage area continues to shrink.

For both coasts, another beautiful day can be expected with the exception of the Northeast, which will see some rain quickly move through.

18 hour model

By Tuesdayday afternoon, with the heaviest rain from Houston up to the Lake Charles Louisiana area on into Mississippi, and area of which can be seen bounded in the Excessive Rainfall outlook, below.

Excessive rainfall

The system that brought all the rain is breaking apart as seen on the model image and precipitation is scattered all across the Plains regions.

A backdoor cold front will hit the Northeast and start to drop the temperature as a low pressure system slides off the coastline.  Rain should still be falling in parts of Maine but it should end before the day is over.

36 hour model

By early Wednesday, the system in the Plains, now reforming in this model image, continues to bring heavy rain and severe weather to the Plains while the snow in the Rockies continues to wind down as high pressure develops.  This precipitation will only make the flood situation in Texas worse.  The Coastlines remain clear and dry under the influence of high pressure with only a break away batch of showers moving through the Northeast.

Current Severe Weather Outlook

Fire Weather Update

Fire Weather

Severe Outlook

Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MARGINAL 80,229 1,476,846 Lubbock, TX…Abilene, TX…Wichita Falls, TX…Midland, TX…Odessa, TX…

Severe Weather Analysis

SUMMARY

Isolated Severe storms will form across parts of West Texas in the late afternoon and evening. Hail and Wind should be the primary threats

Analysis

Surface dew points in the upper 50s to lower 60s are prevalent across much of Central and Western Texas. While response should be weak ahead of the approaching mid-level impulse, boundary layer moisture will change little through this evening.  Instability in this region will be driven heavily by the amount of day time heating which currently differs greatly from model to model, so overall confidence in this forecast is lower than usual.

The reason for this is a large deck of stratus that remains from earlier rainfall which will help limit the amount of sun. Models have widely differing results for this cloud cover except for good agreement near the Dryline where substantial heating will occur.

Deep sheer is not going to be overly robust, but enhancement to the mid-level westerlies is expected as the impulse approaches the area and be strong enough for there to be a risk of multicell cluster splitting of supercells.

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, April 18th

Forecast calls for additional heavy rain as several rivers begin to approach flood stage in Texas and Oklahoma.  Heavy snow will again fall in the Rockies with a few more inches expected while another nice day is in store for the east and west coasts.

The current Surface Analysis

Surface map us

Today’s National Forecast

Weather Forecast map

A nearly stationary front associated with a deep upper-level low will be draped from the Upper Midwest and Great Lakes region southward through the central and southern plains. Moisture from the Gulf of Mexico streaming in ahead of the front will fuel the atmosphere for widespread showers and thunderstorms. Some of the storms may turn severe therefore the Storm Prediction Center has issued a slight risk for portions of the southern Plains today. Heavy rainfall is expected with this weather pattern. Texas will be the most likely area for high rainfall rates over the next couple of days. Southeast Texas has a high risk for flash flooding today, with slight to moderate risk for much of central/eastern Texas and Oklahoma through Wednesday morning. Multi-day accumulations of 3 to 8 inches is forecast from the Ark-La-Tex border to the western Gulf Coast – the highest amounts will be in the vicinity of Galveston, Texas.

The showers and thunderstorms will spread into parts of the Middle/Lower Mississippi Valley into Tuesday, as well as, rain developing along and near the boundary over parts of the central and northern plains. Higher elevation snow and lower elevation rain will develop over parts of the Northern/Central Rockies through Tuesday with accumulations up to 1 foot at the highest elevations of Colorado and Wyoming.

A cold front will slowly sink through the Northeast and into the Mid-Atlantic region by midweek. Rain will develop along the boundary over the Upper Mississippi Valley and expand into the Upper Great Lakes today. The rain will move into parts of Northern New England moving into parts of the Northern Mid-Atlantic by Tuesday.  A few embedded thunderstorms may develop over parts of the Middle Mississippi Valley and parts of the Middle Missouri Valley this afternoon and evening.

Current Model Analysis

6 hour model

The chance for flooding continues to increase on top of the flooding already in place as the rain continues to fall along a slow moving boundary. Heavy rain continues to pour down from Southern Texas up into the Dakotas though most of the flooding rains are confined to areas near and South of the Red River.  Rivers in these locations are already entering their action stages and several are expected to reach their flood stages over the next few days.

In the Rockies, areas of heavy snow continue from Northern New Mexico up into Wyoming in the mountains, which can expect several more inches throughout the day.

For both coasts, another beautiful day can be expected.

18 hour model

By Monday afternoon, rain continues to fall in the Plains and the snow begins to slowly taper off location by location as the boundary pushes east towards the Mississippi River Valley. Dry conditions continue along both coastlines as high pressure dominates.  Here is a look at the excessive rainfall expectation for through this afternoon.

36 hour model

By early Tuesday, the system in the Plains continues to bring heavy rain and severe weather to the Plains while the snow in the Rockies begins to wind down as high pressure develops.  The Coastlines remain clear and dry under the influence of high pressure with only a break away batch of showers moving through the Northeast.

Current Severe Weather Outlook

Fire Weather Update

Fire Weather

No elevated fire risk areas are forecast.

***Severe Weather Analysis***

…SUMMARY…

Isolated Strong to Severe Thunderstorms will form across South and Southeast Texas through the mid evening.

Severe Forecast

Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 34,586 2,257,881 Corpus Christi, TX…Laredo, TX…Brownsville, TX…Harlingen, TX…Victoria, TX…
MARGINAL 44,274 9,995,879 Houston, TX…San Antonio, TX…Austin, TX…Pasadena, TX…Beaumont, TX…

***Analysis***

Multiple areas of thunderstorms are ongoing at this hour across Southeast Texas and the Upper Coast area where heavy rainfall is being produced by a mesoscale convective system. This system is forecast to move east into parts of Western Louisiana later today into overnight.  While forcing in general is weak in this location, the cold pool from this convective system could help to produce a few wet downbursts and some strong winds

Across the Deep South of Texas, Dewpoints are rising into the 60s and 70s and daytime heating between the cloud breaks will allow for redevelopment of storms along and ahead of the front near the remnant outflows. Low level winds should be sufficient for organized multicell clusters and a few supercells that may produce large hail.  It is possible that storms merge and move forward in a southeastward direction and bring the hail and wind risk towards the Lower Texas Coast this evening.

This Week’s Flood Risk

Flood Risk

Yesterday’s Storm Reports

storm reports 2

Robert Millette

Staff Meteorologist

Firsthand Weather

More Texas & Oklahoma Flooding That Will Spread Northeast

3 Day Rainfall Map

I am going to keep tonight’s update brief since I sent out a reasonably detailed newsletter last night, which hopefully most of you have already read by now. As soon as I hit the send button last night, I realized that I forgot to include a couple images, so those are included in this update.

Discussion On Potential Flooding From OK/TX Into Central MS Valley/Ohio Valley:

We are reverting back into a similar pattern that many of us became accustomed to last month. Bermuda high pressure is beginning to build back into the Southeast from the Atlantic, which is really going to heat the temperatures back up into 90s across many regions, especially as the week progresses. A cold front currently extends from the Plains up into the Upper Midwest and is going to continue to push southeast before it eventually stalls out by mid-week over the Ohio Valley. It’s not hard to pick out the cold front that extends across the Plains on the current temperature map below.

Current Temperatures

A trough is going to continue to build into the Southwest, which will push pieces of energy into the Southern Plains. As a response to the overall pattern, surface low pressure is going to likely develop by early to mid-week and move across parts of the Texas Panhandle/Oklahoma, dumping copious amounts of rain. It’ll continue to move northeast, pushing heavy rain into southeast Kansas, Missouri, northern Arkansas, and eventually into the Ohio Valley. Luckily, eastern Texas will be dodging all of this rain. I posted WPC’s 3 day rainfall map (in inches) below to give you a better idea of where the heaviest rain could fall.

3 Day Rainfall Map

As you can see, heavy amounts of rain are on the way. There will be some areas that will easily pick up 4 to 6+ inches of rain with locally higher amounts. Flooding must always be taken seriously, and keep in mind that almost all of the regions that will be getting this rain have already gotten flooding rains over the last several weeks.

Flash Flooding Threat Increasing For Parts of Texas & Oklahoma

HWRF Model Landall

Tropical troubles are brewing for parts of the Southern Plains and South this upcoming work week. The National Hurricane Center (NHC) is monitoring a low-pressure system over the southern Gulf of Mexico, just north of the Yucatan Peninsula, this afternoon, and has given the system a 70% of further development into a Tropical Depression or Tropical Storm over the next day or two. Right now, the system is fighting conditions in the upper-levels that are not conducive for development, however this should change over the next 24-48 hours. With that said, regardless of development into a Tropical Depression or Tropical Storm, this system will bring flooding rains to parts of Texas, parts of Oklahoma, Louisiana, and Arkansas.

Projected Rainfall Totals from CMC Model:

CMC Rainfall Totals

The low will move towards the north-northwest—inching closer to the middle to upper Texas Coast by late Monday into Tuesday. The exact timing and track is still to be resolved over the next 12-24 hours because the models are all over the place with this system. This low, as aforementioned, should develop into a weak Tropical Storm by Monday evening, right before it begins to encounter the Texas Coast. This will spread tropical moisture into Texas only exacerbating the flooding issues the state has dealt with over the past month. As the system tracks northward into the state, it appears it will remain intact relatively well. Not only does this mean rain chances, including flash flooding, will be high, but some gusty winds and possible isolated weak tornadoes are possible on the eastern side of this low (probably east of the I-35 corridor) by Tuesday afternoon through Thursday morning. This means that homes could have substantial damage done to them by the flash floods. If this is the case then they will need to get the Action 1 Restoration services provided by them to help restore the water damage.

HWRF Model Landfall Along Texas Coast:

HWRF Model Landall

HWRF Model Brings System Farther North Towards Dallas:

HWRF Model Dallas

HWRF Model Eventually Brings System Along TX/OK Border:

HWRF Model OK/TX

Some locations may see several inches of rainfall. Right now, the best rain chance will be Tuesday through Thursday, and locations along and east of I-35 will likely see 2-6″ of rain (some areas, especially near the Texas Coast and far eastern Texas/eastern Oklahoma may see 5-10″+ of rain). Flooding and flash flooding are likely during the upcoming work week and are the main threats with this system. Again, the exact timing and track of the storm are up in the air right now, but I will have updates as needed to fine-tune this forecast. If you live along and east of I-35, please prepare now for life threatening flash flooding!

Projected Path from Various Models:

Tropical Storm Bill Track