Forecast and Severe Outlook: Monday, April 25th

While the forecast for today brings a wide mix of news, the real weather stories remain the flooding in Texas and the Tuesday Severe Weather Threat.  For Texas, The Cypress Creek and Colorado River have dropped below flood stage but the majority of rivers in the area remain at or above the minimum flood stage, with the San Bernard River still in Major Flood stage.  These conditions are forecast to crest in the last of these areas over the next 2 days before diminishing completely.

For Tuesday, there remains a Significant risk of Severe Weather with the Storm Prediction Center adding a region of Moderate risk to the map.  There is a good chance that an area of High Risk will be added by tomorrow.   For a quick outline and maps of the event, please read down and see our Severe Weather Section, additional information will be posted Monday afternoon.

The current Surface Analysis

Surface map us

Today’s National Forecast

Weather Forecast map

A developing upper-level low over the Great Basin will move eastward to the Central Rockies by Tuesday evening as weakening low pressure over Upper Midwest and it’s associated front will merge with the storm coming out of the Great Basin by Tuesday morning. The system will produce showers and thunderstorms over parts of the Great Lakes and Upper Mississippi Valley into parts of the Middle Mississippi Valley.  This system will expand into parts of the Lower Great Lakes and Ohio Valley by Monday evening.  Rain will also develop over parts of the Northern High Plains and Northern Plains on Monday morning continuing through Monday night.  Showers and thunderstorms will also develop over parts of the Western Gulf Coast/Lower Mississippi Valley and parts of the Eastern Gulf Coast into the Southern Appalachians on Monday afternoon into evening.

Additionally, the showers and thunderstorms that will move into parts of the Northern Mid-Atlantic by Tuesday morning will extend from the Mid-Atlantic westward to the Western Ohio Valley and Middle Mississippi Valley by Tuesday evening. Rain will also develop over parts of the Upper Great Lakes into New England overnight Monday ending over the Upper Great Lakes by Tuesday afternoon.

Current Model Analysis

6 hour model

On early Monday, A strong but weakening low pressure system will bring rain from the Great Lakes over through North Dakota with rain and snow in Montana, as well as rain along the accompanying cold front from Minnesota down into Kansas and Oklahoma. Thunderstorms have been present with the front overnight Sunday and the risk of severe weather will continue moving east with the front as it heads toward Chicago.

Another low pressure system over Southern Nevada will create an area of instability over the Rockies which will lead to valley rains and mountain snows. Several inches of snow can be expected in the higher elevations, especially over Northern California and Nevada.

In the Eastern portion of the Country, high pressure dominates for a generally warm and clear day with some air mass showers and thunderstorms possible across the Southeast and later in the day in the Northeast as the aforementioned storm moves east over the Lakes.

18 hour model

By Monday afternoon, low pressure slides east over Minnesota and begins bringing rain to Western New York along the warm front. Rain will continue through the Great Lakes region back through North Dakota and Montana with some areas of snow changing to rain during the day.

The low pressure over the Rockies intensifys some and will bring a larger area of snow to the Mountains in Nevada.

The high pressure over the Atlantic will slide South off the Carolinas helping with daytime heating and airmass showers and thunderstorms over Florida and Georgia.

36 hour model

By early Tuesday, the forecast calls for low pressure from the Lakes will shift east to New England as cold air slides south.  This could bring moderate snow to areas north of a line from Watertown New York to Portsmouth New Hampshire.  This line will fluctuate along elevations and will shift as the system moves east.

The low over the Rockies begins to eject out into the Plains over Colorado and the snow will shift east with it over Wyoming and portions of Colorado. Rain will fall down elevation on the Plains from Wyoming through South Dakota and Nebraska.

Current Severe Weather Outlook

Critical Fire Weather Update

Fire Weather

Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
Critical 94,520 5,231,602 Phoenix, AZ…Albuquerque, NM…Mesa, AZ…Glendale, AZ…Chandler, AZ…

A strong mid-level disturbance will amplify over the Intermountain West today, and is forecast to spread strong mid-level flow into the Four Corners region. The Dryline will mark the dividing line between warm and windy conditions and the moistening air to the East.

Surface winds will strengthen area wide beginning late this morning with gusts as high as 60 MPH expected. 2 Critical areas have been delineated on the map in this outlook.  These are the regions that high winds will combine with the lowest Relative Humidity values under 15% over dry fuel beds.

Today’s Severe Weather Outlook

Severe Outlook

Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 29,335 13,108,281 Chicago, IL…Milwaukee, WI…Madison, WI…Aurora, IL…Rockford, IL…
MARGINAL 123,442 12,941,350 Detroit, MI…Grand Rapids, MI…Warren, MI…Sterling Heights, MI…Topeka, KS…

Severe Weather Analysis

SUMMARY

A few strong to severe storms are expected from a portion of the Upper Midwest into the Great Lakes area with a threat for large hail and damaging winds this afternoon and evening. Other strong storms are expected across a portion of the Central High Plains this evening and Northeastern Kansas tonight

 

Analysis

A weakening shortwave trough currently over the Central and Northern Plains is forecast to shift into the Great Lakes. A stalled cold front will extend from Wisconsin southward to Kansas and will impact the warm sector where daytime heating will warm the boundary layer this afternoon.  Storms are expected to redevelop this afternoon from Southern Wisconsin to Northern Illinois.  Wind shear will be sufficient for a few supercells with large hail and damaging winds as the primary threats before activity weakens after sunset.

West of there, as the warm front develops along with the low that is moving out of the Rockies, moist flow will return to the Central Plains. This moisture will allow a few storms to initiate in the upslope flow along the Rockies.  High based supercells capable of downburst winds and large hail are likely across Western Nebraska continuing into the night.  Eastern portions on Nebraska and Kansas will be impacted by the same set up and high based thunderstorms with hail are possible.

Looking forward to Tuesday, as predicted here, a moderate risk for severe weather has been added. Significant severe weather is expected over the Plains.  Any and all preparations you need to make should be completed by tonight.

Tuesday Severe Weather Outlook

day 2 severe

Day 2 Prob. Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SIG SEVERE 175,496 17,072,997 San Antonio, TX…Dallas, TX…Austin, TX…Fort Worth, TX…Oklahoma City, OK…
MODERATE 55,875 3,058,241 Oklahoma City, OK…Wichita, KS…Norman, OK…Edmond, OK…Midwest City, OK…
ENHANCED 79,794 9,650,655 Dallas, TX…Fort Worth, TX…Tulsa, OK…Arlington, TX…Plano, TX…
SLIGHT 136,890 11,357,501 San Antonio, TX…Austin, TX…Kansas City, MO…Omaha, NE…Overland Park, KS…
MARGINAL 211,757 32,736,160 Philadelphia, PA…Baltimore, MD…Washington, DC…Cincinnati, OH…Lexington-Fayette, KY…
Significant Severe Thunderstorms are forecast across parts of the Southern and Central Plains Tuesday afternoon into Tuesday night. Strong, long lived Tornadoes are possible in addition to very large, and potentially giant, hail and strong damaging straight line winds.

This Week’s Flood Risk

Flood Risk

Yesterday’s Storm Reports

storm reports 2

Robert Millette

Staff Meteorologist

Firsthand Weather