Forecast and Severe Outlook: Wednesday April 27th

Severe Thunderstorm Watches from last night are now ending as thunderstorms have left damage from hail and wind in their wakes.  A few tornadoes spawned across the area from Texas up through Indiana but conditions were not a bad as they could have been with the severity of those storms.  Now for a look at today’s forecast.

The current Surface Analysis

Surface map us

Today’s National Forecast

Weather Forecast map

A strong storm over the Central Plains will move eastward to the Eastern Ohio Valley by Thursday evening. The system will produce showers and thunderstorms along and ahead of the associated boundary from parts of the Central and Southern Plains and the Middle and Lower Mississippi Valley that will move eastward to the Mid-Atlantic and Eastern Ohio Valley to the Southeast and parts of the Central Gulf Coast by Thursday.  Rain will also develop over parts of the Northern and Central Plains and the Northern High Plains through Thursday afternoon.  Rain will move into parts of the Upper Mississippi Valley into parts of the Upper Great Lakes overnight Wednesday and move into parts of the Great Lakes and Western Ohio Valley by Thursday evening.  Similarly, highest elevation snow and lower elevation rain will develop over parts of the Northern High Plains and Central Rockies through Thursday morning.

A second storm will move onshore over the West Coast and move southeastward to the Southern Rockies by Thursday evening. Rain will develop over the Pacific Northwest and Northern California Coast on Wednesday morning that will expand inland to parts of the Northern and Central Rockies by Wednesday evening with snow at some of the highest elevations.  The rain will settle over parts of Southern California and the Great Basin and the Central Rockies and Southwest by Thursday morning.  By Thursday evening rain will expand into parts of the Northern Intermountain Region to parts of the Northern High Plains and into parts of Southern California as well as parts of the Southern Rockies and Southern High Plains.  The rain and highest elevation snow will continue over the Great Basin and Southwest to the Central and Northern Rockies through  Thursday evening, too.

Current Model Analysis

6 hour model

On early Wednesday, a strengthening low pressure over the Central Plains will continue to bring heavy rains and severe weather to the region. Rain should be falling from South Central Texas straight up to North Dakota with snow falling in the mountains from Colorado to Montana as two weak low pressure systems help create additional instability over the Rockies.

In the Pacific Northwest, rain should be falling just off the coastline and showers should be expected to move on shore from time to time. This area of rain won’t hold together well and should mostly dissipate during the day.

In the eastern half of the US, rain is forecast to fall from St. Louis east along a frontal boundary straight to the coast of the DelMarVa. Showers and thunderstorms should be expected in Florida during the day and the snow that fell in Northern portions of New England should have moved well into Canada with only a few snow showers remaining in Northern Maine.

18 hour model

Wednesday afternoon, the cold front will move quickly east and shift the axis of severe weather away from the Southern Plains and into the Ohio and Mississippi River Valleys. Heavy rains should be expected in South Dakota and Northern Nebraska.

Snow and shower activity will be more focused over the Pacific Northwest and the Rockies but will diminish in overall coverage.

In the east, the heavier rains in the morning will begin to let up along the DelMarVa but will still continue out in Southern Illiniois and Western Kentucky.

36 hour model

By early Thursday, the next low pressure system should be making its way out of the Rockies by bringing heavy snow into Wyoming and Utah with rain on the Plains from Wyoming east into South Dakota and Nebraska.

For the Northeast and Great Lakes, the system that brought Severe Weather to the Plains on Tuesday will bring rain and snow. Many of the same areas that received snow on Tuesday will see it again on Thursday while areas that received rain will receive another good soaking rain.

 

Current Severe Weather Outlook

Fire Weather Update

Fire Weather

No Critical Fire Weather areas are forecast

Severe Weather Analysis

Summary

 

Strong to Severe Thunderstorms are forecast for the Middle and Lower Mississippi Valley, Western Tennessee Valley and Southeast Texas.

Severe Outlook

Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 279,117 24,136,894 Houston, TX…Memphis, TN…St. Louis, MO…Baton Rouge, LA…Shreveport, LA…
MARGINAL 278,557 35,670,593 Indianapolis, IN…Nashville, TN…Kansas City, MO…New Orleans, LA…Virginia Beach, VA…

Analysis

An upper level low is drifting slowly eastward across the Central Plains. An elongated Mesoscale Convective System, spanning from the Kansas Missouri Border to the Edwards Plateau in Texas, is moving southeastward ahead of this system.  This MCS will slowly die out and the remnants will be over the Louisiana and Texas coastline by lunch time Wednesday.  Locally strong winds and hail are the primary threats with the MCS.

In the wake of this MCS, daytime heating will contribute to upward development and intensification over the Lower Mississippi Valley near the boundary layer. These storms should move Northeast and large scale forcing over the Mid-Mississippi Valley will help them grow.  As the warm front lifts north into Illinois, the earlier activity associated with Tuesday’s severe weather will help to keep the instability low.  While some hail and strong winds are possible, this severe risk remains low.

 

This Week’s Flood Risk

Flood Risk

Yesterday’s Storm Reports

storm reports 2

Robert Millette

Staff Meteorologist

Firsthand Weather