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

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