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

Today’s National Forecast

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

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.

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.

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

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.

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

Yesterday’s Storm Reports

Robert Millette

Staff Meteorologist

Firsthand Weather