Tag Archives: Thunderstorms

Significant Flooding Expected in San Antonio

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Thunderstorms producing tropical rains with extremely heavy a rates will cause flooding across San Antonio this morning. Se me locations have already recorded 5 inches of rain. That kind of rain will cause significant flooding in trouble spots.

…A FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 415 AM CDT FOR
CENTRAL BEXAR COUNTY…

AT 155 AM CDT…NWS METEOROLOGISTS CONTINUED TO DETECT A CLUSTER OF
THUNDERSTORMS PRODUCING VERY HEAVY RAIN OVER THE SAN ANTONIO AREA
AND VICINITY. RAINFALL RATES CONTINUE ELEVATED WITH UP TO 5 INCHES
PER HOUR. FLASH FLOOD IS LIKELY WITH THESE VERY HEAVY RAIN.

LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
WINDCREST…UNIVERSAL CITY…SHAVANO PARK…LIVE OAK…HOLLYWOOD
PARK AND HELOTES.

PRECAUTIONARY/PREPAREDNESS ACTIONS…

EXCESSIVE RUNOFF FROM HEAVY RAINFALL WILL CAUSE FLOODING OF SMALL
CREEKS AND STREAMS…HIGHWAYS AND UNDERPASSES. ADDITIONALLY…COUNTRY
ROADS AND FARMLANDS ALONG THE BANKS OF CREEKS…STREAMS AND OTHER LOW
LYING AREAS ARE SUBJECT TO FLOODING.

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF FLASH FLOODING IS OBSERVED ACT QUICKLY. MOVE
UP TO HIGHER GROUND TO ESCAPE FLOOD WATERS. DO NOT STAY IN AREAS
SUBJECT TO FLOODING WHEN WATER BEGINS RISING.

MOST FLOOD DEATHS OCCUR IN AUTOMOBILES. NEVER DRIVE YOUR VEHICLE INTO
AREAS WHERE THE WATER COVERS THE ROADWAY. FLOOD WATERS ARE USUALLY
DEEPER THAN THEY APPEAR. JUST ONE FOOT OF FLOWING WATER IS POWERFUL
ENOUGH TO SWEEP VEHICLES OFF THE ROAD. WHEN ENCOUNTERING FLOODED
ROADS MAKE THE SMART CHOICE…TURN AROUND…DONT DROWN.

12:40pm Severe Weather Update for this Afternoon

The latest thinking from the National Weather Service folks has not changed much since this morning.  A dryline is expected to push towards the I-35 corridor by early this afternoon eventually bisecting the DFW Metroplex and stretching south/southwest along I-35 to just west of Waco, Temple and Killeen.   Thunderstorms are expected to fire up this afternoon around 4pm-ish along and east of the dryline.  Below are a few high resolution forecast model graphics which show storms initiating pretty much right on top of Dallas county at around 4pm…with additional storms firing up across Collin, Fannin and Hunt counties.  Keep in mind, this is just what a computer thinks, so reality could be slightly different.  But it will give you a good idea as to the favorable locations for storm development this afternoon.  The main threats with any storms that develop will be large hail, dangerous lightning and winds gusting to 50mph or more. Local street flooding could also be an issue under some of the stronger cells.   These storms will also be moving quite fast, so you’ll need to pay special attention to the weather this afternoon and be prepared to seek shelter immediately if a Warning is issued for your location.

4pm HRRR

6pm HRRR

8pm HRRR

Rain & Storms Return to the Forecast

We’re in for a pretty active week with several low pressure disturbances swinging through the state.  The first disturbance will arrive on Monday bringing a cold front and chances of rain mainly for eastern portions of the state.  Spotty areas of showers should begin to develop in central Texas mainly east of the I-35 corridor by early Monday afternoon and spread northeast across south central Texas and up into the DFW metro area and eastward.  A squall line of storms is expected to develop ahead of the approaching cold front southeast of the DFW area towards sunset, then move south southeast towards Houston late tomorrow evening and overnight.   A few of the storms could be strong and contain hail and damaging winds of 60mph.  Below is a look at the position of the trough around noon on Monday with its upper level winds in the range of 50 – 70knots.  Below that is a simulated radar grab of potential squall line position as of 8pm Monday evening.

GFS Jetstream Monday Noon

Nam 8pm Monday storms

Wednesday, a stronger system approaches the state bringing a Pacific cold front with it and better chances for more widespread rain coverage for central to northern parts of the state.  Showers and storms will begin to move up from south central Texas during the day Wednesday overspreading much of the area.  The eastern panhandle and northwest Texas will be under the gun Wednesday evening and overnight into Thursday for the development of severe storms.  Once again, high winds and damaging hail will be the primary threats with this system.  Below is a look of the position of the low at about Midnight going into Thursday with its upper level winds in excess of 55kts driving through the panhandle and northwest Texas.  The simulated radar grab below is from the same time period and shows a line of strong storms to develop over the eastern panhandle and into northwest Texas.  This line will continue to build and travel east across north Texas during the wee morning hours on Thursday, so have your Weather Radios on and be prepared to be awakened by a few thunderboomers! We’ll continue to keep you updated during the week, plus another chance of rain returning next Sunday!

GFS Jetstream Midnight Wed

Nam Midnight Wed

 

Latest Severe Weather Outlook for Tuesday

The Storm Prediction Center just issued their new severe weather forecast for Tuesday. Compared to yesterday’s forecast, the southwestern edge of the severe weather risk has been removed. That is about the only noteworthy change made with this forecast. Much of North and East Texas are still under the gun on Tuesday as a fast-moving line of thunderstorms races through. The severe weather risk zone includes areas along and east from Henrietta, Graham, Eastland, Brownwood, San Saba, Marble Falls, to San Marcos line. The risk looks to stay north of Interstate 10. Inside the severe weather risk is an area where we have more concern. That area, shown in red, extends from just east of the D/FW Metroplex and includes all Northeast and the northern half of East Texas. By the time the squall line reaches the red-shaded area, we expect it to already be mature and producing damaging winds in some areas.

The main concern with this severe weather event will be damaging straight-line winds with a fast-moving squall line. With very strong winds aloft, we cannot rule out a few brief tornadoes. Should any thunderstorms develop ahead of the line or by themselves, they would pose a higher tornado risk. I’ll post a more detailed severe weather discussion later this morning.

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Expanded Severe Weather Risk on Tuesday; Concern Increasing

After analyzing weather model data this morning it is still looking like we’ll end up being busy on Tuesday. As you can already tell by stepping outside, rich moisture has already pushed into the state from the Gulf of Mexico. With our next storm system not due until Tuesday the atmosphere will have plenty of time to moisten up. Not only will the moisture be in place to support thunderstorms, the storm system arriving on Tuesday looks to be supportive of organized thunderstorms. Combine the moist, unstable atmosphere with a strong storm system and you have a recipe for severe thunderstorms. A line of thunderstorms will form during the late-morning hours on Tuesday and gain strength as it pushes eastward during the afternoon hours. With the convective mode expected to be linear, or a line of thunderstorms, the threat for tornadoes will be reduced. If we had discrete thunderstorms then the risk for tornadoes would increase. Data continues to support a fast-moving squall line along a cold front. The main concern with a squall line is straight-line winds, but brief tornadoes are certainly possible as well.

The main uncertainty is how far west will this line of storms develop in Texas and how long will it take for them to organize into something of concern. Compared to yesterday, this zone of concern has been extended further south and west to include more of the state. The orange zone is where we believe severe thunderstorms are possible. Parts of North and Northeast Texas are included in an elevated risk of severe storms. Within this area, we have confidence that severe thunderstorms are more likely with a fast-moving squall line. Don’t pay too much attention to the differences in colors right now. If you’re in or close to the severe risk area, plan on having a way to receive weather information on Tuesday and be sure to check back on Monday for the latest forecast!

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In case you were wondering, Texas is only part of a larger severe weather event on Tuesday with a severe weather outbreak becoming more probable across the Mid-South and even closer to the Great Lakes. This definitely could be the first major severe weather outbreak to strike in 2013. Texas is on the southern edge of this threat. Here is the severe weather outlook for the affected areas for Tuesday.

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