SE TX/SW LA Discussion Thread - Heavy Rainfall Threat

[JenBayles]

I've been wondering the same thing Yankee. The lasted HGX discussion thinking is that these storms will crap out with sunset, but might squeak by College Station before it's all over. Ho hum.... the Dome holds!

[Ptarmigan]

I think those storms will be over us.

[Yankeegirl]

These storms dont look like they are dying down too much... wonder if they will make it all the way here??

[Johnny]

This is from Jeff.


Flash Flood Event for central TX this weekend



Threat for heavy rains for SE TX early next week.



Yet another flash flooding episode this year for central TX with widespread 3-6 inches of rain falling overnight along and W of I-35. An additional 5-15 inches of rainfall is possible over central TX through the next 4 days with the result being significant river flooding over the holiday weekend. Currently the Pedernales River , San Gabriel River , and Guadalupe River are at or above flood stage. Large amounts of inflow from the Llano and Pedernales Rivers will result in substantial rises on the middle Colorado River and the Highland Lakes flood control system. Expected continued excessive rainfall will only worsen ongoing flooding and increase dam releases through the Highland Lakes system.



Locally:



Air mass is once again moist and unstable this morning with radar already showing a few showers moving inland from the Gulf. Rain chances should be around 50% today as daytime heating combined with a moist and unstable air mass will get things going. Main trough axis will remain stalled over C TX through the weekend with drier air entering SE TX from the E later today. This should reduce rain chances Saturday and Sunday while C TX is inundated. Trough axis begins to push eastward Monday with the potential for closed upper to mid level low develop over C TX . Air mass greatly moistens with PWS climbing over 1.75 inches and up to 2.0 inches. With deep tropical moisture in place and a direct flow into TX from the Caribbean excessive rainfall threat will be high. Will likely be addressing a flash flood situation come Monday into Tuesday as slow moving low approaches the area. Given tropical nature of the air mass the “infamous” nocturnal core rains seen with dying tropical systems could show themselves near the center of the low both Monday and Tuesday nights. Rainfall with such events can be on the order of 5-10 inches in 6 hours or less.



The severe threat is generally low through the period although tropical funnels will be possible along the coast for the next several mornings. Main threat will be flash flooding from excessive rainfall rates and eventual river flood problems.

[jasons2k]

This is the latest from Jeff:

***Potential for excessive rainfall and flooding***

Discussion:

Mid level impulse over Kimble County, TX appears to have become warm core this morning and is showing up very nicely on radar sweeps out of Del Rio and KSAT. Core rain event ongoing over the Hill County with 2.0+ per hour rates over the NW side of the closed low while impressive bow moves through the coastal bend with rates of 3.5-4.5 inches per 1-2 hours. Radar over SE TX is quickly filling with unstable air mass and trigger temps. being exceeded. Will need to raise chances over the Matagorda Bay area greatly this afternoon where slow moving excessive rainfall is becoming likely. Totals up to 3-6 inches will be possible. Rest of the area should see just scattered activity.

Next impulse seen over N Mexico is already firing off storms NW of Del Rio and this will move eastward overnight into Saturday. Plume of deep tropical moisture remains along and W of I-45 with PWS at or above 1.8 inches. Tropical air mass is resulting in very high hourly rainfall rates (1.5-3.0 inches). Stalled trough axis with numerous impulse will result in several rounds of thunderstorms through the next 5 days with storms getting closer to Houston each day.

Flash Flood threat will be very high through the weekend over central TX and then into SE TX early next week. Currently LCRA is not operating any flood gate measures on the middle Colorado basin lakes chain however overnight rains in the Llano and Pedernales basins are forecast to result in Lake Travis going to 681 feet Saturday or 4 feet below the conservation pool. An additional 4-10 inches widespread with isolated amounts approaching 20 inches are possible along I-35 through Tuesday. Rainfall of this magnitude will cause major problems.

Flash Flood Watches will be issued this afternoon for C and SC TX into the coastal bend and into N TX/.

Jeff Lindner

[jasons2k]

[jasons2k]

[vbhoutex]

Right now it looks like this mess will do exactly as Jeff has said, which is good for us and not good for our neighbors in C TX. Of course, it has to move sometime and if Jeff is right(he usually is)our Monday and/or Tuesday aren't going to be very nice.

[cctxhurricanewatcher]

Very nice rains here in the Corpus area this AM. I'm guessing anywhere from 2-4 inches. The Farmers and Ranchers are probably grinnning big at the coops this afternoon.

[Extremeweatherguy]

[web]http://www.weatherunderground.com/radar/radblast.asp?zoommode=zoom&num=6&delay=15&rbscale=0.32458695652173913&scale=0.711&noclutter=0&ID=HGX&type=N0R&lat=0&lon=0&label=you&showstorms=31&map.x=409&map.y=186&centerx=484&centery=266&lightning=0&showlabels=1&rainsnow=0[/web]

[Ptarmigan]

This is from Jeff.


Flash Flood Event for central TX this weekend



Threat for heavy rains for SE TX early next week.



Yet another flash flooding episode this year for central TX with widespread 3-6 inches of rain falling overnight along and W of I-35. An additional 5-15 inches of rainfall is possible over central TX through the next 4 days with the result being significant river flooding over the holiday weekend. Currently the Pedernales River , San Gabriel River , and Guadalupe River are at or above flood stage. Large amounts of inflow from the Llano and Pedernales Rivers will result in substantial rises on the middle Colorado River and the Highland Lakes flood control system. Expected continued excessive rainfall will only worsen ongoing flooding and increase dam releases through the Highland Lakes system.



Locally:



Air mass is once again moist and unstable this morning with radar already showing a few showers moving inland from the Gulf. Rain chances should be around 50% today as daytime heating combined with a moist and unstable air mass will get things going. Main trough axis will remain stalled over C TX through the weekend with drier air entering SE TX from the E later today. This should reduce rain chances Saturday and Sunday while C TX is inundated. Trough axis begins to push eastward Monday with the potential for closed upper to mid level low develop over C TX . Air mass greatly moistens with PWS climbing over 1.75 inches and up to 2.0 inches. With deep tropical moisture in place and a direct flow into TX from the Caribbean excessive rainfall threat will be high. Will likely be addressing a flash flood situation come Monday into Tuesday as slow moving low approaches the area. Given tropical nature of the air mass the “infamous” nocturnal core rains seen with dying tropical systems could show themselves near the center of the low both Monday and Tuesday nights. Rainfall with such events can be on the order of 5-10 inches in 6 hours or less.



The severe threat is generally low through the period although tropical funnels will be possible along the coast for the next several mornings. Main threat will be flash flooding from excessive rainfall rates and eventual river flood problems.

Is there a link for Jeff's forecast? Looks like we could a flooding event by Memorial Day. Looks like another core rain event, like Allison, Claudette, and Amelia. Something to keep an eye on. I expect Southeast Texas is in for it too.

[jasons2k]

No - besides, this is the only link you need

[Ptarmigan]

No - besides, this is the only link you need

You were the one making those forecasts I see?

[jasons2k]

It's not a link, it's an email...
-------------------
Anyway - my concern with the system is training. The position of the low will setup feeder bands moving off the GOM right over Houston.

[Ptarmigan]

It's not a link, it's an email...
-------------------
Anyway - my concern with the system is training. The position of the low will setup feeder bands moving off the GOM right over Houston.

Cool. I am afraid you are right that we could have feeder bands over us. I checked radar and there are some storms inching slowly towards us.

[Extremeweatherguy]

storm moving in from my south right now has a mesocyclone indicator on radar. I wonder if I will see any funnel clouds or strong, gusty winds as it moves through?

update: ended up weakening right before reaching me and was just a moderate rain shower.

[jasons2k]

The Fox 26 Hurricane Toolbox was previewed on the news earlier this week:

http://media.myfoxhouston.com/weather/htb/index.html

http://tropics.myfoxhouston.com/index.p ... oad=veIMap

[JenBayles]

Currently experiencing some tropical p*ssdowns under the Bear Creek Dome. Surprise! I'm so NOT happy to read Jeff's update with flooding being such a concern here, but we'll just have to see what happens.

[KatDaddy]

Another widespread Texas flood event over the next few days:

A very serious flood threat is forecasted across the Corpus Christi CWA. Here is an excerpt from this afternoons forecast discussion:

...BUT WE JUST CAN`T TELL WHEN THIS MAY HAPPEN MORE THAN 1
OR 2 DAYS OUT. WILL CONTINUE SPS STATEMENTS CALLING FOR WIDESPREAD 5
TO 10 INCH EVENT TOTALS THROUGH TUESDAY (WHICH INCLUDES TODAYS
TOTALS) W/ ISOLATED AMOUNTS AS HIGH AS 10-15 INCHES POSSIBLE (AND
WON`T BE SURPRISED IF THERE IS SOME VERY ISOLD 15 TO 20 INCH

[jeff]

Not sure when the time period for the main event over SE TX will be. Period from Mon-Wed looks very wet. Comparison event appearing as July 2002 floods in C TX with multiple rounds over several days creating river flooding.

Locally concern for high hourly rainfall rates which can quickly do us in over Harris County. Testament of potential over N Waller Co this afternoon where 4-6 inches fell in a few hours in a much drier air mass than we will face by Monday. Headwaters of Spring Creek will likely exceed banks late tonight with downstream rises at SH 249 and I-45 Saturday into Sunday. Luckily the headwaters are flashy and will go down quickly (likely) by early Saturday AM.