Texas Severe Weather Potential for 4/28 and 4/29

[Johnny]

How about another thread on the possibilities of severe weather for Texas this weekend (Friday night into Saturday). It looks like this one might be a bit more potent than last night.

[Extremeweatherguy]

Here is my post from the other thread:

Here is part of the Afternoon discussion from the NWS concerning the event on Fri/Sat:

THE MODELS ARGUE FOR A GOOD POTENTIAL FOR SEVERE WEATHER
WITH THIS SYSTEM WITH SIGNIFICANT MID LEVEL COOLING TO HELP WEAKEN
THE CAP AND STRONG SPEED AND DIRECTIONAL SHEAR IN PLACE. THE ONLY
POTENTIAL NEGATIVE FACTOR TOWARD SEVERE WEATHER WILL BE THE AMOUNT
OF INSTABILITY PRESENT.

9pm Update:

Here is a look at the 18Z GFS for 66 hrs. out (which turns out to be around daybreak Saturday):

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _066.shtml

and here is the 18Z NAM for the same time period:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _066.shtml
^^Is a few hours slower than the GFS^^

[Extremeweatherguy]

Also..the 0Z GFS for hr. 60 looks even more intense. We could be talking a large scale event here:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _060.shtml

[CrazyC83]

Could April 28-30 be an outbreak to remember?

[jkt21787]

This, like most dynamic systems, is going to largely overhyped. Widespread clouds and rain will limit instability, strong wind fields compensate, only enough to produce a forced low topped squall line with damaging winds, maybe a tornado or two in embedded supercells or LEWPs. This won't be much of anything as it looks now, except for the potential for excessive rainfall and flooding, which will be the major concern with this system, again as it looks now.

It will be something to watch over the next few days in case the situation changes, but right now I see only a slight risk event mainly concentrated towards gulf coastal areas and with damaging winds and heavy rainfall.

[CrazyC83]

I'm in some agreement right now - it seems to be too far south (less influence of the cooler air) and the air mass is not expected to be in good shape. The SPC is really downplaying it right now.

I think the Midwest and Mid-South will continue to get the big outbreaks, with some perhaps going northward into and beyond the Great Lakes and eastward into the Mid-Atlantic.

I feel the worst outbreak of the spring is still to come; I think it will be somewhere around June 2-3.

[wxmann_91]

I feel the worst outbreak of the spring is still to come; I think it will be somewhere around June 2-3.

IMO the pattern will get very condusive for a "Seven Days in May" type setup during the middle part of May. A large western ridge/eastern trough is expected to kill the svr chances for most parts of the U.S. with the exception of the Gulf Coast until early May. Then I think the pattern will reverse, as it many times does, leading to several days (a week probably) of SW flow, like what happened during the Mays of 1977, 2003, and 2004, and the Junes of 1995 and 2005.

[CrazyC83]

I do agree that the pattern is setting up for a monster outbreak after this break ends...look at the second half of March and what followed that. Here is the setup I see:

Last week of May around Memorial Day: Hot, humid weather across much of the eastern US, with a stable southwest flow from the Gulf and all the cold air blocked to the far north of Canada.

June 1: Powerful low forms over the northwestern Plains and a cold front comes down from it. The jet stream separates air in the 60s and low 70s with dewpoints in the 30s in the High Plains the next day from the humid 90s and dewpoints in the 70s to the east.

June 2: Low moves northward over Lake Superior along the jetstream. Cold front triggers an endless swarm of tornadoes in the afternoon and evening across the Plains and Midwest from Minnesota to Oklahoma and east to the Mississippi Valley and across it in the overnight hours. Supercells keep firing up in the air mass.

June 3: The swarm continues as the low moves northeast into far northern Ontario. The Ohio Valley and Great Lakes regions get hammered with endless tornadoes and severe weather that day.

June 4: Even more severe weather and tornadoes in the Mid-Atlantic and Northeast. The setup finally falls apart as the system crosses into the Atlantic and the low itself crosses extreme northern Quebec.

[Extremeweatherguy]

Latest Developments:

SPC - Now has SE Texas in a "Slight Risk" zone for Saturday, but they are still having an issue with the exact timing and the exact scenario that will unfold.

GFS - 6Z run is still as promising as ever. Here is a look at hour 54:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _054.shtml

NAM - The 6Z run is also promising...here it is for hour 54:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _054.shtml

NWS - The NWS in Houston has raised rain chances to 70% with this event. At this time, they are expecting the severe weather (or the bulk of it at least) to come in the form of a strong squall line.

[Johnny]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
750 AM CDT THU APR 27 2006

.DISCUSSION...
ANOTHER BIG EVENT COMING UP FRIDAY EVENING INTO SATURDAY MORNING.
THE 500 MB LOW CURRENTLY NEAR THE BAJA IS FORECAST TO MOVE INTO
SOUTHERN NM BY FRIDAY. THE GFS ENSEMBLE INDICATES BETTER MODEL
CONFIDENCE WITH THE TIMING OF THE SYSTEM OVER SE TX AS DOES A
COMPARISON OF THE GFS AND ECMWF.

TODAY INTO EARLY FRIDAY THE DOWNSTREAM 500 MB RIDGE (FROM THE
LOW) WILL KEEP A MOSTLY DRY WEATHER PATTERN OVERHEAD SE TX. THE
ONSHORE WINDS WILL BRING GULF MOISTURE IN AND WITH A CAP
DEVELOPING ALOFT AM EXPECTING LOW CLOUDS TO FORM TONIGHT AND
EARLY FRIDAY. ON FRIDAY A SHORTWAVE TROUGH WILL HELP DEVELOP AT
LEAST ISOLATED SHOWERS OR THUNDERSTORMS. THE MAIN ACTION BEGINS
FRIDAY EVENING AND AM EXPECTING A SQUALL LINE TO PUSH THROUGH SE
TX. SEVERE WEATHER IS POSSIBLE AND WILL ADDRESS THAT CONCERN IN
THE HAZARDOUS WEATHER OUTLOOK.

AFTER THE FRONT MOVES THROUGH SATURDAY MORNING THERE WILL BE A
DRASTIC REDUCTION IN RAIN CHANCES SATURDAY AFTERNOON. THE 500 MB
LOW SHEARS OUT OVER THE OHIO VALLEY EARLY NEXT WEEK WHILE A ZONAL
FLOW DEVELOPS OVER TX. BY THE MIDDLE OF NEXT WEEK HIGH PRESSURE AT
500 MB IS DEVELOPED BY THE GFS. WITH ONSHORE WINDS...A WARM
PATTERN LOOKS TO RETURN.

[jasons2k]

Looks like once again the timing for us won't be optimal, and I'm concerned that ongoing showers will further limit instability for the main event. We'll probably get a decent squall line or MCS move through with a widespread 1"+ of rain, but it doesn't look like an outbreak for the ages or anything like that to me.

[CajunMama]

I do hope this pans out for y'all. I know you need the rain.

[CrazyC83]

Right now I am thinking rain more than anything...

[Huckster]

Seems like we don't ever get real severe outbreaks here, not any more anyway. It's ALWAYS something...either the instability is lacking, or it's capped, or the energy is too far north, or too far west, or there's no focusing mechanism, or there's not enough moisture, or there's not enough of a cap and storms form too quickly, or there's not enough shear, or the storms go linear (in which case you can BET that Baton Rouge will get nothing), or the time of day is off. It's always something, ALWAYS. What seems incredible to me is that with this current event seems to have so much potential, and yet, at the END OF APRIL, instability and moisture are going to be lacking...on the Gulf Coast! I sure do remember a lot more severe weather when I was younger. Is now how things are supposed to be or are we just in a messed up pattern? I'm thinking the latter. The first hailstorm I remember here was in 1988. I saw hail in 1988, 1989, 1991, 1992 (twice), 1993, 1995, 1996, then in 2003. That's not exactly a scientific analysis, but it seems that severe storms in this area are definitely down. Fortunately, the Gulf South has not shared in the horrible tornado outbreaks farther north, but a little bad weather here would be nice, and definitely some rain, as this drought is getting ridiculous.

[jasons2k]

Hey Huckster,

I know exactly what you mean. It seems to always be something the last few years (here and when I still lived in DFW) and it's harder than pulling teeth to get a decent setup....which once upon a time seemed commonplace. I'm wondering the same myself - what gives and when will things go back to normal...or is this a more permanent shift? Frustrating.

[wxman22]

Here's the latest outlook and discussion:







DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1235 PM CDT THU APR 27 2006

VALID 281200Z - 291200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SRN PLAINS...

...SYNOPSIS...
LARGE WRN U.S. UPPER LOW/TROUGH -- WHICH WILL BE ASSOCIATED WITH THE
PRIMARY SEVERE CONVECTIVE THREAT THIS PERIOD -- IS FORECAST TO
CONTINUE PROGRESSING EWD ACROSS THE ROCKIES AND INTO THE CENTRAL
CONUS THROUGH THE PERIOD.

DIFFERENCES REMAIN WITHIN THE VARIOUS MODEL SOLUTIONS WITH REGARD TO
THE DETAILS OF THE UPPER TROUGH AND ASSOCIATED SURFACE PATTERN...BUT
IN GENERAL EXPECT LOW PRESSURE IN LEE OF THE ROCKIES OVER THE
CENTRAL/SRN PLAINS REGION DURING THE PERIOD. BY LATE IN THE
PERIOD...SURFACE PATTERN SHOULD BECOME MORE WELL DEFINED...WITH A
DEEPENING SURFACE LOW IN THE KS/OK AREA AND A COLD FRONT MOVING EWD
ACROSS TX THROUGH THE END OF THE PERIOD.

...MUCH OF TX AND PARTS OF OK...
EXTENSIVE/WIDESPREAD CONVECTION SHOULD BE ONGOING AT THE START OF
THE PERIOD ACROSS PARTS OF THE CENTRAL AND SRN PLAINS...IN AREA OF
BROAD WARM ADVECTION AHEAD OF MAIN UPPER SYSTEM. THIS COMPLICATES
THE DAY 2 SEVERE FORECAST...IN TERMS OF DELINEATING AREAS WHERE
GREATER DESTABILIZATION -- AND THUS SEVERE POTENTIAL -- WILL EXIST.

ATTM...IT APPEARS THAT A DRYLINE WILL SHIFT EWD ACROSS WRN TOWARD
CENTRAL TX DURING THE AFTERNOON...INTO AN AREA WHERE LESS CONVECTION
MAY BE UNDERWAY. PRESUMING THIS TO BE THE CASE...SEASONABLY-MOIST
BOUNDARY LAYER COMBINED WITH DAYTIME HEATING SHOULD LOCALLY BOOST
MIXED-LAYER INSTABILITY INTO THE 1000 TO 1500 J/KG RANGE.



WITH FAIRLY STRONG LOW-LEVEL WIND FIELD FORECAST BENEATH 70 TO 8O KT
SWLY MID-LEVEL FLOW...DEEP-LAYER SHEAR WILL BE FAVORABLE FOR
SUPERCELL STORMS. THEREFORE...ANTICIPATE THAT AN AREA OF ENHANCED
SEVERE THREAT -- INCLUDING LARGE HAIL AND LOCALLY DAMAGING WINDS
ALONG WITH THE POSSIBILITY OF A FEW TORNADOES

WILL DEVELOP ACROSS
PARTS OF WRN AND CENTRAL TX AND PERHAPS INTO SWRN OK. AS SURFACE
PATTERN BECOMES BETTER DEFINED OVERNIGHT AND COLD FRONT
STRENGTHENS/MOVES SEWD ACROSS THE SRN PLAINS...STORMS COULD EVOLVE
INTO A SQUALL LINE...ALONG WITH A CONTINUED THREAT FOR HAIL/DAMAGING
WINDS. THREAT SHOULD DIMINISH ACROSS MOST AREAS LATE IN THE
PERIOD...AS AVAILABLE INSTABILITY REACHES A DIURNAL MINIMUM.

..GOSS.. 04/27/2006

Looks like they may be hinting at an area being put in a moderate risk...

[PTrackerLA]

At this point I don't really care about severe weather, we're still in a drought and all I want to see is widespread heavy rain because all of next week looks dry.

[wxman22]

Wow look at the HPC rain amounts:

[Extremeweatherguy]

Another thing to think about is that we will likely not see too much rain before the main event...only 20/30% pops for tonight through most of tomorrow. Also, even if this event happens at night...that does not mean it will not be severe. For instance, the storms last Friday occured early in the morning but yet they still produced an F1 tornado and wind gusts up to 66mph in a few places...and the storms early tuesday morning produced hail up to 2" in diameter in College station and Huntsville and hail even covered the ground at Texas A&M...so just because it is dark..that does not mean nothing will happen. BTW: this may not even happen at night. Looking at the models...there is a chance this "main" event will hold off until after sunrise on Saturday.

[Extremeweatherguy]

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _054.shtml
^^12Z GFS run shows the timing of the squall line to be somewhat slower than earlier thought. If we are lucky, this thing could hold off until noon, and may be with a little heating the severe threat will increase.^^