April Weather Discussion.

[wxdata]

Update from San Antonio NWS:

"No development as of 12:30...with the surface trough starting to slow its eastward progress. Current position of the surface trough is from near Hondo...NE to Georgetown. 17Z LAPS analysis shows CAPE values of 2500-3500 J/Kg ahead of the surface trough with little to no CIN. Development is possible between 1-2PM along the I-35 corridor...

[Houstonkid]

NWS Hou dropped the severe wording from forecast for Houston metro and I assume areas south.

Also, what is all of this unexpected sun doing for the cap/instability? Is it even a factor in this situation?

Thanks in advance!

[wxdata]

KLIX mentions a special sounding (NOLA area). I'd assume 18Z, but I could be wrong. Nothing on SPC sounding page yet.

I'd hope LCH and CRP would also do one.

A little surprised that FTW didn't send up a special balloon today.

[wxdata]

18Z RUC analysis shows a somewhat pitiful dryline, with limited convergence and a sloppy dewpoint gradient. But the I-35 corrdior area is in excess of 2000 J/Kg MLCAPE, and MLCINH is below -25J/Kg. Low level helicity pretty tame, but ~50 knots 0-6 km shear, which would support supercells.

That from SPC Meso page. Or, in picture form that fits within this thread, the NIU RUC 1800 forecast/analyzed AUS sounding.

Weak dry line and strong cap continue to keep radar scoops blank in all except northeast Texas. There's a hint of back-building with a line of showers now approaching Tyler.

[wxdata]

From Shreveport NWS:

"The cap off our sounding at about 650-700 mb. Will need a trigger to get things going as we are sorta between shortwaves attm. Things are certainly destabilizing across E TX

[wxdata]

From Lake Charles:

"Full 18z sounding is now in. Indicates cap is gone."

Ruh ro!

[svrwx0503]

Like as been alluded to above, not much convergence being seen currently along the dry line/trough across central Texas with high res visible sat not showing a lot of towering cu either. With the sky becoming partly cloudy across the region and temps warming into the mid to even upper 80s, the latest mesoanalysis shows mixed layer CAPE values in the 1500-3000j/kg range ahead of the dry line and across southeast Texas with still some nice CIN in place across the region. As temps continue to warm and stronger jet energy starts to arrive out of northern Mexico later this evening, we will likely see storm initiate in central Texas and move northeast possibly giving our northwest counties some trouble later on this evening.

Looks like very large hail along with damaging winds will be the main threats with the storms as there is not much in the way of directional shear but there is some decent speed shear and as Ed mentioned enough 0-6 bulk shear to produce some supercells should the convection remain discrete. As the storms develop into a line later this evening the wind damage threat will likely increase with the potential for bowing segments due to the strong mid-upper level wind field. Looks like we will be on weather watch this evening.

[svrwx0503]

Update mesoanalysis from the RUC does show that moisture convergence is slowly increasing along the dryline/trough so I think we might see development start to occur as we get closer towards 4pm. Lots of instability out there for storms to tap into once they go up.

[wxdata]

Here's a nice shot of the dry line at 2:30pm with radar overlaid, stretching from well east of Dallas to just north of San Antonio..

[wxdata]

MESOSCALE DISCUSSION 0350
NWS STORM PREDICTION CENTER NORMAN OK
0250 PM CDT FRI APR 23 2010

AREAS AFFECTED...NERN/E-CNTRL TX...FAR SERN OK...SWRN AR...NWRN LA

CONCERNING...TORNADO WATCH 79...

VALID 231950Z - 232145Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 79 CONTINUES.

WITH AT LEAST ISOLATED TSTM DEVELOPMENT PROBABLE ALONG COLD FRONT
ACROSS NERN/E-CNTRL TX INTO FAR SERN OK...A REPLACEMENT WW MAY
BECOME NECESSARY PRIOR TO 22Z EXPIRATION OF WW 79.

19Z SUBJECTIVE SURFACE ANALYSIS PLACED A COLD FRONT FROM NEAR MLC TO
30 N TYR TO ADS. RECENT VISIBLE SATELLITE AND RADAR IMAGERY INDICATE
TCU/ISOLATED SHOWERS GRADUALLY INCREASING ALONG THIS BOUNDARY.
LARGE-SCALE FORCED ASCENT SHOULD REMAIN WEAK INTO EARLY EVENING...AS
THE REGION LIES WEST OF LOW-LEVEL WAA REGIME SHIFTING NEWD ACROSS
THE LOWER MS VALLEY AND WELL-REMOVED FROM UPSTREAM SHORT WAVE TROUGH
OVER NRN CHIHUAHUA. NEVERTHELESS...MODEST WARM NOSE AT 650 MB
/EVIDENT IN 18Z SHV AND LCH RAOBS/ SHOULD PROVE INSUFFICIENT TO CAP
MIXED-LAYER PARCELS AS SURFACE TEMPERATURES WARM AMIDST UPPER 60S TO
LOWER 70S DEW POINTS. GIVEN THE PRESENCE OF MODERATE INSTABILITY
WITH STRONG DEEP-LAYER SHEAR...SUPERCELL DEVELOPMENT WOULD BE LIKELY
WITH SEVERE HAIL AND LOCALLY DAMAGING WINDS AS THE PRIMARY THREATS.
DESPITE WEAKER LOW-LEVEL FLOW INVOF THE FRONT COMPARED TO AREAS
FARTHER EAST...THE RICHNESS OF BOUNDARY LAYER MOISTURE COULD SUPPORT
A TORNADO OR TWO.

[wxdata]

Noticed that even though the moderate risk is further south, all the storm chasers have moved further north into Kansas and Nebraska.

[wxdata]

3pm update from SPC

http://www.spc.noaa.gov/products/outloo ... _2000.html

"...EAST TX/SOUTHEAST OK TO ARKLATEX TONIGHT...
THE MAIN SOUTHERN STREAM SHORTWAVE TROUGH /WITH ATTENDANT 100+ KT
UPPER JET STREAK/ CURRENTLY OVER THE SOUTHERN ROCKIES/NORTHERN
MEXICO IS FORECAST TO BECOME MORE NEUTRAL TO NEGATIVELY TILTED AND
PIVOT INTO TX/OK LATE TONIGHT. THIS IS LIKELY TO RESULT IN THE RAPID
DEVELOPMENT OF INTENSE THUNDERSTORMS ALONG THE DRYLINE/OVERTAKING
COLD FRONT ACROSS EAST TX/SOUTHEAST OK TO THE ADJACENT ARKLATEX
TONIGHT...WITH STORMS RACING EASTWARD TOWARD THE LOWER MS VALLEY
EARLY SATURDAY MORNING. LARGE HAIL...DAMAGING WINDS...AND TORNADOES
WILL ALL BE POSSIBLE WITH THESE STORMS. THIS ACTIVITY WILL LIKELY BE
THE START OF ANOTHER VERY ACTIVE SEVERE WEATHER DAY ACROSS THE LOWER
MS RIVER VALLEY ON SATURDAY."

[wxdata]

3pm thoughts from Shreveport NWS-

"There will probably be some scattered showers and thunderstorms up until 6 am or so, and one or two may become severe. And then a large squall line will likely develop over east and northeast TX, and move rapidly east after 6 am Saturday morning, getting to Monroe after sunrise. That's pretty much the scenario we are expecting."

[srainhoutx]

HGX thoughts this afternoon...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
317 PM CDT FRI APR 23 2010

.DISCUSSION...
THE UPPER LOW CHURNING OVER EASTERN CO TO MOVE EAST TONIGHT...
DRAGGING A MAIN BOUNDARY (COOL FRONT) ACROSS CENTRAL AND EASTERN
TEXAS THROUGH TOMORROW MORNING. AHEAD OF THIS BOUNDARY...A DRY
LINE/PRE-FRONTAL TROF WILL MAKE IT EAST OF THE I-35 CORRIDOR BEFORE
THIS COOL FRONT CATCHES UP WITH IT DURING THE EARLY-MID EVENING
HOURS. CORE OF THE JET TO COME AROUND THE UPPER TROF AXIS BETWEEN
MIDNIGHT AND SUNRISE HOURS...WITH A NW GULF LL JET FORMING PARALLEL
TO THE COASTLINE. ENERGY ROUNDING THE BASE OF THE LOWER ROCKY MTN
TROF AXIS IS FORECAST TO TRAVEL NORTHEASTWARD OVER CENTRAL TEXAS
AND INTO THE EAST OK/NE TX/NOLA/SO AR REGION THROUGH THE NOCTURNAL
HOURS. AT THE SURFACE...A DENSE CU FIELD HAS FORMED WITHIN A VERY
MOIST ENVIRON (1.4 - 1.6" PWAT) AND A CURRENT ZONE OF CONVERGENCE
JUST TO THE NORTH OF THE CWA MAY BE ALL THAT IS NEEDED FOR LATE PM
LL FOCUS. SO...WITH ALL OF THESE ELEMENTS COMING INTO PHASE
THROUGH MIDNIGHT...THE STAGE IS SET FOR PERIODS OF NORTHERN AND
CENTRAL COUNTY RAIN...SCATTERED STORMS...WITH SOME OF THESE CELLS
(IN A POSSIBLE BROKEN LINE) REACHING SEVERE LIMITS DURING 24/06-12Z.
OF COURSE...THAT MID-LEVEL WARM NOSE WILL HAVE TO ERODE AND ALL
OF THE ABOVE WILL HAVE A HIGHER PROB OF ACTUALLY BEING REALIZED.
CONFIDENCE IS MODERATE...AT BEST...THAT THE CAP WILL BE OVERCOME SO
NOT TOTALLY BITING ON SEVERE AS OF YET.

CONFIDENCE IS HIGHER IN THE FACT THAT OUR FAR NORTHERN COUNTIES
WILL REMAIN UNDER THE GUN FROM A BROKEN QUASI-LINEAR LINE FORMING
JUST EAST OF THE HILL COUNTY...OR RIGHT AHEAD OF THE AFOREMENTIONED
S/W RACING UNDER TROF AXIS NEAR EL PASO. FEEL...IF THE CAP IS BROKEN...
THIS WOULD BE THE FEATURE TO DO IT. SLIGHT RISK FOR SEVERE IS STILL
THE MESSAGE FROM NORTH OF A BRENHAM TO CONROE TO LIVINGSTON LINE.
THE CAP REMAINS TOO STOUT SOUTH OF THIS LINE...SCT SHOWERS AND
ISOLATED (ELEVATED) THUNDER OVER THE SOUTHERN 1/3RD FA AND OVER
MARINE AREAS DURING THIS 06Z TO 12Z WINDOW OF OPPORTUNITY.

ONCE THIS BOUNDARY CLEARS THE COAST TOMORROW AFTERNOON...READY
YOURSELF FOR BEAUTIFUL WEATHER AS SKIES CLEAR OUT AND TEMPERATURES
REGULATE TO NEAR-CLIMO STANDARDS WITHIN A RELATIVELY DRIER AIR
MASS. THE EXTENDED REMAINS DRY...WITH INCREASING HUMIDITY AND
TEMPERATURES THROUGH THE END OF APRIL. IT WILL FEEL MUCH MORE
SUMMER-LIKE NEXT WEEK AS MID-UPPER WESTERLIES ALLOW DAILY TEMPS
TO PEAK OUT IN THE LOWER TO MIDDLE 80S...WHILE ONSHORE FLOW PUMPS
ONCE COMFORTABLE WEEKEND UPPER 40 DEW POINT AIR BACK UP INTO LATE
WEEK MID TO UPPER 60S. 31

[Houstonkid]

Who says HGX dropped severe.
From HGX page, CLL forecast (clicked right on it)

I said it, here is my post again, and it is still true

NWS Hou dropped the severe wording from forecast for Houston metro and I assume areas south

For Jersey Village
Tonight: Showers and thunderstorms likely, mainly after 1am. Cloudy, with a low around 68. South southeast wind between 5 and 10 mph. Chance of precipitation is 60%.

[wxman57]

It's hard to get severe storms between midnight and sunrise, most of the time. At least it looks like the weekend will have pretty good biking weather (this evening, too).

[wxdata]

There be life! Showers developing around the Austin area!

[wxdata]

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
354 PM CDT FRI APR 23 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST TEXAS.

.DAY ONE...TONIGHT

AREAS TO THE NORTH OF A COLUMBUS TO GROVETON LINE HAVE A SLIGHT
RISK OF STRONG THUNDERSTORMS EVOLVING TO SEVERE AHEAD OF SHORTWAVE
DISTURBANCE PASSING UP AND THROUGH CENTRAL TEXAS. THE PRIMARY
STORM THREATS WILL LARGE HAIL AND DAMAGING WINDS.

DURING THE OVERNIGHT HOURS THIS UPPER LEVEL DISTURBANCE WILL
INTERACT WITH A LARGE SCALE COOL FRONT...AND THIS BOUNDARY WILL
SWEEP ACROSS SOUTHEAST TEXAS BY MID SATURDAY MORNING. AHEAD OF
THIS COOL FRONT THE ATMOSPHERE WILL BECOME SOMEWHAT UNSTABLE IN
THE LOWER LEVELS BUT REMAIN CAPPED IN THE MID LEVELS. CLOSER TO THE
FRONT THIS CAP WILL ERODE AND STRONG TO SEVERE THUNDERSTORMS ARE
EXPECTED TO DEVELOP. STORMS SUPPORTING LARGE HAIL AND DAMAGING
WINDS ARE A PROBABILITY NORTH OF INTERSTATE 10. TO THE SOUTH OF
INTERSTATE 10 THE CAP SHOULD LIMIT THUNDERSTORM STRENGTH.

[wxdata]

For those using GRK radar-

"The GRK WSR 88d has died again. We have contacted the contract maintenance people. There is no estimated return to service time."

[wxdata]

Ft. Worth contemplating warning for storms moving into Bell/Falls counties in central Texas...