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

[jasons2k]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
145 PM CDT TUE MAY 2 2006

PRECIP COVERAGE CONTINUES TO INCREASE. HAVE BUMPED POPS TO CHANCE
OVER THE NORTHEAST AND ADDED POPS TO CHAMBERS COUNTY. NO OTHER
CHANGES. 43

[Extremeweatherguy]

here is a look at what the (12Z) GFS model is predicting for Saturday morning:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _096.shtml

Also, here is the NAM for 12am Saturday, looks like it is a bit further west and could mean more of an aim for Houston:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _084.shtml

[Extremeweatherguy]

This was just issued by the SPC:



MESOSCALE DISCUSSION 0723
NWS STORM PREDICTION CENTER NORMAN OK
0317 PM CDT TUE MAY 02 2006

AREAS AFFECTED...SOUTH CENTRAL/SOUTHEAST TX INTO LA

CONCERNING...SEVERE THUNDERSTORM POTENTIAL

VALID 022017Z - 022215Z

AN ISOLATED THREAT FOR DAMAGING WIND GUSTS/PERHAPS LARGE HAIL
APPEARS TO EXIST THROUGH LATE AFTERNOON/EARLY EVENING ACROSS SOUTH
CENTRAL/SOUTHEAST TX INTO LA. A WATCH IS NOT ANTICIPATED.

WITH THUNDERSTORMS ALREADY ONGOING...A FURTHER INCREASE IN AREAL
COVERAGE IS EXPECTED REMAINDER OF THE AFTERNOON ACROSS MUCH OF SOUTH
CENTRAL/SOUTHEAST TX INTO LA ALONG/SOUTH OF SOUTHWARD PROPAGATING
OUTFLOW BOUNDARY/S. SCENARIO SUPPORTED BY MODEST MASS CONVERGENCE
WITHIN A RATHER WARM/MOIST AIRMASS CHARACTERIZED BY NEGLIGIBLE
CONVECTIVE INHIBITION/LOW LFCS. ADJUSTED RUC SOUNDINGS DEPICT A VERY
UNSTABLE AMBIENT AIRMASS...WITH MLCAPE VALUES OF 2500-4000
J/KG...RELATIVELY GREATEST ACROSS SOUTH CENTRAL TX. WEAK VERTICAL
SHEAR -- ESPECIALLY THE CASE ACROSS SOUTHEAST TX INTO LA -- WILL
TEND TO LIMIT STORM ORGANIZATION...HOWEVER THE DEGREE OF
INSTABILITY/STEEP LAPSE RATES WILL SUPPORT AN EPISODIC SEVERE THREAT
INTO EARLY EVENING WITH THE STRONGER STORMS.

..GUYER.. 05/02/2006

[Yankeegirl]

When is this for?

[Yankeegirl]

There sure is a nice line out to the West side of Texas, just west of the Austin area.. where is that going ?

[Extremeweatherguy]

It looks to be moving ESE. If it holds on...then may be they will have to raise Houston's rain chances/severe threat for tomorrow.

[Extremeweatherguy]

Latest 0Z GFS looks A LOT more active for the Fri-Sat timeframe with the storms. Also, it looks like good dynamics will be in place for some severe weather (SPC will probably include Houston in the slight risk area for Friday/Saturday). At this point I would say 20% rain chances for Tomorrow and Thursday, then 30% on Friday, and probably 50% on Saturday. Saturday could also feature multiple rounds of storms...in the form of single or cluster storm groups or large MCS features or squall lines. By late Saturday a "main" squall line will probably come through and mean the end of the storms. Check out the GFS 0Z run here...

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

[Extremeweatherguy]

The SPC is still lagging behind with a slower look to the severe progression over the next few days, but the NWS is seeing something different, as it nows seems that they are starting to bite on the idea of a stormy Fri/Sat, and according to them...the GFS and NAM scenarios both indicate this. Here is the NWS (Houston) discussion:

DISCUSSION...
SUBTROPICAL JET APPROACHING BAJA PENINSULA HAS BEEN EJECTING
IMPULSES. ONE HAS FIRED UP CONVECTION ALONG DRY LINE YESTERDAY
WHICH PUSHED EAST WHILE WEAKENING OVERNIGHT. OUTFLOW BOUNDARIES
OVER CENTRAL TEXAS AND JUST NORTHWEST OF CWFA MAY SERVE AS A
FOCUSING MECHANISM WHEN CONVECTIVE TEMPERATURE IS REACHED THIS
AFTERNOON. WE SHALL CONTINUE WITH SLIGHT CHANCE POPS NORTHERN
TWO THIRDS OF CWFA TODAY. APPROACHING UPPER JET WILL RESULT IN A
MORE DIFFLUENT FLOW ON THURSDAY. 06Z INITIALIZED NAM 12 INDICATE
(AS DID 00Z NAM) CONVECTION OVER NORTH TEXAS MOVING TO OUR NORTHERN
ZONES THURSDAY NIGHT. LATE FRIDAY MAY BE INTERESTING SINCE
PARALLEL NAM AND GFS BOTH INDICATE CLUSTERING OF HIGH QPF VALUES
DURING THE EVENING OVER NORTH TEXAS/NORTHERN HILL COUNTRY WHICH
THEN MOVE TO OUR NORTHERN ZONES FRIDAY NIGHT. THIS APPARENTLY IS
THE RESULT OF A STRONG EJECTED ENERGY FROM APPROACHING UPPER
TROUGH. GOOD DIFFLUENT FLOW ALOFT IS ALSO EVIDENT FROM GFS DURING
THIS PERIOD. GFS EVEN DEVELOPS A STRONG MESO-VORTEX FROM THIS ACTIVITY
AND SHOVES IT TO LOUISIANA ON SATURDAY. WHAT IS WORRISOME IS THAT
THIS SCENARIO (MORE OR LESS) WAS INDICATED BY THE PAST FEW GFS
RUNS AND NOW THE PARALLEL NAM APPEARS TO AGREE. WE SHALL INCREASE OUR
POPS (BUT CAUTIOUSLY) FRIDAY NIGHT AND KEEP IT THROUGH SATURDAY AS
COLD FRONT MOVES ACROSS CWFA. WE SHOULD SEE DRYING LATER SATURDAY
NIGHT AS COLD FRONT PUSHES FARTHER SOUTH TO THE NORTHWEST GULF.
HIGH PRESSURE WILL BE OVER REGION ON SUNDAY GIVING US AT LEAST
HALF A GOOD WEEKEND. ONCE UPPER TROUGH DEPARTS TEXAS...REGION WILL
BE UNDER NORTHWEST FLOW. SURFACE HIGH WILL SHIFT TO EAST OF TEXAS
MONDAY USHERING THE RETURN OF ONSHORE FLOW. FOR EARLY NEXT WEEK...GFS
DO NOT INDICATE ANY UPPER LEVEL IMPULSES MOVING OVER THE REGION.
37

[jasons2k]

We may have some rain today

[Extremeweatherguy]

Based on the 12Z GFS...this is what should happen on Fri/Sat:

Friday Afternoon - Isolated storms develope..a few may be strong. 20% chance of rain (Could go up).

Friday night/Saturday morning - A strong MCS should form in North Texas and head SE toward the Houston area. The current arrival time for this MCS in Houston is looking to be around 3-6am on Saturday morning. The primary threat from this MCS looks to be wind damage with secondary threats of large hail and tornadoes. 60% chance of rain (could go up).

Saturday - Storms should re-fire on Saturday and could be strong to severe with damaging winds, hail and tornadoes. Low pressure should form/intensify over or just east of the area on Saturday as well which may add better dynamics for rain/severe weather. 40% chance of rain (Could go up).


**The NAM model is a little slower and holds the MCS on Saturday off until about 11am - 1pm.**

[jasons2k]

It's raining at my house

Too bad I'm not there to enjoy it.

[Extremeweatherguy]

It's raining at my house

Too bad I'm not there to enjoy it.

really? It's not raining here (yet), but I can see those dark clouds just to my north.

[Extremeweatherguy]

Latest from the NWS:

000
FXUS64 KHGX 032006
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
306 PM CDT WED MAY 3 2006

.DISCUSSION...
SE TX WILL BE CLOSE TO THE THUNDERSTORM ACTION OVER THE NEXT
COUPLE OF NIGHTS. THE ZONAL FLOW ALOFT WILL ALLOW THE SUBTROPICAL
JET TO BE ACTIVE OVER THE SOUTHERN PLAINS FOR THE REMAINDER OF THE
WEEK WITH SE TX COMING UNDER THE FAVORED POSITION FRIDAY NIGHT AND
SATURDAY. THE FRONTAL BOUNDARY TO THE NORTH WILL SAG INTO NE TX BY
THEN AND PROVIDE A LOW-LEVEL FOCUS. THE MODEL CAPE...LI...AND
HELICITY INDICATE A CHANCE FOR SEVERE STORMS FRIDAY NIGHT AND
SATURDAY...ALSO -- PLEASE REFERENCE THE LATEST HAZARDOUS WEATHER
OUTLOOK. FOR NOW WILL UP THE POPS FOR THE EVENT BUT WILL KEEP THEM
BELOW THE LIKELY CATEGORY. THE GFS FORECASTS A WIND SHIFT
BOUNDARY TO MOVE THROUGH TO THE COAST SUNDAY. THIS DOES NOT LINE
UP WITH ITS THETA-E FIELD AND IT MAY WELL BE A MODEL INDUCED
OUTFLOW BOUNDARY. IN ANY CASE...FEEL THAT THE FRONTAL BOUNDARY
WILL REMAIN OVER THE INLAND AREAS AND BE RATHER WEAK. BECAUSE OF
THIS...WILL KEEP A CHANCE OF RAIN INTO SUNDAY.

[Extremeweatherguy]

here is the latest from the NWS....looks like an MCS may reach us both tomorrow night and Friday night...interesting to say the least:

000
FXUS64 KHGX 040216
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
915 PM CDT WED MAY 3 2006

.DISCUSSION...
WILL SEND OUT A QUICK UPDATE TO REMOVE THE MENTION OF EVENING
WORDING AND TWEAK CLOUD COVER...MAINLY COSMETIC CHANGES TO THE
GRIDS. WILL BE MONITORING THE MARINE WINDS WITHIN THE NEXT HOUR OR
SO TO MAKE A DECISION ON WHETHER TO MAKE ANY TWEAKS TO THE CAUTION
FLAGS CURRENTLY FLYING.

OTHERWISE...LOOKS LIKE CHANCES OF PRECIP WILL BEGIN INCREASING
ACROSS THE REGION DURING THE NEXT COUPLE DAYS AS FRONTAL BOUNDARY
CURRENTLY IN OK SLOWLY SAGS INTO N TX. MODELS SHOWING THIS ALONG
WITH A MESSY UPPER LEVEL FLOW WILL ALLOW FOR SEVERAL MCS`S TO
DEVELOP DURING THE NEXT SEVERAL DAYS. ACCORDING TO THE 18Z GFS &
NAM MODELS...ONE COULD AFFECT OUR NE ZONES TOMORROW NIGHT BETWEEN
MIDNIGHT-6AM. THERE`S CURRENTLY PRETTY GOOD AGREEMENT WITH
THIS...AND IF THE 00Z RUNS CONTINUE TO SUPPORT THIS THE MIDNIGHT
CREW MAY NEED TO BUMP UP THE 30% POPS CURRENTLY ADVERTISED THERE.
STILL EXCELLENT AGREEMENT WITH ANOTHER MCS MOVING ACROSS A GOOD
PORTION OF SE TX DURING THE OVERNIGHT HOURS FRIDAY NIGHT INTO EARLY
SATURDAY. ANTICIPATE POPS TO BE ADJUSTED UPWARDS THEN TOO ASSUMING
NO BIG SURPRISES SEEN IN THE NEXT FEW MODELS RUNS. 47/35

[Johnny]

Sounds good to me!!!

[Johnny]

Sounds good to me!!!

[Johnny]

Sounds good to me!!!

[Extremeweatherguy]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
357 AM CDT THU MAY 4 2006

.DISCUSSION...
CONVECTION THAT FIRED UP NEAR DRY LINE OVER WEST TEXAS HAS BECOME
MORE ORGANIZED AND NOW MOVING ACROSS THE WESTERN PORTIONS OF NORTH
TEXAS. ANOTHER AREA OF CONVECTION (ALBEIT LESS ORGANIZED) NOTED OVER
THE WESTERN PART OF THE HILL COUNTRY. RELATIVELY QUIET OVER OUR
CWFA EARLY THIS MORNING. HOWEVER...MOIST AND UNSTABLE AIR MASS ALREADY IN
PLACE OVER OUR REGION. SOUTHERN BRANCH OF UPPER JET APPROACHING SOUTH
PART OF THE LONE STAR STATE TODAY PLACING OUR CWFA OVER THE LEFT EXIT
REGION. WE INCREASED POPS TO CHANCE OVER NORTHERN ZONES TODAY WHILE
LEAVING SLIGHT CHANCE ELSEWHERE. BOTH NAM AND GFS INDICATE CONVECTION
AGAIN FIRING THIS EVENING UP OVER NORTH TEXAS AND MOVING SOUTH
OVERNIGHT. THIS SCENARIO IS AGAIN INDICATED FRIDAY NIGHT. FRONTAL
BOUNDARY OVER NORTH TEXAS EXPECTED MOVE ACROSS OUR REGION LATE
SATURDAY AND THEN EVENTUALLY REACHING THE COASTAL ZONES EARLY
SUNDAY. GFS INDICATE BOUNDARY MAY STALL OVER THIS REGION.
STILL...LOWERING OF PW VALUES IS INDICATED LATE SUNDAY. BUT THIS
SHOULD BE SHORT LIVED. GFS AND ECMWF INDICATE DEVELOPING UPPER
TROUGH OVER SOUTHWEST CONUS EJECTING IMPULSES THAT WILL MOVE OVER
OUR REGION EARLY NEXT WEEK. INCREASINGLY CONFLUENT LOW LEVEL FLOW
INDICATED FOR OUR REGION MONDAY ESPECIALLY OVER SOUTHERN ZONES. WE
SHALL INTRODUCE POPS AGAIN MONDAY AND TUESDAY. SHORT WAVE TROUGH
WILL MOVE EAST OF OUR REGION BY MIDDLE OF NEXT WEEK.