S. Plains Severe April 17th to 19th?

[Ed Mahmoud]

SPC 4-8 days has parts of the Central Plains in the action Days 4 and 5

OK, this hotlink has only about 23 hours to live...

Storms ahead of the dryline way back in the Permian Basin approaching I-35 corridor

NAM solution of storms on what appears to be a returning frontal feature seems more correct to me



Instability per NAM a bit limited, but 50 knots plus of deep shear...




Euro low level wind speeds/surface features, despite a healthy 500 mb feature, don't look too impressive until Sunday, when the system is in the mid-South.


I have a quick look, strong 850 mb flow, and 500 mb flow divergent and cutting ahead of an upper low or trough, as a probable indicator of severe potential.

And the Euro does not seem on board for a big time event, or at least suggests wind dynamics will be limited. At least not 'til Sunday in the mid-South.

[wx247]

This is my favorite time of year... nice warm sunny days and severe weather seasons starts across the Plains! Thanks for the update. I will continue to monitor the thread as the weekend approaches.

Here is the extended severe weather outlook from the SPC:

[JonathanBelles]

I was waiting for this topic to pop up. I am going to be in Dallas from Wednesday to Sunday. What are the chances that I will run into severe weather while I am there?

[Ed Mahmoud]

I was waiting for this topic to pop up. I am going to be in Dallas from Wednesday to Sunday. What are the chances that I will run into severe weather while I am there?

Not sure on severe yet, but an umbrella may not be a bad idea.

[Ed Mahmoud]

Potential local excitement watch.

0Z GFS shows storms approaching HOU area late afternoon Friday, so-so CAPE, but manly-man low level winds...


GFS seems to keep surface based CAPE low around Dallas, and implies more rain than severe. At least the 0Z run. Friday morning, before peak heating, seems the best shot. Of course, a small shift in timing, and we are 3 plus days away, could make a fairly big difference.

[srainhoutx]

Just posted in SE TX/SW LA Topic concerning this. Maybe some badly needed rain for drought parched areas.

[srainhoutx]

DOUBLE POST ALERT
Look at this QPF Update...

[Ed Mahmoud]

May be more a beneficial rain than severe storm system, although some of the rain looks heavy enough for some local flooding, even with abnormally dry or drought conditions over much of the state.

[KatDaddy]

This afternoons Houston-Galveston AFD:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
243 PM CDT TUE APR 14 2009

.DISCUSSION...
LOADS OF SUNSHINE ACROSS SETX THROUGH EARLY AFTERNOON BUT CIRRUS
APPROACHING QUICKLY FROM THE WEST. SHOULDN`T HAVE ANY SIGNIFICANT
IMPACT ON AFTERNOON TEMPS. SURFACE HIGH STILL STRETCHES SOUTH
ACROSS THE AREA FROM NEAR CORSICANA TO RICHMOND. ONLY A WHISPER OF
WIND OVER THE AREA AS OF 2 PM. UPPER TROUGH OVER WA/OR COAST
DROPPING SSE AND UPPER RIDGING FROM NM-SD THIS AFTERNOON AND THE
RIDGE SHOULD AMPLIFY AND TROUGH MOVE INTO THE SRN NV BY WEDNESDAY
AFTERNOON. UPPER RIDGE SLOWS AND LOW DOES AS WELL NEAR THE 4
CORNERS BY THURSDAY MORNING. IMPRESSIVE UPPER DIFFLUENCE SPLIT JET
STRUCTURE AND PW CLIMBING 1.4-1.6 THU...1.5-2.1" ON FRI...AND
1.6-2.0" FOR SATURDAY. DUE TO THE SLOW MOVING UPPER LOW THE
PERSISTENT MOIST-VERY MOIST SOUTHEAST LL FLOW THE REGION APPEARS
TO BE COMING INTO A PERIOD OF HEAVY AND WIDESPREAD RAINFALL
STARTING THURSDAY AND ENDING SUNDAY. MANY LARGE AND SMALL SCALE OUTDOOR
ACTIVITIES PLANNED THIS WEEKEND AND IT WILL BE MESSY. PREVIOUS
EXPECTATIONS OF 2-4 INCHES ISOLATED 4-6 LOOKING CLOSE AND PLAN TO
REISSUE HWO WITH 1-3 AND 5-6 ISOLATED THIS AFTERNOON. THE
THUNDERSTORMS THAT DEVELOP ON FRIDAY MAY BE MORE FOCUSED OVER THE
NW HALF OF THE AREA AND THE SW HALF OF THE REGION SATURDAY. BUT
THIS FAR OUT AM UNWILLING TO HANG MY HAT ON THOSE KIND OF
SPECIFICS YET.

ADDITIONAL ISSUES INCLUDE THE POSSIBILITY OF SEVERE WEATHER
FRIDAY...LLJ 40-60 KNOTS...POTENT S/W IN THE SW FLOW ALOFT AND
SOUNDINGS THAT MOISTEN UP RAPIDLY THROUGH 700 MB EARLY FRIDAY
MORNING. VERY STRONG SHEAR AND MINIMAL IF ANY CAP WILL BE PRESENT
AND A DEEP CIRCULATION THAT SWINGS THROUGH THE WESTERN CWA DURING
THE AFTERNOON HOURS...TORNADOES COULD BE POSSIBLE.

SECONDARY ISSUE IS THE PERSISTENT MODERATE ESE/SE SURFACE FLOW
WILL LIKE RAISE TIDE LEVELS ON THURSDAY AND FRIDAY TO AT LEAST 1
FOOT ABOVE NORMAL AND PERHAPS AS MUCH AS 2.5 FEET. FOR NOW WILL
CARRY WORDING OF 1-1.5 BUT FOLLOWING SHIFTS WILL NEED TO WATCH
THIS CLOSELY.

[wall_cloud]

I think our best chance for severe wx in the Panhandle will be on 4/15-4/16. Tomorrow will likely be marginal coverage given the modest (at best) low level moisture return, but this should improve dramatically by Thursday morning. The dryline should really sharpen over the western TX Panhandle and with more than adequate shear and an approaching shortwave, storms are a good bet. Low clouds may prohibit us from reaching our potential instability but we should see decent coverage anyway. If the clouds break, look out.

[Ed Mahmoud]

Snip from NWS HGX AFD

PREV DISCUSSION (328 AM)...
THE MAIN FOCUS IN THIS FORECAST CYCLE WILL BE THE NEXT STORM
SYSTEM AND ASSOCIATED CONVECTIVE POTENTIAL ACROSS THE AREA
THURSDAY THROUGH SATURDAY NIGHT. SFC HIGH JUST EAST OF THE AREA
WITH CLEAR SKIES/LIGHT WINDS RESULTING IN ANOTHER COOL NIGHT.
ONSHORE FLOW WILL RETURN TODAY AS THE HIGH MOVES EAST OF THE AREA.
SHOULD BE ANOTHER NICE DAY WITH ONLY SCATTERED HIGH CLOUDS
EXPECTED. CLOUD COVER WILL BEGIN TO THICKEN AND LOWER ON THURSDAY
MORNING. SIGNIFICANT LOW LEVEL WARM ADVECTION DEVELOPS THURSDAY
WITH 30-40 KT LOW LEVEL JET TRANSPORTING MUCH DEEPER MOISTURE (PWS
1.4-1.6 INCHES) INTO THE AREA. MODELS ALL IN GOOD AGREEMENT ON A
ROUND OF SCATTERED CONVECTION THURSDAY AFTN IN THE WARM ADVECTION
PATTERN. MODEL FCST SOUNDINGS SHOW A GOOD CAP IN PLACE IN THE
700-800 MB LAYER THURSDAY SO SHRA/TSRA THAT DEVELOP WILL BE
SHALLOW IN NATURE UNDER THE CAP. HAVE BLANKETED 40 POPS ACROSS THE
AREA. THE TIGHTENING PRESSURE GRADIENT WILL RESULT IN BREEZY
CONDITIONS THURSDAY THROUGH FRIDAY. THE STRONG EASTERLY FETCH
ALONG THE COAST WILL RESULT IN ELEVATED TIDE LEVELS THURSDAY
THROUGH FRIDAY.

LARGE UPPER LOW IS EXPECTED TO REACH THE SRN PLAINS BY FRIDAY. A
SERIES OF DISTURBANCES WILL ROTATE AROUND THE UPPER LOW AND CROSS
SE TX IN THE FRIDAY THROUGH SATURDAY NIGHT TIME FRAME. FLOW ALOFT
WILL BECOME VERY DIFFLUENT THIS PERIOD IN ADVANCE OF THE UPPER
LOW. THE APPROACH OF THE SYSTEM WILL ALLOW SOME MID LEVEL COOLING
TO OCCUR SETTING UP VERY STEEP LAPSE RATES BEGINNING FRIDAY. IN
ADDITION...SFC WINDS WILL REMAIN BACKED TO THE EAST/SOUTHEAST
WHICH WILL RESULT IN STRONG LOW LEVEL SHEAR. LATEST GFS FORECASTS
LIS OF -6 TO -9 AND HELICITY VALUES >300 M2/S2 AREA WIDE ON
FRIDAY. IN ADDITION...WILL LIKELY SEE SOME TYPE OF WEST-EAST
ORIENTED SFC BOUNDARY SET UP TO HELP FOCUS DEVELOPMENT. EXPECTING
A LARGE MCS TO DEVELOP OVER CENTRAL/NORTH TX THU NIGHT AND AFFECT
SE TX ON FRIDAY. SEVERE WEATHER WILL BE A POSSIBILITY GIVEN THE
ABOVE MENTIONED PARAMETERS. ON SATURDAY...SE TX GOES INTO THE
RIGHT REAR QUAD OF A 110 KT JET MAX AT 300 MB...WITH ANOTHER ROUND
OF TSRA LIKELY FOR THE AREA. MODELS ONCE AGAIN FORECAST STRONG
INSTABILITY (LIS -4 TO -8) AND HIGH LEVELS OF SHEAR ON
SATURDAY...SO SEVERE WEATHER LOOKS LIKE A POSSIBILITY ONCE AGAIN.
LOCALLY HEAVY RAINFALL WILL BE POSSIBLE FRIDAY THROUGH SATURDAY AS
WELL. HPC`S LATEST QPF FORECAST CALLS FOR 1.5-3.0 INCHES OVER THE
MOST OF THE CWA THROUGH EARLY SATURDAY. GIVEN THE ONGOING DROUGHT
CONDITIONS...THIS WILL MOSTLY BE A WELCOME RAIN ESPECIALLY OVER
WESTERN COUNTIES. IN BETWEEN THE ROUNDS OF CONVECTION WILL LIKELY
SEE A FEW HOURS BREAK. SINCE IT IS IMPOSSIBLE TO TIME THIS THIS
FAR OUT HAVE JUST BLANKETED HIGH POPS (40-60 PCT) AREA WIDE
FRIDAY/SATURDAY. UPPER TROUGH WILL FINALLY CROSS SE TX SATURDAY
NIGHT...WITH RAPID DRYING FROM WEST TO EAST OVERNIGHT. SUNDAY
SHOULD TURN OUT TO BE A NICE DAY WITH SUNSHINE AND LOWER HUMIDITY
IN THE WAKE OF THE SYSTEM. A COLD FRONT WILL CROSS SE TX LATE
SUNDAY. VERY NICE WEATHER IS IN STORE FOR THE FIRST HALF OF NEXT
WEEK AS DRY/CONTINENTAL AIRMASS GETS REINFORCED OVER THE AREA.

[Ed Mahmoud]

Copied and pasted from SETX/SWLA thread, but with extra bonus features, like the discussion of possible severe hail in the San Antonio-San Marcos-New Braunfels-San Antonio I-35 tourism-plex

New GFS stalls the boundary and the heaviest rain just North of Houston.


Of course, as mentioned by Mr. Linder, the exact location of where the outflow boundary/pseudo-stationary front parks is key to who gets heavy rain.

Things look reasonably favorable for some severe if storms can get to Houston Friday afternoon. As mentioned above, any discrete cells that can form ahead of a bigger MCS benefits from uninterrupted inflow South of the MCS, and possibly added helicity along the near stationary boundary


Maybe again Saturday.



................................................................

Bonus feature. Ok, low level instability nearly nil as the GFS forecast QLCS approaches the I-35 corridor Friday morning, but look at the juicy mid-level CAPE forecast on the skew-T!



I'd like a little instability in the lowest couple of kilometers for tornadoes, but there is plenty of shear at all levels, and where the really impressive instability is living, between about 700 and 250 mb, there is some speed and directional shear. Could be some hail, I'd think.

[Ed Mahmoud]

AFD snip buffet...


HGX

GULF MOISTURE AND WARM ADVECTION MAY BE ENOUGH FOR A FEW ISO/SCT
SHOWERS AND THUNDERSTORMS OVER THE AREA. COVERAGE WILL BE BEST
OFF TO THE NW OF THE AREA SO WILL KEEP AT LEAST A 30-40 PERCENT
CHANCE IN THE FORECAST. A STRONG JET STREAK PUNCHING INTO W TX
THU NIGHT MAY KICK OFF A SQUALL LINE WHICH COULD PUSH INTO THE
ARE BY FRI MORNING. THE SQUALL LINE WILL LIKELY BE DISSIPATING AS
IT MOVES INTO THE REGION BUT COULD HELP SET UP A ROUND OF SEVERE
WEATHER. OUTFLOW FROM THE SQUALL LINE COULD SET UP ACROSS THE
NORTHERN PART OF THE CWA. A STOUT WARM SECTOR SOUTH OF THE
BOUNDARY COULD BE UNSTABLE ENOUGH FOR SFC BASED STORMS. THE LLJ
WILL BE QUITE STRONG AS THE UPPER LOW BEGINS TO MOVE INTO THE S
PLAINS. DEEP LAYER SHEAR WILL BE PLENTY STRONG FOR ORGANIZED
STORMS AND 0-3KM SRH MAY BE ON THE ORDER OF 300 M2/S2. THIS
SUGGESTS THE POSSIBILITY OF SUPERCELLS BUT LARGELY DEPENDS ON HOW
MUCH INSTABILITY DEVELOPS. SHOULD 1500-2000 J/KG DEVELOP LIKE THE
GFS SUGGESTS...SEVERE POTENTIAL COULD BE HIGHER. PWAT VALUES
SHOULD BE ON THE ORDER OF 2 STANDARD DEVIATIONS HIGHER THAN
NORMAL FOR THIS TIME OF YEAR SO HEAVY RAINFALL WILL BE A
POSSIBILITY AS WELL. GIVEN DRIER THAN NORMAL
CONDITIONS...FLOODING CONCERNS MAY BE CONFINED TO SATURDAY SHOULD
ENOUGH RAINFALL DEVELOP FRIDAY AND A SECOND CONVECTIVE LINE
MOVES THROUGH THE AREA OVER THE WEEKEND.

THE GFS/NAM SOLUTIONS DO DEVELOP A SECOND ROUND OF CONVECTION
OVER THE REGION AND SHOULD SEE THE TAIL END OF THE UPPER LOW
AFFECT THE REGION. JET STREAK WITH THE LOW SHOULD BE ALIGNED WITH
THE RIGHT REAR QUAD OVER SE TX WITH A MORE DIFFLUENT PATTERN
ALOFT GIVEN SOME INFLUENCE FROM THE SUB TROPICAL JET THAT
STRETCHES ACROSS S TX INTO THE GULF. DYNAMICAL FORCING WILL BE
QUIET STRONG AND WILL KEEP 60 POPS FOR MUCH OF THE AREA FOR
SATURDAY. AGAIN...THERE MAY BE SOME POTENTIAL FOR SEVERE
THUNDERSTORM ACTIVITY BUT HINGES GREATLY ON HOW MUCH OF THE
ATMOSPHERE TURNS OVER DUE TO PREVIOUS CONVECTION AND HOW MUCH
INSTABILITY REMAINS. DEEP AND LOW LEVEL SHEAR WILL AGAIN BE
STRONG ENOUGH FOR STORM ORGANIZATION. A COLD FRONT SHOULD SWEEP
THROUGH THE AREA SAT NIGHT WHICH WILL PUSH THUNDERSTORM ACTIVITY
INTO THE GULF. THE UPPER LOW EJECTS INTO THE MIDWEST ON SUN
ALLOWING FOR DRIER AND CLEAR CONDITIONS.

AMA

ON THURSDAY...A STRONG SHORTWAVE TROF IS EXPECTED TO MOVE ACROSS THE
AREA. THE SYNOPTIC FORCING ASSOCIATED WITH THIS WAVE WILL BE AIDED
BY SEVERAL MESOSCALE FEATURES. AN H25 JET STREAK WILL ROUND THE BASE
OF THE TROF...PUTTING THE PANHANDLES IN THE FAVORABLE LEFT EXIT
REGION AND A DRYLINE IS FORECAST TO SHARPEN OVER THE EXTREME WESTERN
CWA DURING THE AFTERNOON. THE COMBINATION OF THESE FEATURES...IN
INCREASING LOW LEVEL MOISTURE...SHOULD SUPPORT SCATTERED SHOWERS AND
THUNDERSTORMS...SOME SEVERE...DURING THE AFTERNOON AND CONTINUING
THROUGH THE NIGHT. STRONG 0-6KM SHEAR WILL EXIST BUT INSTABILITY
WILL BE A QUESTION MARK. IF WE EXPERIENCE LOW CLOUDS FOR MUCH OF THE
DAY...WE MAY NOT WARM ENOUGH TO REALIZE THE POTENTIAL INSTABILITY.
THIS WOULD LEND TO LESS DISCRETE CELLS AND MORE MULTICELL FAMILIES.
IF WE DO WARM...WE COULD SEE INITIAL SUPERCELLS THAT EVENTUALLY
CONGEAL INTO A LINEAR MCS DURING THE EVENING HOURS THAT WILL
PROPAGATE TO THE EAST OVERNIGHT. SEE THE SWODY2 FOR ADDITIONAL
DETAILS.

EWX is looking at more of a heavy rain producer, but somewhat limited by storm motion, and only mentions 'isolated severe' North of US 90.

[srainhoutx]

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1237 AM CDT THU APR 16 2009

VALID 171200Z - 181200Z

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

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF CNTRL/SCNTRL
TX...

...CNTRL HIGH PLAINS TO SCNTRL TX...

COMPLEXITIES...REGARDING CONVECTION...WILL BEGIN TO INCREASE
EXPONENTIALLY DURING THE DAY2 PERIOD AS SLOW MOVING UPPER LOW
MIGRATES ACROSS THE CNTRL/SRN ROCKIES INTO THE PLAINS. LATEST
GUIDANCE SUGGESTS DAY1 WILL BE CONVECTIVELY ACTIVE WELL INTO THE
OVERNIGHT HOURS...WITH SIGNIFICANT THUNDERSTORM ACTIVITY EXPECTED TO
BE ONGOING AT THE BEGINNING OF THE DAY2 PERIOD FROM THE EDWARDS
PLATEAU OF TX...NWD INTO WRN OK...ARCING NWWD INTO WRN KS. THIS
EARLY MORNING ACTIVITY WILL LIKELY BE ENHANCED BY STRONG LLJ THAT
WILL GRADUALLY SHIFT EAST INTO THE ARKLATEX LATER IN THE DAY.
ALTHOUGH EARLY MORNING COMPLEX MAY EXHIBIT ORGANIZED SQUALL LINE
STRUCTURE...IT/S NOT ENTIRELY CLEAR HOW SEVERE THIS CONVECTION WILL
BE AFTER SUNRISE. OF GREATER CONCERN WILL BE CONVECTIVE
POSSIBILITIES WITHIN DESTABILIZING ZONE ACROSS PORTIONS OF CNTRL
TX...AND PERHAPS IMMEDIATELY AHEAD OF THE UPPER LOW OVER THE HIGH
PLAINS. FORECAST MODELS DIFFER A BIT IN THE PROGRESSION OF SQUALL
LINE ACROSS TX/OK WITH THE GFS MAINTAINING CONSIDERABLE INTENSITY
WITH THIS COMPLEX INTO THE ARKLATEX REGION. AT SOME POINT THE
SQUALL LINE SHOULD OUTRUN ITS UPPER SUPPORT AND WEAKEN. LATEST
THINKING IS GREATER INSTABILITY WILL HOLD ACROSS CNTRL/SCNTRL TX
WHERE A SURGE OF MARITIME TROPICAL AIR SHOULD BE IN PLACE. THIS MAY
BE WHERE RENEWED THUNDERSTORMS COULD DEVELOP AS BOUNDARY LAYER WARMS
ALONG SRN FRINGE OF STRONGER MID LEVEL FLOW. AT ANY RATE...FORECAST
SOUNDINGS FAVOR STORM ROTATION...ESPECIALLY IF MORE DISCRETE
UPDRAFTS CAN DEVELOP LATER IN THE DAY. LARGE HAIL...DAMAGING WINDS
AND PERHAPS AN ISOLATED TORNADO CAN BE EXPECTED.

FARTHER NW...DESPITE MARGINAL LOW LEVEL MOISTURE...STRONG
THUNDERSTORMS MAY DEVELOP IN A NARROW CORRIDOR ALONG THE NRN-ERN
SEMICIRCLE OF UPPER LOW FROM SERN CO INTO EXTREME WRN OK BY
EARLY-MID AFTERNOON. VERY COLD MID LEVEL TEMPERATURES...H5 FROM
-20C TO -26C...WILL OVERSPREAD THE SRN HIGH PLAINS BENEATH THE UPPER
LOW. THUNDERSTORMS SHOULD EASILY DEVELOP ALONG LOW LEVEL
CONVERGENCE ZONE WHERE STRONG HEATING WILL REMOVE INHIBITION
QUICKLY. SHEAR PROFILES SUGGEST SUPERCELLS ARE POSSIBLE. PRIMARY
SEVERE THREAT WILL BE LARGE HAIL...BUT AN ISOLATED TORNADO CAN NOT
BE RULED OUT.

..DARROW.. 04/16/2009

[Ed Mahmoud]

HOU area now in no official RISK area at all per SPC.

If it is just garden variety storms with 2 or 3 inches of rain, I'm ok with that.

But Wall Clouds AMA CWA is smack in the middle of the SWODY1 SLIGHT RISK.


HGX hasn't totally ruled out severe around here per snip from AFD...

UPPER LOW WILL PUSH EAST TOWARD THE PANHANDLE REGION BY LATE FRIDAY.
MODELS IN GOOD AGREEMENT THAT A DISTURBANCE WILL ROTATE AROUND THE
SYSTEM AND CROSS THE AREA FRI AFTN. FLOW ALOFT WILL BECOME
INCREASINGLY DIFFLUENT FRI/FRI NIGHT AS UPPER LOW SLOWLY APPROACHES
FROM THE WEST. AIRMASS BECOMES SIGNIFICANTLY MORE UNSTABLE BEGINNING
FRI MORNING WITH LIS DROPPING TO -4 TO -8 OVER ALL BUT THE NE ZONES.
STRONG LOW LEVEL JET (40 KTS) WILL AID IN FURTHER DEEPENING MOISTURE
LEVELS WITH PWS UP TO AROUND 1.7 INCHES LATE FRIDAY. SFC WINDS WILL
REMAIN BACKED TO THE SOUTHEAST RESULTING IN HIGH VALUES OF LOW LEVEL
SHEAR (HELICITIES >300 M2/S2). CURRENT THINKING IS THAT AN MCS WILL
DEVELOP OVER CENTRAL TX LATE TONIGHT/EARLY FRIDAY AND WORK ITS WAY
INTO SE TX FRI AFTN. ABOVE MENTIONED FACTORS WILL RESULT IN THE
POTENTIAL FOR SEVERE STORMS ESPECIALLY WEST OF I-45 WHERE
INSTABILITY WILL BE GREATEST. IN ADDITION WILL SEE POTENTIAL FOR
LOCALLY HEAVY RAINFALL. A SFC MESOSCALE OUTFLOW BOUNDARY IS LIKELY
TO PUSH ACROSS AT LEAST THE NORTHERN PORTIONS OF SE TX FRI NIGHT.
THE PLACEMENT OF THIS BOUNDARY WILL HAVE A BIG EFFECT ON TEMPS AND
ADDITIONAL CONVECTIVE DEVELOPMENT FRI NIGHT/EARLY SATURDAY. GIVEN
UNCERTAINTY ON HOW THIS WILL EVOLVE HAVE BLANKETED 40/50 POPS AREA
WIDE. THIS BOUNDARY WILL LIKELY RETREAT BACK NORTH SAT MORNING
PLACING ALL OF SE TX IN AN UNSTABLE AIRMASS (LIS -4 TO -6) ONCE
AGAIN. UPPER FLOW WILL REMAIN STRONGLY DIFFLUENT OVER THE AREA
SATURDAY WITH DEEP MOISTURE REMAINING IN PLACE (PWS AROUND 1.7
INCHES). UPPER TROUGH AND SFC DRYLINE WILL SLOWLY CROSS SE TX SAT
AFTN/EVENING RESULTING IN ANOTHER ROUND OF THUNDERSTORMS. WILL SEE
THE POTENTIAL OF ISOLATED SEVERE STORMS AND LOCALLY HEAVY RAINFALL
ONCE AGAIN SATURDAY AFTN/EVENING. HPC 3 DAY QPF FORECAST (THROUGH 12Z
SUNDAY) CALLS FOR WIDESPREAD RAINFALL TOTALS OF 1.5-3.5 INCHES AREA
WIDE. MINOR FLOODING WILL BE A POSSIBILITY WHERE TRAINING OF ECHOES
OCCURS...BUT CURRENT THINKING IS THAT THE FLOOD POTENTIAL WILL BE
MITIGATED BY THE ONGOING DROUGHT CONDITIONS.

At 48 hours from 7pm CDT last night, or Friday late afternoon, GFS shows storms just North of HOU, and forecast skew-T looks reasonably favorable for some severe.


Again Saturday



Early afternoon tomorrow around SAT and points East as the MCS approach look potentially spooky per the GFS, with more than just reasonably favorable conditions for severe.

[Ed Mahmoud]

AMA is on the warm and humid side of the trough late afternoon.



GFS shows storms cranking between 7 and 10 pm.

7 pm forecast AMA sounding. A hint of a weak cap, but low cloud bases and decent helicity, could be a tornado threat. Steep mid level lapse rates and some speed shear in the mid levels, maybe some hail as well.

[Ed Mahmoud]

MESOSCALE DISCUSSION 0481
NWS STORM PREDICTION CENTER NORMAN OK
1120 AM CDT THU APR 16 2009

AREAS AFFECTED...PORTIONS NW TX...ERN/NRN TX PANHANDLE...CENTRAL/ERN
OK PANHANDLE...WRN OK...WRN KS...EXTREME ERN CO.

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 161620Z - 161815Z

POTENTIAL IS INCREASING FOR ISOLATED TO WIDELY SCATTERED AND
MARGINAL SVR HAIL...WITHIN GROWING PLUME OF CONVECTION NOW EVIDENT
FROM SW OK ACROSS NERN TX PANHANDLE TO VICINITY KS/CO BORDER. WHILE
THIS ACTIVITY MOVES N WITH GRADUAL INTENSIFICATION...SOME
BACKBUILDING/FILLING ALSO IS POSSIBLE ACROSS PORTIONS NW TX AND
CENTRAL/NRN PANHANDLE. THIS IS SEPARATE FROM MID-LATE
AFTERNOON/SFC-BASED SVR THREAT DISCUSSED IN DAY-1 OUTLOOK...AND IS
NOT EXPECTED TO BE AS WELL-ORGANIZED.

12Z UPPER AIR ANALYZES AND RUC GUIDANCE INDICATE INCREASING LOW
LEVEL MOISTURE -- ESPECIALLY IN 925-850 MB LAYER -- ASSOCIATED WITH
BROAD/40-50KT SSELY LLJ. MAX MOISTURE TRANSPORT SHOULD CONTINUE
ACROSS THIS REGION...PERHAPS SHIFTING SLIGHTLY WWD AS
PANHANDLES/SWRN KS/SERN CO SEGMENT OF LLJ BACKS AND INTENSIFIES
SOMEWHAT THROUGH EARLY AFTERNOON. THIS REGIME GRADUALLY WILL BECOME
INCREASINGLY JUXTAPOSED WITH ERN EDGE OF MORE ROBUST LARGE-SCALE
ASCENT AND COOLING ALOFT AS CENTER OF BROAD UPPER CYCLONE PIVOTS EWD
THROUGH 4-CORNERS AREA. MODIFIED 12Z RAOBS AND RUC SOUNDINGS
INDICATE ELEVATED MUCAPE IN 1000-1500 J/KG RANGE. PRIMARY LIMITING
FACTOR APPEARS TO BE LACK OF MORE ROBUST SHEAR FOR ELEVATED LIFTED
PARCELS. WITH STRONGEST DEEP-LAYER WINDS REMAINING W OF THIS AREA
AT LEAST UNTIL EARLY-MID AFTERNOON...FCST SOUNDINGS SHOW ONLY SMALL
CHANGES WITH HEIGHT IN DIRECTION/SPEED OF FLOW THROUGH
INFLOW-BUOYANT LAYERS. THIS SHOULD KEEP EFFECTIVE SHEAR MAGNITUDES
BELOW 30 KT IN MOST OF DISCUSSION AREA UNTIL INFLOW PARCELS BECOME
SFC-BASED...LIKELY AROUND MID-AFTERNOON NEAR W EDGE OF THIS
CLOUD/PRECIP AREA WHERE HEATING IS STRONGER. KINEMATIC GEOMETRY
ALSO SHOULD CONTRIBUTE TOWARD MIXTURE OF MULTICELL CLUSTERS AND
LINEAR MODAL TENDENCIES.

..EDWARDS.. 04/16/2009


ATTN...WFO...FWD...OUN...GID...DDC...SJT...GLD...LUB...AMA...
PUB...

[Ed Mahmoud]

I wonder if Wall Cloud is working today...



MESOSCALE DISCUSSION 0482
NWS STORM PREDICTION CENTER NORMAN OK
0156 PM CDT THU APR 16 2009

AREAS AFFECTED...PORTIONS TX SOUTH-PLAINS REGION...TX PANHANDLE...OK
PANHANDLE.

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 161856Z - 162000Z

--- RE-TRANSMITTED ---

SFC-BASED CONVECTION IS DEVELOPING BETWEEN LBB-EVW...WITH ADDITIONAL
CONVECTION POSSIBLE NWD THROUGH CENTRAL PANHANDLE AND SWWD TOWARD
TX/NM BORDER AREA E HOB. DAMAGING GUSTS AND LARGE HAIL WILL BE
POSSIBLE FROM ACTIVITY OVER THIS AREA THROUGH REMAINDER OF AFTERNOON
INTO EVENING.

SFC MESOANALYSIS INDICATES DRYLINE BULGE OVER THIS REGION...WITH
DRYLINE ARCHING THROUGH ERN DALLAM...ERN CASTRO...HALE...WRN LUBBOCK
COUNTIES...THEN SWD TO NEAR MAF. MESOANALYSIS...RADAR REFLECTIVITIES
AND VIS IMAGERY INDICATES BOUNDARY LAYER CONVERGENCE LINE COLLOCATED
WITH DRYLINE N OF LBB COUNTY...THEN EXTENDING SWWD THROUGH NWRN
GAINES COUNTY. DRYLINE SHOULD KEEP MIXING EWD ACROSS MOST OF SOUTH
PLAINS REGION...BUT BECOME MORE NW-SE ALIGNED FARTHER N AS
BACKED/INTENSIFYING LOW LEVEL FLOW PERSISTS ACROSS CENTRAL/NRN
PANHANDLE AND OK PANHANDLE. DRYLINE ACTUALLY MAY RETREAT WWD
SOMEWHAT OVER NRN TX AND OK PANHANDLES AMIDST STRENGTHENING
ISALLOBARIC FORCING...EXTENDING SOME SVR POTENTIAL INTO WHAT NOW IS
DRY AIR MASS. MODIFIED RUC/OBSERVED SOUNDINGS INDICATE VERY STEEP
MIDLEVEL LAPSE RATES ACCOMPANYING ERN EDGE OF COOLING ALOFT
OVERSPREADING REGION. FURTHER DESTABILIZATION ALOFT IS EVIDENT JUST
UPSTREAM OVER SERN NM -- WHERE CONSIDERABLE MIDLEVEL CONVECTION HAS
DEVELOPED OVER VERY DRY NEAR-SFC LAYER. THIS...COMBINED WITH SFC
DEW POINTS 50S F E OF DRYLINE...YIELDS MLCAPE 1500-2000 J/KG
IMMEDIATELY E OF DRYLINE...IN NARROW ZONE OF FAVORABLY STG
INSOLATION W OF CLOUD SHIELD FROM ACTIVITY DISCUSSED IN MESOSCALE
DISCUSSION 481.

FAVORABLE STORM-RELATIVE FLOW IS EXPECTED...GIVEN RELATIVELY BACKED
SFC WINDS EVIDENT IN TX MESONET DATA AND FCST TO CONTINUE BETWEEN
THIS AREA AND CAPROCK. MODIFIED RUC SOUNDINGS SUGGEST SE FLOW WILL
CONTRIBUTE TO FAVORABLE DEEP-LAYER SHEAR...E.G. EFFECTIVE SHEAR
MAGNITUDES 45-50 KT FOR SFC-ROOTED PARCELS. WEAK WINDS JUST ABOVE
SFC...IN 1-2 KM AGL LAYER -- WILL KEEP LOW LEVEL HODOGRAPHS
RELATIVELY SMALL OVER INITIATION AREA. HOWEVER...HODOGRAPHS WILL
EXPAND EWD WITH PROXIMITY TO 40-50 KT LLJ...AND WITH TIME THIS
EVENING.

..EDWARDS.. 04/16/2009




ATTN...WFO...DDC...LUB...AMA...MAF...PUB...

[srainhoutx]

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 155
NWS STORM PREDICTION CENTER NORMAN OK
240 PM CDT THU APR 16 2009

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

OKLAHOMA PANHANDLE
WEST TEXAS INCLUDING THE PANHANDLE

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 240 PM UNTIL
1000 PM CDT.

HAIL TO 2.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 80
STATUTE MILES EAST AND WEST OF A LINE FROM 20 MILES NORTH OF
GUYMON OKLAHOMA TO 50 MILES SOUTH SOUTHEAST OF LUBBOCK TEXAS.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU5).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

DISCUSSION...THUNDERSTORMS WILL CONTINUE TO INCREASE IN COVERAGE AND
INTENSITY THIS AFTERNOON AND EARLY EVENING AS SHORTWAVE TROUGH OVER
NM APPROACHES REGION. STEEP MID LEVEL LAPSE RATES...MODERATE MUCAPE
VALUES...AND FAVORABLE EFFECTIVE SHEAR SUGGEST A RISK OF SUPERCELLS
CAPABLE OF LARGE HAIL AND DAMAGING WINDS. POTENTIAL FOR ISOLATED
TORNADOES COULD ALSO INCREASE THIS EVENING WHEN AN UPGRADE TO A
TORNADO WATCH MIGHT NEED TO BE CONSIDERED.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 450. MEAN STORM
MOTION VECTOR 24035.


...HART

[Ed Mahmoud]

MESOSCALE DISCUSSION 0484
NWS STORM PREDICTION CENTER NORMAN OK
0353 PM CDT THU APR 16 2009

AREAS AFFECTED...PORTIONS TX SOUTH PLAINS...PERMIAN BASIN.

CONCERNING...SEVERE THUNDERSTORM WATCH 155...

VALID 162053Z - 162200Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 155
CONTINUES.

POTENTIAL MAY BE INCREASING FOR RELATIVELY DISCRETE AND POSSIBLY
TORNADIC SUPERCELLS OVER SRN PORTIONS WW AREA...SWD TOP NEAR I-20
ENE OF MAF. TORNADO WW IS BEING CONSIDERED FOR THIS REGION...WHICH
WOULD REPRESENT UPGRADE AND NEW WW NUMBER FOR THOSE OVERLAPPING
COUNTIES ALREADY IN WW 155.

SFC MESOANALYSIS AND VIS IMAGERY INDICATES SHARPENING PSEUDO WARM
FRONTAL ZONE AND CONFLUENCE BAND FROM COKE COUNTY NWWD BETWEEN
BPG-SNK...INTERSECTING DRYLINE OVER DAWSON COUNTY. THIS FEATURE
SHOULD DRIFT NWD...AMIDST NEARLY UNCAPPED MLCAPE NEAR 2000
J/KG...AND SOME POTENTIAL REMAINS FOR DRYLINE TO RETREAT WWD SOME
MORE. AIR MASS ALONG AND N OF THIS BOUNDARY IS CHARACTERIZED BY
LOWER DEW POINT DEPRESSIONS...LOWER LCL...AS WELL AS MORE BACKED/ELY
SFC WINDS THAT YIELD STRONGER 0-1 KM SRH AND STORM-RELATIVE INFLOW.
LBB VWP INDICATES EARLIER RELATIVE WEAKNESSES IN LOW LEVEL FLOW
ABOVE BACKED SFC WINDS ARE WEAKENING AS TIGHTER HEIGHT GRADIENTS
ALOFT GRADUALLY SHIFT E AHEAD OF 4-CORNERS UPPER CYCLONE...A TREND
THAT IS NOT YET MANIFEST AT JTN PROFILER FARTHER E. PRIND LOW-LEVEL
AND DEEP-LAYER SHEAR WILL STRENGTHEN SLOWLY WITH TIME THROUGH
REMAINDER AFTERNOON...AND THAT HODOGRAPHS WILL REMAIN LARGEST ALONG
AND N OF WARM FRONT. THICKENING SHALLOW CONVECTION EVIDENT IN VIS
IMAGERY ALSO INDICATES TSTMS MAY DEVELOP S OF BOUNDARY AND MOVE
NWD...ANY OF WHICH COULD INTENSIFY QUICKLY UPON INTERACTING WITH
MESOBETA SCALE FRONTAL ZONE.

..EDWARDS.. 04/16/2009


ATTN...WFO...SJT...LUB...MAF...



Midland is 81ºF but with a dewpoint of 39ºF, Snyder, is 70ºF with a dewpoint of 56ºF. San Angelo is 76ºF and 60ºF.