April Weather Discussion.

[don]

I'm not really sure why some are saying we could use the rain we've had a wetter than normal winter and we've only recently got into a drier pattern we are nowhere near drought conditions....

[Ptarmigan]

What about peoples' Easter plans, Ptarmigan? Do you think that they would not be ruined if showers/thunderstorms were to come through this area this Sunday?

Actually, I checked NWS and it is suppose to rain on Friday. Sunday has a slight chance of rain. I don't think Sunday will be that rainy. I rather have it rain at night.

[Ptarmigan]

I'm not really sure why some are saying we could use the rain we've had a wetter than normal winter and we've only recently got into a drier pattern we are nowhere near drought conditions....

There is so much pollen and the rain could wash it away.

[wxdata]

What is SE Texas lacking that would cause severe thunderstorms to be much more feasible and widespread

Timing (upper air vs. surface features) and a persistant cap.

[sleetstorm]

So, warmer temperatures would assist in getting a stronger cap to form and stay just long to keep severe thunderstorms from forming too early or soon & keep ordinary thunderstorms from using up a majority of the fuel and leave the severe thunderstorms to struggle with only a very finite provision of fuel? That would save all of the ripe conditions for the really good severe thunderstorms to flourish off of and to really get going, yes or no? Honestly, I do believe that is the way that it works, or at least part of it anyway. Please tell me if I right notion or not.

[srainhoutx]

SPC expands Slight Risk area just a bit. Guidance may not be handling the storm system too well and we may not know the 'finer details' until Friday.




DAY 2 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CDT THU APR 01 2010

VALID 021200Z - 031200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS SRN/E-CENTRAL PLAINS
TO OZARKS AND ARKLATEX...

CORRECTED FOR 15% LINE

...SYNOPSIS...
ERN CONUS MEAN RIDGING AND WRN TROUGHING WILL DOMINATE UPPER AIR
PATTERN OVER CONUS THROUGH PERIOD. STG MID-UPPER LEVEL SHORTWAVE
TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER NRN/CENTRAL
CA AND JUST OFFSHORE SRN CA AS OF 01/05Z -- IS FCST TO MOVE EWD
ACROSS WRN CONUS DAY-1...REACHING NM AND CHIHUAHUA BY BEGINNING OF
DAY-2. THIS FEATURE WILL MOVE EWD ACROSS SRN HIGH PLAINS DURING
DAY...REACHING W-CENTRAL TX AND WRN OK BY 3/00Z...THEN TURNING
NEWD...ASSUMING SLGT NEGATIVE TILT...AND MOVING OVER ARKLATEX AND
OZARK REGIONS BY END OF PERIOD. REASONABLY STG CONSENSUS IS
SOMEWHAT FASTER THAN GUIDANCE FROM PREVIOUS DAYS WITH THIS
SYSTEM...SFC AND ALOFT.

MEANWHILE...LEADING SHORTWAVE TROUGH NOW OVER SRN NV WILL EJECT NEWD
TO DAKOTAS BY 2/12Z...CONTRIBUTING TO REGIME OF HIGH-AMPLITUDE
TROUGHING. QUASISTATIONARY UPPER LEVEL TROUGH AND WEAK EMBEDDED LOW
ARE EVIDENT IN MOISTURE CHANNEL IMAGERY OVER S-CENTRAL GULF NEAR
YUCATAN PENINSULA...SURROUNDED BY STG DRYING ALOFT AND ACCORDINGLY
IMPLIED SUBSIDENCE. NRN STREAM TROUGH - NOW EVIDENT S OF
ALEUTIANS...WILL MOVE SEWD AND AMPLIFY THROUGH PERIOD...REACHING
COASTAL PAC NW AND PERHAPS INLAND CASCADES BY 3/00Z.

AT SFC...FRONTAL ZONE IS ANALYZED FROM WY ACROSS SERN NEB AND SWRN
KS...CURVING NWWD INTO SERN CO..WHERE WEAK CYCLONE IS DRAWN AT ITS
INTERSECTION WITH LEE TROUGH THAT EXTENDS SSEWD ACROSS ERN NM/TX
BORDER REGION. MAIN SFC LOW SHOULD CONSOLIDATE OVER CO DAY-1...THEN
EJECT NEWD AS FRONTAL-WAVE CYCLONE LATE DAY-1 INTO EARLY DAY-2...IN
ADVANCE OF LEAD SHORTWAVE. THIS LOW SHOULD BE LOCATED OVER MN
AROUND BEGINNING OF PERIOD...WITH COLD FRONT SWWD ACROSS ERN
NEB...CENTRAL KS AND NWRN OK. WEAKER/PACIFIC ORIGIN FRONTAL ZONE
AND EFFECTIVE DRYLINE WILL EXTEND SSWWD ACROSS NWRN/WRN OK TO BIG
BEND REGION...WHILE MORE PURE DRYLINE BOUNDARY SPLITS OFF OVER SW TX
AND EXTENDS SSEWD ACROSS ERN COAHUILA. BY 3/00Z...EXPECT COLD FRONT
FROM IA TO CENTRAL MO TO SRN OK AND NW TX...WITH PRECEDING
FRONT/DRYLINE FROM N-CENTRAL TX SWD/SSWWD OVER LOWER RIO GRANDE
VALLEY. BY END OF PERIOD...LATTER BOUNDARY SHOULD REACH ROUGHLY
FROM MID MS VALLEY SWWD ACROSS ERN AR...CENTRAL/SRN LA AND NWRN
GULF.

...SRN/E-CENTRAL PLAINS TO OZARKS AND ARKLATEX...
MULTI-MODAL SVR EPISODE POSSIBLE THROUGH PERIOD...BUT WITH ENOUGH
LIMITING FACTORS STILL EVIDENT TO KEEP PROBABILISTIC MAXIMA WITHIN
CATEGORICAL SLGT-RISK BIN. WRN PART OF OUTLOOK OVER OK/KS
REPRESENTS CONTINUING SVR POTENTIAL FROM LATE DAY-1 PERIOD...AS LINE
OF TSTMS MOVES EWD ACROSS PORTIONS OF THIS REGION WITH POTENTIAL FOR
SVR GUSTS/HAIL. THIS ACTIVITY SHOULD MOVE NEWD EARLY IN PERIOD
WHILE BACKBUILDING SWD...EFFECTIVELY EXPANDING INTO NARROW CORRIDOR
OF ADEQUATE --- BUT NOT IDEAL -- RETURN-FLOW MOISTURE PLUME AHEAD OF
SFC FRONT. ANTECEDENT CLOUD COVER COULD LIMIT FAVORABLE DIURNAL
HEATING TO NARROW CORRIDOR AHEAD OF MAIN CONVERGENCE ZONE...HOWEVER
STRENGTH OF DEEP-LAYER WIND FIELDS SUGGESTS SVR THREAT EVEN AMIDST
WEAK MLCAPE UNDER 1000 J/KG. POSSIBLE DEVELOPMENT OF WEAK
FRONTAL-WAVE LOW OVER OK DURING MIDDAY...WHICH THEN WOULD MOVE
NEWD...ALSO MAY FOCUS ADDITIONAL LOW-LEVEL LIFT.

GREATEST JUXTAPOSITION OF SHEAR AND BUOYANCY MAY BE DURING AFTERNOON
FROM ERN/SRN OK SWD ACROSS CENTRAL TX. IN THAT CORRIDOR...STRONGER
AND LONGER-DURATION SFC HEATING...ALONG WITH SFC DEW POINTS REACHING
60S F AND LIFT INVOF FRONT/DRYLINE...MAY BE SUFFICIENT TO OVERCOME
INITIALLY STRONG CAPPING THAT IS LIKELY AT BASE OF ELEVATED MIXED
LAYER. SUPERCELLS AS WELL AS LINEAR MODES ARE POSSIBLE...WITH LARGE
HAIL...SVR GUSTS AND PERHAPS THREAT OF TORNADOES. SVR THREAT WILL
TRANSLATE EWD INTO WRN AR AND NE TX DURING NIGHTTIME
HOURS...POSSIBLY BUILDING SWD INTO E-CENTRAL/SE TX. SWD EXTENT OF
SUCH DEVELOPMENT WILL BE LIMITED BY STG CINH. SVR POTENTIAL WILL
DIMINISH WITH TIME DURING MID-LATE OVERNIGHT HOURS -- I.E. AFTER
ABOUT 03/06Z...AS UPPER SYSTEM BEGINS TO EJECT AND AS ZONE OF
STRONGEST LOW-LEVEL FORCING EFFECTIVELY OUTPACES EWD SHIFT OF
FAVORABLY UNSTABLE CORRIDOR OF SFC-BASED INFLOW.

....LOWER MO VALLEY TO UPPER MS VALLEY...
BAND OF STG-SVR TSTMS MAY DEVELOP DURING DAY AS FRONTAL FORCING
IMPINGES UPON INCREASING LOW-LEVEL THETAE IN NARROW CORRIDOR FROM
MO-MN. DEEP-LAYER WIND FIELDS WILL BE STG...WITH 50-60 KT EFFECTIVE
SHEAR...BUT ALSO...LIMITED DIABATIC DESTABILIZATION AND MEAN WIND
NEARLY PARALLEL TO BOUNDARY. MLCAPE 500-700 J/KG APPEARS
POSSIBLE...WITH PREDOMINANT LINEAR CONVECTIVE MODE...WITH BOW/LEWP
DEVELOPMENT POSING SOME RISK OF STG-SVR GUSTS OR A BRIEF TORNADO.
SVR POTENTIAL APPEARS TOO CONDITIONAL TO EXTEND CATEGORICAL RISK
THIS FAR N ATTM.

...INLAND PAC NW...
ISOLATED AND PERHAPS WIDELY SCATTERED TSTMS WILL BE POSSIBLE IN
ZONES OF STG LOW-LEVEL WAA AND MID-UPPER LEVEL DPVA PRECEDING
LANDFALLING SHORTWAVE TROUGH. FCST DEEP-LAYER SHEAR PROFILES ALONE
WOULD INDICATE SOME POTENTIAL FOR STG-SVR TSTMS...AND POCKETS OF
SUPPORTIVE SFC HEATING MAY DEVELOP. FCST SOUNDINGS SUGGEST RATHER
MEAGER LOW-LEVEL THETAE...LIMITING BUOYANCY SIGNIFICANTLY.
HOWEVER...ONLY SLGT INCREASE VERSUS CONSENSUS OF CURRENT PROGS WOULD
BE NEEDED TO SUPPORT SOME SVR POTENTIAL. ATTM...THREAT APPEARS TOO
CONDITIONAL TO INTRODUCE PROBABILITIES.

..EDWARDS.. 04/01/2010

[srainhoutx]

HGX thoughts this morning. Good call wxdata. We discussed and you mentioned a couple of days ago that it appeared that the front may stall near SE TX and retreat as a warm front during the weekend as warm air advection returned rather quickly.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
536 AM CDT THU APR 1 2010

.DISCUSSION...
COMPUTER SERVER ISSUES EARLIER DURING THE EVENING KEPT THE 00Z GFS
OUT OF AWIPS AND THE GFE THIS MORNING. HOWEVER...WORKING WITH A
COMBINATION OF AWIPS AND THE INTERNET...WAS ABLE TO GO THROUGH THE
ENTIRE MODEL SUITE.

AT LEAST THREE EPISODES OF SHOWERS AND THUNDERSTORMS WILL AFFECT
SE TX OVER THE NEXT SEVEN DAYS. A SLIGHT CHANCE OF SEVERE WEATHER
WILL ACCOMPANY THE FIRST ROUND ON FRIDAY...AT LEAST FOR THE
NORTHERN PORTIONS OF THE FORECAST AREA. RAIN CHANCES RETURN ON
SUNDAY AND THEN AGAIN BY WEDNESDAY.

A STRONG UPPER TROUGH WILL PUSH ACROSS NORTH TEXAS ON FRIDAY WITH
THE SOUTHERN FRINGES OF THE SYSTEM AFFECTING SE TX. THE 06Z MODEL
RUNS WERE INDICATING THAT A SQUALL LINE WILL LIKELY MOVE ACROSS
THE NORTHERN THIRD OF THE AREA SOMETIME BETWEEN THE LATE AFTERNOON
AND LATE EVENING. ADDITIONAL SHOWERS AND THUNDERSTORMS WILL
PROBABLY DEVELOP ALONG THE COLD FRONT AS IT PUSHES ACROSS THE
REMAINDER OF THE AREA DURING THE EVENING AND EARLY MORNING HOURS.

ISOLATED SEVERE WEATHER CHANCES WILL MAINLY OCCUR AS THE LINE OF
STORMS MOVES ACROSS THE NORTHERN THIRD OF THE AREA. THE MODEL
BUFR SOUNDINGS FORECAST A STRONG CAP IN PLACE THROUGH MID FRIDAY
AFTERNOON. THERE WILL ALSO BE A LOW-LEVEL INVERSION IN PLACE
THURSDAY NIGHT THROUGH ABOUT MIDDAY FRIDAY. WITH THE ABUNDANT LOW-
LEVEL MOISTURE IN PLACE...THIS INDICATES THAT A STRATUS DECK WILL
BE IN PLACE POSSIBLY INTO THE AFTERNOON. THAT WOULD LIMIT THE
HEATING FOR STORM DEVELOPMENT AHEAD OF THE COLD FRONT. THERE IS
SOME UNCERTAINTY ON HOW FAR SOUTH THE STRONGEST STORMS WILL
EXTEND. SO...INSERTED CHANCES FOR SEVERE STORMS IN THE NORTHERN
COUNTIES AND WILL ADDRESS THE SEVERE POSSIBILITIES ELSEWHERE IN
THE HAZARDOUS WEATHER OUTLOOK.

SATURDAY NIGHT AND SUNDAY BOTH THE ECMWF AND GFS RETURN ONSHORE
WINDS AND WARM AIR ADVECTION ACROSS SE TX. BOTH INTRODUCE RAIN
CHANCES AND INDICATE THAT ISOLATED THUNDERSTORMS WILL BE POSSIBLE
BY MID MORNING SUNDAY.

RAIN CHANCES LATE TUESDAY AND WEDNESDAY WILL BE DUE TO ANOTHER
STORM SYSTEM THAT IS EXPECTED TO MOVE ACROSS THE PLAINS.

[srainhoutx]

09Z SREF data looks rather impressive for Central TX and points N and E.

[wxdata]

It seems they are now pointing at late afternoon/early evening Friday for storms passage.

NWS Houston's late morning update:

"THE CAPPING INVERSION WILL REMAIN IN PLACE ON FRIDAY SO AM NOT SURE HOW MUCH CONVECTION WILL FIRE.
NO CHANGES PLANNED FOR FRIDAY AT THIS TIME BUT CURRENT INCLINATION IS THAT POPS WILL BE LOWERED SOUTH OF I-10 ON FRI-FRI NITE."

[wxdata]

Nice graphic from Ft. Worth's NWS

[srainhoutx]

SPC makes some changes to the Slight Risk threat. Areas in Central TX have been removed and things have shifted a bit N and E. With that said and the way guidance is flip flopping from run to run, tomorrow will be interesting to watch unfold...





SPC AC 011720

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1220 PM CDT THU APR 01 2010

VALID 021200Z - 031200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID MO VALLEY REGION
SWD INTO E TX AND EWD INTO THE OZARKS/ARKLATEX AREAS...

...SYNOPSIS...
HIGHLY-AMPLIFIED FLOW PATTERN IS FORECAST TO PERSIST ALOFT THIS
PERIOD...ESPECIALLY OVER THE ERN 2/3 OF THE U.S. AS A TROUGH
EJECTING INTO THE CENTRAL PLAINS IMPINGES ON A STEADFAST RIDGE OVER
THE EAST. MEANWHILE...A SECOND TROUGH IS PROGGED TO MOVE ONSHORE
OVER THE PAC NW THROUGH THE FIRST HALF OF THE PERIOD...BUT THEN
WEAKEN OVERNIGHT AS IT SHIFTS INLAND.

AT THE SURFACE...LOW PRESSURE IS FORECAST TO MOVE SLOWLY ENEWD
ACROSS MN AND VICINITY...WHILE A TRAILING N-S COLD FRONT SHIFTS
ACROSS THE PLAINS STATES THROUGH THE DAY AND INTO THE MS VALLEY
REGION LATE IN THE PERIOD.

...MID MO VALLEY SWD INTO ERN TX AND EWD TO THE OZARKS/ARKLATEX...
THUNDERSTORMS -- AND AT LEAST SOME HAIL/WIND THREAT -- SHOULD BE
ONGOING AT THE START OF THE PERIOD...MAINLY FROM CENTRAL KS SWD INTO
WRN PORTIONS OF N TX ALONG/AHEAD OF THE ADVANCING COLD FRONT. VERY
MODEST INSTABILITY EARLY IN THE DAY SHOULD INCREASE A BIT INTO THE
AFTERNOON AHEAD OF THE ONGOING CONVECTION...AS A NARROW PLUME OF
LOW-LEVEL MOIST ADVECTION CONTINUES AHEAD OF THE FRONT.
HOWEVER...THE SLOW INCREASE IN BOUNDARY-LAYER MOISTENING WILL BE AT
LEAST SOMEWHAT OFFSET BY WHAT SHOULD BE FAIRLY EXPANSIVE PRE-FRONTAL
CLOUDINESS -- SUFFICIENT TO RETARD DAYTIME HEATING TO SOME DEGREE.
NONETHELESS...EXPECT CONVECTION TO EXPAND NNEWD ALONG THE FRONT
TOWARD/ACROSS THE MID MO VALLEY REGION...AND ALSO SWD INTO E CENTRAL
TX -- THOUGH INCREASING CAPPING WITH SWD EXTENT ACROSS TX SHOULD ACT
AS A HINDRANCE TO SWD DEVELOPMENT DESPITE SOMEWHAT MORE FAVORABLE
THERMODYNAMIC EVOLUTION.

WHILE LARGELY MERIDIONAL...DEEP-LAYER WIND FIELD WILL BE QUITE
STRONG...SUPPORTIVE OF ORGANIZED/ROTATING STORMS. MEAN WIND ROUGHLY
PARALLEL TO THE FRONT SUGGESTS A PRIMARILY LINEAR STORM MODE --
POSSIBLY WITH A FEW EMBEDDED ROTATING STORMS/COMMA HEADS. DAMAGING
WINDS SHOULD BE THE MOST SIGNIFICANT SEVERE POTENTIAL...THOUGH
MARGINALLY-SEVERE HAIL MAY BE THE MORE WIDESPREAD SEVERE WEATHER
OCCURRENCE. AN ISOLATED TORNADO OR TWO ALSO CANNOT BE RULED OUT --
WITH THE GREATEST POTENTIAL APPARENT ACROSS E TX WHERE GREATER
LOW-LEVEL MOISTURE AND THUS INSTABILITY ALONG WITH SOMEWHAT LESS
MERIDIONAL FLOW FIELD IS EXPECTED.

THE LINE OF CONVECTION SHOULD CONTINUE EWD OVERNIGHT...WEAKENING
SIGNIFICANTLY AFTER SUNSET ACROSS NRN PORTIONS OF THE RISK
AREA...BUT REMAINING MORE ORGANIZED/POTENTIALLY SEVERE INTO THE
OVERNIGHT HOURS FARTHER S AS STORMS MOVE ACROSS THE OZARKS/ARKLATEX
REGION THROUGH THE END OF THE PERIOD.

..GOSS.. 04/01/2010

[sleetstorm]

SPC expands Slight Risk area just a bit. Guidance may not be handling the storm system too well and we may not know the 'finer details' until Friday.




DAY 2 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CDT THU APR 01 2010

VALID 021200Z - 031200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS SRN/E-CENTRAL PLAINS
TO OZARKS AND ARKLATEX...

CORRECTED FOR 15% LINE

...SYNOPSIS...
ERN CONUS MEAN RIDGING AND WRN TROUGHING WILL DOMINATE UPPER AIR
PATTERN OVER CONUS THROUGH PERIOD. STG MID-UPPER LEVEL SHORTWAVE
TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER NRN/CENTRAL
CA AND JUST OFFSHORE SRN CA AS OF 01/05Z -- IS FCST TO MOVE EWD
ACROSS WRN CONUS DAY-1...REACHING NM AND CHIHUAHUA BY BEGINNING OF
DAY-2. THIS FEATURE WILL MOVE EWD ACROSS SRN HIGH PLAINS DURING
DAY...REACHING W-CENTRAL TX AND WRN OK BY 3/00Z...THEN TURNING
NEWD...ASSUMING SLGT NEGATIVE TILT...AND MOVING OVER ARKLATEX AND
OZARK REGIONS BY END OF PERIOD. REASONABLY STG CONSENSUS IS
SOMEWHAT FASTER THAN GUIDANCE FROM PREVIOUS DAYS WITH THIS
SYSTEM...SFC AND ALOFT.

MEANWHILE...LEADING SHORTWAVE TROUGH NOW OVER SRN NV WILL EJECT NEWD
TO DAKOTAS BY 2/12Z...CONTRIBUTING TO REGIME OF HIGH-AMPLITUDE
TROUGHING. QUASISTATIONARY UPPER LEVEL TROUGH AND WEAK EMBEDDED LOW
ARE EVIDENT IN MOISTURE CHANNEL IMAGERY OVER S-CENTRAL GULF NEAR
YUCATAN PENINSULA...SURROUNDED BY STG DRYING ALOFT AND ACCORDINGLY
IMPLIED SUBSIDENCE. NRN STREAM TROUGH - NOW EVIDENT S OF
ALEUTIANS...WILL MOVE SEWD AND AMPLIFY THROUGH PERIOD...REACHING
COASTAL PAC NW AND PERHAPS INLAND CASCADES BY 3/00Z.

AT SFC...FRONTAL ZONE IS ANALYZED FROM WY ACROSS SERN NEB AND SWRN
KS...CURVING NWWD INTO SERN CO..WHERE WEAK CYCLONE IS DRAWN AT ITS
INTERSECTION WITH LEE TROUGH THAT EXTENDS SSEWD ACROSS ERN NM/TX
BORDER REGION. MAIN SFC LOW SHOULD CONSOLIDATE OVER CO DAY-1...THEN
EJECT NEWD AS FRONTAL-WAVE CYCLONE LATE DAY-1 INTO EARLY DAY-2...IN
ADVANCE OF LEAD SHORTWAVE. THIS LOW SHOULD BE LOCATED OVER MN
AROUND BEGINNING OF PERIOD...WITH COLD FRONT SWWD ACROSS ERN
NEB...CENTRAL KS AND NWRN OK. WEAKER/PACIFIC ORIGIN FRONTAL ZONE
AND EFFECTIVE DRYLINE WILL EXTEND SSWWD ACROSS NWRN/WRN OK TO BIG
BEND REGION...WHILE MORE PURE DRYLINE BOUNDARY SPLITS OFF OVER SW TX
AND EXTENDS SSEWD ACROSS ERN COAHUILA. BY 3/00Z...EXPECT COLD FRONT
FROM IA TO CENTRAL MO TO SRN OK AND NW TX...WITH PRECEDING
FRONT/DRYLINE FROM N-CENTRAL TX SWD/SSWWD OVER LOWER RIO GRANDE
VALLEY. BY END OF PERIOD...LATTER BOUNDARY SHOULD REACH ROUGHLY
FROM MID MS VALLEY SWWD ACROSS ERN AR...CENTRAL/SRN LA AND NWRN
GULF.

...SRN/E-CENTRAL PLAINS TO OZARKS AND ARKLATEX...
MULTI-MODAL SVR EPISODE POSSIBLE THROUGH PERIOD...BUT WITH ENOUGH
LIMITING FACTORS STILL EVIDENT TO KEEP PROBABILISTIC MAXIMA WITHIN
CATEGORICAL SLGT-RISK BIN. WRN PART OF OUTLOOK OVER OK/KS
REPRESENTS CONTINUING SVR POTENTIAL FROM LATE DAY-1 PERIOD...AS LINE
OF TSTMS MOVES EWD ACROSS PORTIONS OF THIS REGION WITH POTENTIAL FOR
SVR GUSTS/HAIL. THIS ACTIVITY SHOULD MOVE NEWD EARLY IN PERIOD
WHILE BACKBUILDING SWD...EFFECTIVELY EXPANDING INTO NARROW CORRIDOR
OF ADEQUATE --- BUT NOT IDEAL -- RETURN-FLOW MOISTURE PLUME AHEAD OF
SFC FRONT. ANTECEDENT CLOUD COVER COULD LIMIT FAVORABLE DIURNAL
HEATING TO NARROW CORRIDOR AHEAD OF MAIN CONVERGENCE ZONE...HOWEVER
STRENGTH OF DEEP-LAYER WIND FIELDS SUGGESTS SVR THREAT EVEN AMIDST
WEAK MLCAPE UNDER 1000 J/KG. POSSIBLE DEVELOPMENT OF WEAK
FRONTAL-WAVE LOW OVER OK DURING MIDDAY...WHICH THEN WOULD MOVE
NEWD...ALSO MAY FOCUS ADDITIONAL LOW-LEVEL LIFT.

GREATEST JUXTAPOSITION OF SHEAR AND BUOYANCY MAY BE DURING AFTERNOON
FROM ERN/SRN OK SWD ACROSS CENTRAL TX. IN THAT CORRIDOR...STRONGER
AND LONGER-DURATION SFC HEATING...ALONG WITH SFC DEW POINTS REACHING
60S F AND LIFT INVOF FRONT/DRYLINE...MAY BE SUFFICIENT TO OVERCOME
INITIALLY STRONG CAPPING THAT IS LIKELY AT BASE OF ELEVATED MIXED
LAYER. SUPERCELLS AS WELL AS LINEAR MODES ARE POSSIBLE...WITH LARGE
HAIL...SVR GUSTS AND PERHAPS THREAT OF TORNADOES. SVR THREAT WILL
TRANSLATE EWD INTO WRN AR AND NE TX DURING NIGHTTIME
HOURS...POSSIBLY BUILDING SWD INTO E-CENTRAL/SE TX. SWD EXTENT OF
SUCH DEVELOPMENT WILL BE LIMITED BY STG CINH. SVR POTENTIAL WILL
DIMINISH WITH TIME DURING MID-LATE OVERNIGHT HOURS -- I.E. AFTER
ABOUT 03/06Z...AS UPPER SYSTEM BEGINS TO EJECT AND AS ZONE OF
STRONGEST LOW-LEVEL FORCING EFFECTIVELY OUTPACES EWD SHIFT OF
FAVORABLY UNSTABLE CORRIDOR OF SFC-BASED INFLOW.

....LOWER MO VALLEY TO UPPER MS VALLEY...
BAND OF STG-SVR TSTMS MAY DEVELOP DURING DAY AS FRONTAL FORCING
IMPINGES UPON INCREASING LOW-LEVEL THETAE IN NARROW CORRIDOR FROM
MO-MN. DEEP-LAYER WIND FIELDS WILL BE STG...WITH 50-60 KT EFFECTIVE
SHEAR...BUT ALSO...LIMITED DIABATIC DESTABILIZATION AND MEAN WIND
NEARLY PARALLEL TO BOUNDARY. MLCAPE 500-700 J/KG APPEARS
POSSIBLE...WITH PREDOMINANT LINEAR CONVECTIVE MODE...WITH BOW/LEWP
DEVELOPMENT POSING SOME RISK OF STG-SVR GUSTS OR A BRIEF TORNADO.
SVR POTENTIAL APPEARS TOO CONDITIONAL TO EXTEND CATEGORICAL RISK
THIS FAR N ATTM.

...INLAND PAC NW...
ISOLATED AND PERHAPS WIDELY SCATTERED TSTMS WILL BE POSSIBLE IN
ZONES OF STG LOW-LEVEL WAA AND MID-UPPER LEVEL DPVA PRECEDING
LANDFALLING SHORTWAVE TROUGH. FCST DEEP-LAYER SHEAR PROFILES ALONE
WOULD INDICATE SOME POTENTIAL FOR STG-SVR TSTMS...AND POCKETS OF
SUPPORTIVE SFC HEATING MAY DEVELOP. FCST SOUNDINGS SUGGEST RATHER
MEAGER LOW-LEVEL THETAE...LIMITING BUOYANCY SIGNIFICANTLY.
HOWEVER...ONLY SLGT INCREASE VERSUS CONSENSUS OF CURRENT PROGS WOULD
BE NEEDED TO SUPPORT SOME SVR POTENTIAL. ATTM...THREAT APPEARS TOO
CONDITIONAL TO INTRODUCE PROBABILITIES.

..EDWARDS.. 04/01/2010

I agree srainhoutx, eveyone in this forum may not know what to expect until the day of the event which is tomorrow into Saturday morning. The timing for severe thunderstorms to develop in southeast Texas just may be right.

[Ptarmigan]

GFS- storms miss us to the North, then the line grows Southward after missing Houston.

About a tenth or less both NAM and GFS. Happens all the time here in Spring. NAM looks particularly nasty TUL to MCI.

Cool surface temps, and a moderate cap about 850 to 700 mb look to keep us mostly dry. 60sF temps at 7 pm Friday, looks like NAM predicting low stratus that never mixes out.



GFS doesn't exactly show a cap, just cool surface temps, and pretty lame lapse rates up to about 650 mb.

Cold water in the Northern Gulf probably cools the near surface airmass, and produces low clouds, which further limit heating.



62.6ºF off Galveston. Wet suit weather. Good thing most rigs have survival suits.

This cooler March has kept a lid on severe weather.

[sleetstorm]

srainhoutx, what about during the night time hours? Does it matter if there are stratus clouds completely covering the sky or no? I am guessing no, but I could be wrong. During the day, yes, we do need full sun in order to be able to get the essential instability that is required to cause thundestorms to form and keep them going until they run out of fuel such as dew points in the sixties and seventies and temperatures in the seventies and warmer, & strong wind shear. Those are just some of the essential components that thunderstorms need to form and become severe.

[srainhoutx]

MESOSCALE DISCUSSION 0233
NWS STORM PREDICTION CENTER NORMAN OK
1150 PM CDT THU APR 01 2010

AREAS AFFECTED...SOUTH CENTRAL NEB/CENTRAL KS TO WESTERN/CENTRAL OK
AND WESTERN NORTH TX

CONCERNING...SEVERE THUNDERSTORM WATCH 41...

VALID 020450Z - 020615Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 41
CONTINUES.

SEVERE TSTM WATCH 41 CONTINUES UNTIL 09Z...WITH A CONTINUED RISK FOR
SEVERE HAIL/DAMAGING WINDS.

MODESTLY BROKEN/NNE-SSW ORIENTED QUASI-LINEAR CONVECTIVE LINE
CONTINUES TO STEADILY PROGRESS EASTWARD ACROSS FAR SOUTH CENTRAL
NEB/CENTRAL KS/NORTHWEST OK EARLY IN THE OVERNIGHT. ADDITIONAL
DEVELOPMENT HAS RECENTLY BEEN NOTED NEAR/SOUTH OF I-40 IN WESTERN
OK...AND THIS MAY ULTIMATELY WARRANT A SOUTHWARD EXPANSION OF SEVERE
TSTM WATCH 41...WITH THE POSSIBILITY OF SOUTHWARD DEVELOPMENT
PERHAPS INTO THE WESTERN PART OF NORTH TX OVER THE NEXT SEVERAL
HOURS.

THE SEVERE EPISODE MAY HAVE ALREADY PEAKED ACROSS MUCH OF CENTRAL
KS/SOUTH CENTRAL NEB GIVEN A DOMINATE LINEAR CONVECTIVE MODE AND A
MODEST/NARROW WARM SECTOR AHEAD OF THE QLCS. NONETHELESS...MAINLY
MARGINAL HAIL/GUSTY WINDS WILL REMAIN POSSIBLE. FARTHER SOUTH...THE
SEVERE THREAT MAY INCREASE TO A DEGREE OVER THE NEXT SEVERAL HOURS
ACROSS WESTERN INTO CENTRAL OK...AS WELL AS ADJACENT PORTIONS OF
NORTH TX. SOME SUPERCELL STRUCTURES CAPABLE OF HAIL MAY BE THE
PRIMARY RISK INITIALLY...BUT NEAR-SEVERE WINDS/PERHAPS EVEN A
TORNADO CANNOT BE RULED OUT WITH MODAL EVOLUTIONS LATER
TONIGHT...ESPECIALLY WHERE SURFACE DEWPOINTS REACH AROUND 60F OR
ABOVE /BASED ON ADJUSTED MODEL SOUNDINGS/.

..GUYER.. 04/02/2010


ATTN...WFO...OAX...TOP...ICT...OUN...GID...DDC...

[srainhoutx]

HGX thoughts this morning...cap looks to be the limiting factor, but I do see some breaks in the low stratus deck and drizzle in NW Harris County this morning. We shall see...

TIGHT SFC PRESSURE GRADIENT RESULTING IN GUSTY SOUTH WINDS ACROSS
THE CWA EARLY THIS MORNING. SFC DEWPOINTS HAVE CLIMBED INTO THE
LOWER/MID 60S...BUT LOW LEVEL MOISTURE REMAINS QUITE SHALLOW WITH
PWS STILL UNDER AN INCH OVER THE AREA. AXIS OF LOW LEVEL JET WILL
SHIFT OVER THE AREA TODAY WHICH WILL ALLOW PWS TO INCREASE TO
1.4-1.6 INCHES BY MIDDAY. UPPER TROUGH NOW OVER NEW MEXICO WILL
SHIFT EAST ACROSS THE SRN PLAINS TODAY. ASSOCIATED SFC DRYLINE NOW
OVER WEST TX WILL APPROACH THE WESTERN CWA LATE THIS AFTN THEN
PUSH SLOWLY ACROSS SE TX TONIGHT. 00Z CRP/LCH SOUNDINGS SHOWED A
MONSTROUS CAP IN THE 700-900 MB LAYER WHICH IS GOING TO BE
DIFFICULT TO OVERCOME. IN ADDITION...EXTENSIVE CLOUD COVER ACROSS
THE AREA TODAY IS LIKELY TO LIMIT SFC HEATING. GFS BUFR SOUNDINGS
EVEN AT KLFK SHOW THE LIKELIHOOD OF THE CAP HOLDING MOST OF THE
DAY. AT 00Z...GFS SHOWS THE BEST LOW LEVEL INSTABILITY (CAPES
1000-2000 J/KG) OVER THE FAR WESTERN/NORTHERN AREAS GENERALLY
WEST OF AN EDNA TO NAVASOTA TO CROCKETT LINE JUST AHEAD OF THE
DRYLINE. SO EXPECTING SEVERE THREAT TO BE LIMITED TO FAR NRN/WRN
ZONES LATE AFTN/EARLY EVENING. THE PRIMARY SEVERE WEATHER THREAT
WILL BE DAMAGING WINDS AND HAIL BUT STRONG LOW LEVEL SHEAR
SUPPORTS AN ISOLATED TORNADO THREAT AS WELL. THE CONVECTION
EXPECTED TO WEAKEN AS IT PUSHES EASTWARD THROUGH THE AREA THIS
EVENING AS AIRMASS QUICKLY STABILIZES. HAVE TAPERED POPS FROM
LIKELY FAR NORTH TO 20S/30S COAST.

[srainhoutx]

SPC Day 1 Update should be out shortly. There is a Severe T Storm Warning NE of OKC at the hour. Could be a busy day.

[srainhoutx]

SPC Update expands the Slight Risk Area...









DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0750 AM CDT FRI APR 02 2010

VALID 021300Z - 031200Z

...THERE IS A SLGT RISK OF SVR TSTMS TODAY INTO TONIGHT FOR E
TX...ERN OK...MO...AR..AND WRN MS...

...SYNOPSIS...
AN INITIAL SHORTWAVE TROUGH AND ASSOCIATED SURFACE CYCLONE WILL MOVE
NEWD FROM ERN SD TO WRN ONTARIO THROUGH TONIGHT. A TRAILING COLD
FRONT AND REMNANT DRYLINE WILL CONTINUE EWD ACROSS THE CENTRAL/SRN
PLAINS...AS THE PRIMARY MID LEVEL TROUGH EJECTS EWD FROM ERN NM/W TX
THIS MORNING TO AR BY TONIGHT.

...N TX INTO CENTRAL/NE OK THIS MORNING...
AN ONGOING BAND OF THUNDERSTORMS /ROOTED NEAR THE GROUND/ WILL
LIKELY PERSIST AND MOVE EWD THROUGH THE MORNING IN THE VICINITY OF
THE REMNANT DRYLINE/COLD FRONT. THIS CONVECTION HAS BEEN SUPPORTED
BY A BELT OF ASCENT IN ADVANCE OF THE SRN HIGH PLAINS SHORTWAVE
TROUGH...WHICH IS MOVING EWD PER WATER VAPOR IMAGERY AND THE
BACKING/ STRENGTHENING FLOW ALOFT NOTED IN REGIONAL PROFILER PLOTS
ACROSS OK/TX. MEANWHILE...AN INFLUX OF BOUNDARY LAYER DEWPOINTS OF
60-65 F ACROSS TX/OK BENEATH THE REMNANTS OF A STEEP MID LEVEL LAPSE
RATE PLUME WILL PROVIDE SUFFICIENT INSTABILITY /MUCAPE OF 1000-1500
J PER KG/ TO MAINTAIN A RISK FOR AT LEAST ISOLATED LARGE HAIL AND
DAMAGING WINDS THROUGH THE MORNING. DEEP-LAYER AND LOW-LEVEL
VERTICAL SHEAR WILL BE FAVORABLE FOR EMBEDDED SUPERCELL AND/OR
BOWING STRUCTURES...ESPECIALLY THIS MORNING WHILE THE LLJ REMAINS
QUITE STRONG ACROSS N TX AND CENTRAL/ERN OK.

...E TX/ERN OK/WRN AR/MO THIS AFTERNOON/EVENING...
THE REMAINS OF THE MORNING CONVECTION WILL LIKELY INTENSIFY DURING
THE AFTERNOON FROM E TX NWD ACROSS ERN OK/WRN AR AS LOW-LEVEL
MOISTURE CONTINUES TO SPREAD NWD...AND AS THE W TX SHORTWAVE TROUGH
REACHES CENTRAL TX AND DOWNSTREAM ASCENT STRENGTHENS. WARM SECTOR
INSTABILITY WILL NOT BE PARTICULARLY STRONG /MLCAPE VALUES AOB 1000
J PER KG/...BUT DEEP-LAYER VERTICAL SHEAR WILL REMAIN FAVORABLE FOR
EMBEDDED BOWING/ROTATING STORMS WITH AN ATTENDANT THREAT FOR
DAMAGING WINDS...HAIL...AND A TORNADO OR TWO. THIS CONVECTION WILL
THEN SPREAD EWD ACROSS LA/AR THROUGH THE OVERNIGHT HOURS...AND
NWD/NEWD ACROSS MO/IL...THOUGH THE SEVERE STORM THREAT FARTHER N AND
OVERNIGHT WILL BE LIMITED BY WEAK INSTABILITY.

...LA/WRN MS OVERNIGHT...
THE STRONG SHORTWAVE TROUGH WILL PIVOT EWD/ENEWD OVER NRN LA/AR
OVERNIGHT AND CONTRIBUTE TO STRONG VERTICAL SHEAR WITHIN THE WARM
SECTOR. SOME CONTINUED INCREASE IN MOISTURE OVERNIGHT WILL HELP
MAINTAIN INSTABILITY AND THE POTENTIAL FOR STORMS ROOTED AT OR NEAR
THE GROUND. ISOLATED DAMAGING WINDS...AND PERHAPS A TORNADO...WILL
REMAIN POSSIBLE INTO EARLY SATURDAY AS CONVECTION REACHES THE MS
RIVER IN ADVANCE OF THE COLD FRONT.

..THOMPSON/ROGERS.. 04/02/2010

[srainhoutx]

MESOSCALE DISCUSSION 0236
NWS STORM PREDICTION CENTER NORMAN OK
0759 AM CDT FRI APR 02 2010

AREAS AFFECTED...NE TX

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 021259Z - 021430Z

HAIL AND ISOLATED DAMAGING WIND GUSTS WILL BE POSSIBLE AS STORMS
INCREASE IN COVERAGE ACROSS NE TX OVER THE NEXT FEW HOURS. WW
ISSUANCE MAY BE NEEDED ACROSS THE REGION DEPENDING ON HOW THE
SITUATION UNFOLDS THIS MORNING.

THUNDERSTORMS ARE CURRENTLY INITIATING WEST OF THE DALLAS/FORT WORTH
METROPLEX ALONG A COLD FRONT AND ON THE WRN EDGE OF A CORRIDOR OF
LOW-LEVEL MOISTURE. SFC DEWPOINTS ACROSS NE TX ARE STEADILY
INCREASING AND SHOULD REACH THE MID 60S F AHEAD OF THE STORMS OVER
THE NEXT FEW HOURS. THIS COMBINED WITH INCREASING DEEP LAYER SHEAR
AND INSTABILITY MAY SUPPORT ISOLATED SUPERCELL DEVELOPMENT. IN
ADDITION...OBJECTIVE ANALYSIS SHOWS A 40 TO 50 KT LOW-LEVEL JET IN
EAST TX. MODEL FORECASTS MOVE THE LOW-LEVEL JET NNEWD ACROSS NE TX
THIS MORNING SUGGESTING LOW-LEVEL FLOW MAY BECOME MORE FAVORABLE FOR
A WIND DAMAGE THREAT ESPECIALLY IF A LINE CAN ORGANIZE. STEEP
MID-LEVEL LAPSE RATES SHOULD ALSO BE SUFFICIENT FOR AN ISOLATED
LARGE HAIL THREAT WITH THE STRONGER CORES.

..BROYLES.. 04/02/2010


ATTN...WFO...FWD...

[srainhoutx]

Perhaps a bit more daytime heating than previously thought as stratus deck is not that thick and a little destabilization could get things firing.