SPC Severe Thunderstorm Watch 203

WW 203 SEVERE TSTM KS NM OK TX 292210Z – 300600Z

WW 0203 Thumbnail Image


URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 203
NWS STORM PREDICTION CENTER NORMAN OK
510 PM CDT SUN APR 29 2012

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

       SOUTHWEST KANSAS
       FAR NORTHEAST NEW MEXICO
       FAR NORTHWEST OKLAHOMA AND THE OKLAHOMA PANHANDLE
       NORTHERN TEXAS PANHANDLE

EFFECTIVE THIS SUNDAY AFTERNOON AND MONDAY MORNING FROM 510 PM
UNTIL 100 AM CDT.

HAIL TO 1.5 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 95
STATUTE MILES EAST AND WEST OF A LINE FROM 30 MILES NORTH
NORTHEAST OF DODGE CITY KANSAS TO 50 MILES EAST SOUTHEAST OF
CLAYTON NEW MEXICO.  FOR A COMPLETE DEPICTION OF THE WATCH SEE
THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).

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...BAND OF TSTMS IN SE CO/NE NM APPEARS TO BE ASSOCIATED
WITH WSW-ENE MID LVL MOISTURE AXIS ROUNDING BASE OF NRN HI PLNS UPR
TROUGH.  AS THE MOIST AXIS CONTINUES EWD AND ASSOCIATED STORMS
DEVELOP STRONGER COLD POOLS...STORMS MAY SUFFICIENTLY STRENGTHEN TO
POSE A THREAT FOR LOCALLY DMGG WIND AND SVR HAIL GIVEN STEEP LOW LVL
LAPSE RATES AND INCREASING SLY LOW LVL INFLOW WITH EWD EXTENT.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 450. MEAN STORM
MOTION VECTOR 26025.


...CORFIDI

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SPC Apr 29, 2012 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook

Day 1 Outlook Thumbnail Image

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT SUN APR 29 2012

VALID 292000Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN AND
CENTRAL HIGH PLAINS ACROSS OK...SRN/ERN KS INTO MO...

...SERN-E CENTRAL KS INTO WRN/CENTRAL MO...
EARLY AFTERNOON SURFACE ANALYSIS SHOWED AN AREA OF RELATIVELY LOWER
PRESSURE CENTERED BETWEEN ICT-EMP WITH A BOUNDARY EXTENDING ESEWD
THROUGH CENTRAL MO TO FAR SRN IL/IND.  ANOTHER BOUNDARY EXTENDED
SSWWD FROM THE ICT/EMP LOW TO A SECOND LOW OVER SOUTH CENTRAL KS.
MEANWHILE...THE BOUNDARY EXTENDING SWWD THROUGH CENTRAL OK HAS
WEAKENED/BECOME ILL-DEFINED...GIVEN SURFACE STREAMLINE ANALYSES
SHOWING DIFFLUENCE...ESPECIALLY INTO WRN OK.

INCREASING DESTABILIZATION ACROSS THE SERN QUARTER OF KS INTO NERN
OK IS SUPPORTING MLCAPE OF 1000-2000 J/KG.  THIS COMBINED WITH
EFFECTIVE BULK SHEAR OF 40-50 KT IS MORE THAN ADEQUATE FOR ORGANIZED
STORMS...INCLUDING SUPERCELLS.  GIVEN THE DEVELOPMENT OF THE MORE
UNSTABLE WARM SECTOR WITH NWD EXTENT...THE SLIGHT RISK AREA HAS BEEN
EXPANDED NWD TO INCLUDE MORE OF EAST CENTRAL KS INTO WEST CENTRAL
MO.  STORMS DEVELOPING IN THIS ENVIRONMENT...ESPECIALLY WITH A
SURFACE WIND HAVING AN ELY COMPONENT WILL HAVE ENHANCED LOW LEVEL
SHEAR...AND THUS A TORNADO THREAT CANNOT BE RULED OUT.  GIVEN THESE
FACTORS...A 5 PERCENT TORNADO PROBABILITY HAS BEEN INTRODUCED ACROSS
SERN-E CENTRAL KS INTO PARTS OF WRN/CENTRAL MO FOR THIS AFTERNOON
AND EVENING.  THIS SLIGHT RISK EXPANSION IS SUPPORTED BY MODEL
GUIDANCE FROM THE 12Z 4KM WRF-NMM/WRF-NSSL AND 16Z HRRR.
HOWEVER...CONSIDERABLE UNCERTAINTY REMAINS REGARDING CONVECTIVE
INITIATION ACROSS THIS AREA.

...SRN HIGH PLAINS...
VISIBLE SATELLITE AND RADAR IMAGERY SHOWED A BOUNDARY EXTENDING FROM
50 NW ABI-20 NW BGS-25 NNE HOB.  THE AIR MASS HAS BECOME MODERATELY
UNSTABLE IN THIS REGION AND THE 16Z HRR AND 12Z 4KM WRF-NMM SUGGESTS
ISOLATED TSTM DEVELOPMENT ACROSS THIS AREA.  THUS...THE SLIGHT RISK
AREA HAS BEEN EXPANDED SWD.

..PETERS.. 04/29/2012

.PREV DISCUSSION... /ISSUED 1136 AM CDT SUN APR 29 2012/

...SRN PLAINS FROM NW ACROSS CNTRL OK TO MO...
A WEAKENING BAROCLINIC ZONE/INVERTED TROUGH AXIS EXTENDS FROM WEST
TX NEWD ACROSS CNTRL OK...AND THEN EAST AS A WARM FRONT FROM MO TO
THE LOWER THE OH VALLEY THIS MORNING. THIS FRONTAL ZONE LIES WITHIN
A BROAD BELT OF DEEP-LAYER CYCLONIC FLOW ON THE SERN FLANK OF A
LARGE SCALE TROUGH CURRENTLY SITUATED OVER THE INTERMOUNTAIN WEST
AND NRN PLAINS. THE LARGE SCALE TROUGH AXIS IS FORECAST TO TRANSLATE
NEWD ACROSS THE CNTRL/NRN PLAINS TO THE UPPER MS VALLEY WHILE
UNDERGOING DEAMPLIFICATION THROUGH MONDAY MORNING. AS THIS
OCCURS...LOW LEVEL FRONTAL ZONE FROM TX TO MO MAY GRADUALLY
LIFT/REFORM NWD WHILE REMAINING SITUATED WITHIN/BENEATH A SWATH OF
40-50KT SWLY FLOW AT MID LEVELS.

SUBSTANTIAL CONVECTIVE OVERTURNING AND LOCAL REINFORCEMENT OF THE
BAROCLINIC BOUNDARY OCCURRED OVERNIGHT FROM PORTIONS OF WEST TX INTO
OK AND CONTINUES ACROSS MO THIS MORNING WHERE AN MCS WAS BEING
SUSTAINED NORTH OF THE FRONT. A WARM/MOIST AIRMASS WILL PERSIST
ALONG AND SOUTH OF THE FRONT TODAY WHERE WARMER TEMPERATURES ALOFT
SHOULD SUBSTANTIALLY LIMIT CONVECTIVE DEVELOPMENT POTENTIAL WITH SWD
EXTENT. SBCAPE NEAR THE BOUNDARY IS FORECAST TO INCREASE TO AROUND
2000 J/KG WITH HEATING OF THE DAY AND EXPECT THAT FOCUSED AND
PERSISTENT LOW LEVEL CONVERGENCE ALONG THE BOUNDARY...IN CONCERT
WITH POCKETS OF STRONGER HEATING...WILL PROMOTE TSTM DEVELOPMENT
FROM NWRN TX NEWD ACROSS OK AND INTO SERN KS AND MO THROUGH THE LATE
AFTERNOON. MODEST EFFECTIVE SHEAR WITHIN THIS ZONE WILL LIKELY
SUPPORT STORM ORGANIZATION WITH MULTICELL TO WEAK SUPERCELL STORM
STRUCTURES POSSIBLE. HOWEVER...FORECAST PROFILES INDICATE THAT MID
LEVEL SWLY FLOW COINCIDENT WITH STRONGEST INSTABILITY WILL WEAKEN
WITH TIME...PERHAPS RESULTING IN AN EVOLUTION TOWARD MORE
MULTICELLULAR STORMS.

SOME INCREASE IN CONVECTIVE VIGOR AND COVERAGE MAY OCCUR INTO THE
EVENING AS INITIAL ACTIVITY TAPS PEAK IN DIURNAL INSTABILITY AND
RESULTANT COLD POOLS ACT TO REINFORCE THE LOW LEVEL BAROCLINIC ZONE
COINCIDENT WITH AN INCREASE IN THE LOW LEVEL JET AND SUBSEQUENT
ISENTROPIC ASCENT ACROSS THE BOUNDARY. EXPECT THIS CONVECTIVE
SCENARIO TO RESULT IN A FEW HAIL AND WIND EVENTS FROM NRN TX TO MO
THROUGH THE PERIOD.

...SRN HIGH PLAINS FROM ERN NM/CO ACROSS WRN KS AND TX/OK PNHDLS...
THE COMBINATION OF POST-FRONTAL OROGRAPHIC LIFT AND STRONG
SURFACE/BOUNDARY LAYER HEATING ACROSS THE FRONT RANGE AND ADJACENT
HIGH PLAINS WILL AID IN BOOSTING CONVECTIVE INSTABILITY ACROSS THESE
AREAS THROUGH THE AFTERNOON. DESPITE GENERALLY MEAGER LOW LEVEL
MOISTURE CURRENTLY ACROSS THE REGION... EVAPOTRANSPIRATION AND
INCREASE IN LOW LEVEL MOISTURE ADVECTION WILL COMBINE WITH
STEEPENING LAPSE RATES AND CONTRIBUTE TO SBCAPE IN THE RANGE OF
500-1000 J/KG. WEAK DPVA WITH APPROACHING SHORT WAVE TROUGH NOW
ACROSS SRN UT SHOULD ARRIVE COINCIDENT WITH MAXIMUM IN DIURNAL
HEATING AND AID AT LEAST ISOLATED TSTM DEVELOPMENT. SUFFICIENT SHEAR
WILL EXIST TO AID UPDRAFT PERSISTENCE/ROTATION WITH A COUPLE OF
SUPERCELLS POSSIBLE. HAIL AND STRONG WINDS APPEAR POSSIBLE WITH THIS
ACTIVITY AS IT DEVELOPS EAST INTO PARTS OF WRN KS AND THE PNHDLS OF
TX/OK INTO THE EVENING.

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SPC Apr 29, 2012 1730 UTC Day 2 Convective Outlook

SPC 1730Z Day 2 Outlook

Day 2 Outlook Thumbnail Image

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 PM CDT SUN APR 29 2012

VALID 301200Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE SRN AND
CENTRAL PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE MID MS
AND OH VALLEYS...

...SYNOPSIS...
THE BLOCKING PATTERN WILL CONTINUE TO BREAK DOWN AND TRANSITION TO
QUASI-ZONAL WITH SEVERAL LOW AMPLITUDE IMPULSES MOVING THROUGH THIS
REGIME.  TWO...SOMEWHAT MORE PROMINENT...IMPULSES SHOULD PROVIDE THE
GREATEST FORCING FOR TSTM DEVELOPMENT ON MON.  THE LEAD SHORTWAVE
TROUGH WILL DEAMPLIFY AS IT TRACKS THROUGH THE GREAT LAKES TO THE
NERN STATES RESULTING IN WEAK HEIGHT FALLS ACROSS THE OH VALLEY. AN
UPSTREAM IMPULSE...NOW MOVING ESEWD THROUGH CENTRAL CA/NV...IS
EXPECTED TO PROGRESS FROM THE FOUR CORNERS REGION INTO THE CENTRAL
HIGH PLAINS REGION BY LATE MON AFTERNOON.

AT 12Z MON...A SURFACE FRONT IS EXPECTED TO EXTEND WNWWD FROM NC
THROUGH ERN KY TO AN AREA OF LOW PRESSURE...ATTENDANT TO THE
PROGRESSIVE UPPER MS VALLEY TROUGH...LOCATED OVER NRN IL.  THIS LOW
WILL TRACK INTO THE LOWER GREAT LAKES...WHILE THE OH VALLEY PORTION
OF THE AFOREMENTIONED FRONT ADVANCES NEWD AS A WARM FRONT...REACHING
CENTRAL NY/PA TO WRN VA BY 12Z TUE. MEANWHILE...A FRONTAL ZONE
TRAILING SWWD FROM NRN IL THROUGH CENTRAL MO WILL ADVANCE ESEWD INTO
THE OH VALLEY. THE TRAILING PORTION OF THIS BOUNDARY EXTENDING INTO
TO NRN OK AND THE NRN TX PANHANDLE SHOULD WEAKEN...BECOMING
ILL-DEFINED. A DRY LINE IS EXPECTED TO SHARPEN FROM WRN KS INTO WRN
TX.

CONVECTION WITH EMBEDDED TSTMS SHOULD BE ONGOING AT THE START OF D2
FROM IN VICINITY AND E/NE OF THE SURFACE LOW NEAR CHICAGO...AND SWWD
ALONG THE TRAILING FRONT INTO OK AND THE TX/OK PANHANDLES.  MODELS
CONTINUE TO SUGGEST TWO AREAS WITH GREATER RISKS FOR SEVERE WEATHER
ON MON...1/ IN THE OH VALLEY...AND 2/ ACROSS PARTS OF THE SRN AND
CENTRAL PLAINS.

...SRN AND CENTRAL PLAINS...
THE SCENARIO FORECAST IN THE INITIAL D2 CONTINUES TO BE SUPPORTED BY
THE LATEST MODELS FOR THIS REGION. LOW LEVEL WINDS INITIALLY WILL BE
VEERED OVER THE CNTRL/SRN PLAINS AS A RESULT OF A LLJ SHIFTING NEWD
TOWARD THE OH VALLEY WITH THE LEAD SHORTWAVE TROUGH. THUS EARLY
CONVECTION MAY GRADUALLY DIMINISH FROM THE WEST ALLOWING FOR AT
LEAST PARTIAL CLEARING IN WRN PORTIONS OF WARM SECTOR FROM WRN KS
SWD THROUGH WRN OK AND WRN TX. IF THIS OCCURS...MODERATE INSTABILITY
WILL DEVELOP WHERE THE EML PLUME WILL ADVECT EWD ABOVE AXIS OF LOW
60S DEWPOINTS SUPPORTING MLCAPE OF 1500-2000 J/KG. POTENTIAL WILL
EXIST FOR STORMS TO REDEVELOP ESPECIALLY WHERE DRYLINE INTERSECTS
RESIDUAL OUTFLOW BOUNDARIES OR WRN EXTENT OF CONVECTIVELY REINFORCED
FRONT AS WELL AS SOME DISTANCE DOWN THE DRYLINE DURING THE
AFTERNOON. FORCING FOR ASCENT ATTENDANT TO THE CA/NV IMPULSE WILL
AID IN THE AFTERNOON/EVENING TSTM DEVELOPMENT.  ACTIVITY WILL
SUBSEQUENTLY SPREAD EWD THROUGH KS INTO PORTIONS OF OK. VERTICAL
SHEAR OF 40-50 KT ACROSS THE SLIGHT RISK AREA WILL SUPPORT
SUPERCELLS WITH ISOLATED LARGE HAIL AND DAMAGING WIND THE MAIN
THREATS...BUT A COUPLE OF TORNADOES CANNOT BE RULED OUT. GIVEN THE
EXPECTED INSTABILITY/SHEAR PARAMETER SPACE AND STEEPENING LAPSE
RATES...THE POTENTIAL EXISTS FOR SOME OF THE HAIL TO BE VERY LARGE.

A STRENGTHENING SLY LLJ MON EVENING/NIGHT AND SUBSEQUENT INCREASE IN
WAA/ISENTROPIC ASCENT SHOULD SUPPORT TSTMS PERSISTING AFTER
DARK...WITH A CONTINUED THREAT FOR SEVERE STORMS.  GIVEN EXISTING
UNCERTAINTY WITH REGARD TO THE EVOLUTION OF THE EARLY CONVECTION...
THIS OUTLOOK WILL MAINTAIN A 15% COVERAGE AREA.

...MID MS VALLEY THROUGH OH VALLEY...
NEW TSTM DEVELOPMENT IS EXPECTED ALONG THE SRN EXTENT OF THE ONGOING
ACTIVITY AS WEAK HEIGHT FALLS SPREAD ACROSS THIS REGION. THE WARM
SECTOR WILL BECOME MODERATELY UNSTABLE...AND THE STORMS WILL REMAIN
EMBEDDED WITHIN SUFFICIENT UNIDIRECTIONAL SHEAR FOR ORGANIZATION AND
A POTENTIAL SEVERE THREAT. SOME OF THE STORMS MAY BECOME CAPABLE OF
PRODUCING ISOLATED DAMAGING WIND AND HAIL THROUGH EARLY EVENING...
MAINTAINING THE SLIGHT RISK ACROSS THIS REGION.

..PETERS.. 04/29/2012

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SPC Apr 29, 2012 1630 UTC Day 1 Convective Outlook

SPC 1630Z Day 1 Outlook

Day 1 Outlook Thumbnail Image

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1136 AM CDT SUN APR 29 2012

VALID 291630Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN HIGH PLAINS TO
NWRN TX AND OK ACROSS SRN KS AND MO...

...SRN PLAINS FROM NW ACROSS CNTRL OK TO MO...
A WEAKENING BAROCLINIC ZONE/INVERTED TROUGH AXIS EXTENDS FROM WEST
TX NEWD ACROSS CNTRL OK...AND THEN EAST AS A WARM FRONT FROM MO TO
THE LOWER THE OH VALLEY THIS MORNING. THIS FRONTAL ZONE LIES WITHIN
A BROAD BELT OF DEEP-LAYER CYCLONIC FLOW ON THE SERN FLANK OF A
LARGE SCALE TROUGH CURRENTLY SITUATED OVER THE INTERMOUNTAIN WEST
AND NRN PLAINS. THE LARGE SCALE TROUGH AXIS IS FORECAST TO TRANSLATE
NEWD ACROSS THE CNTRL/NRN PLAINS TO THE UPPER MS VALLEY WHILE
UNDERGOING DEAMPLIFICATION THROUGH MONDAY MORNING. AS THIS
OCCURS...LOW LEVEL FRONTAL ZONE FROM TX TO MO MAY GRADUALLY
LIFT/REFORM NWD WHILE REMAINING SITUATED WITHIN/BENEATH A SWATH OF
40-50KT SWLY FLOW AT MID LEVELS.

SUBSTANTIAL CONVECTIVE OVERTURNING AND LOCAL REINFORCEMENT OF THE
BAROCLINIC BOUNDARY OCCURRED OVERNIGHT FROM PORTIONS OF WEST TX INTO
OK AND CONTINUES ACROSS MO THIS MORNING WHERE AN MCS WAS BEING
SUSTAINED NORTH OF THE FRONT. A WARM/MOIST AIRMASS WILL PERSIST
ALONG AND SOUTH OF THE FRONT TODAY WHERE WARMER TEMPERATURES ALOFT
SHOULD SUBSTANTIALLY LIMIT CONVECTIVE DEVELOPMENT POTENTIAL WITH SWD
EXTENT. SBCAPE NEAR THE BOUNDARY IS FORECAST TO INCREASE TO AROUND
2000 J/KG WITH HEATING OF THE DAY AND EXPECT THAT FOCUSED AND
PERSISTENT LOW LEVEL CONVERGENCE ALONG THE BOUNDARY...IN CONCERT
WITH POCKETS OF STRONGER HEATING...WILL PROMOTE TSTM DEVELOPMENT
FROM NWRN TX NEWD ACROSS OK AND INTO SERN KS AND MO THROUGH THE LATE
AFTERNOON. MODEST EFFECTIVE SHEAR WITHIN THIS ZONE WILL LIKELY
SUPPORT STORM ORGANIZATION WITH MULTICELL TO WEAK SUPERCELL STORM
STRUCTURES POSSIBLE. HOWEVER...FORECAST PROFILES INDICATE THAT MID
LEVEL SWLY FLOW COINCIDENT WITH STRONGEST INSTABILITY WILL WEAKEN
WITH TIME...PERHAPS RESULTING IN AN EVOLUTION TOWARD MORE
MULTICELLULAR STORMS.

SOME INCREASE IN CONVECTIVE VIGOR AND COVERAGE MAY OCCUR INTO THE
EVENING AS INITIAL ACTIVITY TAPS PEAK IN DIURNAL INSTABILITY AND
RESULTANT COLD POOLS ACT TO REINFORCE THE LOW LEVEL BAROCLINIC ZONE
COINCIDENT WITH AN INCREASE IN THE LOW LEVEL JET AND SUBSEQUENT
ISENTROPIC ASCENT ACROSS THE BOUNDARY. EXPECT THIS CONVECTIVE
SCENARIO TO RESULT IN A FEW HAIL AND WIND EVENTS FROM NRN TX TO MO
THROUGH THE PERIOD.

...SRN HIGH PLAINS FROM ERN NM/CO ACROSS WRN KS AND TX/OK PNHDLS...
THE COMBINATION OF POST-FRONTAL OROGRAPHIC LIFT AND STRONG
SURFACE/BOUNDARY LAYER HEATING ACROSS THE FRONT RANGE AND ADJACENT
HIGH PLAINS WILL AID IN BOOSTING CONVECTIVE INSTABILITY ACROSS THESE
AREAS THROUGH THE AFTERNOON. DESPITE GENERALLY MEAGER LOW LEVEL
MOISTURE CURRENTLY ACROSS THE REGION... EVAPOTRANSPIRATION AND
INCREASE IN LOW LEVEL MOISTURE ADVECTION WILL COMBINE WITH
STEEPENING LAPSE RATES AND CONTRIBUTE TO SBCAPE IN THE RANGE OF
500-1000 J/KG. WEAK DPVA WITH APPROACHING SHORT WAVE TROUGH NOW
ACROSS SRN UT SHOULD ARRIVE COINCIDENT WITH MAXIMUM IN DIURNAL
HEATING AND AID AT LEAST ISOLATED TSTM DEVELOPMENT. SUFFICIENT SHEAR
WILL EXIST TO AID UPDRAFT PERSISTENCE/ROTATION WITH A COUPLE OF
SUPERCELLS POSSIBLE. HAIL AND STRONG WINDS APPEAR POSSIBLE WITH THIS
ACTIVITY AS IT DEVELOPS EAST INTO PARTS OF WRN KS AND THE PNHDLS OF
TX/OK INTO THE EVENING.

..CARBIN/MOSIER/GRAMS/PETERS.. 04/29/2012

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SPC Apr 29, 2012 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook

Day 1 Outlook Thumbnail Image

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0723 AM CDT SUN APR 29 2012

VALID 291300Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE
CENTRAL/SOUTHERN HIGH PLAINS...AND ALONG A CORRIDOR FROM OK INTO
IL/IND....

A LARGE UPPER LOW IS CENTERED OVER WESTERN ND THIS MORNING...WITH A
BROAD REGION OF CYCLONIC FLOW ALOFT OVER MUCH OF THE WESTERN STATES
AND NORTHERN/CENTRAL PLAINS.  MEANWHILE...A WEAK SURFACE BOUNDARY
EXTENDS FROM WEST TX ACROSS CENTRAL OK...THEN INTO PARTS OF MO/IL.
THIS BOUNDARY WILL BE THE FOCUS OF SCATTERED STRONG/SEVERE
THUNDERSTORMS TODAY.

...OK INTO SOUTHERN IL/IN...
CONVECTION HAS BEEN OCCURRING OVERNIGHT ALONG AND NORTH OF THE
SURFACE BOUNDARY...REINFORCING IT AND SUPPRESSING ITS NORTHWARD
MOVEMENT.  A COMBINATION OF AMPLE LOW LEVEL MOISTURE AND SUBSTANTIAL
DAYTIME HEATING WILL HELP TO DESTABILIZE THE AIR MASS ALONG AND
SOUTH OF THE BOUNDARY BY MID AFTERNOON...WITH MLCAPE VALUES OF
AROUND 1500 J/KG AND ONLY WEAK CAPPING.  THIS WILL LIKELY RESULT IN
THE DEVELOPMENT OF SCATTERED THUNDERSTORMS ALONG AND NORTH OF THE
BOUNDARY.  LOW LEVEL VERTICAL SHEAR WILL BE RATHER WEAK...BUT DEEP
LAYER EFFECTIVE SHEAR WILL BE SUFFICIENT FOR MULTICELL OR OCCASIONAL
SUPERCELL STORM STRUCTURES CAPABLE OF HAIL AND GUSTY WINDS.

...CENTRAL/SOUTHERN HIGH PLAINS...
MORNING WATER VAPOR IMAGERY SHOWS A COMPACT UPPER VORT MAX OVER UT.
THIS FEATURE WILL TRACK EASTWARD BY LATE THIS AFTERNOON AND AFFECT
PORTIONS OF CO/NM AND EVENTUALLY KS/TX.  MOST MODEL SOLUTIONS AGREE
WITH DEVELOPMENT OF SCATTERED SHOWERS AND THUNDERSTORMS OVER THE
MOUNTAINS OF SOUTHERN CO/NORTHERN NM.  THIS ACTIVITY WILL TRACK
EASTWARD INTO A PROGRESSIVELY MORE UNSTABLE AIR MASS OVER SOUTHEAST
CO/NORTHEAST NM.  SIMILAR TO AREA FARTHER EAST...LOW LEVEL WINDS
WILL BE RATHER WEAK THOUGH THE AFTERNOON AND EARLY EVENING WHICH
SHOULD LIMIT THE TORNADO POTENTIAL.  HOWEVER...FAVORABLE DEEP LAYER
EFFECTIVE SHEAR WILL PROMOTE SUPERCELL STRUCTURES CAPABLE OF LARGE
HAIL /SOME VERY LARGE/ AND DAMAGING WINDS.  AFTER DARK...MODELS
SUGGEST THE SOUTHERLY LOW LEVEL JET WILL STRENGTHEN AND MAY YIELD A
SOMEWHAT GREATER CHANCE OF A TORNADO OR TWO ACROSS PORTIONS OF THE
TX PANHANDLE INTO SOUTHEAST CO.

..HART/SMITH.. 04/29/2012

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