SPC AC 290600

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0100 AM CDT WED MAY 29 2013

   VALID 291200Z - 301200Z

   ...THERE IS A MDT RISK OF SVR TSTMS ACROSS PORTIONS OF OK/NORTHERN
   TX AND WESTERN/CENTRAL KS...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE PLAINS TO
   MIDWEST/UPPER MS VALLEY...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE
   NORTHEAST STATES/NEW ENGLAND...

   ...SYNOPSIS...
   A VERY ACTIVE/POTENTIALLY WIDESPREAD SEVERE WEATHER DAY IS
   LIKELY...ESPECIALLY ACROSS MUCH OF THE CENTRAL/SOUTHERN PLAINS THIS
   AFTERNOON AND TONIGHT. THE LARGE SCALE PATTERN WILL CONTINUE TO
   AMPLIFY OVER THE CONUS...HIGHLIGHTED AN INCREASINGLY NEGATIVE
   TILT/EAST-NORTHEASTWARD EJECTING SOUTHERN STREAM UPPER TROUGH FROM
   THE CENTRAL/SOUTHERN ROCKIES TO THE PLAINS AND MO VALLEY BY LATE
   TONIGHT.

   ...CENTRAL/SOUTHERN PLAINS TO MO VALLEY/UPPER MIDWEST...
   STRENGTHENING/BACKING MID-LEVEL WINDS ALONG WITH STEADY HEIGHT FALLS
   ARE EXPECTED ACROSS THE CENTRAL/SOUTHERN PLAINS TODAY COINCIDENT
   WITH INCREASINGLY CYCLONIC FLOW ALOFT. THE PRIMARY SURFACE LOW IS
   LIKELY TO DEEPEN ACROSS SOUTHEAST CO/FAR SOUTHWEST KS...WITH ANOTHER
   SURFACE LOW EXPECTED TO DEVELOP/MOVE NORTHEASTWARD IN VICINITY OF
   THE SURFACE FRONTAL ZONE ACROSS THE NORTH-CENTRAL HIGH
   PLAINS/DAKOTAS THROUGH TONIGHT. A SPATIALLY BROAD WARM
   SECTOR...GENERALLY CHARACTERIZED BY MIDDLE TO UPPER 60S F SURFACE
   DEWPOINTS...WILL BE LOCATED TO THE EAST OF THE SOUTHERN HIGH PLAINS
   SURFACE LOW/DRYLINE AND CENTRAL/NORTHERN PLAINS FRONT.

   CONCERNING THE SOUTHERN PLAINS...SOME UNCERTAINTIES EXIST REGARDING
   THE SPECIFIC TIMING AND SPATIAL EXTENT/LOCATIONS OF SURFACE BASED
   DEEP CONVECTIVE INITIATION LATER TODAY. FOR ONE...THE PLAUSIBILITY
   OF RELATIVELY EARLY DEVELOPMENT WITHIN THE WARM SECTOR ACROSS
   OK/NORTH TX BY THE 00Z NAM IS A BIT IN QUESTION...AND COULD POSSIBLY
   BE AN ARTIFACT OF THE NAM BMJ CONVECTIVE SCHEME. EVEN
   SO...APPRECIABLE FORCING FOR ASCENT COINCIDENT WITH INCREASINGLY
   CYCLONIC FLOW ALOFT WILL OVERSPREAD THE SOUTHERN PLAINS RELATIVELY
   EARLY TODAY...AND THIS SHOULD MAKE INCREASING SURFACE BASED DEEP
   CONVECTION LIKELY BY AFTERNOON. THIS INCLUDES POSSIBLE DEVELOPMENT
   WITH THE WARM SECTOR /PENDING CLOUD COVER AND SPECIFIC
   DESTABILIZATION/...BUT A MORE CERTAIN SCENARIO MAY BE FOR SEVERE
   TSTM DEVELOPMENT IN THE IMMEDIATE VICINITY OF THE DRYLINE THIS
   AFTERNOON/EVENING.

   REGARDLESS...POTENTIALLY WIDESPREAD SURFACE BASED SEVERE TSTM
   DEVELOPMENT APPEARS PROBABLE ACROSS PARTS OF THE EASTERN TX
   PANHANDLE/NORTHWEST TX INTO WESTERN AND PERHAPS PARTS OF CENTRAL OK
   IN ADDITION TO WESTERN KS. SCATTERED SUPERCELLS CAPABLE OF VERY
   LARGE HAIL AND SOME TORNADOES WILL BE POSSIBLE...WITH A COUPLE
   POTENTIALLY STRONG TORNADOES WITHIN AN ENVIRONMENT ACCENTUATED BY A
   DIURNALLY STRONG LOW LEVEL JET. A MORE DISCRETE CONVECTIVE MODE IS
   MOST PROBABLE IN THE IMMEDIATE VICINITY OF THE DRYLINE...WITH
   BACKING MID/HIGH LEVEL WINDS ACROSS THE WARM SECTOR LIKELY
   INDICATIVE OF A TENDENCY FOR CLUSTERING OR A MIXED-MODE /BEYOND THE
   INITIAL SEVERAL HOURS/ AS STORMS PROGRESS EASTWARD. AS SUCH...THIS
   ACTIVITY MAY MERGE/CONTINUE EASTWARD TONIGHT ACROSS CENTRAL PORTIONS
   OF KS/OK AND PERHAPS NORTH TX...WITH DAMAGING WINDS/SEVERE HAIL AND
   SOME TORNADO RISK /ESPECIALLY GIVEN A NOCTURNALLY INTENSIFYING LOW
   LEVEL JET/ CONTINUING INTO AT LEAST LATE EVENING IF NOT PARTS OF THE
   OVERNIGHT.

   FARTHER NORTHWEST...LOW LEVEL UPSLOPE/CONVERGENCE IN VICINITY OF
   FRONTAL ZONE SHOULD LEAD TO A SEPARATE CORRIDOR OF SEVERE TSTM
   DEVELOPMENT /INCLUDING SUPERCELLS/ AND A SUBSEQUENT GENERAL EASTWARD
   PROGRESSION ACROSS PORTIONS OF EASTERN CO INTO WESTERN KS AND NEB
   THIS AFTERNOON INTO TONIGHT. AIDED BY A STRENGTHENING LOW-LEVEL JET
   THIS EVENING...STORMS WITHIN THIS CORRIDOR MAY CONSOLIDATE/GROW
   UPSCALE AS THEY SPREAD EAST-SOUTHEASTWARD ACROSS KS/NEB TONIGHT WITH
   A CONTINUED LARGE HAIL/DAMAGING WIND RISK.

   MEANWHILE...OTHER MORE ISOLATED...SEVERE TSTMS/SUPERCELLS CAPABLE OF
   MAINLY LARGE HAIL WILL BE POSSIBLE FARTHER SOUTH-SOUTHWEST NEAR THE
   DRYLINE INTO ADDITIONAL PARTS OF WEST-SOUTHWEST TX. OTHER SEVERE
   TSTMS ARE ALSO PROBABLE ACROSS THE NORTH-CENTRAL PLAINS AS
   CONSEQUENTIAL FORCING FOR ASCENT OVERSPREADS THE WARM SECTOR THIS
   AFTERNOON/EVENING.

   ...NORTHEAST STATES INTO WESTERN/SOUTHERN NEW ENGLAND...
   A SHORTWAVE TROUGH/SPEED MAX WILL CONTINUE EAST-NORTHEASTWARD TODAY
   OVER SOUTHERN PORTIONS OF ONTARIO AND QUEBEC...WITH ONE OR TWO OTHER
   CONVECTIVELY-INDUCED IMPULSES/ASSOCIATED OUTFLOW ALSO FACTORS LATER
   TODAY. TSTMS ARE LIKELY TO DIURNALLY INTENSIFY THIS AFTERNOON AS AT
   LEAST GLANCING FORCING FOR ASCENT OVERSPREADS THE REGION IN
   CONJUNCTION WITH A MID-LEVEL SPEED MAX. AS LOW-LEVEL MOISTURE
   STREAMS INTO THE REGION...STORMS MAY BE QUASI-FOCUSED ON A WARM
   FRONT AND/OR TRAILING SURFACE TROUGH. WHILE SUSTAINED
   MULTICELLS/ORGANIZED LINEAR CLUSTERS CAPABLE OF DAMAGING WINDS
   SHOULD BE THE PRIMARY HAZARDS...AT LEAST 35-40 KT OF DEEP LAYER
   SHEAR IN CONJUNCTION WITH MODERATE INSTABILITY WOULD SUPPORT SOME
   SUPERCELLS. THUS...SEVERE HAIL WILL BE POSSIBLE WITH STORMS THAT
   ACQUIRE UPDRAFT ROTATION...AND A TORNADO OR TWO MAY ALSO BE POSSIBLE
   FOR PORTIONS OF EASTERN NY INTO WESTERN/SOUTHERN NEW ENGLAND.

   ..GUYER/KERR.. 05/29/2013

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