May 12, 2009 0600 UTC Day 1 Convective Outlook
Updated: Tue May 12 06:04:13 UTC 2009
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Categorical Graphic
20090512 1200 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20090512 1200 UTC Day 1 Tornado Probabilities Graphic
Torndao Legend Image
Probabilistic Damaging Wind Graphic
20090512 1200 UTC Day 1 Damaging Wind Probabilities Graphic
Wind Legend Image
Probabilistic Large Hail Graphic
20090512 1200 UTC Day 1 Large Hail Probabilities Graphic
Hail Legend Image
   SPC AC 120600
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0100 AM CDT TUE MAY 12 2009
   
   VALID 121200Z - 131200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NORTH-CENTRAL PLAINS
   AND MISSOURI VALLEY...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF
   WEST/SOUTHWEST TX...
   
   ...NORTHERN/CENTRAL PLAINS...
   CONSIDERABLE UPPER TROUGH/ASSOCIATED COLD FRONT WILL DEVELOP
   EASTWARD OVER THE NORTHERN INTERMOUNTAIN REGION TODAY...WITH
   DOWNSTREAM HEIGHT FALLS AND LEE CYCLOGENESIS ACROSS THE NORTHERN
   HIGH PLAINS. WITH A MOISTURE-RICH AIRMASS CONFINED TO THE SOUTHERN
   PLAINS...MODEST BOUNDARY LAYER MOISTURE /SURFACE DEWPOINTS MAINLY
   40S F TO LOWER 50S/ WILL TEND TO BE A LIMITING FACTOR...ALTHOUGH A
   VERY STEEP LAPSE RATE ENVIRONMENT/STRONG SHEAR AMIDST STRENGTHENING
   FLOW ALOFT /50+ KT AT 500 MB/ WILL SUPPORT A SEVERE RISK THIS
   AFTERNOON/TONIGHT. STORMS SHOULD INITIALLY DEVELOP THIS AFTERNOON
   ACROSS PORTIONS OF SOUTHEAST MT/ADJACENT NORTHEAST WY...AS WELL AS
   THE WESTERN PORTIONS OF SD/NEB...AND SUBSEQUENTLY DEVELOP EASTWARD
   THROUGH EARLY/MID EVENING. GIVEN A WELL-MIXED/STEEP LAPSE RATE
   ENVIRONMENT...DAMAGING WIND GUSTS AND SEVERE HAIL WILL BE THE
   PRIMARY HAZARDS.
   
   ...LOWER/MIDDLE MO VALLEY TOWARD THE MIDDLE/UPPER MS VALLEY...
   STRONG NORTH-NORTHEASTWARD MOISTURE TRANSPORT REGIME WILL CONTINUE
   THROUGH THE DAY ACROSS THE PLAINS AND ADJACENT MIDWEST. ON THE EDGE
   OF A STRONG ELEVATED MIXED LAYER ACROSS THE PLAINS...TSTMS COULD
   DEVELOP AS EARLY AS MIDDAY/EARLY AFTERNOON ACROSS PORTIONS OF THE
   LOWER MO VALLEY...AIDED BY A LOW AMPLITUDE IMPULSE CROSSING THE
   CENTRAL PLAINS. AMPLE VERTICAL SHEAR AND AN UNSTABLE SOURCE REGION
   AIRMASS WOULD SUPPORT A SEVERE HAIL RISK ATOP A RELATIVELY STABLE
   BOUNDARY LAYER. IN THE WAKE OF THESE EARLY DAY/AFTERNOON TSTMS...AN
   INTENSIFYING SOUTHWESTERLY LOW LEVEL JET /50-65 KT/ WILL AGAIN
   RESULT IN AN UPSWING IN TSTM COVERAGE AND HAIL POTENTIAL ACROSS THE
   MIDWEST LATE THIS EVENING/OVERNIGHT...AS A RATHER/MOIST UNSTABLE
   ELEVATED AIRMASS ADVECTS TOWARD THE REGION.
   
   ...WEST/SOUTHWEST TX...
   WITH PERTURBED WESTERLY FLOW ALOFT AND LATE AFTERNOON/EVENING
   ARRIVAL OF LARGE SCALE HEIGHT FALLS ACROSS THE SOUTHERN HIGH
   PLAINS...ISOLATED TO SCATTERED TSTMS SEEM LIKELY TO DEVELOP IN
   VICINITY OF DRYLINE ACROSS PORTIONS OF WEST CENTRAL/SOUTHWEST TX.
   THE REGION WILL BE ON THE SOUTHERN FRINGE OF THE STRONGER
   WESTERLIES...BUT INCREASING HIGH LEVEL FLOW /40 KT AROUND 8 KM/ AND
   AMPLE VEERING WILL SUPPORT SUPERCELLS BY LATE THIS AFTERNOON/EARLY
   EVENING. RATHER STEEP LAPSE RATES AND STRONG INSTABILITY WILL
   SUPPORT LARGE HAIL AS THE PRIMARY RISK.
   
   ...CENTRAL HIGH PLAINS...
   SEVERE POTENTIAL IS MUCH MORE CONDITIONAL ACROSS THE CENTRAL HIGH
   PLAINS IN VICINITY OF DRYLINE...INCLUDING PORTIONS OF FAR EASTERN
   CO/SOUTHWEST NEB/WESTERN KS TO THE OK/TX PANHANDLES. ANY ISOLATED
   TSTMS THAT DEVELOP LATE THIS AFTERNOON/EARLY EVENING WOULD
   CONDITIONALLY BE CAPABLE OF SEVERE HAIL/STRONG WIND GUSTS GIVEN
   AMPLE VERTICAL SHEAR/STEEP LAPSE RATES.
   
   ...EASTERN OK/ARKLATEX TO GULF COAST STATES/FL PENINSULA...
   ISOLATED HAIL/DOWNBURSTS WILL BE POSSIBLE THIS AFTERNOON/EARLY
   EVENING ALONG REMNANT FRONTAL ZONE FROM EASTERN OK/ARKLATEX TO THE
   GULF COAST STATES...AND IN ASSOCIATION WITH THE FL SEA BREEZE. WEAK
   SHEAR/RISING HEIGHTS ALOFT THROUGHOUT THIS CORRIDOR WILL TEND TO
   KEEP THE SEVERE RISK LOCALIZED IN NATURE...AND MAINLY CONFINED TO
   THIS AFTERNOON/EARLY EVENING.
   
   ...SOUTHERN NEW ENGLAND...
   MODEST SURFACE HEATING...COMBINED WITH COLD MID LEVEL TEMPERATURES
   /-25C TO -27C AT 500 MB/ IN ASSOCIATION WITH AN OPEN MID LEVEL
   WAVE...WILL RESULT IN THE DEVELOPMENT OF MODEST SBCAPE AND THE
   POTENTIAL FOR ISOLATED TSTM DEVELOPMENT THIS AFTERNOON ACROSS
   SOUTHERN NEW ENGLAND/PERHAPS LONG ISLAND VICINITY. WITH POTENTIAL
   FOR SURFACE BASED CAPE UP TO 500 J/KG AND A STEEP LAPSE RATE
   ENVIRONMENT...SOME HAIL MAY BE POSSIBLE. WEAK LOW TO MID
   TROPOSPHERIC FLOW WILL LIKELY KEEP THE HAIL THREAT MARGINAL/SPORADIC
   IN NATURE...AND ANY SUCH THREAT WILL QUICKLY WANE AFTER DARK.
   
   ..GUYER/JEWELL.. 05/12/2009
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z