May 20, 2012 0600 UTC Day 1 Convective Outlook
Updated: Sun May 20 05:38:28 UTC 2012
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20120520 1200 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20120520 1200 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Probabilistic Damaging Wind Graphic
20120520 1200 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Probabilistic Large Hail Graphic
20120520 1200 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
   SPC AC 200535
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1235 AM CDT SUN MAY 20 2012
   
   VALID 201200Z - 211200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS TODAY ACROSS PARTS OF THE UPPER
   MIDWEST...
   
   ...SYNOPSIS...
   MODELS INDICATE THAT LARGE-SCALE UPPER RIDGING WILL BUILD ACROSS
   MUCH OF THE INTERMOUNTAIN WEST AND ROCKIES TODAY...AS AN UPPER
   TROUGH APPROACHES THE NORTHERN PACIFIC COAST.  DOWNSTREAM...AS A
   DEEP CLOSED LOW PROGRESSES EASTWARD ACROSS THE CENTRAL CANADIAN
   PROVINCES...AN INCREASINGLY SHEARED SMALLER SCALE IMPULSE IS
   EXPECTED TO LIFT NORTHEAST OF THE MID MISSOURI VALLEY...BEFORE
   TURNING EASTWARD...THEN PERHAPS BEGINNING TO DIG ACROSS THE UPPER
   MIDWEST BY LATE TONIGHT/EARLY MONDAY.  THE ELONGATED UPPER HIGH
   CENTER OVER THE LOWER GREAT LAKES REGION AND NORTHEAST LIKELY WILL
   WEAKEN...BUT BROAD UPPER TROUGHING IS EXPECTED TO PERSIST ACROSS
   MUCH OF THE SOUTHEAST AND EASTERN GULF OF MEXICO INTO THE WESTERN
   ATLANTIC...WITH AN EMBEDDED MID-LEVEL CIRCULATION NEAR THE SOUTH
   ATLANTIC COAST.
   
   RETURN FLOW OF HIGH MOISTURE CONTENT AIR FROM THE WESTERN GULF OF
   MEXICO REMAINS UNLIKELY TO OCCUR...BUT A CONTINUED GRADUAL
   MOISTENING OF THE BOUNDARY LAYER EAST OF THE ROCKIES INTO THE
   APPALACHIANS WILL CONTRIBUTE TO DESTABILIZATION AND AREAS OF
   THUNDERSTORM ACTIVITY TODAY.  THIS IS EXPECTED TO BE MOSTLY FOCUSED
   AHEAD OF THE EASTWARD ADVANCING PORTION OF A CENTRAL U.S. SURFACE
   FRONT...FROM PARTS OF THE OZARK PLATEAU AND MIDDLE MISSISSIPPI
   VALLEY INTO THE UPPER MIDWEST...AS WELL AS ALONG AND NORTH OF ITS
   STALLING PORTION...ACROSS THE SOUTHERN PLAINS.  GIVEN THE CONTINUING
   PRESENCE OF RATHER STEEP MID-LEVEL LAPSE RATES...WITH RELATIVELY
   COOL MID-LEVEL TEMPERATURES...LOW-LEVEL MOISTURE APPEARS SUFFICIENT
   TO CONTRIBUTE TO A THERMODYNAMIC ENVIRONMENT SUPPORTIVE OF AT LEAST
   LOW PROBABILITIES FOR SEVERE HAIL AND SURFACE GUSTS IN MOST AREAS. 
   THIS WILL INCLUDE PORTIONS OF THE TEXAS SOUTH PLAINS...WHERE
   CONSIDERABLY WEAKER MID-LEVEL INHIBITION THAN PRIOR DAYS IS
   FORECAST.
   
   ...UPPER MIDWEST...
   IN ADVANCE OF THE WEAKENING UPPER IMPULSE LIFTING NORTHEAST OF THE
   MID MISSOURI VALLEY...SHEAR/MOMENTUM ASSOCIATED WITH 30-40 KT
   SOUTHERLY LOWER/MID TROPOSPHERIC FLOW MAY ENHANCE STORM DEVELOPMENT
   ACROSS PORTIONS OF CENTRAL AND EASTERN WISCONSIN INTO NORTHERN
   ILLINOIS THIS AFTERNOON.  ONE OR TWO ORGANIZED STORM CLUSTERS APPEAR
   POSSIBLE...WHICH COULD CONTRIBUTE TO A RELATIVE MAXIMUM IN SEVERE
   HAIL/WIND COVERAGE...COMPARED TO AREAS ALONG THE FRONT TO THE SOUTH.
   
   
   ...FLORIDA PENINSULA...
   ALTHOUGH SOME WARMING OF MID-LEVELS IS POSSIBLE ACROSS THE SOUTHERN
   PENINSULA TODAY...MODERATELY STRONG CYCLONIC MID/UPPER FLOW WILL
   PERSIST ACROSS THE REGION.  THIS COULD BE ENOUGH TO ENHANCE
   CONVECTIVE DEVELOPMENT...WHICH IS EXPECTED IN SCATTERED FASHION
   ALONG THE SEA BREEZE FRONTS THIS AFTERNOON...AS LOWER/MID
   TROPOSPHERIC INHIBITION REMAINS RELATIVELY WEAK.  LOCALIZED
   MARGINALLY SEVERE HAIL AND SURFACE WIND GUSTS MAY NOT BE OUT OF THE
   QUESTION.
   
   ...FRONT RANGE OF THE ROCKIES...
   SOUTHEASTERLY UPSLOPE LOW-LEVEL FLOW BENEATH WEAK TO MODERATE
   NORTHWESTERLY MID/UPPER WIND FIELDS WILL CONTRIBUTE TO A FAVORABLY
   SHEARED ENVIRONMENT FOR SUPERCELLS TODAY.  MODEL FORECAST SOUNDINGS
   CONTINUE TO SUGGEST THE DEVELOPMENT OF ONLY VERY WEAK MIXED LAYER
   CAPE ACROSS THE HIGH PLAINS.  HOWEVER... GUIDANCE DOES GENERALLY
   INDICATE THAT AT LEAST ISOLATED TO WIDELY SCATTERED STORM
   DEVELOPMENT IS PROBABLE OFF THE FRONT RANGE.  LARGE HAIL AND LOCALLY
   STRONG WIND GUSTS DO NOT APPEAR OUT OF THE QUESTION...PARTICULARLY
   IN CLOSE PROXIMITY TO THE HIGHER TERRAIN.
   
   ..KERR/ROGERS.. 05/20/2012
   
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