May 25, 2013 1630 UTC Day 1 Convective Outlook
Updated: Sat May 25 16:32:38 UTC 2013
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20130525 1630 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20130525 1630 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
20130525 1630 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
20130525 1630 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.
Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 142,361 773,462 Rapid City, SD...Grand Island, NE...North Platte, NE...Scottsbluff, NE...Lexington, NE...
Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 142,361 773,462 Rapid City, SD...Grand Island, NE...North Platte, NE...Scottsbluff, NE...Lexington, NE...
   SPC AC 251627

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1127 AM CDT SAT MAY 25 2013

   VALID 251630Z - 261200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN AND
   CNTRL PLAINS...

   ...SYNOPSIS...

   LITTLE CHANGE TO THE SYNOPTIC PATTERN IS FORECAST DURING THE D1
   PERIOD WITH UPPER LOWS CENTERED OVER THE PACIFIC NW INTO SWRN CANADA
   AND NEW ENGLAND...AND RIDGING FROM MB/ON SWD INTO THE MID/LOWER-MS
   VALLEY.  WITHIN THE PREVAILING SWLY MIDLEVEL FLOW REGIME FROM THE
   GREAT BASIN INTO NRN/CNTRL HIGH PLAINS...MORNING WATER VAPOR IMAGERY
   SHOWS A WEAK IMPULSE OVER WY WHICH SHOULD CONTINUE NEWD INTO THE
   DAKOTAS TODAY.  ELSEWHERE...A SHEARED VORTICITY MAXIMUM OVER TX WILL
   SLOWLY PROGRESS EWD.

   IN THE LOW LEVELS...AN ELONGATED LEE CYCLONE WILL BE MAINTAINED FROM
   ERN WY INTO SWRN NEB/NERN CO.  A TROUGH/DRYLINE WILL EXTEND SWD FROM
   THE LOW PRESSURE TO ALONG THE TX-NM BORDER WITH AN INVERTED TROUGH
   SITUATED OVER CNTRL OR ERN MT.  A WARM FRONT WILL STRETCH SEWD FROM
   AN INTERSECTION WITH THE LEE TROUGH ACROSS SERN MT INTO THE MID-MO
   VALLEY WHILE AN OUTFLOW BOUNDARY GRADUALLY MODIFIES ACROSS NRN KS. 

   ...NRN/CNTRL HIGH PLAINS THIS AFTERNOON INTO TONIGHT...

   A GRADUAL DEEPENING OF THE LEE CYCLONE WILL RESULT IN THE BACKING
   AND STRENGTHENING OF THE LOW-LEVEL WIND FIELD WHICH...IN TURN...WILL
   ENHANCE THE NWWD FLUX OF AN INCREASINGLY MOIST PBL FROM THE CNTRL
   PLAINS INTO SD.  THIS PROCESS WILL OCCUR BENEATH AN EML...
   CHARACTERIZED BY 700-500-MB LAPSE RATES OF 7.5-8.5 C/KM...PER 12Z
   RAOBS.  WHEN COUPLED WITH DAYTIME HEATING...THE AIR MASS FROM SERN
   MT INTO THE CNTRL PLAINS IS EXPECTED TO BECOME MODERATELY TO
   STRONGLY UNSTABLE WITH MLCAPE VALUES APPROACHING 1500-3000 J/KG.

   ELEVATED TSTMS HAVE ALREADY DEVELOPED THIS MORNING OVER ERN MT INTO
   WRN ND AND NERN WY WHERE DCVA ASSOCIATED WITH ABOVE-MENTIONED
   VORTICITY MAXIMUM AND LOW-LEVEL WAA ARE INTERACTING WITH A STEEP
   LAPSE RATE ENVIRONMENT /SEE 12Z RAP SOUNDING/.  THE MORE RECENT
   STORM DEVELOPMENT NEAR AND N OF THE BLACK HILLS WILL LIKELY PERSIST
   TODAY WITH STORMS EVENTUALLY BECOMING ROOTED WITHIN THE
   DESTABILIZING PBL...ALONG AND S OF SURFACE WARM FRONT.  OTHER
   SURFACE-BASED STORMS SHOULD DEVELOP THIS AFTERNOON ALONG THE LEE
   TROUGH AND/OR FAVORED TERRAIN AS DAYTIME HEATING AND THE INFLUENCE
   OF THE MIGRATORY SHORT-WAVE TROUGH OVERCOME REMAINING CONVECTIVE
   INHIBITION.

   SUPERCELLS APPEAR LIKELY AS THE INITIAL STORM MODE GIVEN A
   VERTICALLY VEERING WIND PROFILE WITH 40-50 KT OF WLY DEEP-LAYER
   SHEAR.  LARGE HAIL WILL BE THE PREDOMINANT HAZARD...THOUGH A FEW
   TORNADOES WILL BE POSSIBLE THIS AFTERNOON INTO EVENING FROM SERN MT
   INTO WRN PARTS OF SD/NEB WHERE A CORRIDOR OF ENHANCED LOW-LEVEL
   SHEAR IS FORECAST.  UPSCALE GROWTH OF STORMS INTO CLUSTERS OR AN MCS
   IS ANTICIPATED LATER THIS EVENING INTO TONIGHT WITH A CONTINUED
   THREAT FOR HAIL AND DAMAGING WINDS.

   ...SRN HIGH PLAINS THIS AFTERNOON AND EVENING...

   THE JUXTAPOSITION OF A MOIST PBL AND EML WILL PROMOTE MODERATE
   INSTABILITY THIS AFTERNOON ALONG THE LENGTH OF THE LEE
   TROUGH/DRYLINE WITH AFTERNOON MLCAPE VALUES OF 1000-2500 J/KG
   FORECAST.  THOUGH LARGE-SCALE FORCING FOR ASCENT WILL REMAIN
   NEGLIGIBLE THROUGH THE PEAK OF THE DIURNAL HEATING CYCLE...LOW-LEVEL
   CONVERGENCE ALONG WITH OROGRAPHIC INFLUENCES WILL PROMOTE ISOLATED
   STORM DEVELOPMENT AMIDST A KINEMATIC ENVIRONMENT FEATURING VEERING
   WINDS WITH HEIGHT.  MARGINAL VERTICAL SHEAR /BULK SHEAR VALUES AOB
   30-35 KT/ MAY LIMIT THE DEGREE OF STORM ORGANIZATION...THOUGH
   ISOLATED OCCURRENCES OF HAIL AND DAMAGING WINDS WILL BE POSSIBLE
   THROUGH THIS EVENING.

   ...CNTRL/SRN TX THIS AFTERNOON INTO TONIGHT...

   THE INFLUX OF A VERY MOIST AIR MASS /I.E. PW VALUES APPROACHING TWO
   INCHES/ SHOULD MAINTAIN SCATTERED TSTMS INVOF MIDLEVEL VORTICITY
   MAXIMUM SLOWLY MOVING ACROSS CNTRL TX.  DEEP-LAYER VERTICAL SHEAR IS
   WEAK...THOUGH THE MOIST/LOW LCL ENVIRONMENT COUPLED WITH MODEST
   LOW-LEVEL SHEAR MAY BE SUFFICIENT TO SUPPORT STORM ROTATION WITH A
   RISK FOR A BRIEF TORNADO.  OTHERWISE...EXCESSIVE RAINFALL WILL
   REMAIN THE PRIMARY HAZARD.

   ..MEAD/MOSIER.. 05/25/2013

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z