Mar 28, 2007 0600 UTC Day 1 Convective Outlook
Updated: Wed Mar 28 10:06:09 UTC 2007
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Public Severe Weather Outlook

The SPC is forecasting ...widespread severe thunderstorms expected over the western half of the southern and central plains this afternoon and tonight....   Please read the latest public statement about this event.

Categorical Graphic
20070328 1200 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20070328 1200 UTC Day 1 Tornado Probabilities Graphic
Probabilistic Damaging Wind Graphic
20070328 1200 UTC Day 1 Damaging Wind Probabilities Graphic
Probabilistic Large Hail Graphic
20070328 1200 UTC Day 1 Large Hail Probabilities Graphic
   SPC AC 280544
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1244 AM CDT WED MAR 28 2007
   
   VALID 281200Z - 291200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF THE GREAT PLAINS
   FROM NWRN TEXAS AND THE EASTERN TEXAS PANHANDLE...WESTERN
   OKLAHOMA...KANSAS AND SOUTH-CENTRAL NEBRASKA...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA
   FROM THE RIO GRANDE VALLEY OF TX NWD TO EXTREME ERN WY AND MUCH OF
   SD...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE CNTRL
   APPALACHIANS...PARTS OF SRN VA...AND MUCH OF NC...NWRN SC...
   
   ...LATEST INDICATIONS SHOW INCREASING CHANCES FOR AN EXTENSIVE SWATH
   OF SEVERE STORMS ACROSS THE GREAT PLAINS LATER TODAY AND TONIGHT...
   
   ...SYNOPSIS...
   LARGE DEEP-LAYER CYCLONE CONTINUES TO EVOLVE ACROSS THE
   INTERMOUNTAIN WEST LATE TONIGHT WITH 110KT MID LEVEL JET MAX
   TRANSLATING THROUGH THE BASE OF THE TROUGH OVER THE LOWER CO RIVER
   VALLEY. EXTENSIVE AREA OF PRONOUNCED MID AND UPPER LEVEL DIFFLUENCE
   AHEAD OF STRONG DPVA WILL OVERSPREAD THE HIGH PLAINS THROUGH LATE
   TODAY COINCIDENT WITH PACIFIC COLD FRONT DEVELOPING EAST OF THE
   ROCKIES. ASSOCIATED LEE-SIDE SURFACE LOW WILL BEGIN THE DAY OVER ERN
   CO/WY AND THEN TRACK ENEWD ACROSS THE NEB PNHDL AND WRN SD AS
   MID/UPPER LEVEL CIRCULATION CLOSES OFF ACROSS WY/CO THROUGH EARLY
   THURSDAY.
   
   IN THE EAST...A LOW AMPLITUDE SHORT WAVE TROUGH WILL CREST RAPIDLY
   AMPLIFYING LARGE SCALE UPPER RIDGE AND SPREAD SEWD ACROSS THE CNTRL
   APPALACHIANS THROUGH TONIGHT. ALTHOUGH HEIGHT FALLS WITH THIS
   IMPULSE ARE MEAGER...A BACK-DOOR FRONT SPREADING SWWD ACROSS VA/NC
   WILL ACT AS A FOCUS FOR STRONGER ASCENT AND SHEAR COINCIDENT WITH
   PEAK IN DIURNAL DESTABILIZATION ACROSS THESE AREAS.
   
   ...CNTRL/NRN GREAT PLAINS...
   AS THE STRONG PACIFIC FRONT SURGES EAST ACROSS THE HIGH PLAINS LATER
   TODAY IT APPEARS THAT IT WILL PROBABLY OVERTAKE DRYLINE FORMATION
   ACROSS PARTS OF NRN KS/SRN NEB. A WEAK QUASI-STATIONARY BOUNDARY
   ALONG THE KS/NEB BORDER MAY ACT AS A WARM FRONT WHERE STRONGER
   FORCING AND SHEAR CAN DEVELOP NEAR THE INTERSECTION WITH THE COLD
   FRONT. TRUE WARM FRONT WITH LARGER SCALE SYSTEM IS HARDER TO DEFINE
   BASED ON RAPID INTENSIFICATION AND EXTENSIVE NATURE OF THE LOW LEVEL
   SLY FLOW DEVELOPING ACROSS THE PLAINS...AND LIMITED N-S AIR MASS
   DISCONTINUITY. HOWEVER...A SECONDARY AREA OF ENHANCED FORCING WILL
   LIKELY OCCUR NEAR AND SE OF THE CENTER OF THE OCCLUDING SURFACE
   LOW...FROM EXTREME ERN WY/MT ACROSS WRN PARTS OF SD/NEB LATER THIS
   AFTERNOON THROUGH THIS EVENING.
   
   SURFACE DEWPOINTS ARE FORECAST TO RANGE FROM THE 50S NORTH TO LOWER
   60S ACROSS NCNTRL KS. SLIGHTLY COOLER TEMPERATURES ALOFT ACROSS NRN
   PARTS OF THE PLAINS WILL OFFSET MORE LIMITED MOISTURE. A FAIRLY
   UNIFORM PLUME OF SURFACE-BASED DESTABILIZATION /MLCAPE 1000-1500 J
   PER KG/ IS EXPECTED TO DEVELOP IN ADVANCE OF THE COLD FRONT FROM
   SWRN SD TO NRN KS BY LATE AFTERNOON. GIVEN MAGNITUDE OF LARGE SCALE
   FORCING FOCUSED ALONG THE FRONT...AND ENHANCED MESOSCALE FORCING
   NEAR AFOREMENTIONED FEATURES...RAPID TSTM DEVELOPMENT IS INDICATED
   IN ALL AVAILABLE GUIDANCE BY ABOUT 21Z. AMBIENT DEEP-LAYER SHEAR
   WILL SUPPORT RAPIDLY MOVING STORMS WITH PERSISTENT/ORGANIZED
   UPDRAFTS CAPABLE OF PRODUCING VERY LARGE HAIL...DAMAGING WINDS...AND
   POSSIBLY A COUPLE OF STRONG TORNADOES.
   
   INCREASING MERIDIONAL COMPONENT OF MEAN WIND AND DEEP-LAYER SHEAR
   VECTORS ORIENTED ALONG THE LINE OF FRONTAL FORCING SUGGEST THAT
   CONVECTION MAY EVOLVE RATHER RAPIDLY INTO QLCS WITH BOWING LINE
   SEGMENTS MOVING AT AROUND 50KT SPREADING DAMAGING WINDS EWD/NEWD
   ACROSS CNTRL NEB AND NCNTRL KS THROUGH THE NIGHT. CONVECTION WILL
   ALSO DEVELOP EWD INTO STRONGLY BACKED SURFACE FLOW WHERE EFFECTIVE
   SRH AROUND 300 M2/S2 WILL PROVIDE MORE THAN AN ADEQUATE ENVIRONMENT
   FOR A COUPLE OF POTENTIALLY STRONG TORNADOES. GREATER TORNADIC
   POTENTIAL WILL OCCUR WITH ANY DISCRETE CELLS...OR LINE BREAKS...IN
   PROXIMITY TO BOUNDARY INTERSECTIONS AND OTHER MESOSCALE FEATURES
   WHERE STORM SCALE INFLOW/DYNAMICS WILL BE LOCALLY ENHANCED.
   
   ...SRN GREAT PLAINS...
   FARTHER SOUTH...SEPARATION BETWEEN DRYLINE AND COLD FRONT MAY BE
   GREATER FROM SWRN KS ACROSS OK/TX. SITUATION APPEARS FAVORABLE FOR
   DRYLINE SUPERCELL INITIATION ACROSS THESE AREAS PRIOR TO COLD FRONT
   ADVANCING EAST AND MERGING WITH THE DRYLINE...MOST LIKELY AFTER
   DARK. HERE TOO...ENVIRONMENT APPEARS VERY SUPPORTIVE OF MYRIAD OF
   SEVERE WEATHER THREATS AS EFFECTIVE BULK SHEAR INCREASES TO OVER
   40KT ACROSS STRONGLY UNSTABLE AIR MASS CHARACTERIZED BY MLCAPE OF AT
   LEAST 2000 J/KG.
   
   OTHER THAN CONFLUENCE ZONE NEAR THE DRYLINE...LACK OF STRONGLY
   DEFINED MESOSCALE BOUNDARIES IN THE WARM SECTOR SUGGEST CELLS MAY 
   REMAIN DISCRETE IN NATURE AS EFFECTIVE SRH LOCALLY INCREASES TO OVER
   300 M2/S2 THROUGH 00Z. SPC ANALOG SOUNDING SYSTEM REVEALS A FEW
   SIGNIFICANT TORNADO MATCHES BASED ON NAM-WRF FORECAST SOUNDINGS FROM
   NWRN TX/WRN OK VALID AROUND 00Z. PRESENT INDICATIONS BASED ON A
   VARIETY OF MODEL GUIDANCE SUGGEST MOST SUPPORTIVE ENVIRONMENT FOR A
   STRONG TORNADO OR TWO MAY EVOLVE IN A RELATIVELY NARROW CORRIDOR
   FROM NWRN TX TO SWRN KS THROUGH EARLY EVENING. PROXIMITY TO GREATER
   LOW LEVEL MOISTURE ACROSS SRN PARTS OF THIS AREA COULD SUPPORT A
   COUPLE OF LONGER-TRACK DANGEROUS STORMS. ADDITIONALLY...SPC HAIL
   MODEL BASED ON NAM-WRF INPUT SOUNDINGS GENERATES HAILSTONE DIAMETERS
   OF 1-3 INCHES ACROSS MUCH OF THE SRN PLAINS AREA WHERE STORM
   INITIATION IS ANTICIPATED LATER THIS AFTERNOON.
   
   TENDENCY FOR STORM MERGERS AND INCREASING FORCING ALONG THE
   ADVANCING COLD FRONT WILL LEAD TO QLCS DEVELOPMENT AFTER DARK. SLOW
   EWD TRANSITION OF THE LARGE SCALE TROUGH BY THIS TIME SUGGESTS THAT
   CONVECTIVE SYSTEM WILL ALSO BE SLOW TO DEVELOP EWD. THIS MAY RESULT
   IN A CONTINUING THREAT FOR DAMAGING WINDS.... HAIL...AND HEAVY RAIN
   OVER THE SAME AREAS THROUGH LATE TONIGHT.
   
   ...SW TX...
   STORM COVERAGE MAY BE LESS ACROSS PARTS OF SWRN TX DUE TO THIS AREA
   BEING FARTHER REMOVED FROM STRONGER LARGE SCALE FORCING.
   HOWEVER...MIXING ALONG THE DRYLINE COUPLED WITH WEAK HEIGHT FALLS
   AND VERY STRONG INSTABILITY COULD LEAD TO EXPLOSIVE TSTM DEVELOPMENT
   BY EVENING. MODELS INDICATE SOME POTENTIAL FOR SUPERCELL TORNADOES
   AND VERY LARGE HAIL AS FAR SOUTH AS THE RIO GRANDE.
   HOWEVER...POTENTIALLY FEWER STORMS DICTATE LOWER PROBABILITIES ALONG
   THE TRAILING PORTION OF THE DRYLINE/FRONT.
   
   ...CNTRL APPALACHIANS ACROSS PARTS OF THE CAROLINAS...
   STRONG HEATING AND MOISTURE FOCUS IN ADVANCE OF BACK-DOOR FRONT WILL
   RESULT IN THE DEVELOPMENT OF MODEST INSTABILITY FROM SWRN VA ACROSS
   WRN/NRN NC THROUGH THE AFTERNOON. LIFT AND SHEAR ALONG THIS BOUNDARY
   WILL BE REINFORCED FURTHER AS MID LEVEL IMPULSE AND ASSOCIATED
   40-50KT SPEED MAX SPREAD SEWD ACROSS THE REGION. THERE IS GOOD
   AGREEMENT IN LATEST GUIDANCE THAT STORMS WILL INCREASE IN COVERAGE
   ACROSS THE APPALACHIANS...AND TRACK ESEWD ALONG THE FRONT THROUGH
   THE AFTERNOON. CELLS CROSSING THE FRONT FROM N TO S COULD ACQUIRE
   LOW LEVEL ROTATION BEFORE BECOMING ELEVATED IN STABLE POST-FRONTAL
   REGIME. PRIMARY THREAT APPEARS TO BE THE POTENTIAL FOR NUMEROUS HAIL
   EVENTS. CONVECTIVE VIGOR SHOULD DIMINISH WITHIN A COUPLE HOURS AFTER
   SUNSET.
   
   ..CARBIN/BOTHWELL.. 03/28/2007
   
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