May 31, 2008 1300 UTC Day 1 Convective Outlook
Updated: Sat May 31 12:52:20 UTC 2008
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the northeast us today....   Please read the latest public statement about this event.

Categorical Graphic
20080531 1300 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20080531 1300 UTC Day 1 Tornado Probabilities Graphic
Torndao Legend Image
Probabilistic Damaging Wind Graphic
20080531 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Wind Legend Image
Probabilistic Large Hail Graphic
20080531 1300 UTC Day 1 Large Hail Probabilities Graphic
Hail Legend Image
   SPC AC 311248
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0748 AM CDT SAT MAY 31 2008
   
   VALID 311300Z - 011200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF THE MID ATLANTIC
   STATES AND NORTHEAST...
   
   ...THERE IS A MDT RISK OF SVR TSTMS OVER SRN KS AND NRN OK...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CNTRL/SRN PLNS EWD
   THROUGH THE OH /TN VLYS INTO WRN NEW ENGLAND AND THE CAROLINAS...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE UPR MS VLY...
   
   ...SYNOPSIS...
   PATTERN WILL REMAIN PROGRESSIVE OVER THE LWR 48 THIS PERIOD.  BROAD
   TROUGH NOW OVER THE GRT LKS WILL CONTINUE E INTO WRN QUEBEC/NY/PA AS
   UPSTREAM RIDGE NOW OVER THE RCKYS/INTERMOUNTAIN WEST BUILDS E INTO
   THE HI PLNS...AND A SERIES OF DISTURBANCES ROUND BASE OF LOW OFF THE
   WA CST.
   
   AT THE SFC...LOW ASSOCD WITH THE GRT LKS SYSTEM WILL MOVE FROM NEAR
   GEORGIAN BAY THIS MORNING TO NRN VT THIS EVENING BEFORE CONTINUING E
   TO THE CANADIAN MARITIMES EARLY SUNDAY.  PRIMARY COLD FRONT TRAILING
   SW FROM THE LOW WILL MOVE E/SE ACROSS NY/PA AND NEW ENGLAND LATER
   TODAY...WHILE WRN END BECOMES MORE OR LESS STATIONARY FROM WRN KY
   INTO NRN PARTS OF AR AND OK.  AHEAD OF THE FRONT...LEE TROUGH E OF
   THE APLCNS AND VARIOUS CONFLUENCE AXES WILL BE ADDITIONAL SOURCES OF
   LOW-LVL UPLIFT.
   
   ...NEW ENGLAND SW TO CAROLINAS/KY/TN...
   A SERIES OF WEAKENING PRE-FRONTAL CONVECTIVE CLUSTERS WILL CONTINUE
   E/ESE ACROSS THE ERN OH VLY AND THE NRN APLCNS THROUGH LATER THIS
   MORNING.  GIVEN MODERATELY TO STRONGLY-SHEARED CYCLONIC FLOW OVER
   REGION...EPISODIC EMBEDDED ROTATING STRUCTURES MAY POSE A CONTINUED
   THREAT FOR ISOLD DMGG WIND GUSTS AND/OR BRIEF TORNADOES.
   
   CLOUD DEBRIS SPREADING DOWNSTREAM FROM THE STORM CLUSTERS WILL
   INHIBIT SFC HEATING OVER MUCH OF THE MID ATLANTIC REGION AND
   NORTHEAST.  BUT EVEN WITH MODEST HEATING...COMBINATION OF STRONG
   WIND FIELD...MODERATE LARGE SCALE FORCING FOR ASCENT AND INCREASING
   LOW-LVL MOISTURE WILL RESULT IN A SETUP FAVORABLE FOR RENEWED STORM
   DEVELOPMENT/SVR WEATHER BY EARLY AFTN.
   
   SATELLITE-DERIVED PW DATA SHOW MOISTURE SPREADING NEWD ACROSS THE
   MID ATLANTIC AND NERN STATES ATTM ALONG TWO AXES...ONE FROM OH INTO
   WRN PA/WRN NY...AND THE OTHER ACROSS THE MID ATLANTIC CSTL PLN.  MID
   60S F SFC DEW POINTS SHOULD REACH ERN PA/SERN NY BY EARLY
   AFTN...WITH UPR 60S FROM MD/DE SWD.  IN ADDITION TO EXPECTED
   REDEVELOPMENT OF OVERNIGHT STORM CLUSTERS...OTHER STORMS LIKELY WILL
   FORM ALONG LEE TROUGH FROM SE NY INTO VA AND THE CAROLINAS...AND
   ALONG/AHEAD OF DIFFUSE COLD FRONT OVER THE WRN SLOPES OF THE
   MOUNTAINS FROM WRN NY SW INTO WV/KY.
   
   60+ KT DIFFLUENT WLY 500 MB FLOW ATOP 30+ KT WSWLY LOW-LVL FLOW WILL
   YIELD AMPLE DEEP SHEAR SUSTAINED SUPERCELLS/BOWS...ESPECIALLY WITH
   STORMS ALONG LEE TROUGH IN THE MID ATLANTIC REGION.  SOMEWHAT WEAKER
   SHEAR WILL EXIST FARTHER S.  ALTHOUGH THE PRIMARY THREATS WILL BE
   DMGG WINDS/HAIL...TERRAIN-INDUCED BACKING OF THE LOW-LVL FLOW ACROSS
   SE NY...AND SLIGHTLY-BACKED NEAR-SFC FLOW INVOF DIFFUSE WARM FRONT
   IN WRN NEW ENGLAND...COULD ENHANCE LOW-LVL STORM ROTATION AND THE
   RISK OF TORNADOES IN THOSE AREAS.
   
   TSTMS SHOULD PEAK AND MOVE OFFSHORE BY EARLY EVENING IN ALL EXCEPT
   PARTS OF SRN VA/CNTRL-ERN CAROLINAS...WHERE LINGERING CELLS MAY
   REMAIN STG/SVR WELL INTO THE EVENING.
   
   ...SRN-CNTRL PLNS INTO OZARKS/LWR OH AND TN VLYS...
   PERSISTENT WAA/RICH MOISTURE INFLOW ON WRN END OF STALLING FRONT HAS
   SUPPORTED OVERNIGHT DEVELOPMENT OF SCTD SVR STORMS OVER SRN KS/FAR
   NRN OK.  THIS ACTIVITY LIKELY WILL PERSIST IN SOME FORM OR ANOTHER
   THROUGH SUNDAY MORNING...WITH ADDITIONAL DEVELOPMENT EXPECTED BOTH
   EWD ALONG FRONT INTO THE WRN KY/TN...AND NW INTO WRN/CNTRL KS.
   
   GIVEN QUALITY OF MOISTURE INFLOW...CONTINUING PRESENCE OF STEEP
   MID-LVL LAPSE RATES...AND MDT MID-LVL FLOW ON SRN EDGE OF THE
   WLYS...THIS ACTIVITY LIKELY WILL PRODUCE PERIODIC BOUTS OF SVR
   WEATHER ACROSS THE REGION AS SBCAPE INCREASES TO 3000 J/KG. 
   ALTHOUGH THE PRIMARY THREAT SHOULD BE VERY LARGE HAIL...LOCALLY DMGG
   WIND COULD ALSO OCCUR...ESPECIALLY IF STORM COLD POOLS CONSOLIDATE
   AND LEAD TO ENHANCED E/SE MCS MOTION.  IN ADDITION...A LOCALIZED
   THREAT FOR TORNADOES COULD ALSO EVOLVE.  SUCH A THREAT WOULD BE
   GREATEST ON WRN/SRN FRINGE OF THE MOST CONCENTRATED ACTIVITY THIS
   AFTN AND EVENING...AS VERY MOIST SWLY LLJ IMPINGES ON OUTFLOW
   BOUNDARY SEGMENTS THAT BECOME STATIONARY AND ROUGHLY PARALLEL TO THE
   WNWLY MEAN FLOW.
   
   ...UPR MS VLY...
   A WEAK DISTURBANCE MOVING SE ON WRN SIDE OF DEPARTING LARGER SCALE 
   TROUGH MAY SUPPORT DIURNALLY-ENHANCED STORMS OVER MN SEWD INTO
   NRN/ERN IA AND NWRN IL.  COLD MID-LVL TEMPERATURES COMBINED WITH
   35-40 KT NWLY MID-LVL FLOW WILL BE SUFFICIENT FOR A FEW SVR STORMS
   WITH HAIL/LOCALLY DMGG WINDS...SIMILAR TO THE ACTIVITY THAT AFFECTED
   PARTS OF THE UPR MS VLY YESTERDAY.
   
   ...CNTRL HI PLNS TO NRN INTERMOUNTAIN REGION...
   SCTD STORMS EXPECTED TO FORM LATE TODAY IN AREA OF WEAK UPSLOPE FLOW
   IN ERN CO/SW NEB N OF STALLED FRONT.  GIVEN 40S F SFC DEWPOINTS AND
   BAND OF 40 KT WLY FLOW ALOFT...A FEW OF THESE COULD BECOME
   SUSTAINED/POSSIBLY ROTATE AND POSE A THREAT FOR HAIL AND PERHAPS AN
   ISOLD TORNADO. 
   
   ELSEWHERE...LEAD IMPULSE MOVING NEWD AROUND SE SIDE OF OFFSHORE LOW
   MAY ENHANCE TSTM DEVELOPMENT OVER PARTS OF ID AND NE ORE LATER
   TODAY/EARLY TONIGHT.  SOME OF THESE MAY TRAIN AND YIELD LOCALLY
   HEAVY RAIN GIVEN DEEP UNIDIRECTIONAL SLY CLOUD-LAYER FLOW.  OTHER
   SCTD...POTENTIALLY STRONG DIURNAL STORMS COULD OCCUR EWD INTO SRN MT
   AND NRN WY.
   
   ..CORFIDI/HURLBUT.. 05/31/2008
   
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