SWODY1
SPC AC 171959
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT SUN JUN 17 2007
VALID 172000Z - 181200Z
..THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND TONIGHT FROM
ERN WY AND THE WRN DAKOTAS INTO THE UPPER GREAT LAKES...
..UPPER GREAT LAKES...
A COUPLE SUPERCELLS HAVE DEVELOPED EARLY THIS AFTERNOON ALONG SRN
FLANK OF WARM ADVECTION CONVECTIVE BAND OVER N-CNTRL/NERN WI VERY
NEAR SURFACE WARM FRONT WHICH EXTENDED FROM E-CNTRL ND SEWD THROUGH
CNTRL WI AS OF 19Z. THIS BOUNDARY IS RAPIDLY LIFTING NEWD WITH
STRONG AIR MASS DESTABILIZATION OCCURRING IN IT/S WAKE WHERE MLCAPES
HAVE INCREASED TO 1500-2000 J/KG. CURRENT GRB VWP INDICATES
LOW-LEVEL VEERING THROUGH THE LOWEST 3 KM AGL WITH 0-1 KM SRH OF
100-150 M2/S2. GIVEN DEEP LAYER SHEAR OF 40-45 KT...ENVIRONMENT
WILL REMAIN SUPPORTIVE OF SUPERCELLS CAPABLE OF LARGE HAIL AND
PERHAPS A COUPLE OF TORNADOES THROUGH THE REMAINDER OF THE AFTERNOON
INTO TONIGHT.
BASED ON 12/18Z OBSERVED SOUNDINGS AND CURRENT RADAR/SATELLITE
TRENDS...IMMEDIATE SEVERE THREAT WILL REMAIN CONFINED TO NERN WI
INTO THE WRN/CNTRL UP OF MI ALONG NERN FRINGE OF STRONGER CAP IN
PLACE OVER THE DAKOTAS. WITH TIME...CAP MAY WEAKEN SUFFICIENTLY
ALONG NRN MN/THE ARROWHEAD PORTION OF WARM FRONT THAT STORMS WILL BE
ABLE TO INITIATE AND BECOME SUSTAINED. SHOULD THIS
OCCUR...COMPARATIVELY STRONGER LOW AND DEEP LAYER SHEAR /THAN POINTS
TO THE SE/ INDICATE A THREAT OF TORNADIC SUPERCELLS.
..ERN WY...NWRN NEB...DAKOTAS INTO RED RIVER VALLEY...
LATEST MESOANALYSIS INDICATES SURFACE LOW OVER S-CNTRL ND WITH
ASSOCIATED WARM FRONT LIFTING NWD THROUGH E-CNTRL ND/NWRN MN.
TRAILING COLD FRONT EXTENDED SWWD THROUGH W-CNTRL SD INTO CNTRL WY.
AS MENTIONED ABOVE...A VERY STRONG CAP HAS BEEN OBSERVED WITHIN
SYNOPTIC WARM SECTOR OVER THE DAKOTAS...AND THIS MAY INHIBIT THE
INITIATION OF STORMS ALONG RETREATING WARM FRONT THROUGH MUCH OF THE
AFTERNOON. SHOULD STORMS BECOME ESTABLISHED INVOF WARM
FRONT...ENVIRONMENT WILL BE QUITE FAVORABLE FOR TORNADIC SUPERCELLS
PER 18Z ABR SOUNDING AND CURRENT GRAND FORKS WIND PROFILES.
A MORE PROBABLE LOCATION OF INITIATION WILL BE ALONG COLD FRONT /OR
PERHAPS POST-FRONTAL AIR MASS/ OVER ERN WY/WRN SD INTO THE NEB PNHDL
WHERE STRONG DIABATIC HEATING IS ALLOWING TEMPERATURES TO WARM
THROUGH THE 90S. DEEP BOUNDARY LAYER MIXING AND RESULTANT 30-40F
TEMPERATURE-DEWPOINT SPREADS INDICATE THE POTENTIAL FOR STRONG COLD
POOL PRODUCTION. WIND PROFILES ARE SUPPORTIVE OF SUPERCELLS WHICH
WILL BE POSSIBLE SHORTLY AFTER INITIATION WITH A THREAT OF HAIL AND
DAMAGING WINDS.
HOWEVER...CONVECTION SHOULD QUICKLY TRANSITION INTO MORE OF A LINEAR
TYPE MODE DRIVEN BY AN ORGANIZED COLD POOL. THE STRONG LARGE-SCALE
FORCING FOR ASCENT AND MODERATELY STRONG WIND FIELDS INDICATE THE
POTENTIAL FOR A BOWING MCS CAPABLE OF DAMAGING WIND CORRIDORS FROM
CNTRL SD/NWRN NEB EWD INTO PARTS OF THE ERN DAKOTAS/WRN MN AND CNTRL
NEB OVERNIGHT.
..NEW ENGLAND INTO THE HUDSON VALLEY...
BROKEN LINE OF STRONG TO SEVERE STORMS CONTINUES THIS AFTERNOON OVER
PARTS OF NERN AND COASTAL ME...DRIVEN LARGELY BY LARGE-SCALE FORCING
FOR ASCENT ASSOCIATED WITH MIGRATORY SHORT WAVE TROUGH. THESE
STORMS ARE EXPECTED TO SLOWLY DIMINISH IN INTENSITY LATE THIS
AFTERNOON INTO EVENING AS THEY ENCOUNTER MUCH MORE STABLE MARINE AIR
MASS. TO THE NW...ADDITIONAL MORE ISOLATED STORM DEVELOPMENT IS
PRESENT OVER THE UPPER HUDSON VALLEY WITHIN RATHER COOL BOUNDARY
LAYER WHERE TEMPERATURES REMAIN LARGELY IN THE 70S. OTHER STORMS
MAY TEND TO DEVELOP IN SAME GENERAL AREA THROUGH THE REMAINDER OF
THE AFTERNOON...PRIOR TO MOVING SEWD. WHILE LOCALLY STRONG WIND
GUSTS AND SOME HAIL WILL BE POSSIBLE...THE MARGINAL INSTABILITY AND
VERTICAL WIND SHEAR SHOULD PRECLUDE A MORE ORGANIZED SEVERE THREAT.
.MEAD.. 06/17/2007
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