SPC AC 221622
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1122 AM CDT SUN JUN 22 2008
VALID 221630Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS FOR A LARGE AREA FROM THE NRN
ROCKIES AND HIGH PLAINS EWD TO THE OH VALLEY...APPALACHIANS...AND
NEW ENGLAND...
...GREAT LAKES/OH VALLEY/NEW ENGLAND THROUGH LATE EVENING...
A SERIES OF EMBEDDED SHORTWAVE TROUGHS IS ROTATING AROUND A BROADER
MID LEVEL LOW OVER LAKE SUPERIOR...WITH THE MORE PRONOUNCED WAVES
MOVING NEWD TOWARD SW QUEBEC...ESEWD FROM IL...AND SSEWD OVER WI/MN.
THE ASSOCIATED SURFACE PATTERN IS QUITE MUDDLED WITH SEVERAL
DIFFUSE SURFACE TROUGHS/FRONTAL SEGMENTS ASSOCIATED WITH THE MID
LEVEL WAVES. BOUNDARY LAYER DEWPOINTS IN THE 60S PRECEDE THE
INITIAL MID LEVEL AND SURFACE TROUGHS FROM THE OH VALLEY INTO NEW
ENGLAND...WHILE RESIDUAL DEWPOINTS IN THE 50S PERSIST ACROSS THE
UPPER GREAT LAKES IN PROXIMITY TO THE MID LEVEL LOW.
THE COMBINATION OF DAYTIME HEATING...MID LEVEL LAPSE RATES OF 7-7/5
C/KM...AND COOL MID LEVEL TEMPERATURES /-15 TO -19 C AT 500 MB/ WILL
CONTRIBUTE TO AFTERNOON MLCAPE VALUES OF 750-1500 J/KG. VERTICAL
SHEAR WILL BE WEAK OVER WI/MI CLOSE TO THE MID LEVEL LOW...AND
SOMEWHAT STRONGER IN A BELT FROM THE MID MS VALLEY ACROSS THE OH
VALLEY TO NEW ENGLAND IN CONJUNCTION WITH 35-50 KT FLOW AROUND 500
MB. IT APPEARS THE SOMEWHAT MORE CONCENTRATED THREAT AREA FOR BOTH
DAMAGING WINDS AND HAIL...WILL STRETCH FROM THE UPPER OH VALLEY
ACROSS CENTRAL PA INTO NY...IN ADVANCE OF THE SHORTWAVE TROUGH AND
DIFFUSE FRONTAL SEGMENT APPROACHING FROM THE W. VERTICAL SHEAR AND
INSTABILITY WILL BE SUFFICIENT FOR ORGANIZED MULTICELL CLUSTERS AND
BOWING SEGMENTS CAPABLE OF PRODUCING DAMAGING OUTFLOW WINDS AND
LARGE HAIL THROUGH LATE EVENING.
...HIGH PLAINS INTO THE NRN ROCKIES THIS AFTERNOON/EVENING...
THE PRIMARY BAROCLINIC ZONE...ASSOCIATED WITH THE GREAT LAKES MID
LEVEL LOW...HAS STALLED ALONG AN AXIS FROM N CENTRAL MT...TO NE
WY...TO WRN AND CENTRAL KS. 12Z SOUNDINGS AND REGIONAL SURFACE
ANALYSES SUGGEST THAT BOUNDARY LAYER DEWPOINTS WILL LIKELY REMAIN IN
THE RANGE OF 48-54 F ACROSS MT...52-56 F FROM WRN SD INTO WRN
NEB...AND 56-60 F ALONG THE BOUNDARY IN KS. AFTERNOON SURFACE
TEMPERATURES WELL INTO THE 80S WILL WEAKEN CONVECTIVE INHIBITION AND
ALLOW AT LEAST WIDELY SCATTERED THUNDERSTORM DEVELOPMENT ALONG THE
FRONT IN KS/NEB...AND THE FRONT/HIGHER TERRAIN FROM NE WY INTO MT.
INSTABILITY WILL BE GREATER FARTHER TO THE SE...BUT THUNDERSTORM
COVERAGE WILL BE ENHANCED ACROSS MT BY THE TRAILING LOBE OF THE
STRONG MID LEVEL TROUGH MOVING NEWD INTO ALBERTA. THE STRONGER
STORMS WILL BE CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING
WINDS...GIVEN THE STEEP LAPSE RATES AND RELATIVELY LARGE
TEMPERATURE-DEWPOINT SPREADS. VERTICAL SHEAR WILL BE SOMEWHAT
STRONGER ACROSS THE CENTRAL HIGH PLAINS...WHERE AN ISOLATED
SUPERCELL WILL ALSO BE POSSIBLE.
..THOMPSON/GRAMS.. 06/22/2008
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z
|
