SWODY3
SPC AC 080715
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0215 AM CDT FRI AUG 08 2008
VALID 101200Z - 111200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
LATEST MODEL GUIDANCE IS IN GOOD AGREEMENT IN THE EVOLUTION OF THE
HIGH AMPLITUDE PATTERN OVER N AMERICA THROUGH THE DAY THREE PERIOD.
THE PRIMARY FEATURES OF INTEREST WILL BE DEEP UPPER LOW WHICH WILL
SHIFT EWD THROUGH THE LOWER GREAT LAKES AND UPSTREAM LOW WHICH WILL
TRANSLATE THROUGH BRITISH COLUMBIA AND ALBERTA. IN THE LOW
LEVELS...THE SURFACE LOW ATTENDANT TO THE FORMER WILL DEVELOP EWD
FROM SWRN ONTARIO INTO THE HUDSON VALLEY. A WARM FRONT WILL
INTENSIFY FROM THIS LOW ESEWD TO THE MID ATLANTIC COAST WITH
TRAILING COLD FRONT PUSHING EWD THROUGH THE LOWER GREAT LAKES.
MEANWHILE...A LEE TROUGH WILL STRENGTHEN SUNDAY OVER THE NRN AND
CNTRL HIGH PLAINS IN ADVANCE OF A COLD FRONT MOVING EWD THROUGH
MT/WY.
...HUDSON VALLEY/SRN NEW ENGLAND TO THE MID ATLANTIC COAST...
STRENGTHENING SLY FLOW ALONG WARM FRONT WILL RESULT IN THE NWD
ADVECTION OF AN INCREASINGLY MOIST BOUNDARY LAYER OFF THE ATLANTIC.
HOWEVER...THERE IS SOME INDICATION THAT PERSISTENT CLOUDS AND/OR
PRECIPITATION MAY TEND TO INHIBIT DAYTIME HEATING AND RESULTANT AIR
MASS DESTABILIZATION. VERTICAL SHEAR WILL INCREASE WITH TIME WITH
APPROACH OF UPPER LOW...NAMELY OVER THE LOWER HUDSON AND DE RIVER
VALLEYS IN CONCERT WITH A BELT OF 40-45 KT MIDLEVEL FLOW ROUNDING
THE TROUGH BASE. AS SUCH...IT APPEARS THAT SOME POTENTIAL WILL
EXIST FOR ORGANIZED/SEVERE STORMS SUNDAY AFTERNOON INTO SUNDAY
NIGHT. ONLY LOW SEVERE PROBABILITIES WILL BE INCLUDED IN THIS
FORECAST GIVEN UNCERTAINTIES IN THE DEGREE OF AIR MASS
DESTABILIZATION.
...NRN AND CNTRL HIGH PLAINS...
MODEST BOUNDARY LAYER MOISTURE /I.E. DEWPOINTS IN THE 50S/ IS
FORECAST E OF LEE TROUGH AND COLD FRONT...AND BENEATH ERN EDGE OF
EML PLUME WITH AIR MASS BECOMING MODERATELY UNSTABLE BY AFTERNOON.
DIURNAL STORM DEVELOPMENT IS EXPECTED ALONG LEE TROUGH AND/OR COLD
FRONT AS LEADING EDGE OF HEIGHT FALLS ASSOCIATED WITH UPPER TROUGH
OVER THE CANADIAN ROCKIES AND NRN INTERMOUNTAIN REGION OVERSPREADS
INSTABILITY AXIS. CURRENTLY...IT APPEARS THAT THE STRONGER MID AND
HIGH-LEVEL WIND FIELDS WILL LAG THE LOW-LEVEL INSTABILITY AXIS TO
THE NW WITH ONLY MARGINAL VERTICAL SHEAR FORECAST ACROSS
AFOREMENTIONED LOW-LEVEL BOUNDARIES. THEREFORE...ONLY LOW
PROBABILITIES WILL BE INCLUDED ATTM.
...ERN OK/AR...
CONSIDERABLE VARIABILITY EXISTS AMONGST MODEL GUIDANCE IN THE
HANDLING OF A MIDLEVEL VORTICITY MAXIMUM MOVING SEWD ACROSS REGION
AND IT/S ASSOCIATED SURFACE PATTERN. BOTH THE NAM AND NAMKF
INDICATE A MORE PRONOUNCED SURFACE LOW WITH A MODERATELY UNSTABLE
AND SUFFICIENTLY SHEARED /FOR STORM ORGANIZATION/ ENVIRONMENT
DEVELOPING TO IT/S E SUNDAY AFTERNOON. IN CONTRAST...THE GFS AND
ECMWF INDICATE BROADER LOW PRESSURE FARTHER SW OVER TX. GIVEN THESE
DIFFERENCES...ONLY LOW PROBABILITIES WILL BE ADDED.
..MEAD.. 08/08/2008
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