SWODY2
SPC AC 100530
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 AM CDT SUN AUG 10 2008
VALID 111200Z - 121200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE NRN AND
CNTRL PLAINS...
...SYNOPSIS...
UPPER LOW OVER THE MID ATLANTIC STATES IS FORECAST TO GRADUALLY
EVOLVE INTO AN OPEN WAVE WHILE LIFTING NEWD THROUGH NEW ENGLAND.
MEANWHILE...PHASING OF SEPARATE SHORT WAVE TROUGHS WILL OCCUR OVER
THE DAKOTAS WHILE ANOTHER UPPER LOW SLOWLY PROGRESSES EWD ACROSS
ALBERTA INTO SASKATCHEWAN. IN THE LOW LEVELS...SURFACE LOW
ATTENDANT TO THE NERN U.S. UPPER SYSTEM WILL DEVELOP NEWD ACROSS SRN
NEW ENGLAND. OVER THE PLAINS STATES...A COLD FRONT WILL PUSH EWD
THROUGH THE NRN PLAINS WITH THE BOUNDARY TRAILING SWWD INTO THE
CNTRL HIGH PLAINS. FARTHER S...A COLD FRONT WILL SLOWLY SAG SWD
THROUGH TX AND THE LOWER MS VALLEY.
...NRN AND CNTRL PLAINS...
LATEST MODEL GUIDANCE IS CONSISTENT IN SUGGESTING THAT A BAND OF
ELEVATED TSTMS WILL BE ONGOING MONDAY MORNING OVER THE WRN DAKOTAS
INTO WRN NEB IN ASSOCIATION WITH LEAD SHORT WAVE TROUGH. THIS
ACTIVITY WILL LIKELY PERSIST THROUGH THE DAY WITH AIR MASS RECOVERY
EXPECTED IN IT/S WAKE ALONG ADVANCING COLD FRONT. HERE...DEWPOINTS
IN THE 50S TO LOWER/MID 60S COUPLED WITH A NARROW EML/STEEP LAPSE
RATE PLUME WILL RESULT IN THE DEVELOPMENT OF A MODERATELY UNSTABLE
AIR MASS WITH MLCAPES APPROACHING 1000-2000 J/KG.
APPROACH OF UPSTREAM SHORT WAVE TROUGH AND FRONTAL FORCING ARE
EXPECTED TO CONTRIBUTE TO THE DEVELOPMENT OF SCATTERED TSTMS BY
MID/LATE AFTERNOON FROM THE WRN OR CNTRL DAKOTAS SWD INTO WRN NEB
AND ERN CO/NWRN KS. THE BEST COMBINATION OF INSTABILITY AND
STRONGER DEEP-LAYER SHEAR /EFFECTIVE BULK SHEARS OF 35-40 KT/ WILL
EXIST ACROSS NEB PORTION OF SLIGHT RISK AREA WHERE ENVIRONMENT WILL
BE SUPPORTIVE OF SUPERCELLS CAPABLE OF LARGE HAIL AND DAMAGING
WINDS. ELSEWHERE...ORGANIZED MULTICELL CLUSTERS APPEAR LIKELY WITH
HAIL AND DAMAGING WINDS POSSIBLE.
...SRN PLAINS INTO LOWER MS VALLEY...
SCATTERED...DIURNAL STORMS WILL OCCUR ALONG COLD FRONT SLOWLY
SAGGING SWD. PRE-FRONTAL AIR MASS OVER WRN/CNTRL TX WILL BE QUITE
HOT WITH 30-40 F TEMPERATURE-DEWPOINT SPREADS. THESE DRIER BOUNDARY
LAYER CONDITIONS WILL LIMIT THE AMOUNT OF CONVECTIVE
INSTABILITY...BUT WILL ALSO ENHANCE EVAPORATIONAL COOLING/STRONG
DOWNDRAFT POTENTIAL IN THE SUB-CLOUD LAYER. OVER E TX INTO THE
LOWER MS VALLEY...BOUNDARY LAYER WILL BE MUCH MORE MOIST AND
SLIGHTLY MORE UNSTABLE. HERE TOO...STRONGER STORMS WILL BE CAPABLE
OF GUSTY WINDS...BUT THROUGH WATER LOADING/WET
MICROBURST PROCESSES.
...HUDSON VALLEY INTO CNTRL/SRN NEW ENGLAND...
BOUNDARY LAYER IS FORECAST TO REMAIN RELATIVELY COOL /TEMPERATURES
IN THE 70S/ BUT MOIST ALONG AND AHEAD OF SURFACE LOW DEVELOPING EWD
ACROSS REGION. HOWEVER...MIDLEVEL TEMPERATURES OF -16 TO -18 C AT
500 MB WILL CONTRIBUTE TO THE DEVELOPMENT OF RELATIVELY STEEP LAPSE
RATES AND RESULTANT WEAK CONVECTIVE INSTABILITY /I.E. MLCAPES
GENERALLY BELOW 1000 J PER KG/. FORCING FOR ASCENT ASSOCIATED WITH
DEEP-LAYER CYCLONE WILL SUPPORT SCATTERED TSTM DEVELOPMENT THROUGH
THE DIURNAL HEATING CYCLE...A FEW OF WHICH COULD BE
STRONG/MARGINALLY SEVERE WITH THE MAIN THREAT BEING HAIL.
..MEAD.. 08/10/2008
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