SWODY1
SPC AC 110544
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1244 AM CDT MON AUG 11 2008
VALID 111200Z - 121200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PART OF THE NRN PLAINS
SWWD TO THE CENTRAL HIGH PLAINS...
...NRN/CENTRAL PLAINS TO SRN HIGH PLAINS...
DEEP UPPER TROUGH CENTERED OVER WRN CANADA SUNDAY NIGHT IS FORECAST
TO TRACK SLOWLY ENEWD INTO ERN ALBERTA/CENTRAL SASKATCHEWAN BY 12Z
TUESDAY...WITH THE SRN EXTENT OF THE ATTENDANT TROUGH SPREADING EWD
FROM THE NRN ROCKIES TO THE NRN PLAINS BY THIS EVENING. HEIGHT
FALLS ATTENDANT TO THIS UPPER TROUGH AND SEVERAL IMPULSES MOVING EWD
ACROSS THE PLAINS TODAY WILL PROVIDE FORCING FOR ASCENT RESULTING IN
CONVECTION FROM THE DAKOTAS SWWD TO THE CENTRAL HIGH PLAINS.
ALTHOUGH THE PRIMARY SURFACE LOW SHOULD MOVE NEWD ACROSS SRN
CANADA...A SECONDARY AREA OF LOW PRESSURE LOCATED ALONG THE TRAILING
COLD FRONT WILL LIKELY TRACK FROM WRN SD TO NWRN MN THIS FORECAST
PERIOD AS THE FRONT SPREADS EWD ACROSS THE DAKOTAS/NEB.
GIVEN THE ORIENTATION OF THE UPPER TROUGH AS IT SPREADS EWD ACROSS
THE NRN/CENTRAL PLAINS TODAY...STRONGEST MID/UPPER LEVEL FLOW IS
EXPECTED TO EXTEND ACROSS SD AND THE CENTRAL PLAINS. THIS WILL
RESULT IN A PLUME OF STEEP LAPSE RATES EXTENDING EWD ACROSS THESE
SAME REGIONS WHERE SURFACE HEATING AND LOW LEVEL MOISTURE WILL
CONTRIBUTE TO A MODERATELY UNSTABLE AIR MASS. TSTMS WILL LIKELY BE
ONGOING AT 12Z TODAY ACROSS ND INTO PARTS OF NRN SD ATTENDANT TO WAA
AND ASCENT AHEAD OF A LEAD IMPULSE. GREATEST DESTABILIZATION SHOULD
OCCUR SWWD OF THE MORNING CONVECTION AND IN ADVANCE OF THE
PROGRESSIVE COLD FRONT FROM CENTRAL SD SWWD INTO NERN CO. STRONGEST
EFFECTIVE BULK SHEAR WILL COINCIDE WITH THIS INSTABILITY CORRIDOR
SUPPORTING ORGANIZED SEVERE STORMS...WITH SUPERCELLS LIKELY OVER THE
SRN HALF OF THE SLIGHT RISK AREA WHERE SHEAR VALUES SHOULD BE AROUND
35 KT. HAIL AND STRONG WIND GUSTS SHOULD BE THE PRIMARY THREATS.
SLY LOW LEVEL WINDS WILL VEER TO WLY ACROSS ERN SD/ERN NEB TONIGHT
AND RESULT IN A WAA REGIME ACROSS PARTS OF MN/IA SUPPORTING AN
OVERNIGHT CONVECTIVE THREAT. WEAK ELEVATED INSTABILITY SHOULD LIMIT
THE SEVERE WEATHER THREAT WITH THIS ACTIVITY.
FARTHER S ACROSS SERN CO AND ERN NM...THE AIR MASS SHOULD BECOME
MODERATELY UNSTABLE. THIS COMBINED WITH 30 KT OF EFFECTIVE BULK
SHEAR SUGGESTS A FEW ORGANIZED STRONG TO SEVERE STORMS WILL BE
POSSIBLE...BUT OVERALL SEVERE WEATHER THREAT AT THIS TIME WARRANTS
ONLY LOW SEVERE PROBABILITIES.
...CENTRAL/NRN TX AND RED RIVER VALLEY EWD TO LOWER MS VALLEY...
DESPITE GENERALLY WEAK MID LEVEL LAPSE RATES EXTENDING EWD ACROSS
THIS REGION...SURFACE HEATING WITHIN A MOIST AIR MASS WILL RESULT IN
MODERATE INSTABILITY ALONG AND EITHER SIDE OF THE SURFACE FRONT.
SLY LOW LEVEL FLOW WILL SUPPORT TSTMS WITHIN WAA REGIME ALONG AND N
OF THE FRONT...WITH RE-STRENGTHENING LLJ FROM E TX INTO THE ARKLATEX
TONIGHT MAINTAINING CONVECTION THROUGH LATE TONIGHT. WEAK MID LEVEL
LAPSE RATES AND DEEP LAYER SHEAR WILL PRECLUDE STORM ORGANIZATION
AND GREATER POTENTIAL FOR SEVERE WEATHER. HOWEVER...STEEP LOW LEVEL
LAPSE RATES ACROSS MUCH OF TX WITHIN THE GENERAL TSTM AREA SHOULD
SUPPORT A FEW STORMS PRODUCING DAMAGING WIND GUSTS.
...SRN NEW ENGLAND TO FAR ERN PA/NJ...
CLOSED UPPER LOW CENTERED OVER PA AT 12Z TODAY WILL PROGRESS EWD AND
SHOULD EVOLVE INTO AN OPEN WAVE ALONG AND JUST OFF THE SRN NEW
ENGLAND COAST TOWARD 12Z TUESDAY. ATTENDANT SURFACE LOW SHOULD MOVE
EWD OFF THE NJ COAST THIS AFTERNOON...WITH THE TRAILING COLD FRONT
REACHING THE COAST OF NC/SC BY EARLY AFTERNOON. GIVEN THE TIMING
FOR THE EWD TRACK OF THE CLOSED LOW...MODELS SUGGEST STRONGER MID
LEVEL FLOW WILL SPREAD OFFSHORE THE MID ATLANTIC COAST PRIOR TO THE
DEVELOPMENT OF GREATER DIURNAL INSTABILITY INLAND. ALTHOUGH A FEW
ORGANIZED STORMS MAY FORM...OVERALL SEVERE WEATHER THREAT SHOULD
REMAIN LOW...WITH ISOLATED HAIL/STRONGER WIND GUSTS ALONG TRACK OF
MID LEVEL COLD CORE ATTENDANT TO CLOSED LOW.
..PETERS/HURLBUT.. 08/11/2008
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