Thursday, August 14, 2008

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 140521
SWODY2
SPC AC 140519

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1219 AM CDT THU AUG 14 2008

VALID 151200Z - 161200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF ERN NM...WRN
TX AND SWRN OK...

...SYNOPSIS...

A COMPLEX LARGE-SCALE PATTERN WILL EXIST OVER THE CONUS DURING THE
DAY TWO PERIOD. UPPER LOW INITIALLY OVER THE LOWER GREAT LAKES WILL
TRANSLATE SLOWLY EWD ACROSS THE NERN STATES. MEANWHILE...A PAIR OF
MID/UPPER-LEVEL CIRCULATIONS WILL EXIST OVER THE CNTRL PART OF THE
NATION...ONE OVER THE CNTRL ROCKIES AND THE OTHER OVER THE MID MO
VALLEY. IN THE LOW LEVELS...A WEAK SURFACE LOW WILL REMAIN
QUASI-STATIONARY OVER ERN KS/WRN MO WITH A COLD FRONT TRAILING SWWD
INTO THE SRN HIGH PLAINS. IN THE E...A COLD FRONT ATTENDANT TO
UPPER SYSTEM WILL PROGRESS EWD THROUGH THE LOWER GREAT LAKES INTO
NEW ENGLAND WITH SRN PORTION OF THIS BOUNDARY EVENTUALLY MOVING OFF
THE MID ATLANTIC COAST.

...SRN HIGH PLAINS INTO OZARK PLATEAU...

CLUSTERS OF TSTMS MAY BE ONGOING FRIDAY MORNING ALONG SURFACE FRONT
IN ASSOCIATION WITH A LEAD SHORT WAVE TROUGH TRANSLATING EWD ACROSS
THE REGION. THIS ACTIVITY WILL LIKELY CONTINUE EWD THROUGH THE
DAY...PERHAPS INTENSIFYING BY AFTERNOON AS DAYTIME HEATING AND A
MOIST BOUNDARY LAYER CONTRIBUTE TO POCKETS OF MODERATE INSTABILITY
WITH MLCAPES APPROACHING 1000-1500 J/KG. WHILE SOME HAIL AND
LOCALLY STRONG WIND GUSTS MAY ACCOMPANY THE MORE INTENSE
STORMS...WEAK MIDLEVEL LAPSE RATES AND DEEP LAYER SHEAR OF GENERALLY
LESS THAN 30 KT SHOULD LIMIT A MORE SUBSTANTIAL SEVERE THREAT.

BOUNDARY LAYER MOISTURE WILL TEND TO DIMINISH WITH WWD EXTENT INTO
THE SRN HIGH PLAINS WITH DEWPOINTS COMMONLY IN THE 50S ALONG AND
AHEAD OF SURFACE FRONT. HOWEVER...THE EWD EXTENSION OF EML/STEEP
LAPSE RATE PLUME CENTERED OVER THE SRN ROCKIES WILL RESIDE OVER ERN
NM INTO WRN TX. THESE LAPSE RATES IN CONCERT WITH THE MODEST
BOUNDARY LAYER MOISTURE WILL CONTRIBUTE TO A MODERATELY UNSTABLE AIR
MASS BY AFTERNOON WITH MLCAPES OF 1000-1500 J/KG.

POST-FRONTAL...OROGRAPHIC UPSLOPE AND FRONTAL FORCING APPEAR TO BE
THE PRIMARY MECHANISMS WHICH WILL FOCUS DIURNAL TSTM DEVELOPMENT
GIVEN THE DISPLACEMENT OF THE PRIMARY UPPER LOW WELL TO THE NW.
FORECAST HODOGRAPHS INDICATE THAT CONSIDERABLE VEERING THROUGH THE
LOWEST 2-3 KM AND MODEST /20-30 KT/ MIDLEVEL FLOW WILL RESULT IN
30-40 KT OF DEEP-LAYER SHEAR. THUS...ENVIRONMENT WILL BE SUPPORTIVE
OF ORGANIZED/ROTATING UPDRAFTS WITH THE PRIMARY SEVERE WEATHER
THREATS BEING LARGE HAIL AND DAMAGING WINDS.

...MID ATLANTIC COAST INTO SRN NEW ENGLAND...

A MOIST LOW-LEVEL AIR MASS WILL EXIST AHEAD OF SURFACE FRONT WITH
DEWPOINTS IN THE 60S. DAYTIME HEATING IN CONJUNCTION WITH THIS
MOISTURE AND HEIGHT FALLS/DYNAMIC COOLING AHEAD OF UPPER LOW WILL
CONTRIBUTE TO POCKETS OF MODERATE INSTABILITY BY AFTERNOON WHERE
MLCAPES WILL APPROACH 1000-1500 J/KG. DEEP-LAYER ASCENT IN LEFT
EXIT REGION OF UPPER-LEVEL JET DEVELOPING INTO THE DELMARVA COMBINED
WITH DPVA IN ADVANCE OF MIDLEVEL CIRCULATION WILL SUPPORT AN
INCREASE IN TSTM COVERAGE AND INTENSITY BY AFTERNOON ALONG FRONT.

MID AND HIGH-LEVEL WIND FIELDS WILL GRADUALLY STRENGTHEN WITH
TIME...BUT LOW-LEVEL SHEAR IS FORECAST TO REMAIN RATHER WEAK.
MOREOVER...MIDLEVEL LAPSE RATES WILL REMAIN QUITE POOR AND THESE
FACTORS SHOULD LIMIT A MORE SUBSTANTIAL SEVERE THREAT. STILL...THE
MORE INTENSE STORMS WILL BE CAPABLE OF DAMAGING WINDS AND PERHAPS
SOME HAIL.

..MEAD.. 08/14/2008

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