SWODY2
SPC AC 030518
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1218 AM CDT MON MAY 03 2010
VALID 041200Z - 051200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A DEEP-LAYER CYCLONE CENTERED INITIALLY OVER SRN SASKATCHEWAN WILL
PROGRESS ESEWD ALONG THE INTERNATIONAL BORDER TOWARD THE UPPER GREAT
LAKES. THIS SYSTEM WILL BE ACCOMPANIED BY A 90-100 KT MIDLEVEL JET
STREAK AND SIGNIFICANT HEIGHT FALLS THAT WILL OVERSPREAD THE NRN
PLAINS AND UPPER MS VALLEY. A PRECEDING... LOWER-AMPLITUDE SHORT
WAVE TROUGH IS EXPECTED TO TRANSLATE EWD THROUGH THE LOWER GREAT
LAKES AND NEW ENGLAND. 00Z MODEL GUIDANCE NOW SUGGESTS THAT THIS
TROUGH WILL REMAIN PHASED/LINKED TO A LOWER LATITUDE PERTURBATION
SHIFTING EWD FROM THE LOWER MS VALLEY TO OFF THE SERN ATLANTIC
COAST. MEANWHILE...UPSTREAM FROM THE N-CNTRL CONUS SYSTEM...DIGGING
MID AND UPPER-LEVEL JET STREAKS WILL SUPPORT THE FORMATION OF A
MIDLEVEL LOW OVER THE PACIFIC NW.
...NERN GULF COAST TO THE SERN ATLANTIC COAST...
TSTMS ARE EXPECTED TO PERSIST THROUGH THE PERIOD ALONG A WSW-ENE
ORIENTED BAROCLINIC ZONE SLOWLY SAGGING SWD INTO NRN FL. WHILE THE
PRE-FRONTAL AIR MASS WILL REMAIN QUITE MOIST WITH DEW POINTS IN THE
70S...LAPSE RATES WILL BE POOR...EFFECTIVELY LIMITING THE DEGREE OF
DESTABILIZATION. NONETHELESS...THE INCREASING INFLUENCE OF THE
MIDLEVEL TROUGH COUPLED WITH 40-45 KT OF DEEP WLY SHEAR MAY YIELD
ISOLATED STRONG-MARGINALLY SEVERE STORMS CAPABLE OF MAINLY STRONG
WIND GUSTS.
...LOWER GREAT LAKES INTO NEW ENGLAND...
SCATTERED TSTMS ARE EXPECTED TO DEVELOP BY LATE MORNING INTO
AFTERNOON ALONG AND AHEAD OF A COLD FRONT SHIFTING EWD THROUGH THE
LOWER GREAT LAKES...AND IN CONJUNCTION WITH STRENGTHENING DCVA IN
ADVANCE OF THE MOBILE...MIDLEVEL TROUGH. WHILE BOUNDARY LAYER
MOISTURE WILL REMAIN SOMEWHAT MARGINAL /I.E. DEW POINTS IN THE 40S
TO AROUND 50 F/...DAYTIME HEATING AND 500 MB TEMPERATURES OF AROUND
-20 C WILL SUPPORT THE DEVELOPMENT OF STEEP LAPSE RATES AND AT LEAST
WEAK CONVECTIVE INSTABILITY.
FORECAST HODOGRAPHS INDICATE A KINEMATIC ENVIRONMENT FEATURING A WLY
WIND FIELD WITH 40-50 KT OF DEEP LAYER SPEED SHEAR. AS SUCH...THE
SETUP WILL FAVOR THE DEVELOPMENT OF A FEW ORGANIZED STORM CLUSTERS
OR LINE SEGMENTS WITH THE THREAT FOR ISOLATED DAMAGING WIND GUSTS
AND PERHAPS SOME HAIL.
...WI/WRN UP OF MI...
CONSIDERABLE INTENSIFICATION TO A SURFACE FRONTAL SYSTEM IS FORECAST
ACROSS THE REGION TUESDAY IN ADVANCE OF A POTENT UPPER LOW AND
ATTENDANT JET STREAKS. HERE TOO...THE WARM SECTOR AIR MASS IS
EXPECTED TO REMAIN RELATIVELY DRY WITH BOUNDARY LAYER DEW POINTS IN
THE 40S TO AROUND 50 F. BUT...THE PRESENCE OF DIABATIC HEATING AND
SUBSTANTIAL HEIGHT FALLS/DYNAMIC COOLING ALOFT WILL RESULT IN
STEEPENING LOW TO MIDLEVEL LAPSE RATES AND MLCAPE APPROACHING
200-500 J/KG.
00Z MODEL GUIDANCE IS CONSISTENT IN SUGGESTING THAT TSTMS WILL
BECOME INCREASINGLY LIKELY NEAR THE SURFACE TRIPLE POINT BY MID TO
LATE AFTERNOON...WITH SUBSEQUENT STORM FORMATION OCCURRING SWWD
ALONG COLD FRONT. VERTICAL SHEAR /BOTH IN THE LOW LEVELS AND
THROUGH A DEEP LAYER/ IS FORECAST TO STEADILY STRENGTHEN... NAMELY
DURING THE EVENING IN CONJUNCTION WITH THE DEVELOPMENT OF A SWLY 50+
KT LLJ.
THE PRIMARY FACTOR LIMITING A MORE SUBSTANTIAL SUPERCELL THREAT
APPEARS TO BE THE MARGINAL CONVECTIVE INSTABILITY AND POTENTIAL FOR
INCREASING CONVECTIVE INHIBITION DURING THE TIME OF MOST RAPID SHEAR
INCREASE /I.E. EVENING/. NONETHELESS...THE THREAT WILL EXIST FOR
SOME HAIL AND DAMAGING WIND GUSTS THROUGH TUESDAY EVENING.
..MEAD.. 05/03/2010
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