Sunday, April 18, 2010

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 180524
SWODY1
SPC AC 180522

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1222 AM CDT SUN APR 18 2010

VALID 181200Z - 191200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...

A HIGH LATITUDE...LARGE AMPLITUDE BLOCKING PATTERN WILL BE
MAINTAINED ACROSS NRN NORTH AMERICA THROUGH THE PERIOD... FEATURING
DEEP UPPER LOWS OVER THE NERN PACIFIC AND CANADIAN MARITIMES...AND
RIDGING OVER CNTRL CANADA. FARTHER S...A MORE PROGRESSIVE
SUBTROPICAL JET WILL EXIST ACROSS NRN MEXICO AND TX EWD THROUGH THE
GULF OF MEXICO AND SRN FL. A MIDLEVEL IMPULSE EMBEDDED WITHIN THIS
SUBTROPICAL AIR STREAM /NOW NEAR CANCUN MEXICO/ WILL TRANSLATE NEWD
ACROSS THE FL PENINSULA LATE TODAY INTO TONIGHT.

...SRN FL PENINSULA...

00Z MODEL GUIDANCE IS SUGGESTIVE THAT A SURFACE LOW WILL ACCOMPANY
THE ABOVE-MENTIONED SHORT WAVE TROUGH THROUGH THE SERN GULF OF
MEXICO AND EVENTUALLY ONTO THE FAR SRN PENINSULA OR THE KEYS LATE
TONIGHT. THE MASS RESPONSE TO THIS DEVELOPING LOW WILL SERVE TO
MAINTAIN A MOIST BOUNDARY LAYER OVER THE AREA WHERE DEW POINTS IN
THE MID 60S TO AROUND 70 F WILL BE COMMON. WHILE LAPSE RATES WILL
REMAIN RATHER WEAK...THIS MOISTURE WILL LARGELY CONTRIBUTE TO
POCKETS OF MODERATE AFTERNOON INSTABILITY WHERE MLCAPE WILL REACH
1000 J/KG.

INCREASED FORCING FOR ASCENT ATTENDANT TO APPROACHING MIDLEVEL
SYSTEM IN CONJUNCTION WITH DEVELOPING SEA BREEZE CIRCULATIONS ARE
EXPECTED TO FOSTER SCATTERED TO NUMEROUS DIURNAL STORMS WITHIN THE
MOIST AND WEAKLY CAPPED ENVIRONMENT. STEADILY STRENGTHENING
MIDLEVEL WIND FIELD ATOP SELY SURFACE WINDS WILL YIELD 30-40 KT OF
DEEP LAYER SHEAR AND 0-1 KM SRH OF AROUND 100 M2/S2. AS
SUCH...SETUP MAY SUPPORT THE DEVELOPMENT OF TRANSIENT SUPERCELL
STRUCTURES CAPABLE OF LOCALLY STRONG WIND GUSTS AND PERHAPS A BRIEF
TORNADO. THIS SEVERE THREAT WILL LIKELY PERSIST OVERNIGHT IN
ASSOCIATION WITH ISOLATED/SCATTERED STORMS WHICH MAY DEVELOP IN
ADVANCE OF THE SURFACE LOW.

...ERN WY/NEB PNHDL SWD THROUGH THE CO FRONT RANGE INTO CNTRL/ERN
NM...

DESPITE THE PRESENCE OF A RELATIVELY DRY BOUNDARY LAYER...STEEP LOW-
TO MIDLEVEL LAPSE RATES WILL CONTRIBUTE TO A WEAKLY UNSTABLE AIR
MASS BY AFTERNOON WHERE MLCAPE MAY APPROACH 500-700 J/KG. MIDLEVEL
HEIGHTS WILL REBOUND SLIGHTLY THROUGH THE DAY IN THE WAKE OF
MIDLEVEL IMPULSE SLOWLY TRANSLATING EWD INTO THE DAKOTAS AND NEB.
NONETHELESS...ISOLATED DIURNAL STORMS APPEAR LIKELY OWING TO THE
COMBINATION OF TERRAIN INFLUENCES AND CONVERGENCE ALONG SURFACE
BOUNDARY STALLED IN THE LEE OF THE HIGHER TERRAIN. THE STRONGER
STORMS WILL BE CAPABLE OF SOME SMALL HAIL...THOUGH THE PROSPECT FOR
ANY SEVERE WEATHER APPEARS QUITE SMALL AT THIS TIME.

..MEAD/SMITH.. 04/18/2010

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