DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 020556
SWODY1
SPC AC 020554

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1154 PM CST SUN MAR 01 2009

VALID 021200Z - 031200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
HIGHLY-AMPLIFIED/OMEGA-TYPE PATTERN IS FORECAST OVER NOAM THIS
PERIOD...WITH LARGE TROUGHS OVER BOTH THE ERN PACIFIC/W COAST REGION
AND OVER THE ERN CONUS. MEANWHILE...AN EXPANSIVE RIDGE BETWEEN THE
TWO TROUGHS IS PROGGED TO SHIFT SLIGHTLY EWD ACROSS THE ROCKIES
TOWARD THE CENTRAL U.S. THROUGH THE PERIOD.

AT THE SURFACE...A LOW OVER THE GULF STREAM -- INITIALLY OFF THE
DELMARVA COAST -- WILL SHIFT NNEWD WITH TIME...JUST E OF CAPE COD
AND THEN INTO THE CANADIAN MARITIMES LATE. FARTHER W...OVER THE ERN
HALF OF THE CONUS...HIGH PRESSURE WILL PREVAIL...WHILE LEE TROUGHING
REMAINS OVER THE HIGH PLAINS DUE TO WLY/SWLY FLOW ACROSS THE
ROCKIES. OVER THE W COAST STATES/GREAT BASIN...THE SURFACE PATTERN
SHOULD REMAIN MORE NONDESCRIPT...WITH THE MAIN LOW TO REMAIN
OFFSHORE THROUGH THE PERIOD.

...NRN CENTRAL VALLEY OF CA...
MID-LEVEL COLD ADVECTION IS FORECAST ACROSS THE W COAST STATES AND
INTO THE GREAT BASIN...AS THE LARGE UPPER TROUGH OVER THE ERN
PACIFIC CONTINUES A SLOW TRANSITION TOWARD/INTO THIS REGION IN A
PIECEMEAL FASHION. THE RESULTING STEEPENING OF MID-LEVEL LAPSE
RATES WITH TIME IN CONJUNCTION WITH LIMITED/LOCAL DIURNAL HEATING
SHOULD RESULT IN THE DEVELOPMENT OF MODEST SURFACE-BASED CAPE /AOB
250 J/KG/ OVER THE NRN CENTRAL VALLEY.

THIS GRADUAL DESTABILIZATION THROUGH THE AFTERNOON WILL LIKELY
SUPPORT AN INCREASE IN CONVECTIVE INTENSITY...AIDED BY A
FAVORABLY-STRONG DEEP-LAYER WIND FIELD. WITH SSELY SURFACE WINDS
FORECAST IN THE CENTRAL VALLEY VEERING/INCREASING TO SWLY AT TO 60
TO 70 KT AT MID LEVELS...SOME POTENTIAL FOR ONE OR TWO
ORGANIZED/ROTATING STORMS APPEARS TO EXIST. THOUGH
MARGINALLY-SEVERE HAIL APPEARS THE MOST LIKELY THREAT...AN ISOLATED
STRONG WIND GUST OR EVEN A BRIEF TORNADO CANNOT BE RULED OUT GIVEN
THE STRENGTH OF THE FLOW FIELD AND LOCALLY-ENHANCED LOW-LEVEL
VEERING WITH HEIGHT OVER THE CENTRAL VALLEY. HOWEVER...WITH AN
OVERALL LACK OF INSTABILITY FORECAST -- AS HEATING REMAINS GENERALLY
HINDERED BY CLOUDS/ONGOING PRECIPITATION -- SEVERE THREAT STILL
APPEARS LOW. THUS...WILL MAINTAIN ONLY LOW SEVERE PROBABILITY/SEE
TEXT FORECAST.

...NRN NV AND VICINITY...
DESPITE MEAGER LOW-LEVEL MOISTURE...COOLING ALOFT ACROSS THE GREAT
BASIN -- PARTICULARLY FROM LATE AFTERNOON ONWARD -- MAY SUPPORT THE
DEVELOPMENT OF MINIMAL CAPE ACROSS NRN NV AND VICINITY /AOB 150
J/KG/. WHILE DEEP-LAYER WIND FIELD WOULD OTHERWISE SUPPORT
ORGANIZED STORMS...THE GENERAL LACK OF INSTABILITY SHOULD PROVE A
SIGNIFICANT LIMITING FACTOR. NONETHELESS...WILL MAINTAIN A
LOW-PROBABILITY THREAT FOR MARGINAL HAIL WITH A STRONGER CELL OR
TWO.

..GOSS.. 03/02/2009

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