Thursday, March 24, 2011

DAY1SVR: Day 1 Convective Outlook Amend 1

ACUS01 KWNS 242155
SWODY1
SPC AC 242154

DAY 1 CONVECTIVE OUTLOOK AMEND 1
NWS STORM PREDICTION CENTER NORMAN OK
0454 PM CDT THU MAR 24 2011

VALID 242150Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF WEST TX...

AMENDED FOR ADDITION OF GENERAL TSTM AREA WRN KS

D1 OTLK HAS BEEN UPDATED TO INCLUDE PORTIONS OF WRN AND NRN KS IN
GENERAL TSTM AREA. A N-S BAND OF TSTMS HAS RECENTLY DEVELOPED FROM
THE ERN OK PNHDL NWD INTO WRN KS IN ADVANCE OF MIDLEVEL TROUGH
LIFTING NEWD THROUGH THE CNTRL ROCKIES. RUC FORECAST SOUNDINGS
SUGGEST THAT TSTMS ARE LIKELY BASED BETWEEN 750-700 MB WITHIN A
STEEP LAPSE RATE ENVIRONMENT WITH MUCAPE OF AROUND 500 J/KG. LATEST
MODEL GUIDANCE SUGGESTS THAT THIS ACTIVITY WILL SHIFT EWD THROUGH
CNTRL INTO ERN KS THIS EVENING WITH THE STRONGER UPDRAFTS CAPABLE OF
HAIL.

..MEAD/DARROW.. 03/24/2011

.PREV DISCUSSION... /ISSUED 1115 AM CDT THU MAR 24 2011/

A STRONG UPPER TROUGH IS PROGRESSING OFF THE EAST COAST
TODAY...WHILE ANOTHER TROUGH ROTATES INTO THE SOUTHWEST STATES.
BETWEEN SYSTEMS AN UPPER RIDGE IS AFFECTING THE CENTRAL PORTIONS OF
THE NATION. OVERALL...A QUIET THUNDERSTORM DAY IS ANTICIPATED OVER
THE MAJORITY OF THE US. THE EXCEPTIONS ARE OVER PORTIONS OF THE
SOUTHERN PLAINS THIS AFTERNOON AND EVENING...AND ACROSS PORTIONS OF
THE PACIFIC COASTAL REGION.

...WEST TX THIS EVENING...
A RATHER DRY AND STABLE SURFACE AIR MASS IS IN PLACE ACROSS MOST OF
OK/TX THIS MORNING. HOWEVER...THE MAF 12Z RAOB AND VISIBLE
SATELLITE IMAGERY INDICATE SUBSTANTIAL MOISTURE IS RETURNING
NORTHWARD JUST ABOVE THE SURFACE. RECENT OBSERVATIONAL TRENDS AND
MODEL GUIDANCE SUGGESTS THAT RAPID BOUNDARY LAYER MOISTENING WILL
CONTINUE THROUGH THE DAY...WITH DEWPOINTS JUMPING THROUGH THE 50S
OVER PORTIONS OF WEST TX BY LATE THIS AFTERNOON. STEEP MID LEVEL
LAPSE RATES ARE IN PLACE WITH A WEAK CAP. THIS IS EXPECTED TO
RESULT IN THE THREAT OF ISOLATED THUNDERSTORMS LATE THIS AFTERNOON
AND EVENING OVER PORTIONS OF WEST TX...PRIMARILY BETWEEN LBB AND
MAF. STRENGTHENING LOW/MID LEVEL WINDS WILL RESULT IN FAVORABLE
VERTICAL SHEAR PROFILES FOR SUPERCELLS CAPABLE OF HAIL AND DAMAGING
WINDS. DESPITE UNCERTAINTY REGARDING COVERAGE OF STORMS...12Z
GUIDANCE LENDS SUFFICIENT CONFIDENCE IN INITIATION THAT THIS SMALL
AREA HAS BEEN INCLUDED IN A SLIGHT RISK.

...NORTHERN CA...
AN UPPER LOW CURRENTLY OFF THE CA/ORE COAST IS FORECAST TO MOVE
INLAND TODAY...WITH A SHORTWAVE TROUGH ROTATING THROUGH THE BASE OF
THE LOW INTO NORTHERN CA. STRONG ONSHORE FLOW...COLD MID LEVEL
TEMPERATURES...AND FAVORABLE LARGE SCALE ASCENT WILL PROMOTE
WIDESPREAD PRECIPITATION OVER NORTHERN CA. A FEW THUNDERSTORMS ARE
POSSIBLE AS WELL IN OROGRAPHICALLY FAVORED AREAS. VERTICAL SHEAR
PROFILES ARE EXPECTED TO BE QUITE FAVORABLE FOR ORGANIZED CONVECTION
IN THE SACRAMENTO VALLEY LATER TODAY...BUT THE THREAT IS CONDITIONAL
ON THE AMOUNT OF DESTABILIZATION THAT CAN OCCUR OWING TO EXTENT OF
CLOUDS/PRECIP. IF A THUNDERSTORM OR TWO CAN BECOME ESTABLISHED IN
THIS AREA...LOCALLY DAMAGING WIND GUSTS OR A BRIEF TORNADO ARE
POSSIBLE.

...OK LATE TONIGHT...
MODELS ARE CONSISTENT IN DEVELOPING A STRONG SOUTHERLY LOW LEVEL JET
ACROSS TX/OK TONIGHT. THIS WILL LEAD TO RAPID
MOISTENING/DESTABILIZATION AS WELL AS STRONG WARM ADVECTION AND LIFT
OVER PORTIONS OF OK. IT APPEARS LIKELY THAT SCATTERED SHOWERS AND
THUNDERSTORMS WILL DEVELOP /MAINLY AFTER MIDNIGHT/ OVER PORTIONS OF
EASTERN/NORTHERN OK AND SOUTHERN KS. THE STORMS ALONG THE SOUTHERN
FRINGE OF THIS AREA MAY PRODUCE HAIL.

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