DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 271301
SWODY1
SPC AC 271259

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0659 AM CST THU FEB 27 2014

VALID 271300Z - 281200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
IN MID-UPPER LEVELS...LARGE-SCALE PATTERN WILL CONTINUE TO FEATURE
MEAN RIDGING FROM CONUS W COAST STATES NNWWD ACROSS ERN AK AND WRN
ARCTIC. LARGE CYCLONIC GYRE CENTERED INVOF HUDSON BAY WILL BE
ORBITED BY SHORTWAVE-VORTICITY SPOKES OF VARYING
AMPLITUDE...INCLUDING TROUGH NOW OVER GREAT LAKES THAT WILL EXIT NEW
ENGLAND TONIGHT. ANOTHER STG SHORTWAVE TROUGH IS EVIDENT IN
MOISTURE-CHANNEL IMAGERY MOVING ASHORE CENTRAL/NRN CA COAST. THIS
PERTURBATION WILL PENETRATE MEAN-RIDGE POSITION TODAY...CROSS
4-CORNERS REGION AND SRN ROCKIES OVERNIGHT...THEN REACH PORTIONS TX
PANHANDLE AND WRN OK BY END OF PERIOD. FARTHER W...HIGH-AMPLITUDE
SHORTWAVE TROUGH WAS EVIDENT OVER NERN PAC W OF CA...AROUND
140-145W. THIS FEATURE SHOULD EVOLVE INTO CLOSED CYCLONE TODAY.
CENTER OF THAT CYCLONE SHOULD REACH TO ABOUT 450 NM W SFO BY
12Z...WITH LEADING EDGE OF ITS DCVA FIELD AND LOW-LEVEL FRONTAL ZONE
REACHING CENTRAL/NRN CA COAST AROUND END OF PERIOD.

AT SFC...COLD FRONT IS MOVING SEWD ACROSS S FL ATTM...PRECEDED BY
THIN/BKN BAND OF SHOWERS OVER PORTIONS FL KEYS AND ADJACENT WATERS.
WARM FRONTOGENESIS IS UNDERWAY FROM ERN CO SEWD TO RED RIVER
REGION...MOVING NEWD. AS MID-UPPER LEVEL WAVE
APCHS...HEIGHT/PRESSURE FALLS WILL OCCUR OVER CENTRAL ROCKIES AND
ADJOINING HIGH PLAINS...RESULTING IN CYCLOGENESIS ALONG CO FRONTAL
SEGMENT AND FURTHER FRONTOGENESIS FARTHER E. BY 00Z...EXPECT LOW
OVER ERN CO WITH WARM FRONT ESEWD OVER SRN KS TO OZARKS REGION. BY
12Z...CYCLONE SHOULD MOVE ALONG FRONT SEWD TO SWRN KS/NWRN OK/NERN
TX PANHANDLE REGION...SLIGHTLY N OR NE OF 500-MB VORTICITY MAX.

...CA TO S-CENTRAL ROCKIES...
CONVECTIVE POTENTIAL ACROSS THIS SWATH IS ASSOCIATED WITH TWO
TEMPORALLY DISTINCT EVENTS THAT HAPPEN TO OVERLAP A LITTLE SPATIALLY
OVER CA.

1. WIDELY SCATTERED TSTMS IN CENTRAL/N-CENTRAL CA SHOULD DIMINISH AS
THEY SHIFT EWD THROUGH SIERRA DURING NEXT FEW HOURS. MODIFIED OAK
SOUNDING SUGGESTS ROUGHLY 200-500 J/KG MUCAPE IS AVAILABLE TO THIS
ACTIVITY UNTIL PASSAGE OF MID-UPPER TROUGH RESULTS IN STABILIZING
CONDITIONS ALOFT. FARTHER E...FROM GREAT BASIN TO S-CENTRAL
ROCKIES...LARGE-SCALE ASCENT/UVV AHEAD OF TROUGH WILL INCREASE
MID-UPPER LEVEL LAPSE RATES...PRIMARILY N OF 130-145 KT SPEED MAX AT
250 MB SHIFTING EWD OVER AZ/NM...IN STEP WITH TROUGH. SFC DIABATIC
HEATING AND MRGL MOISTURE SHOULD SUPERIMPOSE WITH COOLING ALOFT TO
STEEPEN LOW-MIDDLE LEVEL LAPSE RATES AS WELL. NET RESULT SHOULD BE
PATCHES OF 200-500 J/KG MLCAPE DURING AFTN AND SIMILAR MUCAPE VALUES
AS REGIME SHIFTS EWD OVER COOLING LAND AREAS THIS EVENING...WITH
SOME CAPE OCCUPYING SUITABLE THERMAL LAYER ALOFT FOR LTG PRODUCTION.
MOST VIGOROUS CELLS MAY PRODUCE SMALL HAIL AND GUSTY
WINDS...HOWEVER SVR POTENTIAL WILL BE GREATLY RESTRICTED BY LACK OF
MORE ROBUST MOISTURE/BUOYANCY.

2. SECOND ROUND OF PRECIP...PERHAPS WITH EMBEDDED TSTMS...WILL APCH
CA COAST OVERNIGHT AHEAD OF ERN PAC CYCLONE...IN ASSOCIATION WITH
AFOREMENTIONED DCVA/FRONTAL ZONE. THIS ACTIVITY SHOULD AFFECT
PORTIONS CENTRAL/NRN CA COAST AND PERHAPS SRN CA BEFORE 12Z. TIME
SERIES OF FCST SOUNDINGS SUGGESTS CONVECTION MAY BE SFC-BASED IN
MARINE LAYER...WITH PRECONVECTIVE BUOYANCY DEVELOPING ALONG COAST
DURING LAST FEW HOURS OF PERIOD. MLCAPE/MUCAPE IN 200-300 J/KG
RANGE MAY REACH SHORE...WITH VALUES OF 500-600 J/KG OFFSHORE.

...SRN PLAINS...
ISOLATED TO WIDELY SCATTERED CONVECTION MAY DEVELOP IN ZONE OF
LOW-LEVEL WAA...FRONTOGENETIC FORCING AND MEAGER BUT MRGLLY
SUFFICIENT MOISTURE LATE IN PERIOD...MAINLY 09-12Z FROM ERN OK TO
SRN KS. ATTM IT APPEARS THAT BUOYANCY WILL BE VERY WEAK--E.G.
MUCAPE LESS THAN 100 J/KG OVER MOST OF THIS AREA. LTG POTENTIAL
BEFORE 12Z IS NONZERO BUT APPEARS TO CONDITIONAL/WEAK TO INTRODUCE
10% GEN THUNDER AREA ATTM.

..EDWARDS/MARSH.. 02/27/2014

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