DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 201934
SWODY1
SPC AC 201931

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0131 PM CST TUE NOV 20 2012

VALID 202000Z - 211200Z

...NO SVR TSTM AREAS FORECAST...

...PACIFIC NW...

A MARGINAL THREAT OF ISOLATED STRONG WIND GUSTS WILL EXIST UNTIL
AROUND 21Z ALONG A PORTION OF THE WASHINGTON COASTAL COUNTIES WITH
FORCED CONVECTIVE BAND THAT HAS MOVED ONSHORE. INTENSITIES APPEAR TO
HAVE PEAKED...AND ACTIVITY IS EXPECTED TO BEGIN A WEAKENING TREND AS
IT CONTINUES FARTHER INLAND. REF SWOMCD 2121 FOR MORE DETAILS.
OTHERWISE ONLY MINOR ADJUSTMENTS HAVE BEEN MADE TO CURRENT FORECAST.

..DIAL.. 11/20/2012

.PREV DISCUSSION... /ISSUED 1023 AM CST TUE NOV 20 2012/

...WA/ORE/ID/WRN MT REST OF TODAY THROUGH TONIGHT...
A FAST/MOIST WSWLY/WLY MID-LEVEL FLOW REGIME WILL EXTEND FROM THE
PACIFIC NW TO THE NRN ROCKIES DOWNSTREAM FROM A CLOSED CYCLONIC
CIRCULATION CENTERED OFF THE BRITISH COLUMBIA/NW CONUS COAST. WHILE
THE CENTER OF THE CYCLONE WILL MOVE LITTLE DURING THE REMAINDER OF
THE PERIOD...A SERIES OF IMPULSES PIVOTING AROUND THE CYCLONE WILL
MAINTAIN WIDESPREAD PRECIPITATION WITH EMBEDDED ISOLATED DEEPER
CONVECTION. ONE IMPULSE WITH ASSOCIATED LIGHTNING IS CURRENTLY
APPROACHING THE WA COAST...WITH THE 12Z QUILLAYUTE RAOB INDICATING
JUST OVER 200 J/KG OF CAPE FOR A PARCEL LIFTED FROM AROUND 1.5 KFT
AGL. ADDITIONAL UPSTREAM IMPULSES WILL MOVE ASHORE THROUGH THE
REMAINDER OF THE PERIOD AND SUPPORT ISOLATED THUNDERSTORMS AMIDST
7-8-C/KM MID-LEVEL LAPSE RATES FROM AROUND PUGET SOUND WWD TO THE
NWRN WA COAST AND THEN SWD TO THE WRN ORE COAST.

FARTHER EAST ACROSS THE INTERMOUNTAIN WEST TO THE NRN ROCKIES --
I.E. EAST OF THE GENERAL-THUNDERSTORM AREA -- FORECAST SOUNDINGS
INDICATE THE PRESENCE OF ONLY MARGINAL AMOUNTS OF ELEVATED BUOYANCY
THROUGH TONIGHT...AND AN ISOLATED THUNDERSTORM OR TWO CANNOT BE
RULED OUT. HOWEVER...RELATIVELY WARMER 500-MB TEMPERATURES AND ONLY
WEAK DEEP ASCENT SHOULD KEEP THUNDERSTORM COVERAGE SUFFICIENTLY
LIMITED SUCH THAT A GENERAL-THUNDERSTORM AREA IS NOT WARRANTED.

...FAR SERN AZ/SRN NM/TRANS-PECOS REGION OF SWRN TX TONIGHT...
A MID-LEVEL CYCLONE OFF THE CNTRL BAJA CA COAST WILL TRACK ENEWD AND
REACH NEAR THE NRN SIERRA MADRE OCCIDENTALS BY LATE TONIGHT. THE
INFLUX OF RELATIVELY RICHER 750-700-MB MOISTURE BENEATH STEEP
MID-LEVEL LAPSE RATES WILL PROMOTE MARGINAL DESTABILIZATION FOR
ELEVATED PARCELS. WEAK LOW/MID-LEVEL ISENTROPIC ASCENT LEADING THE
CYCLONE MAY SUPPORT ISOLATED THUNDERSTORMS...ESPECIALLY LATE IN THE
NIGHT AND IN CLOSEST PROXIMITY TO THE INTERNATIONAL BORDER...AS
AFFIRMED BY OUTPUT FROM THE EXPERIMENTAL SPC SSEO
CONVECTION-ALLOWING MODEL GUIDANCE.

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