Thursday, September 18, 2008

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 181614
SWODY1
SPC AC 181613

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
ISSUED BY AFWA OFFUTT AIR FORCE BASE BELLEVUE NE
1113 AM CDT THU SEP 18 2008

VALID 181630Z - 191200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
THE MAIN BRANCH OF THE POLAR JET WILL EXTEND ACROSS SRN CANADA WHILE
A WEAKER SRN BRANCH EXTENDS ACROSS NRN MEXICO...THE GULF OF MEXICO
AND CNTRL FL. SATELLITE IMAGERY SHOWS A CLOSED LOW OFF THE WEST
COAST BETWEEN OR AND CA. AN UPPER TROUGH OVER THE S/CNTRL STATES...
ANOTHER UPPER TROUGH OVER THE ERN STATES ARE COMBINED WITH THE SRN
JET TO SUPPORT A STATIONARY FRONT OVER CENTRAL FLORIDA AND GULF OF
MEXICO. N OF THIS FRONTAL SYSTEM SURFACE HIGH PRESSURE DOMINATES
MOST OF THE EAST.

...SRN CA INTO ERN GREAT BASIN/ROCKY MTN REGION...
AREAS OF MONSOONAL MOISTURE COUPLED WITH DAYTIME HEATING...AND
OROGRAPHIC LIFT WILL INITIATE ISOLATED AFTERNOON AND EVENING
THUNDERSTORMS. COOL MID-LEVELS ARE CURRENTLY OVER THE ERN GREAT
BASIN AND ROCKIES WITH 500MB TEMPS -12 TO -14C. THIS WILL PROVIDE
FURTHER DESTABILIZATION SUPPORTING MORE COVERAGE OF TSTMS. OVER SRN
CA THE 500MB TEMPS ARE -08C INDICATING COVERAGE WILL BE MORE
ISOLATED OVER THIS PORTION OF THE AREA.

...NRN ROCKIES INTO THE NRN PLAINS...
A SHORTWAVE TROUGH ASSOCIATED WITH THE NRN JET COUPLED WITH
UPPER-LEVEL DIVERGENCE WILL EXTEND FROM MT TO MN AS IT TRACKS EWD.
THIS WILL HELP INITIATE TSTMS THAT WILL FOCUS ON ASSOCIATED
LOW-LEVEL CONVERGENCE ACROSS SRN MT/NRN WY AND A TROUGH THAT WILL
MOVE EWD ACROSS PORTIONS OF THE DAKOTAS AND MN. THE NAM MODEL
INDICATES UNSTABLE CONDITIONS...LIFTED INDEX -1 TO -5 FROM WRN MT TO
ERN MN. 12Z SKEW-T'S IN THIS AREA SHOW PW'S FROM 0.6 TO 0.9
INDICATING ENOUGH MOISTURE FOR TSTMS.

...FL...
THE TWO UPPER TROUGHS OVER THE S/CNTRL AND SE COUPLED WITH THE
STATIONARY FRONT IN THE GULF OF MEXICO AND FL WILL SUPPORT TSTMS
OVER THIS AREA. ABUNDANT GULF MOISTURE AND CAPE OF 1000-2000 J/KG
IN THIS AREA WILL ALSO BE FAVORABLE FOR TSTMS IN THIS AREA. WEAK
VERTICAL SHEAR INDICATE A LOW POTENTIAL FOR SEVERE.

..AFWA.. 09/18/2008

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