640
FXUS01 KWBC 190738
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
337 AM EDT FRI SEP 19 2008
VALID 12Z FRI SEP 19 2008 - 00Z SUN SEP 21 2008
THE JET STREAM WILL STAY NORTH OF THE U.S./CANADIAN BORDER FOR
THIS FORECAST PERIOD. A RELATIVELY DRY FRONTAL BOUNDARY THAT IS
CURRENTLY OVER ALBERTA...SASKATCHEWAN AND MANITOBA WILL RAPIDLY
DIVE SOUTHEASTWARD...CARVING ITS WAY INTO THE NORTHERN PLAINS.
SCATTERED CONVECTION MAY DEVELOP ALONG THE BOUNDARY...WITH THE
BEST CHANCE OF PRECIPITATION MATERIALIZING IN THE AFTERNOON WHEN
THE DIFFERENCES IN THE TWO AIR MASSES WILL BE MOST PRONOUNCED. ALL
THE WHILE THIS FORECAST PERIOD...THE PARENT LOW OF THIS SYSTEM
WILL BE DEEPENING OVER THE HUDSON BAY REGION...AND PICKING UP
MOISTURE. BEHIND THE COLD FRONT...A DOME OF COLD AND DRY AIR WILL
ADVECT INTO THE NORTHERN PLAINS AND UPPER MIDWEST...GIVING THOSE
REGIONS A TASTE OF AUTUMN.
MOVING INTO THE LOWER MISSISSIPPI VALLEY...MID LEVEL MOISTURE OFF
THE GULF OF MEXICO HAS BEEN PUSHING ITS WAY UP THE MISSISSIPPI
RIVER VALLEY BASIN. TWO WEAK IMPULSES OF ENERGY...FROM TEXAS AND
COLORADO...WILL FORM A SYNERGY AND AMPLIFY THE UPPER LEVEL
TROUGH...AND BY DEFAULT...MAKING THE ATMOSPHERE OVER THE MIDDLE
AND LOWER MISSISSIPPI VALLEY PROGRESSIVELY MORE UNSTABLE.
THUNDERSTORMS AND SHOWERS WILL FIRE UP FRIDAY AND SATURDAY FROM
SOUTHERN LOUISIANA AND MISSISSIPPI TO MISSOURI AND ILLINOIS. THE
BEST CHANCE FOR ACCUMULATIONS WILL BE OVER THE CENTRAL GULF COAST
REGION...WHICH IS CLOSEST TO THE MOISTURE SOURCE AND WHERE THE
MORE EFFICIENT WARM AIR ADVECTION WILL SET UP.
HEADING WEST...A CLOSED LOW THAT IS CURRENTLY OFF THE COAST OF
OREGON AND NORTHERN CALIFORNIA WILL ADVANCE
SOUTHEASTWARD...BRINGING COLD...SOMEWHAT MOIST AND UNSTABLE AIR
INTO NORTHERN CALIFORNIA. ON SATURDAY...THIS ENERGY WILL THEN
RECURVE NORTHEASTWARD MOVING TOWARDS IDAHO. THIS SYSTEM WILL
MOSTLY YIELD LIGHT PRECIPITATION...WITH ENHANCED ACCUMULATIONS IN
THE BLUE AND WALLOWA MOUNTAINS OF OREGON AND OVER PORTIONS OF THE
SALMON RIVER MOUNTAINS IN IDAHO. ON FRIDAY LAST BUT NOT
LEAST...OVER THE FOUR CORNERS REGION...THE UPPER LEVEL RIDGE WILL
HOLD STEADFAST OVER THE INTERMOUNTAIN WEST ON FRIDAY...ENABLING
TEMPERATURES TO SOAR AND ENHANCING CONVECTIVE PROCESSES. EXPECT
LOCALIZED TO SCATTERED THUNDERSTORMS.
SZATANEK
GRAPHICS AVAILABLE AT WWW.HPC.NCEP.NOAA.GOV
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