977
FXUS01 KWBC 191925
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
324 PM EDT MON OCT 19 2009
VALID 00Z TUE OCT 20 2009 - 12Z WED OCT 21 2009
..POTENT WINTER STORM POSSIBLE FOR FRONT RANGE
VERY COOL HIGH PRESSURE WILL CONTINUE TO ALLOW MUCH OF THE EASTERN
U.S. TO DRY OUT SOME AFTER SEEING SEVERAL DAYS RECENTLY OF SOAKING
RAINS AND IN SOME CASES A RARE EARLY SEASON SNOWFALL. ACCOMPANYING
THE COOL HIGH PRESSURE WILL BE ANOTHER RISK OF TEMPERATURES BEING
SUFFICIENTLY COLD ENOUGH MONDAY NIGHT AND EARLY TUESDAY MORNING
FOR A FROST AND POSSIBLY A FREEZE LOCALLY...WITH THE THREAT AREA
INCLUDING THE MID-ATLANTIC...SOUTHERN APPALACHIANS AND INTERIOR
SOUTHEAST. THE HIGH PRESSURE SHOULD NOSE WELL SOUTH EVEN INTO
FLORIDA AND BY THE MIDDLE OF THE WEEK SHOULD BEGIN TO PUSH
OFFSHORE THE EAST COAST WHICH WILL ALLOW SOME WARMER SOUTHERLY
FLOW TO RETURN FOR THE EASTERN THIRD OF THE NATION. AN EXCEPTION
TO THIS SHOULD BE ACROSS THE NORTHEAST AS A WEAK COLD FRONT SHOULD
CROSS THE REGION BY LATE TUESDAY ALONG WITH POSSIBLY SOME
SCATTERED SHOWERS.
IN THE WEST...A STRONG UPPER LEVEL DISTURBANCE IS FORECAST TO DROP
SOUTHEASTWARD ACROSS THE CENTRAL AND SOUTHERN GREAT BASIN TONIGHT
INTO TUESDAY BEFORE THEN AMPLIFYING OVER THE FOUR CORNERS REGION
BY EARLY WEDNESDAY. THIS IS EXPECTED TO HELP SET THE STAGE FOR
POTENTIALLY A SIGNIFICANT WINTER STORM FOR ESPECIALLY THE CENTRAL
ROCKIES AND AREAS A LITTLE FARTHER EAST INVOLVING THE FRONT RANGE
AND ADJACENT HIGH PLAINS AS COLDER AIR SETTLES SOUTHWARD FROM THE
NORTHERN PLAINS. THIS COLDER AIR WILL BE FOLLOWING A FRONTAL
PASSAGE AS A SEPARATE UPPER LEVEL DISTURBANCE ADVANCES EASTWARD
OUT OF THE NORTHERN ROCKIES AND THEN TOWARD THE UPPER MISSISSIPPI
VALLEY BY WEDNESDAY. BOTH OF THESE SYSTEMS WILL ALLOW MUCH OF THE
WIDESPREAD RAIN SHOWER AND HIGH ELEVATION SNOW SHOWER ACTIVITY
CURRENTLY OVER THE OVER THE INTERMOUNTAIN WEST AND THE NORTHERN
ROCKIES TO REFOCUS EVENTUALLY INTO THE FRONT RANGE AREA
NORTHEASTWARD INTO THE NORTH-CENTRAL PLAINS AND STREAKING EASTWARD
INTO THE MIDWEST AS LOW PRESSURE REDEVELOPS IN THE LEE OF THE
ROCKIES. THIS LOW PRESSURE REDEVELOPMENT WILL ALLOW A COLD FRONT
TO ALSO SETTLE SOUTHEASTWARD INTO THE SOUTHERN PLAINS WHERE AN
INCREASINGLY WARM...MOIST AND UNSTABLE AIRMASS WILL BE POOLING.
HENCE THERE WILL BE AN INCREASING THREAT OF
THUNDERSTORMS...INCLUDING AT LEAST AN ISOLATED THREAT OF SEVERE
WEATHER.
ORRISON
GRAPHIC AVAILABLE AT WWW.HPC.NCEP.NOAA.GOV
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