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FXUS01 KWBC 300803
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
403 AM EDT WED SEP 30 2009
VALID 12Z WED SEP 30 2009 - 00Z FRI OCT 02 2009
A STRONG UPPER-LEVEL SYSTEM BARRELING THROUGH THE WESTERN U.S.
WILL BE THE BIG WEATHER STORY FOR THE WEEK AS IT DRIVES EASTWARD.
THIS HIGHLY AMPLIFIED TROUGH HAS ALREADY BROUGHT A MIXTURE OF
PRECIPITATION TYPES TO THE PACIFIC NORTHWEST AND MUCH OF THE
INTERMOUNTAIN WEST. MUCH OF THE RAIN AND SNOW HAS BEEN LIGHT IN
NATURE GIVEN MEAGER MOISTURE IN PLACE. AS THE FRONTAL BOUNDARY
REACHES THE HIGH PLAINS BY LATE WEDNESDAY...THE SYSTEM WILL BISECT
A STEADY PLUME OF GULF MOISTURE FUELING ENHANCED SHOWER AND
THUNDERSTORM ACTIVITY. THE COVERAGE OF PRECIPITATION SHOULD
INCREASE OVER TIME AS THIS DYNAMIC SYSTEM MOVES INTO THE MIDDLE
MISSISSIPPI VALLEY BY THURSDAY MORNING. GIVEN THE STRONG DYNAMICS
ASSOCIATED WITH THIS SYSTEM...SOME OF THE STORMS MAY BECOME SEVERE
ACCORDING TO THE LATEST STORM PREDICTION CENTER CONVECTIVE
OUTLOOK.
THE OTHER THREAT WITH THIS SYSTEM WILL BE THE EXPECTED SNOWFALL
ALONG THE HIGH TERRAIN OF MUCH OF THE INTERMOUNTAIN WEST ALONG
WITH THE CENTRAL/NORTHERN ROCKIES. SNOWFALL AMOUNTS SHOULD REMAIN
ON THE LIGHTER SIDE BUT WITH FAIRLY WIDESPREAD COVERAGE AS SNOW
LEVELS GRADUALLY DROP. BY THURSDAY MORNING...WINTRY PRECIPITATION
IS FORECAST TO EVEN SPREAD INTO THE BLACK HILLS OF SOUTH DAKOTA.
AS THIS ENTIRE SYSTEM PUSHES SOUTH AND EAST...A VERY STRONG
FRONTAL BOUNDARY WILL BRING MUCH COOLER AND DRIER CONDITIONS WITH
IT. FOR INSTANCE...HIGHS ON WEDNESDAY ACROSS THE CENTRAL HIGH
PLAINS ARE EXPECTED TO REACH THE LOW 90S WITH TEMPERATURE DROPPING
IN UPWARDS OF 30 DEGREES BY THE FOLLOWING DAY. ACCOMPANYING THIS
RAPID CHANGE IN THE WEATHER WILL BE STIFF NORTHWESTERLY WINDS
WHICH MAY GUST UP TO 35 TO 40 MPH AT TIMES.
A LARGE CLOSED LOW WILL REMAIN STAGNANT OVER THE NORTHEASTERN U.S.
KEEPING CONDITIONS UNSETTLED OVER THE REGION. UNDERNEATH THE
INFLUENCE OF THIS EXPANSIVE CYCLONE WILL ALLOW FOR CLOUDY
CONDITIONS TO PREVAIL WITH A CHANCE FOR SCATTERED RAIN SHOWERS.
THE IMPACTS WILL BE MOST NOTICEABLE OVER THE INTERIOR NORTHEAST
WHERE HIGHS THE NEXT COUPLE OF DAYS WILL STRUGGLE TO PUSH ABOVE
THE 40S WITH LIMITED DIURNAL CHANGES IN TEMPERATURES OVERNIGHT.
ENHANCED FIRE WEATHER ACTIVITY IS EXPECTED ACROSS THE SOUTHWESTERN
QUARTER OF THE U.S. AS THE STRONG UPPER TROUGH MOVES THROUGH THE
INTERMOUNTAIN WEST. DRY AND WINDY CONDITIONS BEHIND THE FRONTAL
BOUNDARY WILL BE A DRIVING FORCE FOR POSSIBLE BRUSH FIRE ACTIVITY
AS A SURFACE DOME OF HIGH PRESSURE BUILDS OVER THE UPPER
INTERMOUNTAIN WEST.
RUBIN-OSTER
GRAPHICS AVAILABLE AT WWW.HPC.NCEP.NOAA.GOV
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