397
FXUS01 KWBC 192024
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
423 PM EDT SAT SEP 19 2009
VALID 00Z SUN SEP 20 2009 - 12Z MON SEP 21 2009
SIGNIFICANT CHANGES ARE IN STORE AS THE UPPER-LEVEL PATTERN
BECOMES MORE AMPLIFIED BY THE START OF NEXT WEEK. DURING THE PAST
WEEK...THE STRONGEST JET DYNAMICS HAD BEEN LOCATED TO THE NORTH
ACROSS CANADA. HOWEVER...A STRONG UPPER TROUGH WILL SURGE
SOUTHWARD ACROSS THE ROCKY MOUNTAIN CHAIN BRINGING A PRONOUNCED
COOLING TREND TO MUCH OF THE WESTERN HALF OF THE NATION AS THE
START OF AUTUMN IS JUST AROUND THE CORNER.
THE REMAINS OF AN UPPER LOW WHICH RESIDED ACROSS THE SOUTHERN U.S.
WILL FINALLY VACATE THE REGION. ITS REMNANTS WILL BEGIN TO
INTERACT WITH A SERIES OF DISTURBANCES PUSHING THROUGH THE MIDDLE
MISSISSIPPI VALLEY ALLOWING FOR THE HEAVIER COMPLEX OF SHOWERS AND
THUNDERSTORMS TO EDGE NORTHWARD INTO THE OHIO RIVER VALLEY BY
SUNDAY. WHILE THE CONCENTRATED AREA OF PRECIPITATION WILL MOVE
NORTHWARD...SCATTERED THUNDERSTORMS CANNOT BE RULED OUT ACROSS THE
GULF COAST AS MOIST...MILD AIR REMAINS IN PLACE OVER THE REGION.
WHILE MUCH OF THE RAINFALL IS CONSTRAINED TO THE SOUTH AND
WEST...A DOME OF SURFACE HIGH PRESSURE WILL DOMINATE THE
NORTHEASTERN U.S. THIS WEEKEND. VERY PLEASANT CONDITIONS WILL
PERSIST ACROSS THE REGION UNTIL EARLY NEXT WEEK WHEN THE STORM
SYSTEM TO THE SOUTH SLOWLY APPROACHES. BEFORE THIS HAPPENS...A
VERY CHILLY NIGHT IS IN STORE TONIGHT AS CLEAR SKIES AND CALM
WINDS WILL PREVAIL. CURRENTLY...FROST ADVISORIES AND FREEZE
WARNINGS HAVE BEEN ISSUED FOR MANY LOCATIONS FROM NORTHERN
PENNSYLVANIA UP INTO MAINE. TEMPERATURES OVERNIGHT WILL QUICKLY
PLUMMET DOWN TO THE 30S BEFORE DAYTIME HEATING WARMS THINGS UP THE
FOLLOWING AFTERNOON.
THE WEATHER SYSTEM WHICH WILL BRING WIDESPREAD CHANGES TO THE
WESTERN HALF OF THE U.S. IS CURRENTLY MOVING ACROSS THE THE UPPER
INTERMOUNTAIN WEST. THIS SYSTEM IS FORECAST TO QUICKLY DROP SOUTH
AND EAST TOWARD THE PLAINS BY EARLY MONDAY BRINGING MUCH COOLER
WEATHER ALONG WITH GUSTY WINDS. IN FACT...TEMPERATURES BY MONDAY
WILL DROP IN UPWARDS OF 25 DEGREES ACROSS THE PLAINS WITH HIGHS
ONLY EXPECTED IN THE LOW TO MID 60S WITH EVEN COOLER READINGS
ACROSS THE HIGHER TERRAIN. LIGHT SNOW IS NOT OUT OF THE REALM OF
POSSIBILITIES EITHER OVER THE HIGHER PEAKS OF THE CENTRAL ROCKIES.
RUBIN-OSTER
GRAPHICS AVAILABLE AT WWW.HPC.NCEP.NOAA.GOV
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