Prognostic Meteorological Discussion
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691
FXUS01 KWBC 220749
PMDSPD

SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
348 AM EDT FRI SEP 22 2017

VALID 12Z FRI SEP 22 2017 - 12Z SUN SEP 24 2017

...COLD FOR THE WESTERN U.S. AND WARM FOR THE EASTERN STATES...

A DICHOTOMY OF AIR MASSES WILL EXIST ACROSS THE NATION TO END THE
WEEK AND INTO THE WEEKEND, WITH A DEEP TROUGH OVER THE
INTERMOUNTAIN WEST AND A LARGE UPPER LEVEL RIDGE OVER THE EASTERN
U.S.  THIS EQUATES TO BELOW NORMAL TEMPERATURES AND SNOW FOR THE
HIGHER ELEVATIONS OF THE ROCKIES AND GREAT BASIN, AND SUMMER-LIKE
HEAT AND NOTICEABLE LEVELS OF HUMIDITY FROM THE PLAINS TO THE EAST
COAST.  SOME LOCATIONS ACROSS THE OHIO VALLEY AND MIDWEST COULD
SEE HIGHS REACH 90 OR HIGHER, COMPARABLE TO WHAT WAS OBSERVED ON
THURSDAY.

GIVEN THE PRONOUNCED DIFFERENCE IN THESE AIR MASSES, A STRONG COLD
FRONT WILL EXIST FROM THE CENTRAL ROCKIES TO THE NORTHERN PLAINS,
WITH LITTLE IN THE WAY OF EASTWARD PROGRESSION OVER THE NEXT
COUPLE OF DAYS.  STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED TO
DEVELOP ALONG AND AHEAD OF THE FRONT ON FRIDAY ACROSS THE WESTERN
HIGH PLAINS, AND ALSO FOR PARTS OF THE UPPER MIDWEST.  IN
ADDITION, THESE STORMS WILL BE CAPABLE OF PRODUCING EPISODES OF
HEAVY RAIN THAT COULD RESULT IN FLASH FLOODING.

POST TROPICAL STORM JOSE WILL CONTINUE TO WEAKEN WELL OFF NEW
ENGLAND`S COAST THROUGH FRIDAY AND INTO THE WEEKEND, ALTHOUGH IT
IS NOT EXPECTED TO MOVE VERY MUCH.  RAINFALL FROM IT WOULD
PRIMARILY AFFECT COASTAL PORTIONS OF THE NORTHEAST U.S., ALONG
WITH ELEVATED SURF AND HAZARDOUS MARINE CONDITIONS.  IT WILL ALSO
RESULT IN INCREASED CLOUD COVER EAST OF THE APPALACHIANS ON FRIDAY.

D. HAMRICK


GRAPHICS AVAILABLE AT
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP
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