Prognostic Meteorological Discussion
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FXUS01 KWBC 230729
PMDSPD

SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
328 AM EDT SAT SEP 23 2017

VALID 12Z SAT SEP 23 2017 - 12Z MON SEP 25 2017

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

A DICHOTOMY OF AIR MASSES WILL EXIST ACROSS THE NATION THIS
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 SOME SNOW FOR THE HIGHEST ELEVATIONS
OF THE ROCKIES, AND SUMMER-LIKE HEAT AND NOTICEABLE LEVELS OF
HUMIDITY FROM THE PLAINS TO THE EAST COAST.  SOME LOCATIONS COULD
EVEN ACHIEVE RECORD HIGH TEMPERATURES WITH READINGS BREAKING THE
90-DEGREE MARK.  WIDESPREAD AREAS WILL SEE TEMPERATURES RUNNING 10
TO 20 DEGREES ABOVE NORMAL FOR THIS TIME OF YEAR.

GIVEN THE PRONOUNCED DIFFERENCE IN THESE AIR MASSES, A STRONG
FRONTAL BOUNDARY WILL EXIST FROM THE CENTRAL ROCKIES TO THE UPPER
MIDWEST, WITH VERY SLOW EASTWARD PROGRESSION OVER THE NEXT COUPLE
OF DAYS.  SOME STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED TO
DEVELOP ALONG AND AHEAD OF THE FRONT ACROSS THE WESTERN HIGH
PLAINS, AND ALSO FOR PARTS OF THE UPPER MIDWEST ON SATURDAY.  IN
ADDITION, THESE STORMS WILL BE CAPABLE OF PRODUCING EPISODES OF
HEAVY RAIN THAT COULD RESULT IN FLASH FLOODING.  ACROSS THE
EASTERN U.S., THE EFFECTS OF POST TROPICAL STORM JOSE WILL
CONTINUE TO DIMINISH AS THIS SYSTEM WEAKENS.  THE ATTENTION NOW
TURNS TO HURRICANE MARIA AND ITS FUTURE PATH, AND THE NATIONAL
HURRICANE CENTER HAS ADDITIONAL DETAILS ON THAT STORM.

D. HAMRICK


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





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