Prognostic Meteorological Discussion
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000
FXUS01 KWBC 041938
PMDSPD

SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
338 PM EDT FRI SEP 04 2015

VALID 00Z SAT SEP 05 2015 - 00Z MON SEP 07 2015

...HEAVY RAINFALL POSSIBLE FOR PORTIONS OF THE NORTHERN
INTERMOUNTAIN WEST, NORTHERN PLAINS, AND UPPER MIDWEST...

A NEARLY STATIONARY FRONTAL BOUNDARY IS DRAPED THIS AFTERNOON FROM
THE NORTHERN INTERMOUNTAIN WEST EASTWARD ACROSS THE NORTHERN
PLAINS. DUE TO UPPER-LEVEL FLOW THAT IS PARALLEL TO THE SURFACE
BOUNDARY, THE FRONT WILL REMAIN LARGELY IN PLACE THROUGH SATURDAY.
A RELATIVELY STRONG UPPER-LEVEL TROUGH CURRENTLY MOVING INTO THE
PACIFIC NORTHWEST WILL MOVE EAST BY SATURDAY NIGHT INTO SUNDAY,
CAUSING A LOW-PRESSURE SYSTEM TO DEEPEN OVER THE NORTHERN PLAINS,
AND MOVING THE ENTIRE FRONTAL SYSTEM EASTWARD. SEVERAL WEAK WAVES
OF LOW PRESSURE WILL MIGRATE ALONG THE STATIONARY FRONTAL BOUNDARY
THROUGH SATURDAY, BRINGING RATHER WIDESPREAD RAIN AND
THUNDERSTORMS FROM THE NORTHERN INTERMOUNTAIN WEST TO THE NORTHERN
PLAINS AND UPPER MIDWEST. THE UPPER-LEVEL TROUGH WILL BRING
SUFFICIENT COLD AIR AT THE MID-LEVELS FOR RAIN TO MIX WITH SNOW AT
THE HIGHER ELEVATIONS OF MONTANA, IDAHO, AND WYOMING. DUE TO THE
DURATION OF RAIN AND THUNDERSTORMS, HEAVY RAINFALL IS POSSIBLE
FROM PORTIONS OF THE NORTHERN INTERMOUNTAIN WEST EASTWARD ACROSS
THE NORTHERN PLAINS TO PORTIONS OF THE UPPER MIDWEST. SOME AREAS
MAY RECEIVE 1-3 INCHES OF RAIN THROUGH SUNDAY.

A WEAKENING COLD FRONT IS MOVING SOUTHWARD ACROSS THE MID-ATLANTIC
STATES THIS AFTERNOON. THE FRONT WILL USHER A DRIER AND SOMEWHAT
COOLER AIR MASS INTO THE MID-ATLANTIC STATES FOR THE WEEKEND, WITH
AFTERNOON HIGH TEMPERATURES SATURDAY AND SUNDAY EXPECTED TO BE
SLIGHTLY BELOW AVERAGE. SCATTERED SHOWERS AND THUNDERSTORMS WILL
BE POSSIBLE IN THE MOIST AND UNSTABLE AIR MASS AHEAD OF THE FRONT,
FROM PORTIONS OF THE OHIO VALLEY INTO THE SOUTHEASTERN STATES.

MONSOONAL MOISTURE WILL REMAIN IN PLACE ACROSS THE SOUTHWESTERN
U.S., WITH SCATTERED SHOWERS AND THUNDERSTORMS EXPECTED DURING THE
AFTERNOON AND EVENING THROUGH THE WEEKEND ACROSS THE FOUR CORNERS
REGION.

RYAN

GRAPHICS AVAILABLE AT WWW.WPC.NCEP.NOAA.GOV
$$




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