Preliminary Forecasts
Issued by NWS

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000
FXUS02 KWNH 270551
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
150 AM EDT SAT MAY 27 2017

VALID 12Z TUE MAY 30 2017 - 12Z SAT JUN 03 2017

PATTERN OVERVIEW AND MODEL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
THE MODEL GUIDANCE REMAINS RELATIVELY AGREEABLE IN SHOWING
PERSISTENT UPPER TROUGHING ACROSS THE NORTHEAST WHICH MID-LEVEL
RIDGING MOVING FROM THE ROCKIES INTO THE NORTHEAST PLAINS AHEAD OF
AN INVADING AND POTENTIALLY DISJOINTED/SEGMENTED UPPER LEVEL
TROUGH.  FOR THE PRESSURES, 500 HPA HEIGHTS, AND WIND GRIDS USED
AN EVEN SPLIT OF THE 12Z CANADIAN, 12Z UKMET, 12Z ECMWF, AND 18Z
GFS FROM TUESDAY INTO THURSDAY BEFORE USING INCREASING PERCENTAGES
OF THE 12Z ECMWF AND 12Z NAEFS MEANS THEREAFTER.  THE TEMPERATURE,
DEW POINT, PRECIPITATION CHANCES, CLOUD, AND WEATHER GRIDS WERE
BASED ON AN EVEN SPLIT OF THE 12Z NAEFS/12Z ECMWF ENSEMBLE MEAN
AND DETERMINISTIC GFS/CANADIAN/ECMWF GUIDANCE.  THE DAYS 4-7 QPF
WERE BASED ON A ROUGH COMPROMISE OF THE 12Z ECMWF AND 00Z GFS
SOLUTIONS.


WEATHER HIGHLIGHTS
~~~~~~~~~~~~~~~~~~
COOLER THAN NORMAL TEMPERATURES ARE EXPECTED TO CONTINUE INTO NEXT
WEEK ACROSS THE GREAT LAKES AND NORTHEAST DUE TO LINGERING UPPER
LEVEL TROUGHING.  MEANWHILE, WARM CONDITIONS ARE EXPECTED ACROSS
MUCH OF INTERMOUNTAIN WEST DESPITE AN EXPECTED COLD FRONT PASSAGE
WITH SOME ASSOCIATED LATE-SEASON PRECIPITATION.  THE GREATEST
POSITIVE TEMPERATURE ANOMALIES ARE EXPECTED BETWEEN THE COLUMBIA
BASIN AND IDAHO THROUGH THE PERIOD.

MOISTURE ADVECTING NORTHWARD OUT OF THE GULF OF MEXICO WILL FUEL
POTENTIALLY HEAVY RAIN AND THUNDERSTORMS ALONG/AHEAD OF A FRONTAL
BOUNDARY ACROSS PORTIONS OF TX, THE DEEP SOUTH, THE
MID-MISSISSIPPI VALLEY, AND OHIO VALLEY EARLY TO MID WEEK.  THE
TAIL END OF THE BOUNDARY IS EXPECTED TO STALL AND INTERACT WITH A
PAIR OF CLOSED LOWS APPROACHING THE SOUTHERN PLAINS, BRINGING
ADDITIONAL HEAVY RAINFALL TO PORTIONS OF TX, THE LOWER- TO
MID-MISSISSIPPI VALLEY, AND MID-SOUTH LATE NEXT WEEK.

ROTH/KONG
$$





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