Prognostic Meteorological Discussion
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FXUS02 KWBC 211534
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1133 AM EDT FRI JUL 21 2017

VALID 12Z MON JUL 24 2017 - 12Z FRI JUL 28 2017

...PATTERN OVERVIEW/GUIDANCE EVALUATION/PREFERENCES...

THE LARGE SCALE SYNOPTIC PATTERN ACROSS THE U.S. WILL BE
AMPLIFIED, RATHER PROGRESSIVE IN NATURE AND RESEMBLE SUMMER. FOR
THE MOST PART, HEIGHTS WILL BE NEAR AVG OR SLIGHTLY ABOVE AVG
THROUGHOUT THE FORECAST PERIOD WITH PERHAPS THE ONE OR TWO
EXCEPTIONS, THE BELOW AVG HEIGHTS AND TROUGH IN NEW ENGLAND AND
POSSIBLE ABOVE AVG HEIGHTS OVER THE CENTRAL/SRN ROCKIES INTO
CENTRAL/SRN PLAINS WITH THE BUILDING UPPER RIDGE BUT MEANS ARE
LIKELY TOO CONSERVATIVE.

INITIALLY ON DAY 3/MONDAY, A SHORTWAVE PUSHING THROUGH THE GREAT
LAKES REGION WILL BE RESPONSIBLE FOR AN AREA OF LOW PRESSURE WHICH
IS FORECAST TO MOVE INTO THE NORTHEASTERN U.S. MANY SOLUTIONS
FAVOR A SECONDARY CYCLONE TO FORM OFF THE ATLANTIC COAST AS NOTED
IN THE ENSEMBLE SCATTER LOW PLOT. IT APPEARS THIS ELONGATED REGION
OF UPPER TROUGHING SHOULD HOLD ON UNTIL TUESDAY AS MOST ENSEMBLE
MEMBERS DEPICT. IN ITS WAKE AND BY FAR THE MOST ANOMALOUS SHORT
WAVE OVER CENTRAL CANADA, WITH 500-MB HEIGHT ANOMALIES IN THE 1 TO
1.5 SIGMA BELOW AVG, WILL DIG SOUTH AND EAST TOWARD SERN
CANADA/NERN QUAD OF THE COUNTRY. THIS COULD HELP ESTABLISH A SOLID
CLOSED MID TO UPPER LOW OVER SOUTHERN QUEBEC INTO NORTHERN NEW
ENGLAND WITH TROUGH AXIS EXTENDING SOUTH INTO THE MID-ATL
STATES/SOUTHEAST BY NEXT FRI, THE OPERATIONAL GFS/ECMWF ARE MORE
AGGRESSIVE WITH THIS SCENARIO THAN THE MEANS. TURNING FARTHER
UPSTREAM, THERE IS SOME MINOR SPREAD WITH THE CLOSED LOW SHIFTING
INTO BRITISH COLUMBIA AND TROUGH INTO THE PAC NW, BEFORE HEIGHTS
SHEAR OUT NORTH AND EAST TOWARD CENTRAL CANADA. MEANWHILE THE MOST
CONSTANT FEATURE WITH BE THE RIDGE BUILDING OVER THE FRONT RANGE
OF THE CENTRAL TO SOUTHERN ROCKIES AND BUILDING NORTH INTO THE
NORTHERN PLAINS.

THE FORECAST WAS DRIVEN BY A COMBINATION OF THE 06Z GFS/GEFS MEAN
AND 00Z GFS/ECMWF/ECMWF MEAN. UTILIZED A SIGNIFICANT CHUNK OF THE
DETERMINISTIC GFS/ECMWF TO MAINTAIN SOME DETAIL IN THE PRESSURE
PATTERN.


...WEATHER HIGHLIGHTS...

OVERALL...TEMPERATURES ACROSS THE U.S. SHOULD NOT BE TOO ANOMALOUS
IN NATURE WITH FORECAST HIGHS/LOWS BEING WITHIN 5 TO 10 DEGREES OF
CLIMATOLOGY. THE WARM SPOTS ON THE MAP WILL BE ACROSS THE DESERT
SOUTHWEST WITH READINGS EXCEEDING 110 DEGREES ON MANY DAYS WHILE
HIGHS IN THE UPPER 90S ARE LIKELY OVER THE SOUTHERN/CENTRAL
PLAINS. ACROSS THE GREAT LAKES AS WELL AS THE INTERIOR
NORTHEAST...GENERAL TROUGHING COUPLED WITH A FRONTAL PASSAGE
SHOULD AFFORD READINGS TO STICK CLOSER TO THE 70S.

LOOKING AT PRECIPITATION, MON SHOULD FEATURE LOCALLY HEAVY
RAINFALL ACROSS NEW ENGLAND, FROM THE CENTRAL PLAINS/MID MS VALLEY
NEAR A MID-LEVEL CIRCULATION TRAPPED UNDER RIDGE TO
SOUTH/SOUTHEAST, ACROSS THE DAKOTAS INTO MN AND ACROSS THE
SOUTHWEST WITH MONSOONAL MOISTURE. TUES HEAVY PRECIP POSSIBLE FROM
THE MID MS VALLEY TO SOUTH/SOUTHEAST, WITH FRONT FROM UPPER MS
VALLEY BACK WEST INTO WY AND ACROSS THE SOUTHWEST/FOUR CORNERS.
WED FROM THE GREAT LAKES INTO THE UPPER TO MID MS VALLEY INTO
NE/DAKOTAS AND NORTHERN PLAINS/INTER-MOUNTAIN WEST AND TN
VALLEY/SOUTH/SOUTHEAST. THEN NEXT THURS AND FRI, MUCH OF THE EAST
BACK INTO THE MID MS VALLEY AND NORTHERN PLAINS, WITH POSSIBLE
ACTIVE PERIOD FOR THE FOUR CORNERS REGION.


MUSHER/RUBIN-OSTER


$$





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