Prognostic Meteorological Discussion
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FXUS02 KWBC 050448
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1247 AM EDT TUE MAY 05 2015

VALID 12Z FRI MAY 08 2015 - 12Z TUE MAY 12 2015

...OVERVIEW AND GUIDANCE PREFERENCES...

UPPER RIDGING IS FORECAST TO EASE THROUGH THE NORTHEAST AS WELL AS
NW CANADA WHICH FAVORS SUCCESSIVE TROUGHING IN THE WESTERN/CENTRAL
STATES. A PESKY UPPER/SFC AND POTENTIALLY SUBTROPICAL LOW WILL
MEANDER JUST OFF THE SOUTHEAST COAST UNTIL THE UPPER RIDGE TO ITS
NORTH PUSHES INTO THE NW ATLANTIC NEXT WEEK. THE MODELS AND
ENSEMBLES HAVE DONE A DECENT JOB ON THE OVERALL PATTERN... WITH
EXPECTED DIFFERENCES HERE AND THERE IN RECENT RUNS. A BLEND OF THE
18Z GFS/GEFS AND 12Z ECMWF/ECENS MEAN WAS USED FRI/SAT WHICH KEPT
GOOD CONTINUITY OFF THE SE COAST WHILE STAYING WITHIN THE BEST
CONSENSUS. MODELS WERE ALSO IN GOOD AGREEMENT ON THE NEXT UPPER
LOW TO DIG THROUGH THE SW STATES LATER THIS WEEK. BY SUN/MON...
DIFFERENCES EMERGE MORE CLEARLY OFF THE PAC NW COAST WITH INCOMING
ENERGY AS WELL AS OFF THE SE COAST -- THE GFS/GEFS LIE FARTHER SW
THAN THE OTHERS WITH THE `LOST` LOW THOUGH THAT WAS THE TREND
YESTERDAY. A TREND TOWARD A NAEFS/ECENS MEAN BLEND WAS USED BY
NEXT TUE/D7 DUE TO NON-INCONSEQUENTIAL PLACEMENT/TIMING
DIFFERENCES IN THE MIDWEST/GREAT LAKES WITH THE SFC LOW AND FRONT
AS WELL AS DIFFERENCES OFF THE PAC NW COAST WITH PERHAPS YET
ANOTHER CLOSED LOW.


...SENSIBLE WEATHER HIGHLIGHTS...

TEMPERATURE DEPARTURES WILL MOSTLY ALIGN WITH THE UPPER PATTERN...
COOLER THAN AVERAGE IN THE WEST AND WARMER THAN AVERAGE IN THE
EAST... WHICH ALL SHIFTS A BIT FARTHER EAST WITH TIME. THIS WILL
COOL DOWN THE CENTRAL STATES BY EARLY NEXT WEEK AND ALLOW THE WEST
TO REBOUND TO NEAR OR ABOVE AVERAGE. PRECIPITATION WILL FOCUS
ALONG AND DOWNSTREAM OF THE CLOSED LOW... FROM THE GREAT BASIN AND
CENTRAL ROCKIES INTO THE CENTRAL/SOUTHERN PLAINS AND INTO THE
GREAT LAKES. IT STILL APPEARS THAT THE BULK OF THE PRECIPITATION
ASSOCIATED WITH THE OCEAN LOW WILL STAY OFFSHORE... BUT THE MODELS
STILL DO NOT HAVE A GOOD HANDLE ON ITS EVOLUTION... SO CONFIDENCE
IS LOW. ENSEMBLES STILL MAXIMIZE PRECIPITATION OVER CENTRAL OK/TX
THROUGH THE PERIOD... AT THE COINCIDENT AREA OF SOUTHWESTERLY
UPPER FLOW AND SOUTHERLY SURFACE FLOW... AND PW VALUES IN THE +1
TO +2 STND DEV RANGE.


FRACASSO

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