Prognostic Meteorological Discussion
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FXUS02 KWBC 241522
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1122 AM EDT TUE MAY 24 2016

VALID 12Z FRI MAY 27 2016 - 12Z TUE MAY 31 2016

NORTH AMERICAN FLOW PATTERN TAKES ON A MORE SUMMER `LOOK` DURING
THIS MEDIUM RANGE PERIOD--- WITH PROMINENT RIDGING ACROSS ALASKA
AND SOUTHEAST CANADA. AND WITH A JET STREAM THAT WILL BE SHIFTING
NORTHWARD INTO CENTRAL CANADA---RIDGING `SETS UP` OVER THE EASTERN
2/3RDS OF THE LOWER 48.

BLENDING THE 24/00Z GFS/GEFS AND ECMWF/ECENS MEAN MAINTAINED VERY
GOOD CONTINUITY WITH THE PREVIOUS WPC FORECAST THROUGH DAY 5
(SUNDAY)---ESPECIALLY ACROSS THE CENTRAL AND NORTHERN PLAINS
(EITHER SIDE OF 100W LONGITUDE +/- 5deg). AND AFTER DAY
5...TAPERED AWAY FROM THE DETERMINISTIC SOLUTIONS---USING A 60/40
BLEND OF THE ECENS/GEFS MEANS TO GLOSS OVER THE SUBTLE DIFFERENCES
ALONG BOTH COASTS.

WEST COAST...
AFTER DAY 5...THE 24/00Z DETERMINISTIC ECMWF HAS MAINTAINED LESS
THAN DESIRABLE  CONTINUITY OVER ITS PAST THREE RUNS WITH THE
PROGRESSION OF GULF OF ALASKA ENERGY BETWEEN WEST CENTRAL BRITISH
COLUMBIA AND WESTERN MONTANA. THE 24/00Z GFS HAS BEEN A SLIGHTLY
BETTER ALTERNATIVE---THOUGH IT DOES POSSESS A DEEPER AND LESS
PROGRESSIVE TROUGH MIGRATION ACROSS THE PACIFIC NORTHWEST BY/AT
DAY 7.

EAST COAST...
THE 24/00Z CANADIAN MAINTAINS A RATHER COMPACT BUT ENERGETIC 500MB
VORTICITY CENTER ALONG THE NC/SC BORDER AT DAY 7...WHILE THE
GFS/ECMWF MAINTAIN OPEN WAVES AT 500MBS AND BRING A WEAKENED
SURFACE-BASED `DISTURBANCE` ASHORE ON DAY 5 OR DAY 6. THE PROBLEM
WITH USING ANY OF THE 24/00Z DETERMINISTIC GUIDANCE---IS LATITUDE.
A DAY 5 MID-LEVEL DISTURBANCE WOULD BE CENTERED OVER EAST CENTRAL
NC (THE ECMWF) OR CENTRAL SC (THE GFS). AT THE SURFACE---(A
1015MB-1016MB SPOT LOW WORKS)...BUT IT`S EITHER OFFSHORE EAST OF
WILMINGTON NC (ECMWF) OR INVOF CHARLESTON SC (GFS). HERE...TO
BLEND THE MEANS DOES WASH EVERY DETAIL OUT---BUT ACTUALLY
MAINTAINS GOOD CONTINUITY WITH THE PREVIOUS WPC D3-7 GRAPHICS
(DEPICTED AS AN INVERTED TROUGH). THIS SEEMS MORE THAN REASONABLE
WITH LITTLE EVIDENCE FROM THE 24/00Z ECMWF/GFS GUIDANCE THAT A
`VERTICALLY-STACKED` CYCLONE WITH TROPICAL CHARACTERISTICS IS
IMMINENT. PREVIOUS SENSIBLE WEATHER FOLLOWS. VOJTESAK

TROUGHING IN THE WEST WILL MAINTAIN BELOW AVERAGE TEMPERATURES
(ESPECIALLY DAYTIME MAX TEMPERATURES) AND FAIRLY WIDESPREAD BUT
GENERALLY LIGHT RAIN OR HIGHER ELEVATION SNOW. FLOW THROUGH THE
PLAINS SUPPORTS A DAILY THREAT OF RAIN AND STORMS, POSSIBLY
SEVERE, THOUGH PLACEMENT IS UNCLEAR. PLEASE CONSULT THE SPC
OUTLOOKS FOR THE LATEST INFORMATION ON SEVERE THREATS.

FRONTAL BOUNDARY THROUGH THE NORTHERN TIER REMAINS A CHALLENGE TO
TEMPERATURE FORECASTING, ESPECIALLY IN COASTAL AREAS OF THE
NORTHEAST WHERE OCEAN TEMPERATURES ARE STILL COLD AND ONSHORE FLOW
WOULD KEEP THESE AREAS QUITE CHILLY. AREAS SOUTH OF THE FRONT
WOULD FEEL RATHER SUMMER-LIKE -- 70S/80S AND MAYBE NEAR 90F. THE
SOUTHEAST MAY TURN MORE UNSETTLED AS THE INVERTED TROUGH OR WEAK
SFC LOW APPROACH THE REGION. AT THE LEAST, THIS MAY KNOCK DOWN
AFTERNOON MAX TEMPS A BIT THANKS TO MORE CLOUD COVER AND
SHOWERS/STORMS. RAINFALL AMOUNTS VARY QUITE A BIT AMONG THE
ENSEMBLES BUT THE TREND HAS BEEN MORE EVEN PER THE RELATIVELY
DRIER ECMWF ENSEMBLES. FRACASSO

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