Prognostic Meteorological Discussion
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FXAK02 KWNH 021927
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
226 PM EST FRI DEC 02 2016

VALID 12Z TUE DEC 06 2016 - 12Z SAT DEC 10 2016

...COLD TEMPERATURES FOR SOUTHERN AREAS AND THE PANHANDLE NEXT
WEEK...


...GUIDANCE/UNCERTAINTY ASSESSMENT...

SYNOPTIC PATTERN REMAINS RATHER WELL FORECAST THROUGH THE MEDIUM
RANGE. UPPER HIGH INITIALLY OVER NW ALASKA IS FORECAST TO MEANDER
NORTHWESTWARD TOWARD WRANGEL ISLAND WHICH SUPPORTS TROUGHING
THROUGH THE INTERIOR INTO THE GULF. BIGGEST QUESTION IN THE
FORECAST LIES WITH HOW THE LEAD UPPER LOW CROSSING THE AKPEN ON
TUESDAY INTERACTS WITH SHORTWAVE ENERGY AND A SFC LOW ALONG AN OLD
FRONT SOUTH OF 40N. THE ECMWF AND ITS ENSEMBLES HAVE GENERALLY
BEEN NORTH OF THE GFS AND ITS ENSEMBLES WITH VARYING SUPPORT FROM
THE CANADIAN/UKMET. LATEST RUNS (NON-GFS) SHOW A TREND TOWARD A
MORE NORTHERLY BUT ALSO MAYBE WESTERLY TRACK (WRAPPING BACK TO THE
WEST) WHILE THE GFS REMAINS TO THE EAST AND SOUTH. ENSEMBLES LIE
SQUARELY IN THE MIDDLE NEAR CONTINUITY AND AGAIN RELIED ON THAT
CONSENSUS TO FORM THE FORECAST. ADDED SOME DETAIL FROM THE 00Z
ECMWF/CANADIAN AT LEAST INTO WED 12/7 BEFORE THEY TRENDED A BIT
FARTHER WEST THAN THE ENSEMBLE MEANS. AFTER THAT, PARENT LOW
SHOULD DRIFT NORTHWESTWARD AND SLOWLY WEAKEN IN THE GULF AS
ANOTHER WEAK SYSTEM UNDERCUTS THE UPPER HIGH THROUGH THE WESTERN
ALEUTIANS.


...HIGHLIGHTS/THREATS...

STRONG HIGH PRESSURE (>1050MB) WILL SLIDE SOUTHEASTWARD THROUGH
THE YUKON AND NW TERRITORIES OF CANADA WHICH WILL SEND COLD
TEMPERATURES VIA STRONG EASTERLY FLOW INTO THE PANHANDLE (WINDS
30-40KTS POSSIBLE) WHILE THE INTERIOR STAYS TYPICALLY COLD AS
WELL. EVEN USING A BLEND OF THE 00Z ECMWF ENSEMBLE MEAN AND NAEFS
MEAN YIELDED MIN/MAX FORECASTS THAT WERE QUITE COLD. AGAIN
TEMPERED THESE VALUES VIA STATISTICAL FORECASTS (GFSMOS AND
ECMWF-BASED MOS) WHICH WERE UP TO 10 DEGREES MILDER IN THE
PANHANDLE AND SOUTH CENTRAL (THOUGH COLDER IN THE INTERIOR).
OVERRUNNING EVENT FOR THE PANHANDLE REMAINS A STRONG POSSIBILITY
WITH LIGHT TO MODERATE SNOW ATOP A COLD SURFACE AND CONTINUED
BRISK EASTERLY FLOW.


FRACASSO

$$




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