Prognostic Meteorological Discussion
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FXAK02 KWNH 212030
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
329 PM EST SAT JAN 21 2017

VALID 12Z WED JAN 25 2017 - 12Z SUN JAN 29 2017

...WET PERIOD IN STORE FOR MUCH OF THE SOUTH-CENTRAL/SOUTHEASTERN
AK...

GIVEN THE DOMINANCE OF MID-LEVEL RIDGING ACROSS THE WEST COAST OF
NORTH AMERICA...GENERAL TROUGHING WILL BE FAVORED UPSTREAM FROM
THE BERING SEA TO SOUTHEASTERN AK. WITHIN THE LONGWAVE TROUGH
ESTABLISHING ITSELF ACROSS THIS REGION...NUMEROUS EMBEDDED
SHORTWAVES WILL TRAVERSE EASTWARD TOWARD THE GULF OF AK. SOME OF
THESE IMPULSES SHOULD LEAD TO RATHER DEEP SURFACE LOWS ALTHOUGH
MODELS DEPICT QUITE THE VARIANCE AMONG THEIR SOLUTIONS. THE
INITIAL CYCLONE LIFTING THROUGH THE ALEUTIANS ON WEDNESDAY EVENING
IS GENERALLY AGREED UPON WITH MORE UNCERTAINTY WITH FUTURE WAVES
DURING THE PERIOD. IN PARTICULAR...AN AREA OF LOW PRESSURE LIFTING
NORTHWARD TOWARD THE GULF OF AK ON THURSDAY/FRIDAY HAS A GREAT
DEAL OF NORTH/SOUTH SPREAD. THE 00Z ECMWF/UKMET REMAINED ON THE
NORTHERN SIDE OF THE SPREAD WHILE THE 12Z GFS SITS WELL TO THE
SOUTH ALTHOUGH IT DID TREND SLIGHTLY NORTHWARD. LOOKING TOWARD THE
END OF THE PERIOD...MOST OF THE GUIDANCE AGREES ON AMPLIFICATION
TAKING SHAPE OVER SIBERIA BY NEXT WEEKEND. THIS LEADS TO FAIRLY
STRONG HEIGHT FALLS MOVING ACROSS THE WESTERN BERING SEA BY
29/1200Z.

THE FORECAST GENERALLY FAVORED THE USE OF A BLEND OF
DETERMINISTIC/ENSEMBLE MODEL GUIDANCE THROUGH ROUGHLY THURSDAY.
THIS WAS TO GET A BIT MORE INTENSITY ON RELEVANT SURFACE FEATURES
OVER THE GULF OF AK AS COORDINATED WITH LOCAL FORECAST OFFICES.
DURING THIS PERIOD...UTILIZED A 50/50 BLEND OF DETERMINISTIC AND
ENSEMBLE SOLUTIONS WITH THE FORMER CONSISTING OF THE 00Z
ECMWF/UKMET. SAW STRONGER ENSEMBLE SUPPORT FOR THE ECMWF/UKMET
PAIR WITH FEATURES ON THE MAP THROUGH DAY 5/THURSDAY.
THEREAFTER...SHIFTED TOWARD A STRICT ENSEMBLE APPROACH TAKING AN
EQUAL BLEND OF THE 00Z ECMWF/NAEFS ENSEMBLE MEANS.

MUCH OF THE COLDEST AIR DURING THE PERIOD WILL REMAIN ACROSS THE
NORTHERN EXTENT OF THE STATE. HOWEVER...THESE REGIONS SHOULD
BECOME MILDER IN TIME AS LOWS RISE TOWARD THE NEGATIVE SINGLE
DIGITS. IN TERMS OF PRECIPITATION THREATS...AN ACTIVE PERIOD OF
SHORTWAVE PASSAGES WILL MAINTAIN UNSETTLED CONDITIONS FROM
SOUTH-CENTRAL AK EASTWARD INTO THE SOUTHEASTERN PORTION OF THE
STATE.


RUBIN-OSTER

$$





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