Prognostic Meteorological Discussion
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FXAK02 KWNH 041857
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 PM EDT MON MAY 04 2015

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

...ALASKAN PATTERN OVERVIEW AND SENSIBLE WEATHER/THREATS
HIGHLIGHTS...

THE SLOW PROGRESSION OF AN AMPLIFIED MID-UPPER LEVEL TROUGH STILL
SUPPORTS A LEAD ORGANIZED SURFACE LOW TRACK OVER THE GULF OF AK
INTO FRI AND THE WEEKEND. EXPECT UNSETTLED GULF MARITIME
CONDITIONS AND TERRAIN ENHANCED PRECIPITATION WRAPPED INTO SRN AK.
AN AMPLIFIED RIDGE BUILDS IN ADVANCE FROM WRN CANADA TO A WARMED
ALASKAN INTERIOR/N SLOPE INTO NEXT WEEKEND BEFORE NRN STREAM
HEIGHT FALLS EASE IN. UNDERNEATH...FORECAST SPREAD AND UNCERTAINTY
IS GREATER WITH SEVERAL COMPLEX INTERMEDIATE LOWS/UNSETTLING
WEATHER THAT WORKS NEAR/SOUTH OF THE ALEUTIANS THEN SW AK DAYS 5-7
SAT-NEXT MON THAT SHOULD EMERGES INTO THE GULF OF AK IN THE WAKE
OF THE LEAD SYSTEM. THIS MAY BE FOLLOWED BY A DEEPER LOW APPROACH
TOWARD THE WRN ALEUTIANS IN ABOUT A WEEK OR SO THAT ACTUALLY SEEMS
BETTER REPRESENTED BY ENSEMBLE CLUSTERS. DETERMINISTIC MODELS ARE
STILL QUITE VARIED THOUGH.

...GUIDANCE AND UNCERTAINTY ASSESSMENT...

THE WPC ALASKAN MEDIUM-RANGE PRODUCT SUITE WAS PRIMARILY DERIVED
FROM THE 00 UTC ECMWF FRI AS PER COORDINATION WITH WFO ANCHORAGE
THAT OFFERRED PREFERENCE FOR ASSOCIATED FRONTAL AND PRESSURE
GRADIENT DETAILS. QUICKLY INCREASING FORECAST SPREAD SAT FAVORS
QUICK TRANSITION FROM DETERMINISTIC GUIDANCE TO THE 06 UTC GEFS
MEAN FOR THE REST OF THIS FORECAST PERIOD. THIS ENSEMBLE MEAN
SEEMED TO PROVIDE THE BEST TRANSITION...BUT OVERALL MEDIUM-RANGE
PREDICTABILITY IS BELOW AVERAGE.

SCHICHTEL



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