Prognostic Meteorological Discussion
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FXAK02 KWNH 021818
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ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
218 PM EDT SAT MAY 02 2015

VALID 12Z WED MAY 06 2015 - 12Z SUN MAY 10 2015

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

SLOWED PROGRESSION OF AN AMPLIFIED MID-UPPER LEVEL TROUGH SUPPORTS
A SURFACE LOW TRACK FROM JUST SOUTH OF THE ALEUTIANS MIDWEEK TO
THE GULF OF AK LATE NEXT WEEK. EXPECT UNSETTLED MARITIME
CONDITIONS OVER THE GULF WITH MODEST PRECIPITATION WORKING MAINLY
INTO COASTAL AREAS. THIS LOW SHOULD MEANDER/REFORM OVER THE GULF
INTO NEXT WEEKEND AS THE SUPPORTING TROUGH ALOFT GAINS NEGATIVE
TILT AND SLOWS WITH BUIDLING OF AN AMPLIFIED DOWNSTREAM RIDGE
BUILDING FROM WRN CANADA NWWD INTO A WARMED ALASKAN INTERIOR.
MID-LATE WEEK NRN STREAM ENERGIES HELD OVERTOP THIS RIDGE COULD
ALLOW FOR SOME FRONTAL PUSH OVER THE N SLOPE/NW AK. ANOTHER
ORGANIZED LOW AND UNSETTLING WEATHER MAY SLOWLY WORK INTO THE
ALEUTIANS DAYS 6-8...BUT WITH MORE FORECAST SPREAD UNCERTAINTY.

...GUIDANCE AND UNCERTAINTY ASSESSMENT...

THE WPC ALASKAN MEDIUM-RANGE PRODUCT SUITE WAS PRIMARILY DERIVED
FROM A COMPOSITE BLEND OF REASONABLY COMPATABLE GUIDANCE FROM THE
12 UTC GFS...00 UTC ECMWF AND 00 UTC GEFS/NAEFS/ECMWF ENSEMBLE
MEANS WED/THU. QUICKLY INCREASING FORECAST SPREAD BY FRI SEEMS TO
FAVOR INCREASED RELIANCE ON JUST THESE STILL COMPATABLE ENSEMBLE
MEANS THROUGH NEXT WEEKEND. MANUALLY ADDED OFFSHORE SURFACE LOW
DEPTH AND BUMPED UP WINDS CONSIDERING SUPPORT ALOFT COMMON TO MOST
GUIDANCE. THE OVERALL SOLUTION MAINTAINS DECENT WPC CONTINUITY AND
SYSTEM AMPLITUDE/SLOW PROGRESSION OFFERS NEAR AVERAGE
UNCERTAINTY...BUT THE PATTERN SEEMS TO BE SLOWLY LOSING
PREDICTABILITY.

SCHICHTEL



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