Prognostic Meteorological Discussion
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FXAK02 KWNH 281921
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
321 PM EDT SAT MAR 28 2015

VALID 12Z WED APR 01 2015 - 12Z SUN APR 05 2015

...PATTERN/SENSIBLE WEATHER HIGHLIGHTS...

THIS ALASKAN MEDIUM RANGE FLOW PATTERN FEATURES SIGNIFICANT LOW
TRACKING ACROSS THE GULF OF ALASKA WED-SAT. THIS ACTIVE LOW SHOULD
FAVOR HIGH WIND/WAVES AND MODEST TO TERRAIN ENHANCES LOCALLY
HEAVIER PCPN POTENTIAL SPREADING ACROSS SW/SRN AND PORTIONS OF
SERN AK. THIS ALL OCCURS HELD UNDERNEATH INTERIOR AK HIGH PRESSURE
GRADUALLY BUILDING CONCURRENT WITH A GRADUAL DEMISE OF UNSETTLING
MIDWEEK NW/NRN AK MID-UPPER LEVEL TROUGHING. WELL
UPSTREAM...ADDITIONAL WELL ORGANIZED LOW DEVELOPMENT OVER THE WRN
TO CENTRAL ALEUTIANS THU THROUGH NEXT SUNDAY SHOULD ALSO BE QUITE
ACTIVE ACROSS THE REGION ALONG WITH A WIDESPREAD WRAP-AROUND PCPN
POTENTIAL PATTERN.

..GUIDANCE/UNCERTAINTY/CONTINUITY ASSESSMENT...

WPC ALASKAN MEDIUM RANGE SURFACE FRONTS/PRESSURES AND 500 MB PROGS
ALONG WITH ASSOCIATED HPCGUIDE HIGH RESOLUTION SENSIBLE WEATHER
GRIDS HAVE BEEN PRIMARILY DERIVED FROM A BLEND OF THE 12 UTC
GFS/00 UTC ECMWF WEDNESDAY. DECIDED TO LEAN MORE ON THE 00 UTC
ECMWF AFTER COORDINATION WITH THE ANCHORAGE WFO FOR THE GULF OF
ALASKA AND ALSO IN CONSIDERATION OF NWRN/NRN ALASKAN MID-UPPER
LEVEL TROUGH AMPLITUDE CONTINUITY. FORECAST SPREAD AND EMBEDDED
SYSTEM UNCERTAINTY GROWS RAPIDLY THEREAFTER IN A PATTERN WITH
BELOW NORMAL PREDICTABILITY OVERALL. THIS LEADS TO PREFERENCE FOR
A MAIN EMPHASIS ON A 30-70 BLEND OF THE 06 UTC GEFS MEAN AND 00
UTC ECMWF ENSEMBLE MEAN DAYS 5-8 THU-SUN THAT MAINTAINS SLIGHTLY
BETTER CONTINUITY THAN OTHER ENSEMBLE SYSTEM COMBINATIONS. EVEN
SO...CONTINUITY WAS NOT OPTIMAL THROUGH THESE LONGER TIME FRAMES.

SCHICHTEL

$$




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