Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1
000
FXAK02 KWNH 251900
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT WED MAY 25 2016

VALID 12Z SUN MAY 29 2016 - 12Z THU JUN 02 2016

THE COMPLICATED BLOCKING PATTERN CONTAINING A SHORT WAVELENGTH AND
RAPIDLY GROWING SPREAD WITHIN THE GUIDANCE IS EXPECTED TO PERSIST
THROUGH THE MEDIUM RANGE PERIOD WITH A VARIETY OF END RESULTS
POSSIBLE. WHAT`S GENERALLY AGREED UPON THOUGH IS FOR GRADUAL
RETROGRESSION OF THE SMALL UPPER HIGH OVER ALASKA WHICH THEN
SUPPORTS A HIGHER POTENTIAL FOR SOME UNSETTLED CONDITIONS IN THE
FORM OF CHANGING TEMPERATURES AND INCREASED PRECIPITATION TO
AFFECT THE REGION. AT LEAST BEGINNING THE PERIOD THE DETERMINISTIC
AND ENSEMBLE SOLUTIONS ARE REASONABLY WELL-CLUSTERED WITH ABOUT 60
PERCENT 12Z GFS/00Z ECMWF USED TO START ALONG WITH 40 PERCENT FROM
THE 00Z ECMWF ENSEMBLE MEAN AND 06Z GEFS MEAN. BY DAY 5
THOUGH...THE GFS QUICKLY OPENS UP AND ACCELERATES A CLOSED LOW
TOWARD THE GULF OF ALASKA...WHICH SEEMS COUNTER TO THE EARLIER
SLOW MOTION OF THE BLOCK. THUS...HAVE ABANDONED THIS SOLUTION IN
FAVOR OF THE ECMWF CAMP. HOWEVER BY DAY 6 THE ECMWF BEGINS TO SHOW
ITS OWN CHALLENGES WITH A SUSPICIOUSLY DEEP LOW OVER THE WESTERN
ALEUTIANS...WITH IT ABANDONED AS WELL IN FAVOR OF THE ENSEMBLE
MEANS. FROM DAY 7 ONWARD THE MEANS PREVAIL AS THEY ARE THE MOST
REALISTIC SOLUTIONS THAT REMAIN.

REGARDING SENSIBLE WEATHER...THE POSITIVE ANOMALY FAVORS WELL
ABOVE NORMAL TEMPERATURES FOR MOST AREAS WITH MORE PRECIPITATION
POSSIBLE FOR COASTAL AREAS IF THE GFS VERIFIES AND MORE
PRECIPITATION POSSIBLE FOR SOME MAINLAND AREAS LATE IN THE PERIOD
IF THE ECMWF VERIFIES. BOTH SCENARIOS AREA ASSOCIATED WITH LOW
CONFIDENCE...WITH THE MORE INTERMEDIATE ENSEMBLE MEANS MORE
PREFERRED TO ADDRESS THE PRECIPITATION CHANCES.

JAMES

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.