Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 151249
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
449 AM AKDT TUE APR 15 2014

.ANALYSIS AND UPPER LEVELS...
A COMPLEX PATTERN IS TAKING SHAPE OVER THE GREAT LAND THIS
MORNING. THE MOST PROMINENT FEATURE ALOFT IS AN UPPER LOW
CENTERED OVER THE CENTRAL BERING SEA WITH A RIDGE OF HIGH PRESSURE
OVER THE CANADIAN ARCTIC NOSING WESTWARD INTO CENTRAL/SOUTHERN
ALASKA. A WEAKENING FRONTAL BOUNDARY STRETCHES FROM THE NORTH OF
THE BERING SEA LOW PRESSURE THROUGH THE PRIBILOF ISLANDS
SOUTHEASTWARD OVER THE ALASKA PENINSULA INTO THE SOUTHWESTERN
GULF. THE MAIN WESTERLY JET STREAM IS WELL TO THE SOUTH OF THE
ALEUTIANS WHILE A WEAK UPPER LOW CENTER IS LINGERING IN THE GULF
OF ALASKA. THE EASTERLY FLOW BETWEEN THE GULF LOW AND THE CANADIAN
HIGH PRESSURE IS REMINISCENT OF A SUMMERTIME PATTERN WITH EMBEDDED
EASTERLY WAVES. WIDESPREAD MID-LEVEL CLOUDINESS IS ASSOCIATED
WITH THIS FEATURE AS WELL AS LIGHT RAIN IN THE NORTHERN GULF. BOTH
OF WHICH SHOULD PUSH WESTWARD TODAY AS THE FLOW BECOMES MORE
EASTERLY. TEMPERATURES WERE ABOVE NORMAL TODAY WITH ABUNDANT
SUNSHINE UNDER THE RIDGE OF HIGH PRESSURE ACROSS THE SOUTHCENTRAL
BUT HAVE FALLEN QUICKLY WITH THE LOSS OF DAYTIME HEATING.

&&

.MODEL DISCUSSION...
GUIDANCE IS IN REASONABLE AGREEMENT WITH THE GENERAL SYNOPTIC
PATTERN BUT SOME DETAILS OF THE COMPLEX SURFACE LOW DEVELOPMENT IN
THE GULF ARE NOT WELL AGREED UPON. GUIDANCE IS HINTING AT A DOUBLE
BARREL SURFACE LOW DEVELOPMENT IN THE CENTRAL GULF ON WEDNESDAY
WITH A WEAKER LOW TO THE WEST AND STRONGER CENTER OF CIRCULATION
TO THE EAST. FOR THE PAST COUPLE DAYS GLOBAL MODELS HAVE BEEN
SHOWING A VIGOROUS SURFACE LOW MOVING UP TOWARD AND JUST WEST OF
THE PANHANDLE. MOST MODELS HAVE FLIP-FLOPPED ON POSITION AND
STRENGTH AT LEAST SOMEWHAT SO CONFIDENCE IN THIS FEATURE IS LOWER.
HOWEVER THE DYNAMICS DEPICTED IN ANY MODEL DOES NOT SUPPORT A
STRONGER SURFACE LOW SUCH AS THE GFS/GEM ARE DEPICTING. THE
FORECAST PACKAGE IS BASED MORE ON THE ECMWF/NAM IN THE SHORT TERM.
THOUGH CONFIDENCE IS LACKING IN THIS FEATURE IT SHOULD STAY
CONFINED TO THE GULF SO OVERALL FORECAST CONFIDENCE IS AVERAGE.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...MIDDLE AND HIGH LEVEL CLOUDS WILL CONTINUE
TO OVERSPREAD MUCH OF THE AREA TODAY WITH INCREASING LIGHT RAIN
ALONG THE NORTH GULF COAST. SOME SHOWERS COULD MAKE IT OVER THE
MOUNTAINS INTO THE COOK INLET REGION BUT THE BULK OF THE
PRECIPITATION WILL STAY CONFINED TO THE NORTH GULF COAST. 850 MB
TEMPERATURES ARE SLIGHTLY WARMER TODAY WHICH WOULD AGAIN SUPPORT
WARMER SURFACE TEMPERATURES BUT CLOUD COVER WILL KEEP
TEMPERATURES FROM REACHING AS HIGH AS YESTERDAY. SHOWERS WILL
STAY IN THE FORECAST...MAINLY FOR THE GULF COAST THROUGH WEDNESDAY
THEN A STRONGER SYSTEM WILL MOVE TOWARD THE SOUTHCENTRAL LATER IN
THE WEEK.

SOUTHWEST ALASKA...

A WEAK SHORTWAVE WILL CONTINUE TO BRING SCATTERED SNOW SHOWERS AND
CLOUDS ACROSS THE KUSKOKWIM DELTA THIS MORNING. AS THIS SHORTWAVE
PUSHES INTO THE NORTHERN BERING SEA LATE THIS MORNING...SNOW
SHOWERS WILL COME TO AN END AND SKY CONDITIONS WILL BRIEFLY
IMPROVE. A DECAYING COLD FRONT WILL MOVE ACROSS THE ALASKA
PENINSULA THIS MORNING AND CONTINUE TO PUSH SLOWLY TOWARD THE
BRISTOL BAY AND KUSKOKWIM DELTA AREAS THIS AFTERNOON. THIS WILL
BRING ANOTHER PUSH OF MOISTURE TO THE REGION...RESULTING IN
INCREASED CLOUD COVER AND A RETURN OF RAIN AND SNOW SHOWERS. THESE
SHOWERS WILL MOVE ONSHORE THIS AFTERNOON AND SPREAD INLAND
OVERNIGHT TONIGHT AND WILL LIKELY LINGER THROUGH AT LEAST THURSDAY
AFTERNOON AS THE FRONT STALLS OUT AND SLOW DECAYS OVER SOUTHWEST
ALASKA.

BERING SEA/ALEUTIANS...

A LARGE COMPLEX LOW WILL CONTINUE TO SLOWLY WEAKEN AS IT WOBBLES
BACK AND FORTH ACROSS THE CENTRAL AND WESTERN BERING SEA THROUGH
THE SHORT TERM. THE 500 MB LOW IS BECOMING CUT OFF FROM THE LONG
WAVE FLOW RESULTING IN THE SLOW PROPAGATING SURFACE LOW SEEN ON
SATELLITE. THIS WILL CONTINUE TO BRING NUMEROUS RAIN SHOWERS
(SCATTERED SNOW SHOWERS AT NIGHT) ACROSS THE ALEUTIAN ISLANDS...MAINLY
TO THE EAST OF KISKA ISLAND.

&&

.LONG TERM FORECAST...

THE OVERALL WEATHER PATTERN WILL BEGIN TO SHIFT OVER THE WEEKEND
FOR MAINLAND ALASKA. THE BROAD UPPER TROUGH OF LOW PRESSURE THAT
WILL BRING CLOUDS AND PRECIPITATION CHANCES DURING THE WEEK WILL
BEGIN TO PUSH SOUTH INTO THE GULF OF ALASKA. THIS WILL ALLOW HIGH
PRESSURE TO MOVE IN ACROSS THE INTERIOR OF ALASKA AND CONSUME MOST
OF MAINLAND ALASKA BY THE BEGINNING OF THE WORK WEEK. NEAR NORMAL
TEMPERATURES WILL PERSIST THROUGH THE PERIOD.

GUIDANCE CONTINUES TO STRUGGLE ACROSS THE BERING SEA AND ALEUTIAN
ISLANDS AS MODELS DISAGREE ON HOW THE UPPER LEVEL LOW UTILIZES A
SERIES OF SHORT WAVES THAT ENTER THE MAIN TROUGH STARTING LATE
THURSDAY. THIS LEADS TO A DIFFERENCE IN LOW POSITION/INTENSITY AS
A LOW PASSES TO THE SOUTH OF OR NEAR THE ALEUTIAN CHAIN EARLY NEXT
WEEK. REGARDLESS OF THE OUTCOME...IT LOOKS LIKE ANOTHER WET AND
WINDY PERIOD OF WEATHER IS IN STORE THE ALEUTIAN ISLANDS...WITH
THE NORTHERN BERING SEA LIKELY TO REMAIN DRIER.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.
&&

$$

MTL/MMC APR 14



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