Area Forecast Discussion
Issued by NWS Anchorage, AK

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968
FXAK68 PAFC 260259
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
559 PM AKST TUE NOV 25 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS A DEEP (506 DM AT 500 MB) UPPER LOW OVER THE WESTERN
BERING SEA WITH TWO DEVELOPING LOWS AROUND IT...ONE JUST SOUTH OF
THE CENTRAL ALEUTIANS AND ON SOUTHWEST OF THE WESTERN ALEUTIANS.
THERE IS A BUILDING RIDGE TO THE EAST OF THIS LOW ALONG THE WEST
COAST OF ALASKA. THERE IS A TROUGH OVER THE PANHANDLE AND THE YUKON
TERRITORY. A WEAK UPPER LEVEL "WAVE" IS OVER SOUTH CENTRAL ALASKA
PRODUCING SOME SHOWERS...MAINLY OVER HIGHER ELEVATIONS INLAND SUCH
AS THE TALKEETNA MOUNTAINS.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN VERY GOOD AGREEMENT THROUGH 84 HOURS.
THIS LEADS TO HIGHER THAN NORMAL CONFIDENCE IN THE FORECAST FOR
THE AFTERNOON PACKAGE. MODELS OF CHOICE FOR THE FIRST 48 HOURS OF
THE FORECAST ARE THE NAM AND REGIONAL GEM FOR THEIR BETTER
HANDLING OF SMALL SCALE DETAILS.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

SPOTTY SNOW SHOWERS ACROSS PORTIONS OF COOK INLET NORTHWARD TO THE
ALASKA RANGE AND TALKEETNA MOUNTAINS WILL DIMINISH TONIGHT AS
UPPER LEVEL RIDGING BUILDS OVER THE REGION. THE OFFSHORE PRESSURE
GRADIENT WILL TIGHTEN TONIGHT AS A WEAK UPPER DISTURBANCE MOVES
ALONG THE EASTERN PERIPHERY OF THE AFOREMENTIONED RIDGE...WHICH
WILL HELP TO INCREASE GAP WINDS THROUGH THURSDAY...ESPECIALLY
FROM PRINCE WILLIAM SOUND EASTWARD. PATCHY FOG WILL BE POSSIBLE
NEAR COOK INLET AS THE HIGH BUILDS ALOFT...BUT OTHERWISE PLEASANT
CONDITIONS WILL PREVAIL THROUGH THE THANKSGIVING HOLIDAY.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...

A RELATIVELY DRY PERIOD IS EXPECTED ACROSS MUCH OF SOUTHWEST ALASKA
THROUGH THANKSGIVING DUE IN LARGE PART TO AN UPPER LEVEL RIDGE
THAT CONTINUES TO STRENGTHEN OVER SOUTHWEST ALASKA. SUBSIDENCE
ASSOCIATED WITH THIS RIDGE WILL ALLOW CLOUD COVER TO GRADUALLY
DIMINISH OVER THE NEXT SEVERAL DAYS. THIS WILL ALLOW AREAS TO
RADIATE OUT MORE OVERNIGHT THAN OVER THE PAST SEVERAL DAYS WHICH
WILL LEAD TO MORE SEASONAL TEMPERATURES. IN THE MEAN TIME...A WEAK
UPPER LEVEL DISTURBANCE RIDING ALONG THE NORTHERN PERIPHERY OF
THE RIDGE NEAR THE KUSKOKWIM DELTA WILL PRODUCE SCATTERED SNOW
SHOWERS OVER THE KUSKOKWIM DELTA AND ISOLATED SNOW SHOWERS OVER
PARTS OF THE LOWER KUSKOKWIM VALLEY. AN ISOLATED SHOWER OF LIGHT
FREEZING RAIN CANNOT BE RULED OUT OF THE KUSKOKWIM DELTA AT THIS
TIME AS THE 00Z RAOB FROM PABE SHOWS THERE IS A SMALL POCKET OF
WARM AIR ALOFT. ANY FREEZING PRECIPITATION WOULD BE SHORT LIVED
AND LITTLE TO NO IMPACT.

FOG WILL BE A CONCERN ACROSS THE KUSKOKWIM VALLEY AND THE BRISTOL
BAY AREA TONIGHT. THE MARINE LAYER THAT BROUGHT AREAS OF DENSE
FOG TO DILLINGHAM AND SURROUNDING AREAS REMAINS INLAND AND
VISIBILITIES HAVE ALREADY BEGUN TO DROP. THIS TREND SHOULD
CONTINUE THROUGH THE OVERNIGHT HOURS...WITH THE REST OF THE
BRISTOL BAY AREA SEEING SOME PATCHY FOG. THE LOWER KUSKOKWIM
VALLEY WILL HAVE SOME BREAKS IN THE CLOUDS WHICH SHOULD ALLOW SOME
LOCATIONS IN THE VALLEYS TO SATURATE LEADING TO SOME PATCHY FOG.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

AN AREA OF LOW PRESSURE OVER THE NORTH PACIFIC CONTINUE TO MAKE
QUICK PROGRESS TOWARD THE CENTRAL AND ALEUTIANS. THIS WILL ALLOW
RAIN TO OVERSPREAD THE CENTRAL AND EASTERN ALEUTIANS AND INTO THE
BERING SEA. IN ADDITION...STORM FORCE WINDS WILL BE SEEN OVER THE
COASTAL WATERS NEAR THE CENTRAL ALEUTIANS...WITH A LARGE AREA OF
GALES EXTENDING FROM THE WESTERN ALEUTIANS...TO THE EASTERN
ALEUTIANS AND INTO THE CENTRAL BERING SEA. A SECOND LOW FROM THE
NORTH PACIFIC WILL IMPACT THE WESTERN ALEUTIANS STARTING WEDNESDAY
MORNING AND PUSH INTO THE CENTRAL BERING SEA BY THURSDAY MORNING.
THIS WILL BRING ANOTHER LARGE SWATH OF GALE FORCE WINDS TO THE
WESTERN HALF OF THE BERING SEA WHICH WILL PERSIST THROUGH AT LEAST
THANKSGIVING. THIS IN TURN WILL FORM A COMPLEX LOW PATTERN OVER
THE BERING SEA...WHICH WILL KEEP ELEVATED RAIN CHANCES IN THE
FORECAST THROUGH THE REMAINDER OF THE WEEK.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
BY FRIDAY...THERE IS INCREASING MODEL AGREEMENT THAT THE GENERAL
PATTERN RECENTLY WITH A TROUGH OVER THE BERING AND A RIDGE OVER
THE MAINLAND WILL BEGIN TO BREAK DOWN. THIS WILL BEGIN LATE ON
FRIDAY AS THE BERING TROUGH AND ASSOCIATED SURFACE LOW MOVE
TOWARDS THE BERING STRAIT...AND RIDGING QUICKLY BUILDS OVER THE
BERING. THERE IS A POTENTIAL THAT A WEAK SHORTWAVE RIDING OVER TOP
OF THIS BUILDING RIDGE COULD BRING SNOW TO SOUTHCENTRAL LATE
SATURDAY/EARLY SUNDAY...HOWEVER THERE IS NOT ENOUGH CONFIDENCE IN
THIS BEYOND JUST A CHANCE OF SNOW.

A MUCH BETTER CHANCE OF ACTIVE WEATHER THROUGHOUT THE SOUTHERN
MAINLAND LOOKS TO OCCUR EARLY NEXT WEEK. THIS IS WHEN A LOW
MOVING INTO THE EASTWARD INTO THE GULF MERGES WITH AN ARCTIC
TROUGH DESCENDING THROUGH THE MAINLAND ON TUESDAY. THIS LOOKS TO
BRING A PERIOD OF STORMY WEATHER TO THE GULF COAST...EASTERN
BERING...AND SOUTHERN MAINLAND NEXT WEEK. IT IS ALSO IMPORTANT TO
NOTE THAT THERE IS VERY GOOD MODEL AGREEMENT THAT RIDGING WILL NOT
REFORM ANYWHERE FROM THE MAINLAND OR NORTHWEST CANADA NEXT WEEK.
THIS IS A MAJOR CHANGE FROM THE PERSISTENT PATTERN MUCH ALASKA HAS
BEEN UNDER THE INFLUENCE OF FOR THE PAST FEW WEEKS...A CLEAR
SIGNAL THAT THE AREA WILL EXPERIENCE A PROLONGED PATTERN CHANGE.
THIS LACK OF RIDGING WILL ALSO CUT OFF THE DEEP MOIST/WARM
SOUTHERLY FLOW...INCREASING SNOW CHANCES OVER INTERIOR LOCATIONS
GOING INTO NEXT WEEK.

&&


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

&&

$$



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