Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 231322
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
522 AM AKDT THU OCT 23 2014

.ANALYSIS AND UPPER LEVELS...

PERSISTENT UPPER LEVEL TROUGHING OVER THE REGION IS BEGINNING TO
LOSE ITS GRIP OVER THE STATE AS A STOUT FRONT OVER THE WESTERN
BERING STRENGTHENS AN EASTERN BERING RIDGE...WITH THE ASSOCIATED
NORTH PACIFIC JET STREAM MOVING SOUTHEAST TOWARD THE WESTERN U.S.
COAST. THE EASTERN SIBERIA UPPER LOW COMPLEX DRIVING THE WARM
FRONT THROUGH THE BERING WILL SLOWLY MOVE EAST THROUGH THIS
WEEKEND...SHIFTING THE POLAR JET STREAM AND ASSOCIATED BAROCLINIC
ZONE FARTHER NORTH. THIS WILL DECOUPLE THE POLAR AND SUBTROPICAL
JETS...AND WILL USHER IN A FASTER ZONAL FLOW PATTERN.

&&

.MODEL DISCUSSION...

MODELS ARE IN EXCELLENT AGREEMENT THROUGH SATURDAY BEFORE THEY
BEGIN TO RAPIDLY DIVERGE SUNDAY AND BEYOND. THE GLOBAL GUIDANCE
CONTINUES TO STRUGGLE WITH THE DEVELOPMENT OF A TROUGH OVER THE
BERING SEA...AND ITS INTERACTION WITH A SUBTROPICAL LOW (WHICH
ALSO INCLUDES THE REMNANTS OF FORMER TROPICAL STORM ANA). THE GFS
FAVORS A WEAKER INTERACTION WHILE THE ECMWF AND CANADIAN GDPS ARE
MORE AGGRESSIVE. THE FORMER SCENARIO WOULD RESULT IN RIDGING
BUILDING OVER THE STATE MONDAY THROUGH THURSDAY NEXT WEEK WHILE
THE ECMWF/CANADIAN GDPS WOULD FAVOR DEVELOPING PRECIPITATION AS
EARLY AS LATE MONDAY INTO TUESDAY ACROSS MUCH OF SOUTHERN ALASKA.
FOR THE TIME BEING...THE SHORT TERM FORECAST INTO THE WEEKEND IS
VERY HIGH CONFIDENCE...WITH LOW CONFIDENCE BEYOND THE WEEKEND. THE
GFS AND ECMWF WERE FAVORED IN THE SHORT TERM WITH A BLENDED WPC
APPROACH FOR THE EXTENDED.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
ANOTHER QUIET DAY ACROSS SOUTHCENTRAL AS THE AREA HOLDS ON TO A
DRY OFFSHORE FLOW. RAIN AND SNOW SHOWERS ACROSS PARTS OF THE NORTH
GULF COAST INTO THOMPSON PASS WILL QUICKLY END THIS MORNING.
NORTHERLY GAP WINDS WILL CONTINUE THROUGH TODAY BEFORE
DIMINISHING. A FAST MOVING FRONT WILL MOVE INTO THE AREA THIS
EVENING AND FRIDAY...SPREADING CLOUDS AND RAIN AND SNOW SHOWERS
ACROSS THE REGION...ESPECIALLY OVER THE MOUNTAINS AND ACROSS THE
COPPER BASIN. INTERIOR LOCATIONS FROM ANCHORAGE WEST WILL ONLY SEE
A GLANCING BLOW AS THE ALASKA AND ALEUTIAN RANGES WILL DOWNSLOPE
MOST OF THE MOISTURE OUT. SNOW AND RAIN SHOWERS WILL LINGER OVER
THE COPPER BASIN AND NORTH GULF COAST INTO SATURDAY.

SOUTHWEST ALASKA...
A FAST MOVING FRONT WILL RAPIDLY TRACK FROM WEST TO EAST TODAY
THROUGH TONIGHT...SPREADING RAIN AND SNOW ACROSS THE REGION. LIGHT
ACCUMULATING SNOW WILL BE POSSIBLE...ESPECIALLY ACROSS THE
INTERIOR LOCATIONS WHERE COLD AIR WILL LINGER LONGER.
OTHERWISE...COASTAL LOCATIONS CAN EXPECT TO RAPIDLY CHANGE TO RAIN
WITH A BRIEF SHOT OF INITIAL SNOW. WESTERLY ONSHORE FLOW WILL
LINGER BEHIND THE FRONT...WITH EXTENSIVE CLOUD COVER PERSISTING
AFTER THE FRONT CLEARS.

BERING SEA/ALEUTIANS...
A FAST MOVING FRONT TRACKING ACROSS THE BERING WILL CLEAR THE
EASTERN BERING TONIGHT LEAVING LARGELY DRY CONDITIONS ACROSS MOST
OF THE ALEUTIANS AND BERING SEA HEADING INTO THE WEEKEND.

&&

.LONG TERM FORECAST...

MODELS CONTINUE TO STRUGGLE IN THE EXTENDED...AT LEAST PARTIALLY
DUE TO NO SATELLITE DATA BEING INGESTED. AGREED WITH WPC
ASSESSMENT THAT THE PREVIOUS FORECAST SHOULD ONLY BE MODIFIED
SLIGHTLY BY VARIOUS ENSEMBLE RUNS FOR NOW.

THE CURRENT SOLUTION BRINGS A WEAK TROUGH INTO THE NORTHEAST GULF
OF AK LATE SUN THAT PERSISTS INTO MIDWEEK WITH SPOTTY
PRECIPITATION AT BEST FOR MOST OF SOUTHCENTRAL AND THE GULF COAST.

A FRONT FROM A LOW OVER EASTERN RUSSIA WILL MOVE ACROSS THE BERING
ON TUE...AND A SECOND LOW OVER THE NORTHERN BERING WILL BRING A
SECOND FRONT TO THE WESTERN AK COAST ON THU. TIMING AND STRENGTH
OF BOTH OF THESE SYSTEMS IS STILL UNCERTAIN...BUT SMALL CRAFT TO
GALES ARE POSSIBLE ALONG WITH RAIN MIXING WITH SNOW THROUGH THE
MIDDLE OF NEXT WEEK.

SOUTHWEST AK WILL BE DRY UNTIL RAIN AND SNOW SHOWERS ARRIVE WITH
THE INITIAL FRONT TUE AND THE SECOND FRONT THU.

-DS

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...MARINE WEATHER STATEMENT 138 150.
         GALE 150.
FIRE WEATHER...NONE.

&&

$$

AHSENMACHER OCT 14



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