Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 261410
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
510 AM AKST WED NOV 26 2014

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL PATTERN THIS MORNING IS CHARACTERIZED BY A
SPRAWLING LONGWAVE TROUGH OVER THE WESTERN BERING SEA AND A STOUT
RIDGE OVER THE WEST COAST OF ALASKA. THREE DISTINCT LOWS EMBEDDED
WITHIN THE BERING TROUGH ARE SPREADING RAIN AND STRONG WINDS OVER
A WIDE SWATH OF THE BERING. THE MAIN LOW IS ANCHORED JUST EAST OF
THE KAMCHATKA PENINSULA...WITH TWO ADDITIONAL LOWS ROUNDING THE
EASTERN PERIPHERY OF THE LONGWAVE. THE FIRST OF THESE FEATURES IS
A POTENT SHORTWAVE TRACKING RAPIDLY NORTHWARD THROUGH THE CENTRAL
BERING...WITH AN ATTENDANT SURFACE FEATURE TRACKING JUST WEST OF
THE PRIBILOF ISLANDS AND BRINGING STORM FORCE WINDS TO THE CENTRAL
BERING. ANOTHER STRONG LOW OVER THE NORTH PACIFIC IS FOLLOWING
CLOSELY ON THE HEELS OF THIS SYSTEM AS IT MOVES TOWARDS THE
CENTRAL ALEUTIANS. MEANWHILE...FAIRLY BENIGN CONDITIONS PREVAIL
ACROSS MUCH OF THE SOUTHERN MAINLAND AS THE RIDGE STRENGTHENS
OVERHEAD. PATCHY FOG HAS DEVELOPED FROM BRISTOL BAY INTO THE LOWER
KUSKOKWIM VALLEY AS SKIES BEGIN TO CLEAR OUT. A SUBTLE MESOSCALE
FEATURE OVER NORTHERN COOK INLET IS BRINGING LIGHT SNOW SHOWERS TO
THE ANCHORAGE BOWL...WITH MOSTLY CLOUDY SKIES ACROSS THE REMAINDER
OF SOUTHCENTRAL ALASKA AND GUSTY OUTFLOW WINDS THROUGH FAVORED
AREAS ALONG THE GULF COAST.

&&

.MODEL DISCUSSION...
MODELS CONTINUE TO BE IN VERY GOOD AGREEMENT THROUGH THE END OF
THE WORK WEEK...LENDING AN ABOVE AVERAGE DEGREE OF CONFIDENCE TO
THE SHORT TERM FORECAST. MAINLY USED THE GFS FOR THE SYSTEMS OVER
THE BERING AND THE GEM REGIONAL/NAM OVER THE GULF AND SOUTHCENTRAL
AK FOR THEIR SUPERIOR HANDLING OF SMALL SCALE DETAILS.

&&

CB
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
ASIDE FROM A FEW SPOTTY SHOWERS PRECIP HAS COME TO AN END ACROSS
SOUTHCENTRAL ALASKA DUE TO DEVELOPMENT OF OFFSHORE FLOW OUT AHEAD
OF AN UPPER LEVEL RIDGE BUILDING IN FROM THE WEST. SOME COLDER
AIR HAS FILTERED THROUGH THE ALASKA RANGE...BUT WITH A MORE
WESTERLY COMPONENT TO FLOW IN THE LOW LEVELS THERE HAS NOT BEEN
MUCH OF AN OFFSHORE PUSH OF THE COLDER AND DRIER AIR. THEREFORE
MID TO UPPER LEVELS HAVE CLEARED OUT BUT THERE IS STILL A LOT OF
LOW LEVEL MOISTURE LINGERING ACROSS SOUTHCENTRAL.

THIS WILL CHANGE TODAY AND TONIGHT AS THE RIDGE UNDERGOES AMPLIFICATION
THANKS TO A COUPLE OF STRONG STORM SYSTEMS OVER THE ALEUTIANS AND
BERING RIDING UP THE WEST SIDE OF THE RIDGE. THIS AMPLIFICATION
WILL CAUSE LOW LEVEL FLOW OVER SOUTHCENTRAL TO SHIFT TO NORTHERLY
WHICH WILL FORCE COLDER AIR OVER INTERIOR ALASKA SOUTHWARD INTO
THE COPPER RIVER BASIN. THIS WON`T BE A VERY DEEP ARCTIC AIR MASS
SO COLD ADVECTION OUT INTO THE NORTHERN GULF WILL BE WEAK. THAT
MEANS THIS WILL PRIMARILY BE A GAP WIND EVENT AND WINDS WON`T
EXTEND VERY FAR FROM THE EXIT OF THE GAPS. THE UPPER RIDGE WILL BE
SLOW TO PROGRESS EASTWARD SO GAP WINDS WILL HANG ON A LITTLE
LONGER THAN ORIGINALLY THOUGHT...LIKELY THROUGH AT LEAST LATE
THURSDAY IN THE EASTERN PRINCE WILLIAM SOUND REGION AND COPPER
RIVER DELTA.

MEANWHILE...BACK OVER COOK INLET THE SHIFT TOWARD MORE NORTHERLY
FLOW SHOULD HELP KICK SOME OF THE LOW CLOUDS OUT OF THE
REGION...BUT NOT ALL. FLOW WILL WEAKEN DURING THE DAY AND BECOME
LIGHT TONIGHT AS THE RIDGE MOVES OVERHEAD. AS SKY COVER DECREASES
SURFACE TEMPERATURES WILL DROP AND HELP STEEPEN INVERSIONS.
THUS...EXPECT AREAS OF FOG TO FORM ESPECIALLY OVER COOK
INLET INCLUDING KNIK AND TURNAGAIN ARMS. DETERMINING THE EXACT
LOCATION AND EXTENT OF THE FOG AND LOW CLOUDS IS NEARLY
IMPOSSIBLE. THUS FORECAST CONFIDENCE FOR CLOUD COVER...FOG...AND
TEMPERATURES FROM THE ANCHORAGE AREA ON DOWN TO KENAI AND SOLDOTNA
IS LOW.

&&

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

PERIODS OF LIGHT RAIN OR FREEZING RAIN AND SNOW WILL GRAZE THE
COAST OF THE KUSKOKWIM DELTA THROUGH EARLY THURSDAY...WITH THE
NEXT FRONT MOVING INLAND THURSDAY TO BRING A CHANCE OF
RAIN...FREEZING RAIN...AND/OR SNOW TO BETHEL AND SURROUNDING
COMMUNITIES. WITH A LOW-LEVEL WARM SLOT SUGGESTED BY
MODELS...INCLUDED A MENTION OF FREEZING RAIN BEGINNING THURSDAY
AFTERNOON THROUGH FRIDAY FOR THIS AREA.

TOWARD BRISTOL BAY...LARGE-SCALE SUBSIDENCE UNDERNEATH UPPER LEVEL
HIGH PRESSURE WILL HELP TO PUSH THE LOW-LEVEL INVERSION TO NEAR
THE SURFACE...TRAPPING ANY LOW-LEVEL MOISTURE WHICH WILL BE
FAVORABLE FOR FOG THROUGH LATE THURSDAY MORNING. THERE IS SOME
QUESTION AS TO HOW MUCH THE FOG BURNS OFF THROUGH THE DAY...SO
THERE IS AT LEAST SOME CHANCE OF AT LEAST SOME PATCHY FOG IN THE
AFTERNOON AND EVENING HOURS AS WELL.

THE NEXT WEATHER MAKER WILL MOVE IN FROM THE WEST LATE THURSDAY
AFTERNOON AND BRING A CHANCE FOR RAIN...FREEZING RAIN...AND/OR
SNOW...WITH THIS THREAT SLOWLY EXTENDING EASTWARD TOWARD FRIDAY.

&&

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

MAIN IMPACTS THE NEXT COUPLE OF DAYS WILL BE WITH WINDS AND WAVES
AS TWO POWERFUL STORM-FORCE LOWS MOVE ACROSS THE AREA. THE LOW IN
THE CENTRAL BERING SEA THIS MORNING IS PACKING QUITE A PUNCH WITH
STORM-FORCE WINDS AND SEAS APPROACHING 25 FEET JUST SOUTH AND WEST
OF THE PRIBILOFS. THIS LOW WILL MOVE NORTH QUICKLY AND BEGIN TO
WEAKEN TONIGHT IN THE NORTHERN BERING...BUT WILL BE QUICKLY
FOLLOWED BY ANOTHER STORM-FORCE LOW TO IMPACT THE CENTRAL
ALEUTIANS LATER TODAY AND THEN THE CENTRAL BERING TONIGHT INTO
THURSDAY WITH MAINLY HIGH-END GALES. ADDITIONAL DISTURBANCES
PUSHING EAST ACROSS THE ALEUTIANS LATE THURSDAY INTO FRIDAY WILL
BRING AN ADDITIONAL PERIOD OF GALE-FORCE WINDS TO THE WESTERN AND
CENTRAL ALEUTIANS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

ON FRI UPPER TROUGHS OVER EASTERN SIBERIA AND WELL SOUTH OF
KAMCHATKA BEGIN MOVING. BY LATE SAT THE TROUGHS MERGE EAST OF
KAMCHATKA...REMAIN OVER THE BERING THROUGH TUE AND THEN CROSS THE
EASTERN ALEUTIANS DURING THE MIDDLE OF NEXT WEEK. AHEAD OF THIS
MERGER AN UPPER RIDGE DEVELOPS OVER THE BERING AND REPLACES THE
RIDGE OVER MAINLAND AK EARLY NEXT WEEK. AT THE SURFACE A DECAYING
LOW DISSIPATES OVER THE NORTHERN BERING BY FRI NIGHT. ON SAT THE
LOW ASSOCIATED WITH THE UPPER LOW SOUTH OF KAMCHATKA MOVES INTO
THE BERING. AT THIS POINT MODEL GUIDANCE GIVES A WIDE VARIETY OF
POSSIBLE TRACKS FOR THE LOW...RESULTING IN LITTLE CONFIDENCE IN A
SOLUTION. THE FORECAST UTILIZES WPC GUIDANCE...WHICH HAS THE LOW
MOVE ACROSS THE SOUTHERN BERING SAT NIGHT THROUGH EARLY TUE WHEN
IT RETURNS TO THE NORTH PACIFIC. OVER THE EASTERN DOMAIN A WEAK
LOW DEVELOPS BY SUN OVER THE NORTHERN GULF...AND BY TUE NIGHT A
FRONT ASSOCIATED WITH THE BERING LOW BEGINS TO AFFECT THE GULF
COAST.

THE GULF COAST WILL BE GENERALLY WET THROUGH TUE...WITH SOME RAIN
AND SNOW CROSSING THE COASTAL MOUNTAINS INTO SOUTHCENTRAL ONLY ON
SAT. SOUTHWEST AK WILL HAVE SNOW MIXING ALONG THE COAST WITH RAIN
AT TIMES INTO SAT. DRY CONDITIONS WILL ARRIVE ON SUN BETWEEN
SYSTEMS...AND THEN RAIN AND SNOW WILL AFFECT THE BRISTOL BAY ZONE
MON AND TUE WITH SOME SNOW POSSIBLE IN THE KUSKOKWIM ZONES. THE
BERING AND ALEUTIANS WILL HAVE SOME DRYING FROM WEST TO EAST ON
FRI. RAIN AND WIND THEN RETURN ON SAT AND PERSIST INTO EARLY NEXT
WEEK.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORMS 176 179 185
         GALES 127 170 172 173 174 175 177 178 180 181.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...CB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CC
LONG TERM...DS



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