Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 251334
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
534 AM AKDT WED MAR 25 2015

.ANALYSIS AND UPPER LEVELS...
THE BLOCKING HIGH THAT HAS BEEN ENTRENCHED OVER THE SOUTHERN
MAINLAND FOR THE PAST SEVERAL DAYS IS BEGINNING TO SHIFT EASTWARD
INTO THE YUKON TERRITORY THIS MORNING...SIGNALING AN IMMINENT
PATTERN CHANGE AS A DEEP NORTH PACIFIC LOW CENTERED APPROXIMATELY
400 MILES SOUTH OF KODIAK ISLAND BEGINS TO TRACK NORTHWARD INTO
THE WESTERN GULF OF ALASKA ACCOMPANIED BY A GALE FORCE FRONT. RAIN
ASSOCIATED WITH THIS SYSTEM IS SPREADING OVER KODIAK ISLAND AND
THE ALASKA PENINSULA. IN THE MEANTIME...BENIGN CONDITIONS LINGER
ACROSS MUCH OF THE SOUTHERN MAINLAND IN THE WAKE OF THE DEPARTING
RIDGE. A FEW SNOW SHOWERS ARE BRUSHING COASTAL PORTIONS OF THE
KUSKOKWIM DELTA IN THE VICINITY OF A WEAKENING FRONTAL
BOUNDARY/INVERTED TROUGH THAT STRETCHES ACROSS THE SOUTHEASTERN
BERING. THIS FEATURE IS ALSO PRODUCING AREAS OF BLOWING SNOW OVER
THE PRIBILOF ISLANDS AS WELL AS RAIN SHOWERS AND GUSTY NORTHERLY
WINDS OVER THE EASTERN ALEUTIANS.

&&

.MODEL DISCUSSION...
MODELS GENERALLY HAVE A GOOD HANDLE ON THE SYNOPTIC PATTERN
THROUGH THE SHORT TERM...WITH THE MAIN FEATURES OF INTEREST BEING
THE LOW AND ASSOCIATED FRONT TRACKING NORTHWARD THROUGH THE GULF.
SOME MINOR DIFFERENCES BEGIN TO EMERGE BY THURSDAY AFTERNOON AS
THE LOW APPROACHES KODIAK ISLAND...WITH THE MAJORITY OF THE
GUIDANCE TAKING THE LOW NORTH OF KODIAK INTO THE COOK INLET/KENAI
PENINSULA REGION WHEREAS THE GFS HOLDS THE LOW FARTHER SOUTH OVER
THE ISLAND. THEREFORE...STAYED AWAY FROM THE GFS IN THE MORNING
FORECAST AND PRIMARILY UTILIZED THE NAM FOR ENHANCED DETAIL.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (TODAY THROUGH THURSDAY
NIGHT)...
A LARGE STORM SYSTEM SOUTH OF KODIAK IS SLOWLY MAKING
ITS WAY NORTHWARD TOWARD SOUTHCENTRAL WITH DETERIORATING
CONDITIONS ACROSS THE GULF WATERS. THE BRUNT OF STORM WILL BE FELT
ALONG THE GULF COAST AND KODIAK ISLAND AS A FRONTAL BOUNDARY OVER
THE SOUTHERN GULF TRACKS NORTH AND WEST...BRINGING HEAVY RAIN AND
WIDESPREAD MAXIMUM GALE TO MINIMUM STORM FORCE WINDS. THE FRONT
WILL ELONGATE AS IT REACHES THE NORTHERN TO WESTERN GULF COAST AND
RAPIDLY WEAKEN AS IT MOVES ONSHORE. A WEAKENING FRONT COMBINED
WITH STRONG CROSS MOUNTAIN FLOW TENDS TO KEEP INLAND AREAS DRY. IN
THIS CASE THERE IS A STRONG UPPER LEVEL SHORT-WAVE WITH DEEP
CONVECTION NOTED THIS MORNING OVER THE SOUTHERN GULF. THIS WAVE
WILL WEAKEN AS IT CROSSES SOUTHCENTRAL TONIGHT...BUT PROVIDES THE
BEST CHANCE OF SEEING A FEW SHOWERS. WITH TEMPERATURES STILL
EXPECTED TO WARM WELL ABOVE FREEZING THIS AFTERNOON THE LOW LEVELS
WILL NOT HAVE A CHANCE TO COOL DOWN MUCH BEFORE THE UPPER WAVE
MOVES THROUGH. THUS IT LOOKS LIKE MOST OF WHAT DOES FALL WILL BE
IN THE FORM OF RAIN. IN THE FEW MOUNTAIN PASSES COLD ENOUGH FOR
SNOW EXPECT VERY LITTLE ACCUMULATION.

THE LOW CENTER WILL FOLLOW SLOWLY BEHIND THE FRONT BRINGING ANOTHER
BATCH OF WIND AND RAIN...ONCE AGAIN MAINLY TO THE GULF COAST. THE
LOW WILL DISSIPATE AS IT MOVES ONSHORE SOMEWHERE ALONG THE WEST
COAST. MORE IMPORTANTLY...PRESSURE RISES BEHIND THE LOW WILL KICK
UP WINDS FROM THE KENAI PENINSULA TO TURNAGAIN ARM/WEST ANCHORAGE
AND THE MATANUSKA VALLEY THURSDAY AFTERNOON THROUGH THURSDAY NIGHT.
THIS WILL RESULT IN FAIRLY WARM OVERNIGHT LOWS IN THESE AREAS.

FIRE WEATHER...INCREASING GAP WINDS OUT AHEAD OF THE FRONT TODAY
WILL PRODUCE INCREASED FIRE DANGER TO THE MATANUSKA VALLEY WHERE
A RED FLAG WARNING IS IN EFFECT. THE PRIMARY WIND TODAY WILL COME
OUT OF THE MATANUSKA VALLEY. LATE THURSDAY AFTERNOON AND EVENING
A STRONG GUSTY SOUTHEAST WIND WILL DEVELOP OUT OF THE KNIK RIVER
VALLEY. WITH INCREASED MOISTURE AND CLOUD COVER ON THURSDAY RELATIVE
HUMIDITIES ARE NOT EXPECTED TO BE AS LOW AS TODAY. HOWEVER...THERE
IS POTENTIAL THAT AS STRONG DOWNSLOPE WINDS KICK IN THE TEMPERATURE
COULD JUMP AND RELATIVE HUMIDITY PLUMMET APPROACHING RED FLAG
CRITERIA FOR A BRIEF PERIOD OF TIME.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE MAINLAND CONTINUES TO BE RIGHT ON THE PERIPHERY OF THE CURRENT
STORM TRACK BETWEEN AN INLAND RIDGE AND UPPER LEVEL LOW OVER THE
NORTHERN PACIFIC/GULF. THE FRONT WILL STRETCH OUT OVER THE ALASKA
PENINSULA TODAY WHILE GRAZING THE WESTERN CAPES. INTERIOR BRISTOL
BAY SHOULD REMAIN DOWNSLOPED AND DRY WITH GUSTY EASTERLY WINDS.
TEMPERATURES WILL CONTINUE TO REMAIN ABOVE NORMAL DESPITE
INCREASING CLOUD COVER OVER MOST OF THE MAINLAND. THE UPPER LEVEL
LOW PRESSURE DRIFTS OVERHEAD ON THURSDAY BRINGING A BETTER CHANCE
FOR RAIN AND SNOW SHOWERS.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A WEAK WARM FRONT PUSHES ACROSS THE BERING TODAY BRINGING
WIDESPREAD RAIN TO THE EASTERN ALEUTAINS AND ALASKA PENINSULA. ON
THE COLD SIDE OF THE FRONT...DEVELOPING SNOW AND GUSTY NORTHERLY
WINDS HAVE PROMPTED THE ISSUANCE OF A BLOWING SNOW ADVISORY FOR
THE PRIBILOF ISLANDS. THE PRECIPITATION SHIELD WILL RUN RIGHT UP
TO THE ISLANDS WHICH COULD MEAN LIGHT SNOW LINGERS AT SAINT GEORGE
THROUGH THE NIGHT WHILE SAINT PAUL DRIES OUT. BLOWING SNOW WITH
VISIBILITIES REDUCED TO ONE HALF MILE WILL CONTINUE THROUGH THE
DAY TODAY.

&&

.LONG TERM FORECAST (FRIDAY THROUGH TUESDAY)...
WIDESPREAD RAIN WILL CONTINUE FOR THE GULF COAST ON FRIDAY AS A
BROAD SHORTWAVE TROUGH SLOWLY MOVES OVERHEAD...WHILE A SEPARATE
SHORTWAVE WILL BRING RAIN AND SNOW TO THE SOUTHWEST MAINLAND.
ANCHORAGE AND THE MATANUSKA VALLEY WILL ONCE AGAIN REMAIN LARGELY
DOWNSLOPED FROM THIS SYSTEM...THOUGH A FEW SLOP-OVER RAIN SHOWERS
ARE POSSIBLE...ESPECIALLY ON FRIDAY EVENING AS THE SHORTWAVE
PASSES OVERHEAD. ON SATURDAY A GALE FORCE FRONT ASSOCIATED WITH
ANOTHER NORTH PACIFIC LOW WILL MOVE INTO THE SOUTHERN GULF AS A
WAVE WRAPS AROUND THE SOUTHERN END OF THE BERING SEA TROUGH. THIS
FRONT WILL CONTINUE TO PROGRESS NORTHWARD...AND GIVE COASTAL
COMMUNITIES ANOTHER ROUND OF RAIN THAT SHOULD CONTINUE THROUGH THE
UPCOMING WEEKEND.

FOR THE BERING SEA AND THE ALEUTIANS...THEY WILL REMAIN IN
PERSISTENT NORTHERLY FLOW THROUGH THE WEEKEND. THE EASTERN BERING
SEA/ALEUTIANS AND THE BRISTOL BAY AREA WILL RECEIVE THE EFFECTS
FROM THE NORTH PACIFIC LOW AS IT STALLS OVER THE KODIAK ISLAND
AREA. THE PRECIPITATION WILL SPREAD OVER INTO THE EASTERN BERING
SEA/ALEUTIANS THROUGH THE WEEK. THIS PATTERN WILL BEGIN AGAIN WITH
THE NEXT LOW TRACKING TOWARDS KODIAK ISLAND BY SATURDAY. THE
TEMPERATURES WILL REMAIN WELL ABOVE FREEZING ALONG THE EASTERN
ALEUTAINS AND THE BRISTOL BAY AREA. BY MONDAY A SERIES OF WEAK
WAVES WILL ENTER THE WESTERN ALEUTIANS AND MOVE EASTWARD ALONG THE
ALEUTIAN CHAIN. THIS WILL BRING WARMER TEMPERATURES WITH RAIN TO
THE WESTERN/CENTRAL BERING SEA AND ALEUTIANS THROUGH
TUESDAY...EXCEPT FOR A WINTRY MIX FARTHER NORTH IN THE BERING SEA
WITH THE COOLER TEMPERATURES.

FOR EARLY NEXT WEEK...THE MODELS ARE ALL IN GOOD AGREEMENT THAT
THE BERING SEA TROUGH WILL MOVE INTO THE GULF AHEAD OF AHEAD OF A
DEEPER SYSTEM HEADING TOWARDS THE WESTERN ALEUTIANS FROM
KAMCHATKA. THIS TROUGH HOWEVER WILL LIKELY STALL OUT AND SLOWLY
DISSIPATE OVER THE GULF AND SOUTH MAINLAND AS PERSISTENT RIDGING
OVER NORTHWEST CANADA INHIBITS ANY FURTHER EASTWARD PROGRESSION.
THIS WILL KEEP LOW PRESSURE OVER THE GULF INTO TUESDAY...WITH
INCREASING CHANCES OF RAIN/SNOW OVER SOUTHCENTRAL AS THE LOW
WEAKENS.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...BLOWING SNOW ADVISORY 195.
MARINE...STORM 130 131 138
         GALE 119 120 125 132 136 137 139 150 155 160 179
         HEAVY FREEZING SPRAY 179.
FIRE WEATHER...RED FLAG WARNING 111.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...CB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ML
LONG TERM...DEK/PD



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