Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 271433
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
533 AM AKST SAT DEC 27 2014

.ANALYSIS AND UPPER LEVELS...
AN UPPER LEVEL AMPLIFIED RIDGE IS POSITIONED FROM 51N 147W IN THE
NORTH PACIFIC OCEAN EXTENDING TO THE NORTHWEST THROUGH THE ALASKA
PENINSULA INTO SOUTHWEST ALASKA TO THE EASTERN SIBERIAN REGION.
ON THE BACKSIDE OF THE RIDGE THERE IS A CLOSED LOW NEAR THE
WESTERN ALEUTIANS WITH AN ASSOCIATED TROUGH EXTENDING THROUGH THE
BERING SEA AND THROUGH THE CENTRAL ALEUTIANS INTO THE PACIFIC.
THIS IS REFLECTED AT THE SURFACE WITH A WEATHER FRONT LOCATED
THROUGH THE CENTRAL BERING SEA EXTENDING THROUGH THE CENTRAL
ALEUTIANS NEAR NIKOLSKI THIS MORNING. THE SATELLITE IMAGERY IS
SHOWING THE OCCLUDED SURFACE LOW WEST OF SHEMYA WITH SCATTERED
SHOWERY PRECIPITATION THROUGH THE WESTERN ALEUTIANS BEFORE
TRANSITIONING TO STRATIFORM CLOUDS AND RAIN OVER THE EASTERN
BERING/AK PEN. THE ASCAT SCATTEROMETER WINDS ARE SHOWING THE GULF
WITH NORTHWESTERLY SMALL CRAFT WINDS. THE SATELLITE IMAGERY HAS
MAJORITY OF THE GULF UNDER HIGH PRESSURE WITH MARINE LAYER STRATUS
NEAR KODIAK ISLAND AND THE NORTHERN GULF. THE SURFACE OBSERVATIONS
IN THE COPPER RIVER BASIN THIS MORNING HAVE BEEN REPORTING LOW
STRATUS CEILINGS WITH POOR VISIBILITIES.

&&

.MODEL DISCUSSION...
THE MODELS ARE HANDLING THE OCCLUDED LOW NEAR SHEMYA WELL AND THE
HIGH PRESSURE BUILDING INTO THE GULF THIS MORNING. THE MODELS THEN
STRUGGLE WITH THE NORTH PACIFIC LOW THAT APPROACHES THE CENTRAL
ALEUTAINS JUST SOUTH OF UNALASKA BY MONDAY MORNING. DURING THIS
SAME TIME FRAME THE MODELS ARE DEPICTING A STRONG RIDGE BUILDING
ALONG THE NORTHERN GULF COAST. THE GRADIENT ALONG THE ALASKA
PENINSULA NORTHWARD THROUGH THE ALASKA RANGE WILL STRENGTHEN
THROUGH THE WEEKEND. THIS HAS RESULTED IN AN ISSUANCE OF A HIGH
WIND WATCH FOR THE INTERIOR BRISTOL BAY REGION MAINLY THROUGH THE
GAPS IN THE ALEUTIAN RANGE. THE CHALLENGE WILL BE WITH THE TIMING
OF THE WEATHER FRONT TO SOUTHWEST ALASKA WHICH WILL ENHANCE THE
POTENTIAL FOR GUSTY HIGH WINDS THROUGH THE ALASKA RANGE AND THE
TURNAGAIN ARM WINDS THIS WEEKEND. THE FORECAST CONFIDENCE REMAINS
BELOW AVERAGE DUE TO THE UNCERTAINTY WITH THE AFOREMENTIONED
SYNOPTIC FEATURES.

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

SUBSIDENCE AND DECREASING HIGHER CLOUDS WITH A BUILDING RIDGE ARE
PRODUCING AREAS OF LOW CLOUDS AND FOG ACROSS THE REGION. A WEATHER
FRONT MOVING NORTH TOWARD THE GULF WILL BRING INCREASING CLOUDS
WITH RAIN TO KODIAK ISLAND SUNDAY MORNING. RAIN AND SNOW WILL
SPREAD TO THE KENAI PENINSULA LATE SUN AFTERNOON AND TO THE NORTH
GULF COAST ON MON. EXCEPT FOR UPSLOPE CONDITIONS ALONG THE ALASKA
RANGE (WEST COOK INLET/WEST SUSITNA VALLEY)...STRONG SE CROSS
BARRIER FLOW SHOULD MINIMIZE PRECIPITATION WEST OF THE CHUGACH
MOUNTAINS. WINDY CONDITIONS WILL ALSO ACCOMPANY THE NORTHWARD
ADVANCING FRONTAL SYSTEM. GALES WITH LOCAL STORMS (BARREN ISLANDS)
WILL SPREAD ACROSS THE COASTAL MARINES TONIGHT THROUGH SUN. STRONG
GAP FLOWS ACROSS THE KENAI PEN AND ANCHORAGE BOWL ARE ALSO
EXPECTED TO DEVELOP LATE TONIGHT AND CONTINUE INTO MON.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
AN AMPLIFIED RIDGE OF HIGH PRESSURE WILL PERSIST OVER THE
SOUTHWEST REGION THROUGH SATURDAY BRINGING A WARMING TREND
THROUGHOUT THE REGION. THE ONSHORE FLOW WILL REMAIN THROUGH
THE WEEKEND BRINGING MORE STRATUS AND FOG TO THE INTERIOR AREAS.
THE BIGGEST CONCERN WILL BE THE INCREASED PRESSURE GRADIENT OVER
THE WEEKEND WITH EAST TO SOUTHEASTERLY WINDS. THIS HAS RESULTED
IN AN ISSUANCE OF A HIGH WIND WATCH MAINLY THROUGH GAPS IN THE
ALEUTIAN RANGE LATE SATURDAY NIGHT THROUGH SUNDAY EVENING. THERE
WILL BE WIDESPREAD PRECIPITATION ACCOMPANIED WITH THE WEATHER
FRONT THAT WILL TRACK INTO THE REGION BY SATURDAY EVENING AS THE
SYSTEM MOVES INLAND OVER THE WEEKEND. THIS WILL BRING WARMING
TEMPERATURES ABOVE FREEZING FOR MAJORITY OF THE REGION EXCEPT FOR
A WINTRY MIX OVER THE AHKLUN MOUNTAINS.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)..
THE OCCLUDED STORM FORCE LOW NORTHWEST OF SHEMYA WILL CONTINUE TO
BRING GALE FORCE SOUTHERLY WINDS THROUGH THE WESTERN ALEUTIANS
EXTENDING INTO THE WESTERN BERING SEA THROUGH EARLY SUNDAY. THE
EASTERN BERING SEA WILL HAVE THE WEATHER FRONT TRACKING THROUGH
THIS WEEKEND RESULTING IN GALE FORCE WINDS. THESE WINDS WILL
EXTEND INTO THE NORTHERN BERING SEA BEFORE DIMINISHING BY THE END
OF THE WEEKEND. THE MAJORITY OF THE BERING SEA WILL REMAIN IN THE
WARM SOUTHERLY FLOW RESULTING IN ANY PRECIPITATION FALLING AS RAIN
EXCEPT A WINTRY MIX IN THE NORTHERN BERING SEA WITH COOLER
TEMPERATURES.

&&

.LONG TERM FORECAST (MONDAY THROUGH FRIDAY)...

MONDAY WILL BEGIN WITH A LARGE NORTH PACIFIC LOW MOVING ACROSS THE
EASTERN ALEUTIAN ISLANDS INTO THE SOUTHEAST BERING SEA...WITH A
STOUT WARM FRONT ACROSS THE WESTERN GULF OF ALASKA. THIS PATTERN
WILL FAVOR HEAVY RAIN FROM KODIAK TO THE KENAI PENINSULA
COAST...WITH A MIX OF RAIN AND SNOW TURNING TO ALL SNOW ACROSS
SOUTHWEST ALASKA. THE PRESSURE GRADIENT WILL INCREASE ACROSS LARGE
NORTH-SOUTH TRENDING MOUNTAIN RANGES...WITH STRONG EAST-
SOUTHEASTERLY GAP WINDS IMPACTING LOCATIONS DOWNWIND OF THE ALASKA
RANGE AND CHUGACH MOUNTAINS. A WARM CHINOOK WILL TRACK THROUGH
SOUTHWEST ALASKA ON TUESDAY AS THE BERING LOW TRACKS NORTH TOWARD
NUNIVAK ISLAND...WITH A WEAKER CHINOOK TRACKING ACROSS
SOUTHCENTRAL ALASKA. RAIN WILL REMAIN MODERATE TO HEAVY ACROSS
COASTAL LOCATIONS TUESDAY...BUT STRONG DOWNSLOPE SHADOWING WILL
KEEP MOST INLAND LOCATIONS LARGELY DRY. THE RIDGE OVER EASTERN
ALASKA WILL WEAKEN LATE TUESDAY AND WEDNESDAY AS THE BERING TROUGH
FLATTENS OUT THE RIDGE...WITH THE HEAVIEST PRECIPITATION MOVING
EAST TOWARD THE ALCAN...AND DRIER AND COOLER AIR MOVING IN BEHIND
THE TROUGH THURSDAY. THE GLOBAL NUMERICAL GUIDANCE...WITH SOME
DISCREPANCY...ARE ALL HINTING AT A BLOCKING HIGH FORMING OVER
ALASKA LATE WEEK...WITH A DRY OFFSHORE PRESSURE GRADIENT CLEARING
THE REGION OUT HEADING INTO THE WEEKEND. THIS PATTERN WOULD
EVENTUALLY YIELD COOLER TEMPERATURES AT OR EVEN SLIGHTLY BELOW
NORMAL.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WATCH ZONE 161.
MARINE...STORMS 130 131.
         GALES 132 136 137 138 139 141 150 155 160 165 170 174
               178 180 181 185 351 352 411 414.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...PD
SOUTHCENTRAL ALASKA...RMC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PD
LONG TERM...JA


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