Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 271249
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
449 AM AKDT WED MAY 27 2015

.ANALYSIS AND UPPER LEVELS...

THE MASSIVE UPPER LEVEL RIDGE CENTERED OVER THE ALCAN IS BEING
UNDERCUT BY A SMALL UPPER LOW CURRENTLY OVER SOUTHEAST AK THIS
MORNING. A LARGER UPPER LOW ENCOMPASSES MOST OF THE BERING. AT
THE SURFACE...A SLOWLY WEAKENING LOW IS OVER THE WESTERN BERING AS
ITS ASSOCIATED SHOWER PRODUCING FRONT IS OVER SW AK. HIGH
PRESSURE OVER THE GULF EXTENDS OVER MUCH OF THE MAINLAND...
INTERRUPTED ONLY BY A THERMAL TROUGH DRAPED NORTH OF THE AK RANGE
AND NOSING INTO THE COPPER RIVER BASIN.

&&

.MODEL DISCUSSION...

MODELS ARE IN AGREEMENT THAT THE RIDGE OVER MAINLAND AK WILL
REBUILD TODAY. AN UPPER TROUGH WILL RIPPLE ALONG ITS WESTERN
FLANK THU AND FLATTEN THE NORTHERN EXTENT OF THE RIDGE FRI NIGHT.
THIS WILL ALLOW THE SW AK FRONT TO WEAKEN AND MOVE EAST AS AN
AREA OF MOISTURE...REACHING THE ALCAN BY FRI MORNING. THE THERMAL
TROUGH WILL EDGE ACROSS THE AK RANGE INTO THE COPPER RIVER BASIN
THIS AFTERNOON AND THEN MAKE A MORE SUBSTANTIAL INTRUSION OVER
MOST OF THE COPPER RIVER BASIN ON THU WHERE IT WILL INTERACT WITH
THE MOISTURE REMNANT OF THE SW AK FRONT. MODELS ARE ALSO IN
AGREEMENT THAT THE CURRENT BERING LOW WILL DISSIPATE TONIGHT...BUT
AN INTENSIFYING NORTH PACIFIC LOW WILL REACH THE ALEUTIANS BY THU
MORNING AND THEN CROSS INTO THE BERING. THE FORECASTS UTILIZE THE
EC IN THE WEST AND THE NAM IN THE EAST...THE LATTER HAVING PERFORMED
WELL IN PINPOINTING POSSIBLE THUNDERSTORM AREAS.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
HIGH PRESSURE WILL BUILD OVER SOUTH CENTRAL ALASKA TODAY AND
THURSDAY WITH A WARMING TREND ON TAP. SOME LINGERING MOISTURE
OVER THE COPPER RIVER BASIN WILL KEEP A CHANCE OF SHOWERS FOR THAT
AREA...AND A SLIGHT RISK OF DIURNAL THUNDERSTORMS WITH SLIGHTLY
UNSTABLE CONDITIONS. AN UPPER LEVEL SHORT WAVE ASSOCIATED WITH THE
BERING LOW WILL SKIRT THE AREA TO THE WEST AND THEN NORTH ON
THURSDAY...HELPING TO KEEP THE CONDITIONS UNSTABLE IN THE COPPER
RIVER BASIN.

&&

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

A STALLED AND WEAKENING FRONTAL ZONE WILL REMAIN OVER THE
SOUTHWEST COAST THROUGH THIS EVENING BEFORE WEAKENING. MOST OF
THE RAINFALL ASSOCIATED WITH THIS WILL BE OVER THE KUSKOKWIM DELTA
AND WESTERN CAPES. INLAND LOCATIONS WILL REMAIN DRY AND WARMER
TODAY. ON THURSDAY...THE WEAKENED UPPER LEVEL LOW WILL MOVE
EAST...SPREADING SOME MID LEVEL CLOUDS AND A FEW SHOWERS ACROSS
THE LOWER KUSKOKWIM VALLEY AND BRISTOL BAY...BUT MOST LOCATIONS
WILL JUST REMAIN DRY. HIGH PRESSURE ALOFT WILL THEN SETTLE IN
THROUGH FRIDAY BEFORE ANOTHER FRONT TRACKS TOWARD THE COAST.
PATCHY OVERNIGHT FOG WILL GENERALLY REMAIN RELEGATED TO COASTAL
LOCATIONS.

&&

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

A BROAD LOW OVER THE WESTERN BERING...WITH THE ASSOCIATED FRONT
OVER THE EASTERN BERING...WILL WEAKEN TODAY BEFORE A STRONG LOW
FOR THIS TIME OF YEAR MOVES INTO THE WESTERN BERING AND ALEUTIANS
TONIGHT AND THURSDAY. THE LOW IS EXPECTED TO TRACK IN THE VICINITY
OF KISKA...WITH STRONG SOUTH TO SOUTHEAST MAX GALE FORCE WINDS
IMPACTING THE WESTERN AND CENTRAL ALEUTIANS. STORM FORCE WIND
GUSTS WILL ALSO IMPACT THE REGION...WITH GUSTY WINDS EXTENDING TO
THE EASTERN ALEUTIANS AS THE LOW MOVES NORTH ON THURSDAY AND
THURSDAY NIGHT. MODERATE TO HEAVY RAIN WILL ALSO SPREAD OVER THE
BERING AS THE FRONTAL ZONE TRACKS EAST.

&&

.LONG TERM FORECAST (DAYS 4 THROUGH 7)...

A PATTERN CHANGE MAY BE UNDERWAY STARTING FRIDAY...AS AN UPPER
LEVEL TROUGH EXITS THE SOUTHCENTRAL MAINLAND TO THE NORTH AND
PUSHES FURTHER INTO THE INTERIOR BY THE WEEKEND. MODELS ARE IN
FAIR AGREEMENT WITH POSITIONING AND STRENGTH OF THIS FEATURE...BUT
BEGIN TO STRUGGLE AS TIME PROGRESSES THROUGH THE WEEKEND. THE EC
AND CANADIAN MODELS SHOW THIS FEATURE JOIN UP WITH A TROUGH
ASSOCIATED WITH A LOW OVER NORTHERN CANADA...SPLITTING THE RIDGE
INTO A CLOSED HIGH OVER THE CHUKCHI SEA AND A BROAD AREA OF HIGH
PRESSURE SOUTH OF THE GULF. THIS WOULD ESSENTIALLY RESULT IN
SHOWERY CONDITIONS DEVELOPING OVER PARTS OF THE SOUTHCENTRAL
INTERIOR SATURDAY THROUGH EARLY NEXT WEEK. ON THE OTHER
HAND....THE GFS SHOWS THIS ENERGY TRACK EASTWARD OVER NORTHWEST
CANADA SATURDAY...WITH A SEPARATE WAVE OVER THE INTERIOR PUSHING
SOUTHWARD OVER THE SOUTHCENTRAL INTERIOR BY SUNDAY AFTERNOON. THIS
WOULD RESULT IN DRIER CONDITIONS OVER THE SOUTHCENTRAL INTERIOR
THROUGH MUCH OF THE WEEKEND WITH SHOWERY CONDITIONS DEVELOPING
SUNDAY AFTERNOON THROUGH EARLY NEXT WEEK. AT THE SURFACE...MODELS
ARE IN FAIR AGREEMENT WITH THE HIGH OVER THE GULF RETREATING TO
THE SOUTH...AS LOWER PRESSURE NOSES IN FROM NORTHWESTERN CANADA
THROUGH EARLY NEXT WEEK. HOWEVER...WITH THE MODEL DISCREPANCIES IN
THE UPPER LEVELS...FORECAST CONFIDENCE REGARDING THE ABOVE
MENTIONED FEATURES REMAINS BELOW AVERAGE.

FURTHER WEST...AS THE LOW OVER THE FAR WESTERN BERING AND THE
ASSOCIATED FRONT OVER THE SOUTHWEST COAST WEAKENS FRIDAY
NIGHT...HIGHER PRESSURE WILL BRIEFLY BUILD OVER THE BERING AND
ALEUTIANS. THIS WILL GIVE THE THE SOUTHWEST MAINLAND AND MUCH OF
THE BERING/ALEUTIANS A QUICK BREAK IN THE RAINY AND WINDY
CONDITIONS THROUGH SUNDAY...BEFORE ANOTHER FRONTAL SYSTEM TRACKS
INTO THE WESTERN ALEUTIANS FROM THE WEST SUNDAY. WET AND WINDY
CONDITIONS WILL PICK BACK UP OVER THE WESTERN BERING/ALEUTIANS
SUNDAY AFTERNOON AS THE FRONT MOVES THROUGH...THEN WEAKEN AS
SPREADS EASTWARD OVER THE CENTRAL ALEUTIANS INTO EARLY NEXT WEEK.
MODELS CONTINUE TO STRUGGLE WITH THE TIMING AND STRENGTH OF THIS
FEATURE...LEADING TO LOWER THAN NORMAL FORECAST CONFIDENCE IN THE
ARRIVAL TIME OF THE WINDS AND PRECIP INTO THE WESTERN AND CENTRAL
ALEUTIANS/BERING.

&&


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

&&

$$

SYNOPSIS AND MODEL DISCUSSION...DS
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA
LONG TERM...TP



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