Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 290008
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
408 PM AKDT THU APR 28 2016

.ANALYSIS AND UPPER LEVELS...

STACKED LOW PRESSURE THROUGH ALL LEVELS OF THE ATMOSPHERE IS
CENTERED ABOUT 100 NM SOUTH OF THE SOUTHERN TIP OF THE ALASKA
PENINSULA. THIS CENTER IS PART OF A MUCH LARGER BROAD CYCLONIC
FEATURE THAT ENCOMPASSES THE ENTIRE ANCHORAGE OFFICE AREA OF
RESPONSIBILITY. WITHIN THE BROAD CYCLONIC ENVELOPE...NUMEROUS
SHORTWAVE DISTURBANCES ARE ROTATING AROUND THE BROAD LOW...KEEPING
MOST REGIONS IN A FAIRLY DYNAMIC...IF NOT IMPACTFUL...WEATHER
PATTERN.

AT THE SURFACE...A GALE-FORCE FRONT ALONG THE NORTH GULF COAST
CONTINUES TO WEAKEN AS IT PUSHES THROUGH THE INNER WATERS AREAS.

&&

.MODEL DISCUSSION...

MODELS ARE IN GREAT AGREEMENT SYNOPTICALLY. GRIDS LARGELY UTILIZED
HIGHER RESOLUTION MODELS SUCH AS THE NAM AND GEM REGIONAL FOR
THEIR BETTER RESOLVING OF WINDS NEAR LOCAL EFFECT AREAS.

&&

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

ANOTHER COASTAL RIDGE WILL BEGIN TO STRENGTHEN LATE THIS AFTERNOON
INTO THIS EVENING AND PROVIDE ANOTHER ISALLOBARIC PUSH TO ALLOW
GUSTY WINDS THROUGH THE GAPS IN TURNAGAIN ARM...PORTAGE VALLEY AND
THE KNIK RIVER VALLEY TO BE ON THE RISE. MODELS HAVE BEEN IN GOOD
AGREEMENT WITH THIS FEATURE FOR THE PAST SEVERAL DAYS AND HAVE
STRENGTHENED WINDS BETWEEN 5 AND 10 MPH THROUGH THESE GAPS BASED
OFF OF CURRENT SURFACE AND SATELLITE TRENDS. THESE GUSTY WINDS
WILL CONTINUE THROUGH AT LEAST SUNDAY AS THE PRESSURE GRADIENT
ONLY GETS TIGHTER AS ANOTHER FRONTAL BOUNDARY PUSHES THROUGH THE
GULF OF ALASKA ON SATURDAY. THIS FRONTAL BOUNDARY WILL BE MUCH
STRONGER THAN THE SERIES OF FRONTS OBSERVED EARLIER IN THE WEEK
AND SHOULD PRODUCE A STRONG BARRIER JET ALONG THE NORTHERN GULF
COAST.

WINDS APPROACHING OR EXCEEDING 50 KTS COULD BE SEEN NEAR
MIDDLETON ISLAND AND JUST OFFSHORE OF CORDOVA WITH GALE FORCE
WINDS LIKELY TO PUSH INTO THE ENTRANCE OF PRINCE WILLIAM SOUND. AS
WITH ALL FRONTS MOVING THROUGH THE GULF OF ALASKA...THE NORTHERN
GULF COAST WILL BE IN STORE FOR A DELUGE AS PRECIPITATION UPSLOPES
ALONG THE COASTAL RANGE. INTERIOR LOCATIONS LOOK LARGELY ON THE
DRY SIDE AS THE FRONT STRUGGLES TO MAKE ANY PROGRESS INLAND BUT
SOME MODEL RUNS PROVIDE A FEW WEAK SHORTWAVES WHICH COULD ALLOW
PRECIPITATION TO MOVE INLAND FOR A BRIEF PERIOD OF TIME. SOME
DIURNAL CONVECTION WILL BE POSSIBLE ALONG THE ALASKA RANGE AND THE
WRANGELL MOUNTAINS BUT IT STILL APPEARS LAPSE RATES AND
INSTABILITY WILL BE TOO UNFAVORABLE TO SUPPORT THUNDERSTORMS AT
THIS TIME.

&&

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

THE WEAK FRONTAL SYSTEM CURRENTLY STRETCHED ACROSS THE BRISTOL BAY
AREA WILL CONTINUE TO FALL APART WITH SHOWERS BECOMING MORE
SCATTERED IN COVERAGE OVERNIGHT. THE NEXT TROUGH WILL ROTATE
THROUGH ON FRIDAY BRINGING MORE NUMEROUS SHOWERS TO THE BRISTOL
BAY AREA IN THE MORNING AND THE KUSKOKWIM VALLEY AND DELTA IN THE
AFTERNOON. SHOWERS WILL TAPER BACK OFF FRIDAY NIGHT AND SATURDAY AS
A STRONGER FRONT MOVES INTO THE SOUTHWEST GULF AND INCREASES DRIER
NORTHEASTERLY FLOW OVER SOUTHWEST ALASKA.

&&

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

THE LOW CENTERED JUST SOUTH OF THE THE EASTERN ALEUTIANS WILL
CONTINUE TO WEAKEN AS IT TRACKS SLOWLY EAST TONIGHT THEN
DISSIPATES SOUTH OF COLD BAY FRIDAY MORNING. THE MEAN LARGER SCALE
UPPER LEVEL LOW CENTER WILL REMAIN IN THIS GENERAL AREA AS A
DEVELOPING LOW FROM THE NORTH PACIFIC TRACKS INTO THE SOUTHWESTERN
GULF FRIDAY NIGHT AND SATURDAY. UPPER LEVEL RIDGING WILL BUILD
INTO THE WESTERN ALEUTIANS FRIDAY THEN SHIFT EAST OVER THE
CENTRAL ALEUTIANS AND BERING ON SATURDAY AS THE NEXT INCOMING
FRONTAL SYSTEM APPROACHES THE WESTERN ALEUTIANS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
AN UPPER LEVEL CLOSED LOW AT 500 MB WILL TRACK NEAR KODIAK BY
SATURDAY WITH AN ASSOCIATED SHORTWAVE DIGGING INTO THE BASE OF THE
LONGWAVE TROUGH. THIS FEATURE WILL RESULT IN THE STRONG SOUTHERLY
JET STREAM IN THE GULF BEFORE TRANSITIONING TO A MORE
SOUTHEASTERLY FLOW. THIS RESULTS IN AN NEGATIVELY TILTED AMPLIFIED
RIDGE OVER THE YUKON TERRITORY EXTENDING INTO THE ALASKA RANGE AND
CENTRAL INTERIOR. THEREFORE...SEVERAL SHORTWAVES WILL MOVE THROUGH
THE SOUTHCENTRAL AND THE GULF THROUGH TUESDAY. THIS SYNOPTIC
PATTERN WILL BRING PLENTY OF MOISTURE AND HEAVY RAIN AT TIMES TO
THE NORTHERN AND WESTERN COASTAL COMMUNITIES THROUGH WEDNESDAY.

WHILE THE BERING AND THE ALEUTIANS WILL START OUT WITH A SHOWERY
REGIME WITH NORTHERLY TO NORTHEASTERLY FLOW THIS WEEKEND...A GALE
FORCE LOW WILL DROP DOWN OFF THE KAMCHATKA PENINSULA BY SATURDAY
WITH AN ASSOCIATED WEATHER FRONT MOVING THROUGH THE WESTERN
ALEUTIANS BY SATURDAY EVENING. THIS LOW PRESSURE SYSTEM WILL THEN
TRACK ALONG THE CHAIN HEADING THROUGH MIDWEEK. THIS WILL BRING A
SWATH OF STRATUS WITH RAIN AND GUSTY SOUTHEASTERLY WINDS AS THE
FRONT MOVES THROUGH THE WESTERN ALEUTIANS THIS WEEKEND. AS THIS
SYSTEM MOVES ALONG THE CHAIN THIS WILL PRODUCE A SHOWERY WEATHER
REGIME ON THE BACKSIDE OF THE LOW PRESSURE. THE WESTERN BERING AND
THE ALEUTIANS WILL TRANSITION TO NORTHEASTERLY FLOW AS THE LOW
PRESSURE SYSTEM MOVES EAST HEADING INTO THE MIDWEEK TIMEFRAME.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...119 120 130 131 132 136 137 138 150.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...CC
SOUTHCENTRAL ALASKA...MMC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
LONG TERM...PD



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