Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 280027
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
427 PM AKDT FRI MAR 27 2015

.ANALYSIS AND UPPER LEVELS...

THE OVERALL PATTERN REMAINS UNCHANGED FROM PREVIOUS DAYS...WITH A
BROAD LONGWAVE TROUGH OVER THE NORTH PACIFIC AND A MEAN UPPER LOW
POSITION NEAR THE EASTERN ALEUTIANS. A STRONG 175 KT ZONAL JET
LIES SOUTH OF THE ALEUTIANS NEAR 40N. NUMEROUS EMBEDDED SHORTWAVES
ROTATING AROUND THE BASE OF THE LONGWAVE TROUGH ARE GETTING AN
INFUSION OF ENERGY FROM THE CYCLONIC SIDE OF THIS JET...RESULTING
IN MULTIPLE WEAK LOW CENTERS SOUTH OF OUR AREA. ONE OF THE
SHORTWAVES HAS INTENSIFIED MORE THAN THE OTHERS WITH THE HELP OF
SOME UPPER DIFFLUENCE AND LOW-LEVEL THERMAL ADVECTIONS...AND HAS
RESULTED IN THE DEVELOPMENT OF A 970 MB LOW SEVERAL HUNDRED MILES
SOUTH OF KODIAK ISLAND. THIS LOW WILL BE THE PRIMARY WEATHER-MAKER
ACROSS THE REGION FOR THE NEXT 24-48 HOURS AS AN ASSOCIATED FRONT
IS VISIBLE ON SATELLITE IMAGERY SURGING NORTHWARD TOWARD THE GULF
OF ALASKA AND KODIAK ISLAND.

THE BREAK BETWEEN SYSTEMS HAS ALLOWED SOME BREAKS OF SUN TO
DEVELOP OVER INLAND AREAS OF SOUTHCENTRAL AND SOUTHWEST
ALASKA WITH CROSS-BARRIER FLOW CONTINUING TO KEEP THE MAJORITY OF
SHOWER ACTIVITY CONFINED TO THE GULF COAST. GUSTY SOUTHEAST WINDS
AROUND THE COOK INLET POPULATION CENTERS HAVE AGAIN REVERSED AS
PRESSURE GRADIENTS ARE BEGINNING TO FAVOR NORTHERLY/DOWN-INLET
FLOW IN ADVANCE OF THE AFOREMENTIONED LOW SOUTH OF KODIAK.

OUT WEST...ON THE "COLD" SIDE OF THE LONGWAVE TROUGH....GENERAL
NORTHERLY FLOW CONTINUES WITH CONTINUING SHOWER ACTIVITY. MOST OF
THE PRECIP REMAINS FOCUSED ALONG A STATIONARY AND DECAYING FRONTAL
BOUNDARY IN A FAIRLY NARROW CORRIDOR FROM THE PRIBILOF ISLANDS DOWN
TO THE ATKA/DUTCH HARBOR AREA.

&&

.MODEL DISCUSSION...

THE MODELS ARE IN SUBSTANTIALLY BETTER AGREEMENT TODAY RELATING
TO THE EVOLUTION OF THE PRIMARY FEATURE OF CONCERN WHICH IS THE
LOW SOUTH OF KODIAK. THE NAM CONTINUES TO BE VERY NOISY AND
INCONSISTENT...EVEN AS EARLY AS LATE TONIGHT...THOUGH THE GLOBAL
MODELS (GFS/ECMWF/GEMGLB) ARE ALL IN PRETTY DECENT AGREEMENT
TAKING THE LOW UP INTO THE SOUTHWEST GULF BY SATURDAY EVENING
BEFORE THE STORM WEAKENS SUBSTANTIALLY AND RECURVES WESTWARD BACK
TOWARD THE BASE OF THE LONGWAVE TROUGH. THE ECMWF IS THE PREFERRED
MODEL TODAY...THOUGH SOME HI-RES GEM-RGL WAS ALSO USED TO BUMP
WINDS UP IN THE VICINITY OF LOWER COOK INLET...THE BARREN
ISLANDS...AND SHELIKOF STRAIT.

&&

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

A FRONT MOVING ACROSS THE GULF WILL BRING RAIN TO KODIAK
TONIGHT THROUGH SUN...AND WILL ENHANCE RAIN ALONG THE REST OF THE
NORTH GULF COAST THROUGH THE WEEKEND. SHOWER ACTIVITY WILL ALSO
EDGE ACROSS THE KENAI AND CHUGACH MOUNTAINS...AND AT HIGHER
ELEVATIONS SOME SNOW IS EXPECTED OVERNIGHT TONIGHT AND SAT.
MATANUSKA WINDS WILL INCREASE SAT AFTERNOON AHEAD OF THE
FRONT...BUT RH VALUES SHOULD NOT FALL BELOW CRITICAL LEVELS. ON
SUN...THE ASSOCIATED LOW TAKES UP RESIDENCE OVER KODIAK AND SOUTHERLY
FLOW RESUMES SO SOME SHOWER ACTIVITY WILL CONTINUE ALONG THE COAST
EARLY NEXT WEEK.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2...SAT AND
SUN)...THE PATTERN WILL BE CONTROLLED BY ONE LOW CURRENTLY IN
NORTHERN BRISTOL BAY AND ANOTHER IN THE NORTH PACIFIC. THE BRISTOL
BAY LOW WILL PULL AWAY TO THE WEST AND WEAKEN THROUGH THE
OVERNIGHT HOURS. AS IT DOES SO...ANY LINGERING SNOW AND RAIN
SHOWERS SHOULD CONTINUE TO DIMINISH THROUGH SATURDAY MORNING. THEN
THE LOW OVER THE NORTH PACIFIC WORKS ITS WAY INTO THE NORTHERN
GULF OF AK. THIS SHOULD SERVE TO BRING THE WINDS AROUND TO MORE OF
A NORTHEASTERLY DIRECTION FOR MUCH OF SOUTHWEST AK. THIS OFFSHORE
FLOW WILL BRING DRYING CONDITIONS FOR MOST PLACES AND SHOULD ALLOW
OVERNIGHT TEMPERATURES TO COOL TO MORE SEASONAL LEVELS. GUSTY
WINDS AND LIGHT PRECIPITATION FROM THE GULF LOW SHOULD ONLY BE
ABLE TO REACH THE ALEUTIAN RANGE AND THE WESTERN PORTION OF THE
ALASKA PENINSULA.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2...SAT AND
SUN)...THE MOST INTERESTING WEATHER WILL BE UNDER THE WEAKENING
DEFORMATION ZONE CURRENTLY STRETCHING FROM THE PRIBILOF ISLANDS
TOWARDS THE CENTRAL ALEUTIANS. GUSTY NORTHERLY WINDS AND SOME
COLDER AIR ARE MAKING FOR SOME BLOWING SNOW CONDITIONS FOR THE
PRIBS AND FOR ATKA. THESE CONDITIONS WILL PERSIST THROUGH INTO
SATURDAY MORNING AS THIS SYSTEM SLOWLY WEAKENS. A NEW LOW ROLLS
OFF THE KAMCHATKA PENINSULA ON SATURDAY AND SHOULD SPREAD SOME LIGHT
RAIN AND SNOW IN THE WESTERN ALEUTIANS BY THE AFTERNOON/EVENING
HOURS. THIS LOW WILL THEN STRETCH OUT AND FALL APART IN THAT SAME
REGION ON SUNDAY. MEANWHILE...NORTHWEST TO NORTHEAST FLOW COULD
BRING SOME LIGHT RAIN AND SNOW SHOWERS...MAINLY TO THE BERING
SIDE...OF THE CENTRAL AND EASTERN ALEUTIANS SUNDAY.

&&

.LONG TERM FORECAST (MONDAY THROUGH FRIDAY)...
THE SAME WEATHER PATTERN WILL CONTINUE THROUGH NEXT WEEK WITH THE
FIRST NORTH PACIFIC LOW TRACKING SOUTH EAST OF KODIAK ISLAND BY
MONDAY. THIS LOW TRACKS TO THE NORTHERN GULF BY TUESDAY BEFORE
DISSIPATING BY WEDNESDAY. THE SECOND LOW WILL ENTER THE GULF BY
WEDNESDAY AND TRACK TO THE SOUTHEASTERN GULF BY FRIDAY. THIS WILL
CONTINUE TO BRING WARM TEMPERATURES TO SOUTHCENTRAL REGION.
RESULTING IN WIDESPREAD RAIN TO THE COASTAL AREAS WITH THE FIRST
SYSTEM THROUGH THE MIDWEEK...THEN SCATTERED RAIN SHOWERS ALONG THE
COAST WITH SECOND SYSTEM BY END OF THE WEEK. THE INLAND AREAS WILL
CONTINUE TO REMAIN DRY DUE TO DOWNSLOPING OVER THE MOUNTAINS
THROUGH THE WEEK.

THE EASTERN BERING SEA AND BRISTOL BAY REGION WILL HAVE SCATTERED
RAIN SHOWERS THROUGH THE MIDWEEK WITH NORTHEASTERLY WINDS AND
PRECIPITATION SPILLING OVER FROM THE LOW POSITIONED NEAR KODIAK
ISLAND. BY TUESDAY...THE WESTERN ALEUTIANS WILL HAVE A NORTH
PACIFIC LOW TRACK INTO THE AREA AND MOVE PARALLEL TO THE ALEUTIAN
BEFORE TRACKING TO THE GULF BY THURSDAY. THIS WILL BRING WARMER
TEMPERATURES OUT AHEAD OF THE SYSTEM AND COLDER AIR ON THE
BACKSIDE OF THE LOW AS IT CONTINUES TO MOVE EASTWARD. THE
PRECIPITATION WILL REMAIN ALONG THE CHAIN AND SPREAD OVER INTO THE
LOWER PORTIONS OF THE BERING SEA. PRECIPITATION WILL RAIN BEFORE
CHANGING TO SNOW ON THE BACKSIDE OF THE LOW WITH THE COOLER
TEMPERATURES. THE NEXT NORTH PACIFIC LOW WILL TRACK INTO THE
WESTERN ALEUTIANS BY FRIDAY BRINGING WARMER TEMPERATURES TO GULF
WITH SOUTHERLY FLOW. WHILE...THE MODELS WERE IN SLIGHTLY BETTER
AGREEMENT AND THE ECMWF MODEL STILL CONTINUES TO BE MORE
CONSISTENT FROM OTHER MODELS. THEREFORE...HPC USED A STRONGER BLEND
OF THE EC/GFS ENSEMBLES THROUGH THE EXTENDED OUTLOOK. THE FORECAST
CONFIDENCE IS AVERAGE GOING INTO NEXT WEEK.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 119 120 130 131 132 136 137 138 139 150 173 174 176
         179 351 352 413 414.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...AD
SOUTHCENTRAL ALASKA...DS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MO
LONG TERM...PD


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