Area Forecast Discussion
Issued by NWS Anchorage, AK

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

000
FXAK68 PAFC 121254
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
454 AM AKDT SAT APR 12 2014

.ANALYSIS AND UPPER LEVELS...
IMPRESSIVELY COLD CLOUD TOPS ARE OVERTAKING MUCH OF THE
SOUTHCENTRAL AHEAD OF A STRONG COMPACT SHORT-WAVE MIGRATING INTO
THE NORTHERN BERING SEA. THE FRONTAL BOUNDARY ASSOCIATED WITH THE
SYSTEM WRAPS AROUND THE PRIBILOF ISLANDS THROUGH DUTCH HARBOR IN
THE FORM OF A BACK BENT OCCLUSION. THE OCCLUDED/WARM FRONT IS
PUSHING OVER THE KUSKOKWIM DELTA WHILE THE COLD FRONT STRETCHES
SOUTH OVER THE ALASKA PENINSULA.

THE SHORT-WAVE IS BECOMING THE NEW CENTER OF CIRCULATION OF THE
UPPER LOW COMPLEX OVER THE CENTRAL ALEUTIANS/BERING SEA. TO THE
EAST OF THE SYSTEM STRONG SOUTHERLY FLOW THROUGH THE COLUMN IS
PUMPING UP THE RIDGE AND PRODUCING A MOUNTAIN WAVE OVER THE ALASKA
PENINSULA. THICK CIRRUS STREAMS NORTHWARD OVER THE SOUTHCENTRAL
OBSCURING ANY FRONTAL FEATURES BENEATH. A SECONDARY SHORTWAVE IS
ROUNDING THE TROUGH FURTHER SOUTH IN THE PACIFIC AND WILL BE THE
NEXT PLAYER IN ACTIVE WEATHER FOR THE SOUTHCENTRAL.

&&

.MODEL DISCUSSION...
GUIDANCE REMAINS IN GREAT SYNOPTIC AGREEMENT THROUGH THE NEXT
COUPLE DAYS WITH THE BERING SEA LOW PRESSURE SYSTEM AND DEVELOPING
WAVE MOVING TOWARD KODIAK ISLAND LATE TONIGHT. DIFFERENCES START
TO SHOW BETWEEN MODELS AS THE KAMCHATKA UPPER LOW PROPAGATES
EASTWARD AND THE UPPER TROUGH FRAGMENTS AS RIDGING AHEAD OF THE
INCOMING LOW PRESSURE SYSTEM PINCHES OFF SOME VORTICITY. THE
AMERICAN DETERMINISTIC MODELS AND ENSEMBLE MEAN GUIDANCE KEEP THE
RESULTANT SURFACE LOW FURTHER NORTH TOWARD KODIAK WHILE THE
EUROPEAN AND CANADIAN GUIDANCE KEEP THE LOW FURTHER SOUTH IN THE
GULF. FORECAST CONFIDENCE WITH THIS PACKAGE IS AVERAGE.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...THE FIRST FRONT IS BEGINNING TO DISSIPATE AS
IT MOVES NORTHWARD OVER THE KENAI PENINSULA. THE BEST CHANCES TO
SEE PRECIPITATION WILL BE THE LEEWARD SIDES OF THE ALASKA/ALEUTIAN
RANGE AND WESTERN PRINCE WILLIAM SOUND. MOST AREAS FROM THE
WESTERN KENAI THROUGH THE MATANUSKA VALLEY WILL STAY DOWNSLOPED
BUT THE STRAY SHOWER CAN NOT BE COUNTED OUT. A BETTER CHANCE FOR
RAIN AND SNOW WILL COME WHEN THE NEXT TROUGH AND FRONT MOVES
NORTHWARD ON SUNDAY BUT AGAIN THE FRONT WILL BE DISSIPATING AND
UPPER WAVE DE-AMPLIFYING SO THE BEST CHANCES WILL REMAIN ALONG THE
NORTH GULF COAST AND WESTERN SUSITNA VALLEY. FOR THE ANCHORAGE
AREA THE BIGGEST IMPACT WILL BE THE TURNAGAIN ARM WIND GUSTING
TOWARD 30 TO 50 MPH.

SOUTHWEST ALASKA...

A WARM FRONT WILL CONTINUE TO PUSH THROUGH SOUTHWEST ALASKA FROM
SOUTH TO NORTH THROUGHOUT THE DAY TODAY...ALLOWING FOR PRECIPITATION
TO OVERSPREAD THE AREA. AS PRECIPITATION MOVES INTO THE KUSKOKWIM
DELTA AND THE LOWER KUSKOKWIM VALLEY...A MIX OF RAIN AND SNOW WILL
BE SEEN. THIS MIX WILL TRANSITION TO RAIN BY THE EARLY AFTERNOON
HOURS. HOWEVER...LOW LYING VALLEYS WILL LIKELY SEE A LONGER
DURATION OF SNOW AS WARMER AIR WILL HAVE A DIFFICULT TIME
DISPLACING THE COOLER AIR TRAPPED IN THE VALLEYS. STRONG
SOUTHEASTERLY FLOW ALOFT HAS CREATED LARGE AREAS OF DOWNSLOPE OFF
OF THE ALASKA AND ALEUTIAN RANGES OVERNIGHT AS EVIDENT ON THE PAKC
88D. THE OOZ AND 12Z PAKN RAOB VERIFIES THE DOWNSLOPING...AS A
SIGNIFICANT SURFACE DRY LAYER EXISTS FROM THE COMPRESSIONAL
WARMING AND DRYING OF THE AIR AS IT MOVES OFF THE MOUNTAINS.

AS THE UPPER LEVEL TROUGH PUSHES THROUGH THE AREA LATE TONIGHT AND
INTO EARLY SUNDAY...THE LOW LEVEL WINDS WILL BEGIN TO SHIFT TO A
MORE SOUTHERLY DIRECTION. THIS WILL ALLOW FOR RAIN TO FILL IN
ACROSS AREAS THAT WERE PREVIOUSLY DOWNSLOPED. PRECIPITATION WILL
THEN TAPER OFF ON SUNDAY FROM WEST TO EAST WITH THE PASSAGE OF THE
UPPER LEVEL TROUGH. A BRIEF REPRIEVE IN PRECIPITATION WILL BE SEEN
SUNDAY AFTERNOON INTO EARLY MONDAY MORNING AS ANOTHER WARM FRONT
WILL APPROACH THE AREA FROM THE WEST.

BERING SEA/ALEUTIANS...

A NORTH PACIFIC LOW CROSSED THE EASTERN ALEUTIANS OVERNIGHT AND
HAS PUSHED INTO THE EASTERN BERING SEA. THE LOW WILL CONTINUE TO
TRACK TOWARD THE PRIBILOF ISLANDS TODAY AND THEN PHASE WITH
SEVERAL POTENTIAL VORTICITY ANOMALIES AS IT PUSHES NEAR SAINT
MATTHEW ISLAND. A SIGNIFICANT DRY SLOT HAS BEEN OBSERVED ON
SATELLITE AND WILL MOVE OVER THE PRIBILOF ISLANDS THIS MORNING.
THIS WILL BRING AN END TO THE PRECIPITATION...BUT AS MOISTURE AND
WARMER AIR IS ADVECTED NORTHWARD...THE POTENTIAL FOR FOG WILL
CONTINUE TO INCREASE OVER THE PRIBILOF ISLANDS AND SURROUNDING
WATERS. SCATTERED SNOW SHOWERS WILL BE SEEN AHEAD OF THE FRONT AND
WILL BE MAINLY CONFINED TO THE NORTHERN HALF OF THE BERING SEA.
ANOTHER AREA OF LOW PRESSURE WILL SKIRT ACROSS THE WESTERN AND
CENTRAL ALEUTIANS ON MONDAY...BRINGING ANOTHER CHANCE FOR RAIN AND
SNOW TO THE AREA.

&&

.LONG TERM FORECAST...

ALL GUIDANCE POINTS TO AN UNSETTLED WEATHER PATTERN OVER THE
BERING SEA THROUGH EARLY NEXT WEEKEND AS AN AREA OF LOW PRESSURE
WILL MOVE INTO THE BERING SEA ON TUESDAY AND SLOWLY DRIFT EASTWARD
DURING THE WEEK. HOWEVER...MODELS ARE HAVING A DIFFICULT TIME
DISTINGUISHING WEAK UPPER LEVEL SHORTWAVES WHICH WILL ROTATE
AROUND THE PARENT LOW. NEVERTHELESS...MOSTLY CLOUDY SKIES AND
SCATTERED RAIN SHOWERS (AND A FEW SNOW SHOWERS) WILL CONTINUE
ACROSS THE ALEUTIAN CHAIN THROUGH THE EARLY WEEKEND. OVER THE
MAINLAND...A TRIPLE POINT LOW WILL DEVELOP ALONG A FRONT ATTACHED
THE THE AFOREMENTIONED LOW. THE TRACK AND PLACEMENT OF THIS LOW IS
STILL DIFFICULT TO ASCERTAIN AT THIS TIME...BUT GUIDANCE HINTS
THAT THIS LOW WILL TRACK INTO THE NORTHERN GULF. THIS WILL BRING
RAIN SHOWERS TO THE GULF COAST...BUT SHOULD LEAVE THE INTERIOR OF
ALASKA MAINLY DRY WITH NEAR NORMAL TEMPERATURES.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE...130 131 138 155 160 172 176 177 180
FIRE WEATHER...NONE.

&&

$$



$$

MTL/MMC APR 14



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.