Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 192142
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
142 PM AKDT SAT JUL 19 2014

.ANALYSIS AND UPPER LEVELS...
AFTERNOON SATELLITE ANALYSIS YIELDS A FEW DOMINANT FEATURES. THE
BIGGEST FEATURE FOR THE DAY IS A LARGE STACKED LOW THAT SITS NORTH
OF POINT BARROW. DROPPING SOUTH FROM THIS LOW IS A WEATHER FRONT
THAT HAS BEEN CROSSING THE ENTIRE STATE. AS OF THIS AFTERNOON...IT
HAD MOVED ACROSS THE ANCHORAGE AREA AND WAS MARCHING ACROSS PRINCE
WILLIAM SOUND. SHOWERS /OCCASIONALLY HEAVY/ DEVELOPED IN RESPONSE
AND ARE SEEN ON PAIH/S 88D...SLIDING EAST. ACROSS THE WESTERN
HALF OF THE STATE IS THE SECOND FRONT THAT STRETCHES FROM POINT
LAY TO EAST OF NOME...SOUTHWEST OF NORTON SOUND AND NEAR ST PAUL.
ACROSS THE ALEUTIANS IS A RIDGE THAT CONTINUES TO BUILD TO THE
NORTH AND EAST...BRINGING CONTINUED SUMMER FOG AND STRATUS TO THE
ALEUTIAN CHAIN AND BERING SEA.

&&

.MODEL DISCUSSION...
IN THE IMMEDIATE TERM AND UPPER LEVELS...ALL MODELS SEEM TO HAVE A
GOOD HANDLE ON THE CURRENT SYNOPTIC PICTURE. THERE ARE NO
APPRECIABLE DIFFERENCES IN TIMING OF THE H50 TROUGH SLIDING EAST
AND NO NOTABLE DIFFERENCES WITH THE BIGGER TROUGH DIGGING ACROSS
WESTERN ALASKA. MODELS BEGIN TO DIVERGE AT F36 TO ABOUT F42 WITH
AN UPPER LEVEL LOW BEING FORMED ACROSS PWS ON THE SOUTHERN
PERIPHERY OF THE TROUGH AS THE POLAR JET SHOOTS SOUTH AND
ATTEMPTS TO WRAP AROUND THE BASE OF THE TROUGH. SIMILAR TO THE
OVERNIGHT MODELS AND ANALYSIS...AND DESPITE HAVING A GOOD HANDLE
AND GOOD AGREEMENT WITH EACH OTHER...THEY DID NOT HAVE A GOOD
HANDLE ON OVERALL PRECIP THAT WAS ASSOCIATED WITH THE FIRST FRONT.
GIVEN THAT...WOULDNT BE OVERLY SURPRISED TO SEE PRECIP SHUT OFF A
LITTLE SOONER THAN WHAT THE MODEL GROUPS ARE HINTING...AND THE
GRIDS TYPICALLY REFLECT AN END FROM WEST TO EAST BY THE MID
MORNING HOURS. FOR THE FORECAST PACKAGE...A MIX OF PERSISTENCE AND
ECMWF WERE USED WITHIN THE AER DOMAIN WITH NAM IN THE SHORT TERM
AND GFS/ECMWF IN THE MEDIUM RANGE FOR THE ALU DOMAIN.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
THE FIRST OF TWO WEATHER MAKERS ALREADY MOVED ACROSS THE AREA
TODAY AND SHOULD BE EAST OF PWS BY THIS AFTERNOON. THERE WERE NO
SIZABLE RAINS THAT FELL WITH ONLY 2 HUNDRETHS ACROSS MUCH OF THE
AREA /WITH PALMER SEEING A FAIR BIT MORE/. BREAKS OF SUN ARE
EXPECTED INTO THE EVENING. THE SECOND FRONT THAT IS MOVING ACROSS
WESTERN ALASKA WILL BE THE NEXT PLAYER IN THE FORECAST AREA OVER
NIGHT AS RAINS ARE AGAIN EXPECT TO INCREASE INTO THE LATE HOURS.
AGAIN...NOT MUCH RAIN IS ANTICIPATED WITH ONLY A FEW HUNDREDTHS OF
AN INCH FOR MOST NON-MOUNTAINOUS AREAS. BERING SEA RIDGING IS DUE
TO BUILD IN BEHIND THIS FRONT LATER TOMORROW AND ESPECIALLY ON
MONDAY...BRINGING A RETURN TO 70 DEGREE WEATHER AND BLUE SKIES
INTO THE START OF THE WORK WEEK.

SOUTHWEST ALASKA...
THE SECOND FRONT IS QUICKLY SWEEPING ACROSS WESTERN COASTAL
AREAS...WITH BETHEL ALREADY BEING IMPACTED. A PROMINENT BACK EDGE
IS CLEARLY VISIBLE ON RADAR ALREADY...AND IT THE OVERALL SHOWER
ACTIVITY WITH THIS FRONT SHOULD ONLY REMAIN ONLY A FEW HOURS LONG
AS IT MOVES THROUGH. AREAS EAST...SUCH AS PAKN/PADL AND PAIL WILL
BE SEE CONDITIONS DROP SOON AS THE RAIN APPROACHES AND WINDS FLIP
AROUND TO THE NORTHWEST. REPRIEVE IS ON THE WAY AS WINDS TURN BACK
SOUTHWESTERLY AND TEMPERATURES REBOUND AGAIN. PRECIP WILL RETURN
AS A WEAKENING UPPER LEVEL LOW SOUTH OF THE WESTERN ALEUTIAN CHAIN
GETS CAUGHT UP IN THE FLOW AND SLOWLY MOVES TOWARDS THE AKPEN BY
MID WEEK.

BERING SEA/ALEUTIANS...
SUMMERTIME RIDGING WILL KEEP THE AREA GENERALLY QUIET THROUGH THE
WEEKEND...WITH THE USUAL MARINE LAYER AND FOG PREVAILING. LOW
PRESSURE SOUTH OF SHEMYA WILL SLOWLY APPROACH THE AREA SUNDAY AND
BEYOND...INCREASING OVERALL CHANGES FOR RAIN INTO THE EARLY WEEK.

&&

.LONG TERM FORECAST...
IT STILL LOOKS LIKE THE LOW MOVING THROUGH THE CENTRAL ALEUTIANS
ON MONDAY WILL STALL OUT IN THE NORTHERN GULF BY MID WEEK. THIS
WILL KEEP THE SOUTHERN MAINLAND GENERALLY CLOUDY WITH A CHANCE OF
RAIN. TOWARD THE LATTER PART OF NEXT WEEK THERE IS REASONABLE
CONFIDENCE THAT THIS LOW WILL MOVE FAR ENOUGH SOUTH INTO THE
PACIFIC THAT THE RIDGING OVER THE BERING SEA SHOULD MOVE OVER
SOUTHWEST ALASKA AND BRING SOME PARTIAL CLEARING TO SOUTH CENTRAL.
THIS PATTERN WILL KEEP THE THREAT OF BERING SEA STRATUS MOVING
OVER SOUTHWEST MAINLAND...ESPECIALLY ALONG THE COAST. SOUTHCENTRAL
WILL REMAIN AT RISK FOR MAINLY AFTERNOON AND EVENING SHOWERS OVER
THE MOUNTAINS AS AN UPPER LEVEL TROUGH WILL REMAIN OVER SOUTH
CENTRAL WITH COOLER AIR ALOFT.

&&

.MARINE DISCUSSION...
WITH A POTENT JET DIVING SOUTH ACROSS THE WESTERN HALF OF THE
STATE...COUPLED WITH A LOW TO BE DEVELOPED ACROSS PWS...GUSTY AND
STRONG WINDS ARE EXPECT TO IMPACT COASTAL ZONES OF PZK130/131/138
AND 150 THE MOST...THROUGH GAPPED AND CHANNELED TERRAIN. MODEL
GUIDANCE HAS BEEN PRETTY CONSISTENT WITH THE ADVERTISEMENT OF
SUSTAINED WINDS IN THE UPPER 20 KT RANGE...WITH GUSTS IN THE LOW
TO MID RANGE GALE REGION. THIS IS SLATED TO CONTINUE AND REALLY
RAMP UP INTO THE OVERNIGHT HOURS...PEAKING BY TOMORROW AFTERNOON.
WITH THE SEASON BEING SUMMER...AND COLD AIR ADVECTION NOT BEING
THE STRONGEST...NOT SEEING THE ODDS OF HAVING THE OCCNL STORM
FORCE GUSTS REMAINS PRETTY LOW...RATHER WOULD EXPECT TO SEE HIGHER
END GALES BE THE MAXIMUM OF THIS EVENT.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.
&&

$$

SHEA/EZ JUL 14



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