Dense Fog Advisory 2, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
507 AM AKST WED JAN 13 2016

.ANALYSIS AND UPPER LEVELS...
MAINLAND ALASKA REMAINS SITUATED BETWEEN A PAIR OF UPPER LEVEL
LOWS THIS MORNING...WITH ONE LOCATED NEAR NORTON SOUND AND THE
OTHER OVER THE NORTHEAST PACIFIC DRIFTING SLOWLY TOWARDS THE
SOUTHERN PANHANDLE. A SHARP TROUGH AXIS EXTENDS SOUTHEAST FROM
THE BERING LOW ACROSS THE AKPEN AND KODIAK ISLAND INTO THE CENTRAL
GULF. LIGHT SNOW CONTINUES TO FALL ACROSS THE COOK INLET REGION
AS A DEFORMATION BAND TAKES SHAPE FROM THE NORTHERN KENAI
PENINSULA ACROSS THE ANCHORAGE BOWL AND INTO THE SOUTHERN SUSITNA
VALLEY...WITH SNOWFALL BEING FURTHER ENHANCED BY LIFT FROM A WEAK
UPPER DISTURBANCE MOVING UP THE INLET. PRECIPITATION HAS TAPERED
OFF ACROSS THE SOUTHWEST MAINLAND AS THE BERING LOW PULLS OFF TO
THE NORTH...BUT THE COMBINATION OF ONSHORE FLOW AND WEAK MID LEVEL
RIDGING HAS CONTRIBUTED TO WIDESPREAD FOG FORMATION OVER THE
BRISTOL BAY REGION. FARTHER WEST...A BROAD COMPLEX LOW CONTINUES
TO SPIN SOUTH OF THE ALEUTIANS...BRINGING SHOWERY CONDITIONS TO
MUCH OF THE CHAIN.

&&

.MODEL DISCUSSION...
MODELS REMAIN IN GOOD AGREEMENT WITH RESPECT TO THE SYNOPTIC
PATTERN. GUIDANCE HAS ALSO BEGUN TO CONVERGE ON SOME SMALLER
SCALE DETAILS SUCH AS HOW QUICKLY THE TROUGH PUSHES THROUGH
SOUTHCENTRAL AK AS IT LIFTS NORTHWARD TODAY...THUS IMPACTING HOW
LONG SNOWFALL WILL LINGER ACROSS THE COOK INLET REGION TONIGHT
INTO THURSDAY MORNING. MAINLY UTILIZED HIGHER RESOLUTION NAM
GUIDANCE FOR THE MORNING PACKAGE GIVEN THE STRONG OVERALL
AGREEMENT.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE PRECIPITATION BAND THAT IS OVER THE KENAI PENINSULA AND THE
COOK INLET AREA WILL CONTINUE TO MOVE WESTWARD THIS MORNING. THE
HEAVIEST SNOWFALL IS ALREADY WEST OF ANCHORAGE...AND SNOW COULD
BRIEFLY END THIS MORNING. THE BAND WILL BEGIN TO BE PUSHED
EASTWARD LATE TODAY AS THE UPPER LEVEL TROUGH OVER KODIAK MOVES
NORTHWEST. THIS WILL PUT THE ANCHORAGE AREA AND MATANUSKA VALLEY
BACK INTO MORE STEADY SNOWFALL LATER TODAY INTO THIS EVENING. THE
UPPER LEVEL TROUGH WILL SPLIT APART AS IT CROSSES SOUTH CENTRAL
ALASKA TONIGHT INTO THURSDAY. UPPER LEVEL HIGH PRESSURE WILL
BUILD IN FROM THE SOUTHWEST BEHIND THIS TROUGH THURSDAY AND
THURSDAY NIGHT...DRYING THINGS OUT OVER THE AREA.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A SHORTWAVE ASSOCIATED WITH AN UPPER LEVEL LOW OVER NORTON SOUND
WILL BRING SNOW SHOWERS MAINLY TO THE NORTHERN DELTA COAST THIS
MORNING...THEN DIMINISH AS THE LOW MOVES OFF TO THE NORTH. OVER
BRISTOL BAY...WEAK ONSHORE FLOW THAT DEVELOPED BEHIND RAIN/SNOW
SHOWERS THAT MOVED THROUGH THE AREA YESTERDAY BROUGHT WIDESPREAD
STRATUS/FOG OVERNIGHT...BUT THIS IS QUICKLY DIMINISHING AS THE
SHORTWAVE MOVES OVERHEAD. THIS WILL BRING LOCALIZED AREAS OF DENSE
FOG EARLY THIS MORNING THAT WILL QUICKLY DISSIPATE BY LATE
MORNING. RIDGING OVER THE BERING SEA WILL THEN BRING CLEARING
SKIES THROUGHOUT THE AREA THIS AFTERNOON WITH WINDS TURNING
OFFSHORE...WHICH SHOULD KEEP WIDESPREAD FOG FROM REDEVELOPING
TONIGHT. THE LOW COMPLEX SOUTH OF THE AKPEN WILL THEN CLIP
SOUTHERN BRISTOL BAY AND THE AKPEN LATE THURSDAY-FRIDAY...BRINGING
GUSTY EASTERLY WINDS TO THOSE AREAS...BUT OTHERWISE MOSTLY SUNNY
AND DRY CONDITIONS.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS AND ALASKA PENINSULA (DAYS
1 AND 2)...
THE COMPLEX LOW JUST SOUTH OF THE ALEUTIANS WILL DOMINATE WEATHER
THROUGHOUT THE REGION FOR THE REST OF THE WORK WEEK. WIDESPREAD
RAIN/SNOW WILL DEVELOP OVER THE EASTERN AND CENTRAL ALEUTIANS WITH
GALE FORCE WINDS BY THIS EVENING...AND THEN SPREAD NORTHWARD TO
THE PRIBILOF ISLANDS ON THURSDAY. WINDS OVER THE WESTERN-CENTRAL
BERING WILL THEN BEGIN TO DIMINISH ON THURSDAY EVENING AS THE LOW
COMPLEX BEGINS TO DISSIPATE. TO THE EAST...WINDS WILL BEGIN TO
INCREASE IN ADVANCE OF THE NEXT LOW CENTERED JUST SOUTH OF THE
GULF.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

A STRONG JET CROSSING THE PACIFIC WILL SPIN UP SMALL...DIFFICULT
TO FORECAST LOWS JUST SOUTH OF THE FORECAST AREA ON THU. IN ORDER
TO MAKE THIS MORE MANAGEABLE...THE FORECAST UTILIZES AN ENSEMBLE
APPROACH TO SMOOTH OUT SOME OF THESE FEATURES. THIS SOLUTION
YIELDS AN UPPER LEVEL LOW SOUTH OF THE AKPEN ON THU THAT SPINS IN
PLACE UNTIL IT DRIFTS OVER KODIAK ON TUE. AT THE SURFACE THIS WILL
APPEAR AS A LARGE LOW SOUTH OF THE AKPEN...WITH A TROUGH
STRETCHING ACROSS THE WESTERN ALEUTIANS. ANOTHER ASSOCIATED TROUGH
WILL MANIFEST ITSELF AS A DECAYING OCCLUDED FRONT STRETCHING ALONG
THE SOUTHERN BORDER OF THE GULF OF AK. THE PARENT SURFACE LOW WILL
REMAIN ESSENTIALLY STATIONARY AS IT SLOWLY WEAKENS IN PLACE BEFORE
MOVING OVER KODIAK ISLAND ON TUE.

AS THIS SYSTEM SLOWLY ROTATES IT WILL BRING COASTAL RAIN AND
PERIODS OF INTERIOR SNOW SHOWERS TO THE CHUGACH AND TALKEETNA
MOUNTAINS FRI NIGHT THROUGH TUE...AND DRY CONDITIONS OVER SW AK
UNTIL RAIN AND SNOW SHOWERS CROSS THE ALEUTIAN RANGE INTO THE
BRISTOL BAY ZONE BY THE WEEKEND. RAIN AND SNOW SHOWERS WILL
MIGRATE WEST ACROSS THE ALEUTIANS THROUGH EARLY NEXT WEEK.
CONFIDENCE WITH THIS FORECAST IS BELOW AVERAGE UNTIL THE MAIN LOW
SOUTH OF THE AKPEN BECOMES CONTROLLING BY THE WEEKEND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...150 155 165 170 172 173 175
				 177 179 411 412 413 414.
		 HEAVY FREEZING SPRAY...160 185.

&&

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

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