Small Craft Advisory 679, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
416 PM AKDT FRI AUG 28 2015

.ANALYSIS AND UPPER LEVELS...

MASSIVE UPPER LEVEL RIDGE PERSISTS OVER THE WESTERN AND CENTRAL
BERING THIS AFTERNOON...WITH CUT-OFF LOWS OVER THE EASTERN GULF OF
AK AND SOUTH OF KAMCHATKA...AS WELL AS CENTERED NORTH OF BARROW.
AT THE SURFACE...THINGS LOOK SIMILAR AS THE ATMOSPHERE IS
VERTICALLY STACKED. HIGH PRESSURE IS CENTERED JUST SOUTH OF THE
CENTRAL ALEUTIANS...WITH A SMALL LOW OVER THE EASTERN GULF...AND
BROADER LOWS SOUTH OF KAMCHATKA AND NORTH OF BARROW. A STRONG
PRESSURE GRADIENT BETWEEN THE HIGH AND THE GULF LOW IS SLOWLY
WEAKENING...BUT IS STILL PRODUCING UNSEASONABLY STRONG WINDS
ACROSS KODIAK ISLAND AND NEAR VALDEZ. A MOISTURE RICH WEATHER
FRONT IS DRAPED AROUND THE BERING HIGH AND BEGINNING TO MAKE ITS
WAY INLAND ALONG THE SOUTHWEST AK COAST.

&&

.MODEL DISCUSSION...

MODELS ARE IN EXCELLENT AGREEMENT. THE BERING RIDGE WILL MOVE
SOUTH...ALLOWING THE SURFACE AND UPPER LOWS NEAR KAMCHATKA TO
REACH THE EXTREME WESTERN BERING DURING THE WEEKEND. THE UPPER
LOWS NORTH OF BARROW AND OVER THE EASTERN GULF WILL BEGIN TO MERGE
INTO A BROAD TROUGH OVER THE EASTERN HALF OF MAINLAND AK...WHILE
THEIR SURFACE REFLECTIONS MERGE INTO A GIANT AREA OF LOW PRESSURE
THAT HAS EMBEDDED LOWS ALONG THE NORTHEAST GULF COAST AND OVER THE
YUKON TERRITORY BY THE END OF THE WEEKEND.

THE PRESSURE GRADIENT CURRENTLY OVER THE AKPEN WILL SLOWLY
DIMINISH THROUGH THIS EVENING AS THE FRONT MOVES INLAND OVER
SOUTHWEST AK...BUT THEN BRIEFLY REDEVELOPS SAT NIGHT INTO EARLY
SUN AS A NEW RIDGE POKES INTO THE BERING FROM EASTERN RUSSIA. THIS
WILL MERGE WITH THE HIGH WHICH BY THEN IS SOUTH OF THE ALEUTIANS
AND WILL PLAY A ROLE EARLY NEXT WEEK.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE NORTHERLY OUTFLOW WINDS WILL CONTINUE THROUGH THE WEEKEND. THE
STRONG GUSTY NORTHERLY GAP WINDS THROUGH WHITTIER...VALDEZ...THOMPSON
PASS AND KODIAK ISLAND WILL BEGIN TO DIMINISH DURING THE EVENING.
THIS WILL COINCIDE WITH THE CONTINUAL WEAKENING OF THE PRESSURE
GRADIENT AS THE SURFACE LOW IN THE EASTERN GULF MOVES FARTHER
EASTWARD. THE NORTHERLY WINDS WILL BRING COOLER TEMPERATURES WITH
LOW TEMPERATURES NEAR FREEZING IN THE VALLEYS WITH THE CLEAR
SKIES TONIGHT. THERE IS A CHANCE THAT THE COLDER AREAS OF THE
MATANUSKA VALLEY AS WELL AS PARTS OF EAST ANCHORAGE MAY SEE
TEMPERATURES DROP TO THE FREEZING MARK TONIGHT. THE BIGGEST FACTOR
WILL BE THE CLOUD COVER AND WHILE IT SHOULD BE MOSTLY CLEAR SOME
HIGH CLOUDS MAY MAKE IT INTO THE REGION TOWARD MORNING WHICH WOULD
BE ENOUGH TO KEEP TEMPERATURES ABOVE FREEZING OVER ALL AREAS.  BY
SATURDAY AN UPPER LEVEL SHORTWAVE WILL DROP DOWN FROM THE NORTH
AND BRING A SLIGHT CHANCE OF SHOWERS THROUGH THE ANCHORAGE BOWL.
THIS SYNOPTIC FEATURE WILL INCREASE THE PRESSURE GRADIENTS
BRINGING THE STRONG GUSTY GAP WINDS BACK INTO PICTURE BY EARLY
SUNDAY MORNING FOR THE SOUTHCENTRAL REGION.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
ANOTHER ROUND OF RAIN IS IN STORE FOR THE SOUTHWEST MAINLAND THIS
EVENING...AS AN UPPER LEVEL WAVE AND ASSOCIATED FRONTAL SYSTEM AT
THE SURFACE STRETCH AROUND THE NORTHEASTERN PERIPHERY OF THE RIDGE
OVER THE BERING SEA. RAIN ALONG THE SOUTHWEST COAST WILL SPREAD
INLAND OVER MUCH OF THE SOUTHWEST MAINLAND TONIGHT...BEFORE
BECOMING MORE SHOWERY BY SATURDAY AFTERNOON AS THE SURFACE LOW
TRACKS THROUGH THE ALASKA PENINSULA AND INTO THE WESTERN GULF OF
ALASKA. CONDITIONS WILL DRY OUT FAIRLY QUICKLY SATURDAY AFTERNOON
AND EVENING AS GUSTY NORTHWEST FLOW PUSHES ACROSS THE AREA...WITH
THE STRONGEST GUSTS REMAINING MOSTLY CONFINED TO THE ALASKA
PENINSULA. HOWEVER...SCATTERED SHOWERS WILL LIKELY PERSIST
FURTHER INLAND ESPECIALLY ALONG THE MOUNTAINS WITH A SHORTWAVE
DROPPING SOUTH SUNDAY AND SUNDAY NIGHT.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
STRONG RIDGING WHICH HAS BROUGHT WIDESPREAD FOG AND STRATUS OVER
THE BERING AND PARTS OF THE ALEUTIAN CHAIN OVER THE PAST FEW DAYS
WILL SLOWLY START TO RETREAT INTO THE NORTHERN PACIFIC...AS AN
UPPER LEVEL DISTURBANCE EXITING NORTHEASTERN RUSSIA TONIGHT TRACKS
INTO THE NORTHERN BERING BY TOMORROW MORNING. THIS FEATURE WILL
CONTINUE TO TRACK SOUTHEAST OVER THE EASTERN BERING/ALEUTIANS...
BRINGING ANOTHER ROUND OF RAIN AND GUSTY WEST TO NORTHWEST FLOW
TO THE EASTERN HALF OF THE BERING AND ALEUTIAN CHAIN. THIS WAVE
WILL QUICKLY WORK ITS WAY THROUGH THE EASTERN BERING/ALEUTIANS BY
SUNDAY MORNING...USHERING IN A SHOT OF COLDER TEMPERATURES FROM
THE NORTH...ALONG WITH DIMINISHING GUSTS AND A TRANSITION TO
SHOWERY CONDITIONS. FURTHER WEST...MOIST SOUTHERLY FLOW WILL
CONTINUE TO DOMINATE WESTERN ALEUTIANS/BERING...AS THEY REMAIN ON
THE WESTERN PERIPHERY OF DEEP RIDGING OVER THE CENTRAL BERING
THROUGH SATURDAY. A FRONTAL SYSTEM ASSOCIATED WITH A VERTICALLY
STACKED LOW WEST OF THE WESTERN ALEUTIANS WILL CLIP THE AREA BY
SUNDAY MORNING...BRINING A WET AND WINDY CONDITIONS TO THE WESTERN
ALEUTIANS THROUGH MONDAY MORNING.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...MON THROUGH FRI)...MODELS
ARE IN FAIRLY GOOD AGREEMENT FOR THE EARLY PART OF NEXT WEEK. SO
FOR THE TIME BEING...FORECAST CONFIDENCE IS RELATIVELY HIGH. THE
HIGHLIGHT OF THIS PERIOD WILL BE THE TRANSITION FROM FAIRLY
STRONG...COOL NORTHWEST FLOW THROUGH MUCH OF SOUTH CENTRAL TO A
CALMER AND SLIGHTLY WARMER PATTERN. THE AREA OF THE LOW PRESSURE
IN THE NORTHEAST GULF WILL WORK IN COMBINATION WITH A DEVELOPING
HIGH OVER THE BRISTOL BAY AREA ON MONDAY TO KEEP THE PRESSURE
GRADIENT TIGHT. BUT AS THIS LOW PULLS FURTHER TO THE SOUTH AND
EAST ON TUESDAY...HIGHER PRESSURE WILL BUILD OVER SOUTHWEST
ALASKA. THIS WILL KEEP THINGS DRY ACROSS JUST ABOUT ALL OF THE
SOUTHERN HALF OF THE MAINLAND THROUGH TUESDAY. TEMPERATURES SHOULD
BE ABLE TO REBOUND TO A FEW DEGREES AS WELL WITH THE FLOW BECOMING
MORE WESTERLY AND 850 MB TEMPERATURES CLIMBING 5 TO 6 DEGREES
CELSIUS.

THE MORE ACTIVE WEATHER WILL BE OVER THE BERING SEA TO START THE
WEEK. THE REMNANTS OF TYPHOON ATSANI WILL CONTINUE TO DRIFT OVER
THE FAR WESTERN BERING. WHILE WINDS SHOULD ALL BE BELOW SMALL
CRAFT LEVEL...IT WILL KEEP A CHANCE FOR RAIN IN THE FORECAST. IT
WILL ALSO LEAVE A DECAYING WARM FRONT ALONG THE CENTRAL AND
EASTERN ALEUTIANS. A WEAK WAVE TRIES TO DEVELOP ALONG THIS
BOUNDARY AS WE GET TO WEDNESDAY. THIS IS WHERE MODELS START TO
DIFFER WITH THE GFS BEING RATHER AGGRESSIVE WITH THIS WAVE AND
SWINGING ANOTHER STORM THROUGH THE BERING STRAIT. MEANWHILE...THE
EC IS MUCH WEAKER AND ONLY BRINGS LIGHT RAIN TO THE SOUTHWEST.
BOTH GLOBAL MODELS SHOW SIGNS OF CYCLOGENESIS IN THE GULF BY THE
LATTER HALF OF THE WEEK WHICH WOULD MEAN A RETURN TO COOLER AND
WETTER WEATHER FOR MUCH OF THE MAINLAND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 130 131 132 150 155 165.
FIRE WEATHER...NONE.
&&

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