Small Craft Advisory 877, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ANCHORAGE AK
412 PM AKST TUE NOV 4 2014

UPDATED SOUTHWEST ALASKA BERING SEA AND ALEUTIANS SECTIONS

.ANALYSIS AND UPPER LEVELS...
THERE IS A LOW OVER THE GULF OF ALASKA. A WEAK UPPER LEVEL SHORT-
WAVE/FRONT IS MOVING EAST ALONG THE NORTH GULF COAST WITH PRECIP
CURRENTLY ABOUT AS FAR WEST AS CORDOVA. THERE IS A HIGH AMPLITUDE
RIDGE OVER THE CENTRAL/EASTERN BERING ALONG ABOUT 170 WEST
LONGITUDE. A NEGATIVELY TILTED OCCLUDED FRONT IS OVER THE
CENTRAL/WESTERN BERING AND MOVING EAST. THIS FRONT IS ASSOCIATED
WITH A LOW CENTERED OVER THE SHELIKHOV GULF (THE NORTHEAST CORNER
OF THE SEA OF OKHOTSK). PRECIPITATION FROM THIS FRONT IS ABOUT AS
FAR EAST AS SEGUAM ISLAND.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN FAIRLY GOOD AGREEMENT THROUGH ABOUT 60
HOURS (THURSDAY AFTERNOON) INTO THE FORECAST. THERE ARE SOME
DIFFERENCES ON THE EXACT LOCATION OF A LOW THAT FORMS SOUTH OF
ALASKA PENINSULA WEDNESDAY AFTERNOON AND MOVES EAST/NORTHEAST
AFTER THAT...BUT THIS DOES NOT NEGATIVELY IMPACT THE FORECAST VERY
MUCH. THE MODELS THEN SHOW A FAIR AMOUNT OF SPREAD WITH THE
ARRIVAL OF A DEVELOPING STORM SOUTHWEST OF THE WESTERN ALEUTIANS
(THE REMNANTS OF FORMER SUPER- TYPHOON NURI). THE ECMWF IS THE
FURTHEST WEST AND SLOWEST AND DEEPEST...WITH THE CANADIAN AND NAM
IN THE MIDDLE AND FASTEST AND WEAKEST...AND THE GFS FURTHEST EAST
AND IN-BETWEEN ON SPEED AND DEPTH. LOOKING AT THE GFS ENSEMBLES
AND THE PARALLEL GFS IT LOOKS LIKE A SOLUTION CLOSER TO THE ECMWF
IS PREFERRED. ONE THING ALL MODELS AGREE UPON IS THAT IT WILL BE A
VERY STRONG STORM.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
AN UPPER LEVEL LOW POSITIONED OVER THE SOUTHWESTERN GULF WILL
CONTINUE TO HAVE WEAK SHORTWAVES ROTATING AROUND THE LOW THROUGH
WEDNESDAY NIGHT. THIS WILL BE REFLECT AT THE SURFACE AS AREA OF
BROAD LOW PRESSURE OVER THE NORTHWESTERN GULF BEFORE DISSIPATING
BY WEDNESDAY EVENING. THIS WILL BRING MORE RAIN TO THE NORTHERN
GULF COASTLINE SPREADING INTO THE PRINCE WILLIAM SOUND THROUGH
WEDNESDAY NIGHT. THE PRECIPITATION WILL PREDOMINANTLY BE ALL RAIN
EXCEPT FOR SOME MIXING WITH SNOW AS THE PRECIPITATION MOVES INLAND
AND INTO HIGHER ELEVATIONS. BY THURSDAY MORNING THERE WILL BE
DRYING OUT IN THE SOUTH CENTRAL ALASKA REGION AS THE PRECIPITATION
MOVES SOUTH TOWARDS KODIAK ISLAND.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A RELATIVELY QUIET PATTERN WILL TAKE SHAPE FOR THE NEXT FEW DAYS.
WEAK LOW PRESSURE THAT DISSIPATED THIS MORNING HAS ALLOWED FOR A
VERY SHARP RIDGE OVER THE EASTERN BERING TO SLIDE INTO THE AREA.
THIS WILL MAKE FOR DRY AND COLD WEATHER WITH WEAK TO MODERATE
OFFSHORE FLOW. WITH OPEN WATER ALONG MUCH OF THE COAST...LOCAL
GUSTS AND STRATUS/FOG DEVELOPMENT ARE LIKELY AS SOON AS THE COLD
INTERIOR AIR INTERACTS WITH THE WATER. A TRIPLE POINT LOW WILL
FORM JUST SOUTH OF THE ALASKA PENINSULA LATE WED. THIS WILL ONLY
BE A GLANCING BELOW FOR MOST OF THE SOUTHWEST WITH PRECIPITATION
MOSTLY REMAINING ON THE EAST SIDE OF THE ALEUTIAN RANGE.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
IT LOOKS AS IF THE FRONT ACROSS THE CENTRAL ALEUTIANS HAS JUST
ABOUT PEAKED WITH GALES REPORTED THIS MORNING AT SEVERAL BUOYS.
THE STRONG RIDGE OVER THE EASTERN BERING HAS JUST ABOUT HALTED ITS
EASTWARD PROGRESS AS ITS PARENT LOW STARTS TO RETROGRADE OVER
EASTERN RUSSIA. THE 175 KT NORTH PACIFIC JET RUNNING PARALLEL TO
THE CHAIN LOOKS LIKE IT WILL GIVE THE FRONT JUST ENOUGH PUSH TO
MAKE IT INTO DUTCH HARBOR LATER THIS EVENING. WINDS WILL CONTINUE
TO INCREASE THERE OVERNIGHT AND PRECIPITATION SHOULD START BY
EARLY MORNING. THE PRIBILOFS WILL SEE INCREASING SOUTHEAST
WINDS...BUT SHOULD ONLY SEE SOME LIGHT RAIN AND SNOW SHOWERS. AFTER
THIS...THE FRONT WILL JUST CONTINUE TO WEAKEN AS IT GETS STRETCHED
OUT ACROSS THE BERING. BUILDING HIGH PRESSURE ACROSS THE WESTERN
ALEUTIANS SHOULD SERVE TO TIGHTEN THE GRADIENT ENOUGH TO KEEP
GALES FOR MUCH OF THAT AREA THROUGH THURSDAY.

&&

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

THE MEDIUM RANGE FORECAST BEGINS WITH AN AREA OF LOW PRESSURE
SOUTH OF THE ALASKA PENINSULA...WITH A WEAK RIDGING OVER THE
SOUTHERN BERING SEA. HIGH PRESSURE OVER THE INTERIOR OF ALASKA
BEGINS TO SHIFT EASTWARD INTO THE YUKON TERRITORY. THE AFOREMENTIONED
LOW SOUTH OF THE ALASKA PENINSULA WILL SLOWLY PUSH TO THE NORTH
AND EAST TOWARD KODIAK ISLAND. BY LATE FRIDAY INTO SATURDAY
MORNING...THIS LOW WILL MOVE VERY CLOSE TO KODIAK ISLAND AND DRIVE
A WARM FRONT THAT WILL CLASH AGAINST THE NORTHERN GULF COAST.
THIS WILL BRING A PERIOD OF WET WEATHER AND WARMER TEMPERATURES TO
SOUTHCENTRAL ALASKA. ONE OF THE BIGGEST IMPACTS FROM THIS LOW WILL
BE HOW IT WILL AMPLIFY THE OVERALL LONGWAVE TROUGH OVER THE
CENTRAL BERING SEA...WHICH IN TURN AMPLIFIES THE PACIFIC NORTH
AMERICAN RIDGE.

ATTENTION THEN TURNS TO WHAT IS SHAPING OUT TO BE A VERY POWERFUL
STORM SYSTEM THAT WILL BEGIN TO IMPACT THE WESTERN BERING SEA
EARLY FRIDAY AFTERNOON. THE POST-TROPICAL REMAINS OF SUPER TYPHOON
NURI (CURRENTLY LOCATED APPROXIMATELY 700 NM SOUTH OF TOKYO) WILL
RE-CURVE FROM THE NORTH PACIFIC AND MOVE INTO THE FAR WESTERN
BERING SEA FRIDAY AFTERNOON. AS THIS SYSTEM MAKES A TRANSITION
FROM TROPICAL TO EXTRA-TROPICAL CHARACTERISTICS...IT WILL
INTERACT WITH A STRONG JET COUPLING AT 500 MB (130 KNOTS) AND AT
200 MB (200 KNOTS). THIS WILL PROMOTE STRONG DIVERGENCE ALOFT
WHICH WILL ALLOW RAPID CYCLOGENESIS TO OCCUR AS THE LOW PUSHES
FROM THE NORTH PACIFIC INTO THE BERING SEA. MODEL AVERAGES HAVE
THE LOW DEEPENING FROM AROUND 970 MB FRIDAY AT 06Z TO THE 918-922
RANGE BY SATURDAY AT 06Z. THIS WILL LIKELY LEAD TO A LARGE SWATH
OF STORM AND HURRICANE FORCE WINDS ALONG THE WESTERN AND CENTRAL
ALEUTIANS FRIDAY AND SATURDAY...WITH STRONG WINDS AND HIGH SEAS
PUSHING EASTWARD DURING THE WEEKEND AND INTO EARLY NEXT WEEK.

THERE IS STILL A BIT OF DISAGREEMENT ON LOW PLACEMENT WHILE HEIGHT
FIELDS AND DERIVED PRESSURE FIELDS CONTINUE TO DEPICT A DEEP LOW
IN THE 918 MB TO 922 MB RANGE. THE GFS APPEARS TO BE THE OUTLIER
AS IT PUSHES THIS STRONG LOW EASTWARD MUCH QUICKER THAN THE REST
OF THE SYNOPTIC MODELS. WITH THE WAY THAT THE PACIFIC NORTH
AMERICAN RIDGE IS EXPECTED TO AMPLIFY...A SLOWER TRACK EASTWARD
SEEMS TO BE THE MORE LIKELY SCENARIO...WHICH IS DEPICTED THE THE
ECMWF AND GEM. REGARDLESS OF THE SOLUTION...STRONG WINDS AND HIGH
SEAS WILL IMPACT MUCH OF THE BERING SEA...WITH THE POTENTIAL FOR
COASTAL FLOODING/STORM SURGE ALONG THE WEST COAST OF ALASKA.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 176 177 178 185 411 412 413.
FIRE WEATHER...NONE.

&&

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