Small Craft Advisory 978, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
459 AM AKST TUE DEC 8 2015

.ANALYSIS AND UPPER LEVELS...THE LONGWAVE PATTERN CONTINUES TO BE
SLOW TO CHANGE. OVER THE BERING...THE PARENT LOW HAS DROPPED DOWN
INTO THE LOW 960S AND IS PARKED VERY NEAR DUTCH HARBOR. SEVERAL
WAVES OF ENERGY CONTINUE TO SPIN AROUND IT. IN THE GULF OF
ALASKA...THE LOW IS STRENGTHENING DOWN INTO THE LOWER 950 MB
RANGE. IT IS SLOWLY MAKING ITS WAY NORTH AS IT PUSHES AN INITIAL
WARM FRONT INTO THE GULF COAST THIS MORNING. MEANWHILE OVER THE
MAINLAND...THE HIGH PRESSURE THAT HAS BROUGHT A FEW DAYS OF CLEAR
AND COLD WILL START TO GIVE WAY TO THE INCOMING LOW FROM THE GULF.
THIS IS CREATING AN INCREASING PRESSURE GRADIENT ACROSS MUCH OF
SOUTH CENTRAL WHICH WILL RESULT IN ANOTHER ROUND OF COLD OUTFLOW
WINDS. THE PRIMARY AREAS TO FEEL THESE WINDS WILL BE THE NORTH-
SOUTH ORIENTED GAPS SUCH AS THE MATANUSKA RIVER VALLEY...THOMPSON
PASS...AND SEWARD. AS THESE WINDS HAVE SLOWLY BEEN CREEPING UP
OVERNIGHT...THERE HAS BEEN SIGNIFICANTLY LESS FOG FORMATION THAN
THE PAST FEW NIGHTS. THE ONE EXCEPTION TO THIS IS THE COPPER
RIVER BASIN WHERE LOW STRATUS AND FOG ARE FAIRLY WIDESPREAD.

&&

.MODEL DISCUSSION...SEEMS LIKE A BROKEN RECORD...BUT MODELS ARE
STILL STRUGGLING TO NAIL DOWN THE DETAILS WITH THE LOW IN THE
GULF...EVEN JUST 24 HOURS OUT. AFTER ALL THE VARIATIONS THAT CAME
IN ON MONDAY'S MODEL RUNS...THE EC REMAINS THE MOST CONSISTENT.
HOWEVER...DUE TO ITS LACK OF RESOLUTION...THIS FORECAST PACKAGE
UTILIZED A BLEND OF THE EC AND THE GFS. THIS KEEPS MOST OF THE
PRECIPITATION CONFINED TO THE COASTAL AREAS AND KODIAK ISLAND AT
LEAST THROUGH THE DAY ON WEDNESDAY. THEN...EXACTLY WHERE THE LOW
TRACKS WILL HAVE FAIRLY SIGNIFICANT RAMIFICATIONS ON THE FORECAST.
IF IT GOES FURTHER NORTH AND WEST LIKE THE GFS...THIS WOULD MAKE
FOR A BETTER CHANCE OF BRINGING RAIN AND SNOW FURTHER INLAND DURING
THE LATTER HALF OF THE WEEK. THE EC PRESENTS A SOLUTION ON WED
NIGHT WHERE A WEAK COLD UPPER LEVEL TROUGH FROM THE WEST IS ABLE
TO PROVIDE ENOUGH LIFT UNDER THE WRAP-AROUND MOISTURE FROM THE
GULF TO CREATE A FEW INCHES OF SNOW ACROSS THE COOK INLET REGION.
OUT WEST...MODELS ARE IN RELATIVELY DECENT AGREEMENT IN THE SHORT
TERM SO THE HIGHER RESOLUTION GEM-REGIONAL WAS USED AND FORECAST
CONFIDENCE IS MODERATE TO HIGH. THE SMALL FEATURES ROTATING
THROUGH THE PATTERN WILL CONTINUE TO BE DIFFICULT TO PINPOINT.
PLEASE SEE THE LONG TERM DISCUSSION FOR HOW THE MODELS ARE
HANDLING A MORE SIGNIFICANT SYSTEM OVER THE BERING DURING BY LATE
WEEKEND.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE LARGE AND STRONG STORM SYSTEM MAKING ITS WAY INTO THE GULF OF
ALASKA THIS MORNING WILL BRING A RETURN TO MORE ACTIVE WEATHER...
THOUGH THE BULK OF IMPACTS WILL BE ALONG THE GULF COAST/PRINCE
WILLIAM SOUND/KODIAK ISLAND. SATELLITE IMAGERY SHOWS THAT MULTIPLE
WEAK LOWS HAVE FORMED IN THE CIRCULATION AROUND THE MAIN LOW CENTER.
THIS HAS TIGHTENED UP THE PRESSURE GRADIENT ALONG THE WARM OCCLUDED
FRONT EVEN MORE WITH STORM FORCE GUSTS BEING OBSERVED AT BUOY 46085
IN THE SOUTHERN GULF. THEREFORE HAVE INCREASED WINDS FOR THE GULF
OFFSHORE TO STORM FORCE AND COASTAL AREAS FURTHER NORTH AND WEST
TO MAX GALE FORCE. HAVE ALSO INCREASED GAP WINDS ALONG PRINCE
WILLIAM SOUND AND NORTH GULF COAST WHICH WILL RAMP UP LATER TODAY
AS THE FRONT LIFTS NORTH ACROSS THE GULF AND A LITTLE BIT OF COLD
AIR SITTING OVER INTERIOR SOUTHCENTRAL IS ADVECTED SOUTHWARD.

AS MENTIONED IN THE MODEL DISCUSSION NUMERICAL GUIDANCE HAS BEEN
STRUGGLING WITH THE TRACK OF THIS SYSTEM. THE FORMATION OF ADDITIONAL
WEAK LOWS WILL ONLY COMPLICATE THE MATTER. THIS PRESENTS QUITE A
CHALLENGE FOR THE FORECAST OF PRECIPITATION OVER SOUTHCENTRAL.
BASED ON THE COMMON TREND IN THE MODELS TOWARD A FURTHER NORTH AND
WEST TRACK OF THE MAIN SURFACE LOW...CONFIDENCE IS INCREASING THAT
AT LEAST SOME PRECIP WILL MAKE IT INLAND. THEREFORE...HAVE UPPED
POPS ACROSS THE BOARD WITH LIKELY TO CATEGORICAL POPS ALONG THE
COASTAL ZONE AND FAIRLY BROAD BRUSH CHANCE POPS INLAND. THE OTHER
RAMIFICATION OF THIS CHANGE IS THAT TEMPERATURES WILL WARM
UP...WITH LOCATIONS ALONG THE COAST RISING ABOVE FREEZING AND
PRODUCING ALL RAIN AND INLAND LOCATIONS WARMING UP OUT OF THE
RECENT COOL SPELL. OVERALL FORECAST CONFIDENCE FOR THE NEXT
COUPLE DAYS IS AVERAGE WHILE CONFIDENCE IN THE PRECIP FORECAST
(ESPECIALLY INLAND) IS LOW.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...

WITH LOW PRESSURE IN THE GULF...AND ARCTIC HIGH PRESSURE NORTH OF
THE REGION...THE MAIN STORY FOR THIS FORECAST PERIOD WILL CONTINUE
TO BE RATHER STRONG OFFSHORE WINDS AND CONTINUED COLD TEMPERATURES.
THIS WILL ALLOW FOR RATHER COLD WIND CHILLS HEADING INTO THURSDAY.
A WEAKENING FRONTAL ZONE MOVING EAST INTO THE BERING WILL SUPPORT
RAIN AND SNOW ALONG THE ALASKA PENINSULA TODAY BEFORE MOVING
EAST...WITH A FEW FLURRIES ALONG THE REMAINING COASTLINES BEFORE
DRYING OUT TONIGHT.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

THE PERSISTENT PATTERN OF COLD NORTHERLY FLOW ACROSS THE WESTERN
BERING WITH WARMER EAST TO SOUTHEAST FLOW ACROSS THE CENTRAL AND
EASTERN BERING WILL CONTINUE TODAY AND TONIGHT AS AN UPPER TROUGH
OVER BRISTOL BAY MOVES EAST THEN STALLS THROUGH WEDNESDAY. ANOTHER
UPPER LEVEL TROUGH WILL MOVE INTO THE WESTERN BERING AND DIG INTO
THE NORTH PACIFIC WEDNESDAY AND THURSDAY...WITH THE REMNANTS OF
THE FRONT MOVING BACK EAST...ALLOWING FOR SOME OF THE COLDER AIR
OVER THE WESTERN BERING SEA TO MOVE EASTWARD...SPREADING RAIN AND
SNOW SHOWERS WITH IT. THE OVERALL PRESSURE GRADIENT WILL WEAKEN
WEDNESDAY AND THURSDAY...ALLOWING THE GALE FORCE NORTHERLY WINDS
ACROSS THE WESTERN AND CENTRAL BERING TO SLACKEN.

&&

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

THE LONG WAVE TROUGH OVER THE BERING...WHICH HAS BEEN A SEMI-
PERMANENT FEATURE LATELY...WILL BEGIN TO SHIFT EASTWARD OVER THE
SOUTHERN MAINLAND AND WESTERN GULF BY THE END OF THE WEEK. BRIEF
RIDGING WILL BUILD OVER THE MAINLAND BEHIND THE TROUGH SATURDAY...
BUT IS QUICKLY REPLACED BY ANOTHER LONGWAVE TROUGH SETTING UP
OVER MUCH OF THE BERING THROUGH EARLY NEXT WEEK.

AT THE SURFACE...A GALE FORCE FRONT OVER THE CENTRAL GULF
WEDNESDAY WILL SLOWLY WEAKEN THROUGH THE END OF THE WEEK...BEFORE
EVENTUALLY TRACKING SOUTHEASTWARD TOWARD THE PANHANDLE BY THE
WEEKEND. THIS WILL KEEP MUCH OF THE ACTIVE WEATHER CONFINED TO THE
GULF AND EASTERN BERING THROUGH SATURDAY. GENERAL OFFSHORE FLOW
AND SLIGHTLY DRIER CONDITIONS ARE EXPECTED FOR MUCH OF THE
SOUTHCENTRAL INTERIOR DURING THIS TIME PERIOD...WITH THE
EXCEPTION OF THE AREAS SURROUNDING THE GULF COAST. AREAS AROUND
THE GULF COAST WILL EXPERIENCE A SERIES OF FRONTS ROTATING AROUND
THE LOW...BRINGING SOME GUSTY WINDS AND PRECIPITATION TO THE AREA
THROUGH SATURDAY NIGHT. WHILE OVER THE BERING...BROAD NORTHERLY
GALE FORCE WINDS WILL BRING COLD AIR ADVECTION SNOW SHOWERS TO THE
AREA. BY THE BEGINNING OF THE WEEKEND...MODELS CONTINUE TO
STRUGGLE WITH THE SPECIFICS OF A STRONG NORTH PACIFIC LOW AND ITS
ASSOCIATED FRONT TRACKING THROUGH THE ALEUTIAN CHAIN AND BERING
SEA. THIS SYSTEM HOLDS THE POTENTIAL TO BRING STRONG WINDS AND
ROUGH SEAS TO THE AREA AS IT TRAVERSES THROUGH THE BERING AND INTO
THE KUSKOKWIM DELTA COAST BY THE BEGINNING OF NEXT WEEK. HOWEVER...
GIVEN THE MAJOR MODEL DIFFERENCES DURING THIS TIME FRAME...FORECAST
CONFIDENCE REMAINS LOW ON THE EXACT TRACK AND STRENGTH OF THIS SYSTEM.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...HEAVY FREEZING SPRAY...127 140 180 181 185
         GALE...119 120 127 128 130-132 136-139 150 173-181 185

&&

SYNOPSIS AND MODEL DISCUSSION...MSO
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA
LONG TERM...TP/MMC