Small Craft Advisory 869, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
517 AM AKST SUN NOV 2 2014

.ANALYSIS AND UPPER LEVELS...
A LARGE PERSISTENT UPPER LEVEL LOW IS CENTERED OVER BRISTOL
BAY...THE AK PEN...AND SOUTHWEST AK THIS MORNING. AN UPPER RIDGE
IS OVER THE KAMCHATKA PENINSULA AND A WEAK WAVE IS MOVING OVER
SOUTHEAST AK. AT THE SURFACE...A WEAK LOW IS JUST SOUTH OF THE
KENAI PENINSULA...WHILE THE MAIN LOW IS OVER BRISTOL BAY.

BANDS OF PRECIPITATION ARE MOVING AROUND THE NORTHERN FLANK OF THE
GULF LOW...WITH RAIN ALONG THE COAST MIXING WITH SNOW OVER THE
KENAI AND CHUGACH MOUNTAINS. AROUND THE BRISTOL BAY LOW...LIGHT
SNOW IS FALLING OVER SOUTHWEST AK WITH RAIN AND SNOW SHOWERS
ALONG THE ALEUTIANS.

&&

.MODEL DISCUSSION...
MODELS ARE IN EXCELLENT AGREEMENT THROUGH 48 HOURS. BY MON NIGHT
THE SW AK UPPER LOW WILL DRIFT TO THE GULF OF AK...WITH EMBEDDED
LOWS SOUTHEAST OF KODIAK ISLAND AND NEAR SOUTHEAST AK. THE BROAD
UPPER RIDGE OVER KAMCHATKA WILL BECOME OF MUCH HIGHER AMPLITUDE AS
IT DRIFTS TO THE CENTRAL BERING...AND A TROUGH OVER ASIA WILL MOVE
OFFSHORE AND DEVELOP INTO A SIGNIFICANT UPPER LOW WEST OF
KAMCHATKA.

AT THE SURFACE...THE LOW SOUTH OF THE KENAI WILL CROSS THE
SOUTHERN KENAI PENINSULA AND COOK INLET BEFORE MOVING INLAND AND
DISSIPATING THIS AFTERNOON. THE BRISTOL BAY LOW WILL SLOWLY WEAKEN
AS IT MAKES ITS WAY ACROSS THE AKPEN THIS EVENING AND THEN INTO
THE GULF OF AK BY MON NIGHT. ANOTHER LOW WILL DEVELOP TODAY WELL
SOUTH OF THE GULF AND HEAD INTO SOUTHEAST AK MON AFTERNOON INTO
TUE MORNING.

IN THE WEST...NORTHWEST FLOW OVER SOUTHWEST AK WILL
SLOWLY WEAKEN THROUGH TUE MORNING. THE SAME FLOW OVER THE BERING
WILL SLOWLY WEAKEN THROUGH MON NIGHT AS THE RIDGE MOVES OVERHEAD.
THE SIGNIFICANT UPPER LOW FORMING FROM THE TROUGH OVER ASIA WILL
HAVE A SURFACE LOW THAT DEVELOPS WEST OF KAMCHATKA MON MORNING.
AN ASSOCIATED FRONT WILL MOVE FROM THE WESTERN ALEUTIANS AND
BERING TO THE CENTRAL ALEUTIANS MON AFTERNOON THROUGH TUE
MORNING.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE GENERAL FLOW OVER THE GULF OF ALASKA AND SOUTHCENTRAL REMAINS
THE SAME AS THE PAST COUPLE DAYS...WITH FEATURES MOVING NORTHWARD
ACROSS THE GULF THEN ROTATING WESTWARD AS THEY REACH SOUTHCENTRAL.
SIMILAR TO SATURDAY MORNING THERE IS A SURFACE LOW OVER THE
NORTHERN GULF POISED TO TRACK WESTWARD ACROSS THE SOUTHERN KENAI
PENINSULA. HOWEVER...TODAYS LOW IS WEAKER AND MORE COMPACT AND THE
UPPER LEVEL TROUGH HELPING TO STEER IT WESTWARD IS MUCH WEAKER.
THEREFORE EXPECT MUCH LESS PRECIP TO FALL OVER THE WESTERN KENAI
PENINSULA. ALSO...THE AIR MASS HAS WARMED A LITTLE AND WILL
CONTINUE TO GRADUALLY WARM TODAY SO PRECIP IN THE HOMER AREA (NEAR
SEA LEVEL) WILL FALL MAINLY AS RAIN. OTHER THAN THIS FEATURES A
SERIES OF UPPER LEVEL WAVES WILL CONTINUE TO MOVE OVERHEAD THROUGH
MONDAY...PRODUCING A STEADY SUPPLY OF SHOWERS FOR THE GULF COAST
AND PRINCE WILLIAM SOUND. INLAND AREAS WILL REMAIN PREDOMINANTLY
DRY AS A PERSISTENT DRY AIR MASS IN THE LOW LEVELS KEEPS ANY
PRECIP FALLING ALOFT FROM REACHING THE GROUND.

THE PATTERN WILL BEGIN TO SHIFT MONDAY AS THE MAIN LOW CURRENTLY
OVER BRISTOL BAY MOVES INTO THE WESTERN GULF AND DISSIPATES.
INCREASING OFFSHORE FLOW WILL LEAD TO DRYING ALONG THE NORTH GULF
COAST MONDAY NIGHT. ARRIVAL OF A DEEP LOW OVER THE EASTERN GULF
WILL HELP TIGHTEN PRESSURE GRADIENTS LEADING TO WEAK COLD
ADVECTION AND DEVELOPMENT OF GAP WINDS ALONG THE NORTH GULF
COAST MONDAY NIGHT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
LIGHT SNOW IS FALLING OVER THE BRISTOL BAY AREA EARLY THIS
MORNING. EXPECT SNOW TO DIMINISH LATE THIS MORNING. AREAS OF RAIN
WILL AFFECT THE ALASKA PENINSULA TODAY...MAINLY FROM PILOT POINT
SOUTHWARD. ANOTHER AREA OF RAIN AND SNOW WILL DEVELOP THIS
AFTERNOON...MAINLY ALONG THE ALEUTIAN RANGE FROM ILIAMNA NORTHWARD
WITH LITTLE ACCUMULATION. THERE IS A SLIGHT CHANCE FOR SNOW EARLY
TODAY OVER THE KUSKOKWIM VALLEY. THE DELTA SHOULD REMAIN SNOW
FREE. NORTHERLY WINDS WILL CONTINUE OVER THE MAINLAND GENERALLY 5
TO 10 MPH EXCEPT UP TO 20 MPH ALONG THE KUSKOKWIM DELTA COAST. THE
AREA STAYS UNDER THE INFLUENCE OF THE WEAKENING LOW PRESSURE
SYSTEM THROUGH MONDAY BUT CHANCES FOR PRECIPITATION AND WINDS WILL
DIMINISH THROUGH MONDAY NIGHT.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A DISTURBANCE IN THE UPPER LEVEL SYSTEM WILL BRING RAIN AND SNOW
FROM THE EASTERN ALEUTIANS THROUGH THE ALASKA PENINSULA TODAY.
WINDS WILL SWITCH FROM WESTERLY TO NORTHWESTERLY BRINGING SOME
SLIGHTLY INCREASED FLOW THROUGH CHANNELED TERRAIN. BEGINNING
TONIGHT A WEAK COLD ADVECTION REGIME SETS UP OVER MOST OF THE
CENTRAL AND EASTERN BERING SEA. SEA SURFACE TEMPERATURES AND
TEMPERATURES OFF THE SURFACE REMAIN CONDUCIVE FOR INSTABILITY RAIN
AND SNOW SHOWERS FROM ADAK THROUGH THE ALASKA PENINSULA. THESE
SHOWERS WILL LINGER THROUGH MONDAY NIGHT BEFORE DIMINISHING.
USUALLY THIS PATTERN WILL BRING AN INCREASED THREAT FOR WINDS
ESPECIALLY THROUGH CHANNELED TERRAIN...HOWEVER WITH A WEAKENING
LOW LEVEL CIRCULATION WINDS OFF THE SURFACE ARE NOT THAT MUCH
HIGHER THAN IN THE BOUNDARY LAYER...AND COLD ADVECTION IS NOT THAT
IMPRESSIVE SO CURRENT FORECAST THINKING IS THAT THE MAIN DRIVER OF
ANY GUSTY WINDS WILL BE GAP RELATED FORCING UNDER STRONG WIND
CRITERIA. THE MEAT OF THE COLD ADVECTION WILL COME OVERNIGHT
TONIGHT SO THE STRONGEST WINDS SHOULD RESIDE IN THAT TIME PERIOD.
A WARM FRONT ENTERS THE WESTERN BERING SEA MONDAY AFTERNOON
BRINGING RAIN AND FOG AND GUSTY SOUTHERLY WINDS TO THE WESTERN
ALEUTIANS.

&&

.LONG TERM FORECAST (TUE-SAT)...

THE MEDIUM RANGE FORECAST WILL BEGIN WITH BROAD LOW PRESSURE OVER
THE GULF AS THE LOW CURRENTLY OVER BRISTOL BAY CONTINUES TO TRACK
EASTWARD INTO THE MIDDLE OF THE WEEK. THIS WILL KEEP SHOWERY
WEATHER AND GUSTY WINDS ALONG THE GULF COAST FOR MUCH OF THE WEEK
WITH SHOWERS OCCASIONALLY PUSHING INLAND AS VARIOUS UPPER
DISTURBANCES ROTATE THROUGH THE AREA. MEANWHILE...HIGH PRESSURE
WILL BUILD OVER THE CENTRAL AND EASTERN BERING DURING THE MIDDLE
OF THE WEEK WITH ANOTHER LOW CENTERED OVER THE KAMCHATKA
PENINSULA. AN ASSOCIATED FRONT WILL MOVE THROUGH THE WESTERN AND
CENTRAL BERING DURING THE MIDDLE OF THE WEEK ACCOMPANIED BY RAIN
AND GALE FORCE WINDS BEFORE WEAKENING AND DISSIPATING WEST OF
DUTCH HARBOR AND THE PRIBILOF ISLANDS AS IT ENCOUNTERS THE HIGH
OVER THE EASTERN BERING.

FOR THE EXTENDED TERM...ATTENTION TURNS TO THE POTENTIAL FOR A
POWERFUL STORM TO MOVE INTO THE BERING SEA LATE IN THE WEAK AS
THE REMNANTS OF CURRENT TYPHOON NURI INTERACT WITH A 200 KNOT JET
STREAK OVER THE NORTHWEST PACIFIC. SIGNIFICANT DISCREPANCIES
REMAIN...BUT MODELS CONTINUE TO HINT AT A VERY DEEP LOW ENTERING
THE WESTERN BERING LATE FRIDAY OR SATURDAY...WITH THE 00Z RUNS OF
THE EC/GFS/GEM ALL DEPICTING A LOW RANGING FROM 924-938 MB MOVING
INTO THE AREA IN THAT TIME FRAME. CONFIDENCE IN THIS OUTCOME
REMAINS VERY LOW AS MANY DETAILS MAY CHANGE IN THE COMING
DAYS...AND ALSO GIVEN THE TENDENCY FOR MODELS TO HANDLE TROPICAL
REMNANTS POORLY. HOWEVER...THIS FEATURE WILL CONTINUE TO BE
MONITORED CLOSELY OVER THE COMING DAYS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE
MARINE...GALE WARNING 178
FIRE WEATHER...NONE

&&

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