Small Craft Advisory 898, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST TUE NOV 11 2014

.ANALYSIS AND UPPER LEVELS...

THE UPPER LEVEL TROUGH REMAINS OVER THE BERING THIS AFTERNOON
WITH A MASSIVE BLOCKING RIDGE OVER THE WEST COAST OF NORTH AMERICA
INCLUDING THE EASTERN HALF OF ALASKA. EMBEDDED WITHIN THE BERING
TROUGH ARE WEAKENING CUT-OFF LOWS NEAR THE CENTRAL ALEUTIANS AND
SOUTH OF DUTCH HARBOR. AT THE SURFACE...A WEATHER FRONT IS
ENTERING THE SOUTHERN GULF ON ITS WAY TO KODIAK ISLAND...A LOW
SOUTH OF DUTCH HARBOR IS WEAKENING IN PLACE...AND A STILL
SIGNIFICANT LOW IS OVER THE EXTREME NORTHWESTERN BERING.

&&

.MODEL DISCUSSION...

MODELS ARE IN SUFFICIENTLY GOOD AGREEMENT INITIALLY TO UTILIZE
THE NAM SOLUTION FOR WIND DETAIL...AND THEN THE MORE STABLE EC
BECOMES PREFERRED AT THE END OF THE 48 HOUR FORECAST.

AT UPPER LEVELS THE RIDGE CLOSES OFF OVER THE YUKON AND ALCAN
THROUGH THU AFTERNOON...WHILE THE BERING TROUGH TRANSLATES
SOUTHEAST AND BECOMES A CLOSED CUT-OFF LOW SOUTH OF THE AKPEN.

WITH REGARD TO SURFACE DEVELOPMENT...THE FRONT OVER THE SOUTHERN
BERING WILL REACH KODIAK ISLAND AND THE NORTHWEST GULF COAST
TONIGHT WITH A VERY TIGHT PRESSURE GRADIENT DEVELOPING ACROSS THE
AK RANGE. THE FRONT WILL THEN SLIDE SOUTHWEST ALONG THE ALASKA
PENINSULA ON WED. FROM WED NIGHT INTO THU IT WILL BECOME CAUGHT UP
IN THE FLOW AROUND A NEW LOW THAT FORMS WED WELL SOUTH OF THE
AKPEN...AND WHICH RAPIDLY DEEPENS AS IT MOVES TO JUST SOUTH OF
COLD BAY THU AFTERNOON.

WHILE THIS IS HAPPENING...THE SIGNIFICANT LOW OVER THE NORTHWEST
BERING WILL MOVE TO NEAR ATKA BY WED NIGHT...RAPIDLY WEAKENING
DURING THE TRANSIT AND FINALLY DISSIPATING.

&&

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

GUSTY WINDS ACROSS THE WESTERN GULF AND SURROUNDING INLAND
LOCATIONS WILL CONTINUE TO GUST THROUGH WEDNESDAY AS THE TIGHT
PRESSURE GRADIENT ALONG SURFACE PERSISTS. WINDS TAPER OFF
SIGNIFICANTLY WEDNESDAY NIGHT ACROSS THE MATANUSKA VALLEY AND
TURNAGAIN ARM...HOWEVER GUSTY WINDS CONTINUE ACROSS THE WESTERN
GULF AND COOK INLET THROUGH THURSDAY MORNING. SEVERAL SHORTWAVES
WILL MOVE THROUGH THE GULF INTO THE SOUTHERN MAINLAND THROUGH
WEDNESDAY. WITH A WARM SOUTHEASTERLY FLOW JUST OF THE SURFACE...MOST
LOCATIONS WILL SEE RAIN WITH MIXED PRECIPITATION INLAND. KODIAK IS
EXPECTED TO RECEIVE THE HIGHEST RAINFALL AMOUNTS THROUGH
THURSDAY...WITH MODERATE TO HEAVY RAINFALL TONIGHT INTO WEDNESDAY
MORNING. RIDGING BUILDING INTO SOUTHEAST ALASKA WILL BRING A DRIER
PATTERN INTO THE SOUTHERN MAINLAND AT THE END OF THE WEEK.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A VERY STRONG THERMAL GRADIENT IS SETTING UP ACROSS THE AREA AS
COLD AIR FROM THE BERING SEA IS BEING PUSHED EASTWARD AND CLASHING
WITH VERY WARM AIR MOVING IN FROM THE GULF OF ALASKA. AIDED BY AN
IMPRESSIVE 130 KT SOUTHERLY JET...WINDS ACROSS THE AREA AND
ESPECIALLY ACROSS BRISTOL BAY HAVE BEGUN TO INCREASE. THE SECOND
OF TWO SHORTWAVES MOVING NORTH ALONG THE STATIONARY FRONT IS
EVIDENT ON SATELLITE IMAGERY SOUTH OF KODIAK ISLAND. AS THIS
DISTURBANCE PASSES JUST SOUTH OF BRISTOL BAY LATE TONIGHT...WINDS
WILL REACH PEAK INTENSITY AS THE STRONG PRESSURE GRADIENT IS
SQUEEZED EVEN MORE. NOT ONLY WILL WINDS ACCELERATE THROUGH THE
GAPS NEAR ILIAMNA LAKE...BUT A LAYER OF STABLE AIR ALOFT MAY HELP
SPREAD SOME OF THE STRONGEST WINDS FURTHER WEST AND AWAY FROM THE
IMMEDIATE VICINITY OF THE ALEUTIAN RANGE. MEANWHILE...HEAVY
PRECIPITATION ASSOCIATED WITH THE STALLING FRONT OVER THE AREA IS
ALREADY SPREADING INTO BRISTOL BAY AND THE LOWER KUSKOKWIM VALLEY.
MOST OF THIS WILL FALL AS RAIN...BUT SOME MIXING WITH SNOW CANNOT
BE RULED OUT IN HEAVIER PRECIP NEAR THE KILBUCK MOUNTAINS AND
ACROSS PARTS OF THE KUSKOKWIM DELTA. THIS PATTERN OF WIDESPREAD
RAIN AND GUSTY WINDS WILL CONTINUE THROUGH WEDNESDAY AFTERNOON
BEFORE A MORE SIGNIFICANT LOW PRESSURE SYSTEM IN THE NORTH PACIFIC
DRIFTS FAR ENOUGH NORTH TO WEAKEN THE STATIONARY FRONT AND PUSH
THE PRECIP OUT INTO THE EASTERN BERING.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A BROAD AND COMPLEX LOW PRESSURE SYSTEM WILL REMAIN ANCHORAGE OVER
THE BERING SEA FOR THE NEXT FEW DAYS. MULTIPLE WEAK LOW CENTERS
AND SUBTLE REINFORCEMENT OF COLD AIR FROM EASTERN RUSSIA WILL
RESULT IN A CONTINUATION OF THE SHOWERY PATTERN FOR MOST OF THE
AREA. TEMPERATURES ARE STILL WARM ENOUGH TO SUPPORT MOST RAIN AS
THE DOMINANT PRECIPITATION TYPE...EXCEPT THE WESTERN 1/3 OF THE
BERING/ALEUTIANS WHERE A RAIN/SNOW MIX CAN BE EXPECTED.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE DOMINANT FEATURE IMPACTING SOUTHCENTRAL ALASKA THROUGH THE
EARLY PART OF NEXT WEEK WILL BE THE STOUT RIDGE OVER THE WEST
COAST OF CANADA PROMOTING MOIST SOUTHEASTERLY FLOW ACROSS THE
GULF. A DEVELOPING CLOSED UPPER HIGH WILL REMAIN OVER THE YUKON
TERRITORY THROUGH FRIDAY AND SERVE TO KEEP RAIN CONFINED TO KODIAK
ISLAND AND THE SOUTHERN KENAI PENINSULA AS OTHER PORTIONS OF
SOUTH CENTRAL SEE CLEARING SKIES. THE RIDGE AXIS WILL THEN SHIFT
BACK TO THE EAST THIS WEEKEND ALLOWING PRECIPITATION TO RETURN
ALONG THE NORTH GULF COAST...WITH CLOUDIER SKIES AND PERIODS OF
SHOWERS FARTHER INLAND. PERSISTENT SOUTHERLY FLOW WILL CONTINUE
TO YIELD ABOVE NORMAL TEMPERATURES WELL INTO NEXT WEEK.

MEANWHILE...A SHOWERY REGIME WILL PREVAIL ACROSS THE BERING FOR
MUCH OF THE NEXT WEEK BENEATH A RELATIVELY DIFFUSE UPPER LEVEL
TROUGH CENTERED OVER THE FAR WESTERN BERING WITH MULTIPLE
EMBEDDED LOW CENTERS. THE HEAVIEST PRECIPITATION WILL BE
CONCENTRATED OVER THE EASTERN BERING AS A NORTH PACIFIC LOW TRACKS
NEAR DUTCH HARBOR LATE THIS WEEK AND AN ASSOCIATED WARM FRONT
PUSHES WESTWARD FROM THE SOUTHWEST MAINLAND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM WARNING 130 131.
         GALE WARNING 119 120 132 136 137 138 139 141 150.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...DS
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AD/JR
LONG TERM...CB