Small Craft Advisory 1053, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
510 AM AKST TUE DEC 30 2014

.ANALYSIS AND UPPER LEVELS...
WHILE THE HIGH AMPLITUDE PATTERN CONTINUES IT APPEARS AS IF THE
LAST MAJOR DISTURBANCE IN THE TROUGH IS LIFTING OUT TOWARD THE
BERING STRAIT. THE UPPER LEVEL RIDGE HAS BARELY PROPAGATED TO THE
EAST OVER THE LAST 24 HOURS WHILE THE LONG LIVED BERING SEA UPPER
LEVEL LOW/TROUGH IS BEGINNING TO GET SQUEEZED BY A QUICKLY
DEEPENING KAMCHATKA LOW PRESSURE SYSTEM. THERE STILL IS SOME
MOISTURE WITHIN THE SOUTHERLY UPPER LEVEL JET THE DEEPEST MOISTURE
AND COLDEST CLOUD TOPS HAVE MOVED INTO THE NORTHERN PORTION OF THE
STATE.

THE HIGH WIND WARNING REMAINS IN EFFECT FOR TURNAGAIN ARM AND THE
HIGHER ELEVATIONS OF ANCHORAGE. MCHUGH CREEK HAS BEEN NEAR WARNING
LEVEL FOR MOST OF THE DAY WHILE THE STRONG DOWN INLET GRADIENT HAS
KEPT THE UPPER ELEVATIONS VARIABLE IN DIRECTION AND QUITE A BIT
LOWER IN MAGNITUDE. AS THE BERING SEA SURFACE LOW GAINS
LATITUDE...STRONGER SOUTHEAST GUSTS ARE BEGINNING TO MANIFEST
THEMSELVES AT THE HIGHER ELEVATIONS.

THE MAIN FRONT IS CURRENTLY HANGING UP ALONG THE NORTH GULF COAST
BRINGING A WIDE AREA OF GALE TO STORM FORCE WINDS ACROSS THE GULF.
THE COOK INLET REGION IS REMAINING WIDELY DOWNSLOPED EXCEPT FOR
THE KACHEMAK BAY AREA WHICH IS EXPERIENCING RAIN SHOWERS.

&&

.MODEL DISCUSSION...
GUIDANCE REMAINS IN PRETTY GOOD AGREEMENT WITH BOTH THE UPPER
LEVEL AND SURFACE FEATURES IN THE PATTERN. THE MAIN DISCREPANCY IN
THE NEXT FEW DAYS IS THE THE POSSIBILITY OF A TRIPLE POINT LOW
ASSOCIATED WITH THE KAMCHATKA LOW/FRONT. BOTH VARIANTS OF THE
CANADIAN MODEL DEVELOP A STRONG CIRCULATION ON THE FRONT BUT THIS
SOLUTION DOES NOT SEEM LIKELY...HOWEVER WATER VAPOR IMAGERY DOES
SHOW ENHANCED MOISTURE/LIFT IN THIS REGION.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE FRONT MOVING TOWARD SOUTHCENTRAL AND ACCOMPANYING WAVE
HEADING TOWARD THE AK PEN WILL CONTINUE WINDY CONDITIONS ACROSS
THE GULF AND SOUTHCENTRAL TROUGH TONIGHT. WARNING LEVEL WINDS
ACROSS TURNAGAIN ARM AND HIGHER ELEVATIONS WILL DIMINISH A LITTLE
THIS MORNING BUT SHOULD INCREASE AGAIN BY MID TO LATE MORNING AND
PEAK EARLY THIS AFTERNOON. AS THE FRONT SWEEPS ACROSS SOUTHCENTRAL
TONIGHT STRONG PRESSURE RISES ON THE BACK SIDE WILL BRING BRISK
SOUTHERLY FLOWS AND WARMING ACROSS MUCH OF THE AREA. RAIN IS
EXPECTED ALONG COASTS WITH MIXED PRECIPITATION TYPES INLAND. TEMPS
COOL ACROSS SOUTHCENTRAL WITH COLD ADVECTION FROM THE WEST ON WED.
AT THAT POINT MIXED RAIN AND SNOW SHOULD GIVE WAY TO SNOW SHOWERS.
UPSLOPE FLOW COULD BRING SIGNIFICANT SNOW AMOUNTS TO THE EASTERN
AND NORTHERN SUSITNA VALLEY TONIGHT THROUGH WED EVENING.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (TUESDAY AND WEDNESDAY)...
WINDS HAVE BEGUN TO TAPER OFF ACROSS THE BRISTOL BAY AREA AS THE
PRESSURE GRADIENT SLOWLY BEGINS TO RELAX AND BECOME LESS FAVORABLY
ORIENTED. GUSTY EASTERLY WINDS WILL CONTINUE TO BE SEEN THIS
MORNING...MAINLY NORTH OF DILLINGHAM AND GRADUALLY TAPER OFF
THROUGH THE REMAINDER OF THE DAY. AS THESE WINDS WEAKEN...SO WILL
THE CROSS BARRIER FLOW WHICH HAS KEPT MUCH OF THE PRECIPITATION AT
BAY ACROSS THE ALASKA PENINSULA. COINCIDING WITH THE WEAKENED
CROSS BARRIER FLOW WILL BE A POTENT SHORTWAVE ROUNDING THE BASE OF
THE UPPER LEVEL TROUGH. THIS WILL ACTUALLY AID IN USHERING COLDER
AIR BACK INTO THE REGION AND POTENTIALLY ALLOW FOR SNOW TO MIX
WITH THE RAIN SEEN ACROSS MUCH OF THE AREA. FOLLOWING THE PASSAGE
OF THE SHORTWAVE...PRECIPITATION CHANCES BEGIN TO TAPER OFF AND
SKIES BEGIN TO CLEAR BY LATE WEDNESDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (TUESDAY AND WEDNESDAY)...
AN AREA OF LOW PRESSURE OVER THE EASTERN BERING SEA WILL CONTINUE
TO LIFT NORTH TOWARD THE BERING STRAIT AND CHUKCHI SEA THROUGHOUT
THE DAY. THIS WILL KEEP 30 KT WINDS GOING ACROSS THE EASTERN
BERING SEA THROUGH EARLY THIS EVENING BEFORE HIGH PRESSURE BUILDS
NORTHWARD FROM THE NORTH PACIFIC. THIS WILL BRING A PERIOD OF
ABNORMALLY NICE WEATHER ACROSS THE EASTERN ALEUTIANS AND PRIBILOF
ISLANDS (MOSTLY CLEAR SKIES AND LACK OF PRECIPITATION CHANCES) BY
THIS EVENING AND LAST THROUGH AT LEAST WEDNESDAY EVENING.
CONDITIONS DO NOT LOOK AS FAVORABLE ACROSS THE WESTERN HALF OF THE
BERING SEA AS A 951 MB KAMCHATKA LOW MOVES TOWARD THE WESTERN
ALEUTIANS AND PUSHES A FRONT INTO THE WESTERN BERING SEA. THIS
FRONT WILL COLLIDE WITH THE AFOREMENTIONED RIDGE AND STALL OVER
THE CENTRAL ALEUTIANS ON WEDNESDAY. ANOTHER BLAST OF STRONG WINDS
(POSSIBLY AS HIGH AS 70 MPH NEAR SHEMYA) AND PRECIPITATION IS
EXPECTED OVER THE NEXT SEVERAL DAYS FOR THE WESTERN AND CENTRAL
ALEUTIANS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
AN UPPER LEVEL LOW WILL FORM OVER THE NORTHERN GULF COAST WITH A
GALE FORCE LOW REFLECTED AT THE SURFACE NEAR YAKUTAT BY THURSDAY
AFTERNOON. THIS LOW WILL GRADUALLY MOVE WESTWARD AND BECOME
NEARLY STATIONARY OVER THE NORTHERN GULF HEADING INTO THE WEEKEND
BEFORE DISSIPATING BY SATURDAY MORNING. THIS LOW PRESSURE SYSTEM
WILL BRING GALE FORCE WINDS TO THE GULF AND EXTEND THROUGH THE
BARREN ISLANDS AREA BEFORE TAPERING OFF BY FRIDAY AFTERNOON. THE
ECMWF/GFS WERE IN BETTER AGREEMENT AND NAM KEPT THE SYSTEM
FARTHER EAST AND SEEMED TO BE THE OUTLIER. WHILE...HIGH PRESSURE
OVER THE YUKON TERRITORY WILL START TO GRADUALLY MOVE SOUTHWARD
THROUGH MONDAY. THIS WILL AID IN OFFSHORE FLOW THROUGH THE
SOUTHCENTRAL REGION AND THE PRESSURE GRADIENT WILL STRENGTHEN
THROUGH THE WEEKEND. THE TEMPERATURES WILL BE MODIFIED WITH THE
WARMER AIR ADVECTION ALONG THE NORTHERN GULF EXCEPT COOLER
TEMPERATURES INLAND AS THE HIGH PRESSURE OVER THE YUKON TERRITORY
MOVES CLOSER THROUGH THE WEEKEND. THE HIGH PRESSURE RIDGE COMBINED
WITH CONTINUED OFFSHORE FLOW WILL KEEP MAJORITY OF THE PRECIPITATION
ALONG THE NORTHERN GULF COASTLINE WITH A WINTRY MIX ALONG THE
COASTLINE AND MAINLY SNOW INLAND WITH THE COOLER TEMPERATURES.

THE MODELS CONTINUE IN GOOD AGREEMENT WITH THE BLOCKING HIGH FROM
THE BEAUFORT SEA EXTENDING SOUTHWARD IN THE LOWER KUSKOKWIM VALLEY
FROM THURSDAY GOING INTO THE WEEKEND. THIS WILL BRING COOLER
TEMPERATURES INTO SOUTHWEST/SOUTHCENTRAL ALASKA REGION. THE
ECMWF/GFS MODELS WERE IN DECENT AGREEMENT WITH THE NORTH PACIFIC
STORM FORCE LOW APPROACHING THE WESTERN ALEUTIANS BY THURSDAY
AFTERNOON. THE NAM CONTINUES TO BE THE OUTLIER AND PUSHES THE LOW
FARTHER EAST. BY THURSDAY EVENING THE WEATHER FRONT ASSOCIATED
WITH THIS SYSTEM WILL MOVE THROUGH THE WESTERN ALEUTIANS NEAR
SHEMYA BRINGING STRONG GUSTY SOUTHERLY WINDS ACCOMPANIED BY
ABUNDANT MOISTURE AND RAIN SPILLING OVER INTO THE WESTERN BERING
SEA. THIS LOW WILL TRACK OVER THE KAMCHATKA PENINSULA WITH THE
WEATHER FRONT MOVING EASTWARD NEAR PRIBILOF ISLANDS EXTENDING
SOUTHWARD THROUGH DUTCH HARBOR BY SATURDAY BEFORE THE FRONT FALLS
APART BY SUNDAY OVER THE EASTERN BERING SEA. THE SECOND NORTH
PACIFIC STORM FORCE LOW WILL APPROACH JUST SOUTH OF SHEMYA BY
SUNDAY MORNING BEFORE TRACKING WESTWARD. THIS WILL BRING A LARGE
SWATH OF GUSTY WINDS ACCOMPANIED BY RAIN THROUGH THE WESTERN
ALEUTIANS AND PORTIONS OF THE WESTERN BERING SEA THROUGH THE
WEEKEND. THE SOUTHWEST ALASKA REGION WILL BE UNDER THE INFLUENCE
OF A RIDGE OF HIGH PRESSURE WITH CONTINUE OFFSHORE FLOW RESULTING
IN DRIER CONDITIONS WITH TEMPERATURES CONTINUING TO COOL THROUGH
MONDAY.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WARNING...101
MARINE...STORM WARNING...130 131 177 178
         GALE WARNING...119 120 125 139 150 173 174 175 176
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...MTL
SOUTHCENTRAL ALASKA...BC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MMC
LONG TERM...PLD