Small Craft Advisory 780, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
444 PM AKDT TUE OCT 7 2014

.ANALYSIS AND UPPER LEVELS...
IN THE UPPER LEVELS THERE IS A LOW THAT IS IN THE EASTERN INTERIOR WITH
ANOTHER LOW JUST SOUTHWEST OF ATTU. IN BETWEEN THERE IS THE UPPER
LEVEL RIDGE THAT STRETCHES FROM THE NORTHERN BERING SEA TO ACROSS
KODIAK ISLAND. THIS IS BRINGING NORTHWEST FLOW ALOFT TO MOST OF
THE MAINLAND PART OF SOUTHERN ALASKA. THE SURFACE PATTERN IS A BIT
MORE SIMPLE WITH HIGH PRESSURE OVER MAINLAND ALASKA WITH A
DISSIPATING LOW IN THE NORTHERN GULF OF ALASKA. THE BIG WEATHER
MAKER IS SOUTH OF THE ALEUTIANS WHERE THE REMNANTS OF FORMER
TYPHOON PHANFONE ARE USURPING THE ENERGY FROM THE LOW THAT HAS NEE
IN THE WESTERN BERING SEA. THE FRONT ASSOCIATED WITH THE WESTERN
BERING SEA LOW IS STILL GOING STRONG ACROSS THE ALEUTIANS AND
SOUTHERN BERING SEA BUT IT WILL GET ABSORBED INTO THE FORMER
TYPHOON REMNANTS OVER THE COURSE OF THE NEXT DAY.

&&

.MODEL DISCUSSION...
MODELS ARE DOING A FINE JOB WITH THE SYNOPTIC PATTER WHICH PRETTY
MUCH CONSISTS OF HANDLING THE STRONG LOW SOUTH OF THE ALEUTIAN
ISLANDS. THE ONLY REAL QUESTION AT THIS POINT IS THE SPEED AT
WHICH THIS LOW MOVES INTO THE GULF OF ALASKA LATE THIS WEEK. BY
FRIDAY AFTERNOON THE ECMWF IS ABOUT 300 MILES FARTHER NORTHEAST
THAN THE GFS MODEL. AFTER THIS THE LOW WILL BECOME COMPLEX AND
THE MODELS ENTER INTO SOME MORE SIGNIFICANT DIFFERENCES IN
STRUCTURE OF THIS LOW THIS WEEKEND.

&&

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
MOST OF SOUTHCENTRAL ALASKA WILL REMAIN CLEAR THROUGH TOMORROW
UNDER THE NORTHWEST FLOW ALOFT. THE COPPER RIVER BASIN IS THE BIG
EXCEPTION WHERE STRATUS HAS SETTLED INTO THE LOWER PARTS OF THE
BASIN AND ARE NOT BURNING OFF. THESE CLOUDS WILL LIKELY PERSIST
UNDER THE UPPER LEVEL LOW AND MAY TOUCH OFF SOME SNOW SHOWERS
ALONG THE MOUNTAINS AS THE LOW MOVES SOUTHWARD TONIGHT. THERE IS A
CHANCE A FEW CLOUDS WILL MOVE INTO THE SUSITNA VALLEY BUT IT
LOOKS MOSTLY RELEGATED TO THE COPPER RIVER AT THIS TIME. BY
WEDNESDAY NIGHT THE FRONT ASSOCIATED WITH THE STRONG LOW SOUTH OF
THE ALEUTIANS WILL MOVE INTO THE GULF AND BRING RAIN TO KODIAK
ISLAND. THIS FRONT WILL OVERSPREAD THE REMAINDER OF SOUTHCENTRAL
THURSDAY.

SOUTHWEST ALASKA...
WHILE CLOUD COVER WILL BE LIMITED FROM THE FRONT ASSOCIATED WITH
THE STRONG LOW SOUTH OF THE ALEUTIANS THE PRESSURE GRADIENT WILL
INCREASE OVERNIGHT INTO TOMORROW. THIS WILL INCREASE WINDS OVER
THE AREA AND THERE WILL BE OVERALL BREEZY CONDITIONS THROUGH
FRIDAY. CLOUDS AND POSSIBLY SOME RAIN WILL MOVE INTO THE BRISTOL
BAY AREA FROM THE FRONT ON THURSDAY.

BERING SEA/ALEUTIANS...
THE STRONG FRONT OVER THE ALEUTIANS ISLANDS AND SOUTHERN BERING
SEA WILL GET ABSORBED BY THE STRONG LOW SOUTH OF THE ALEUTIANS
WEDNESDAY LATE AFTERNOON OR EVENING. THIS WILL KEEP STRONG WINDS
IN THE EASTERN AND CENTRAL ALEUTIANS AS WELL AS THE PRIBILOF
ISLANDS. DUE TO THE WAY THESE SYSTEMS ARE MOVING AND INTERACTING
THERE WILL BE PERSISTENT RAINFALL INTO THURSDAY AS WELL.

&&

.LONG TERM FORECAST (SAT-TUE)...THE "LEFTOVER" TROUGH IN THE GULF
OF AK TO START THE PERIOD WILL BE REINFORCED BY ENERGY DROPPING
INTO THE AREA FROM THE NORTH. MODELS ARE ALREADY IN RELATIVELY
GOOD AGREEMENT ON THIS NORTHERN TIER ENERGY SLIDING DOWN THE EAST
FLANK OF THE RIDGE OVER THE BERING TOWARDS BRISTOL BAY EARLY SAT.
THE BIGGEST DIFFERENCE IS HOW THEY HANDLE THE TRACK OF THE LOW AS
IT MOVES S OF 60N. THE GFS/GEM GLOBAL DRIVE IT FURTHER SOUTH INTO
THE TROUGH OVER THE GULF. THE EC ON THE OTHER HAND HOLDS IT OVER
BRISTOL BAY BEFORE TRACKING IT NE RIGHT THROUGH SOUTH CENTRAL. THE
MOST SIGNIFICANT PIECE OF THIS IS THAT THE EC WOULD BRING A ROBUST
ROUND OF COLD AIR ADVECTION INTO THE AREA THROUGH THE END OF THE
WEEKEND. 850 MB TEMPERATURES BY MONDAY MORNING ON THE GFS ARE
PROGGED TO BE AROUND -2C OVER ANCHORAGE WHILE THE EC PAINTS NEARLY
-10C. WITH LINGERING MOISTURE FROM THE TROUGH IN THE GULF...THE EC
SOLUTION WOULD BRING WIDESPREAD SNOW TO SOUTH CENTRAL BY EARLY
NEXT WEEK. IF THE GFS/GEM SOLUTION WERE TO PAN OUT...LOWER
ELEVATIONS WOULD LIKELY JUST SEE SOME MORE LIGHT RAIN WITH MIXED
PRECIPITATION HIGHER UP.
MEANWHILE OVER THE BERING AND ALEUTIANS...THINGS SHOULD BE
TRENDING DOWNWARD IN TERMS OF PRECIPITATION CHANCES AND WINDS. A
RIDGE WILL BUILD EARLY IN THE WEEK AND SHOULD KEEP MOST OF THE
ACTIVE WEATHER SOUTH AND NORTH OF THE AREA.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 132 138 150-165 171 174-185.
         STORM 170 172 173.
FIRE WEATHER...NONE.
&&

OCT 14