Small Craft Advisory 977, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST FRI DEC 6 2013

.ANALYSIS AND UPPER LEVELS...THE UPPER LEVEL RIDGE OVER THE GULF OF
ALASKA AND MOST OF MAINLAND ALASKA IS ATTEMPTING TO REASSERT ITSELF
OVER THE REGION AFTER BEING PUSHED EASTWARD THE PAST TWO DAYS. BY THE
END OF THE WEEKEND THE RIDGE WILL WEAKEN AND ELONGATE IN PLACE. THE
WEAKENING OVER MAINLAND ALASKA CAN ALREADY BE SEEN IN THE AMOUNT OF
CLOUD COVER RIDING OVER THE RIDGE ACROSS THE STATE.
FARTHER WEST THERE IS A LONG WAVE UPPER LEVEL LOW NEAR THE SEA OF
OKHOTSK WITH A CUT OFF LOW IN THE PACIFIC SOUTH OF THE ALASKA
PENINSULA. THIS PATTERN IS CREATING A STRONG FEED OF WARM AND MOIST
AIR INTO THE EASTERN BERING SEA AND SOUTHWEST ALASKA.

.MODEL DISCUSSION...MODEL AGREEMENT IS IMPROVING IN THE REGION NEAR
THE EASTERN ALEUTIANS AND EASTERN BERING SEA WITH THE LOW COMPLEX.
WHILE THE NAM IN PARTICULAR IS STILL DRAGGING BEHIND ON THE MOVEMENT
OF THE SECONDARY LOW THE ECMWF...GFS...UKMET ALL HAVE CONVERGED
NICELY WITH ONLY CENTRAL PRESSURE A POINT OF CONTENTION.
IN THE EASTERN PART OF THE FORECAST AREA THERE ARE NOT SIGNIFICANT
DIFFERENCES IN THE SYNOPTIC FEATURES. THE RESOLUTION ON THE NAM
HOWEVER MAKES IT THE FAVORED SOLUTION AS IT IS STILL CAPTURING SOME
DETAIL THAT IS DRIVING THE PRECIPITATION OVER THE COOK INLET REGION
BETTER THAN THE OTHER MODELS.

.SHORT TERM FORECAST...
SOUTHCENTRAL...THE REMAINING AREAS OF RAIN AND FREEZING RAIN IN THE
COOK INLET REGION AND UP THE SUSITNA VALLEY SHOULD BE RAPIDLY COMING
TO AN END BY EARLY EVENING. AFTER THIS THERE WILL LIKELY BE FOG
DEVELOPING OVER A GOOD PART OF THE AREA. THE FOG WILL LIKELY BE DENSE
AT TIMES WITH A GOOD POSSIBILITY OF FREEZING DRIZZLE SATURDAY AND
SUNDAY AS THE WARM CORE UPPER LEVEL RIDGE CAUSES A SUBSIDENCE
INVERSION THAT TRAPS THE MOIST AIR AT THE SURFACE.
TEMPERATURES WILL REMAIN WELL ABOVE NORMAL WITH A NUMBER OF PLACES
ABOVE FREEZING AGAIN AN SATURDAY...WITH SOME COOLING OCCURRING BY
SUNDAY.
THE COPPER RIVER BASIN AND NORTH GULF COAST SHOULD MAINLY ONLY SEE
SOME CLOUDS WITH LESS IN THE WAY OF FOG AS THERE HAS NOT BEEN THE
PRECIPITATION IN THE AREA AND THE STRENGTH OF THE SUBSIDENCE
INVERSION IN THOSE AREAS SHOULD BE LESS.

SOUTHWEST...THE RIDGE BUILDING BACK INTO THE AREA IS PUSHING THE BULK
OF THE MOISTURE FARTHER WEST INTO THE BERING SEA AS COMPARED TO THE
LAST FEW DAYS. THERE REMAINS A TIGHT PRESSURE GRADIENT OVER THE COAST
OF THE SOUTHWEST MAINLAND AS WELL AS OVER THE ALASKA PENINSULA AND
EASTERN/CENTRAL ALEUTIANS. TEMPERATURES ARE WELL ABOVE NORMAL FOR THE
AREA IN THIS WARM AIRMASS AND WILL REMAIN WARM THROUGH SATURDAY
BEFORE COOLING SOME ON SUNDAY. FOG WILL BE AN ISSUE THIS WEEKEND AS
THE WARM CORE UPPER LEVEL RIDGE CAUSES A SUBSIDENCE INVERSION THAT
TRAPS THE MOIST AIR AT THE SURFACE. THERE IS ALSO A GOOD CHANCE FOR
THERE TO BE DRIZZLE AND FREEZING DRIZZLE IN ASSOCIATION WITH THIS FOG
FOR AREAS NEAR THE COAST.

.LONG TERM FORECAST...THE UPPER LEVEL RIDGE WILL BREAKDOWN AND A
PATTERN CHANGE WILL BE UNDERWAY AT THE BEGINNING OF NEXT
WEEK...HOWEVER MODEL AGREEMENT DIVERGES ON SOLUTIONS MONDAY AND
BECOMES OUT OF PHASE SYNOPTICALLY BY TUESDAY. THE GENERAL MID LEVEL
PATTERN REBUILDS ANOTHER RIDGE OVER NORTHWEST ALASKA WHILE AN ACTIVE
PATTERN OF LOW PRESSURE SYSTEMS DEVELOP SOUTH OF THE ALEUTIANS AND
MOVE EAST. THIS PATTERN WILL KEEP SOUTHWEST AND SOUTHCENTRAL DRIER
WITH WETTER CONDITIONS OVER THE ALEUTIANS AND SOUTHERN GULF OF
ALASKA. AN EASTERLY POLAR WAVE LOOKS TO PUSH A COLD FRONT INTO
SOUTHWEST ALASKA BY MIDWEEK AND INTO THE EAST BERING BY THURSDAY.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 150 155 160 165 170 172 175 176 179 180.
         STORM 173 174.
FIRE WEATHER...NONE.

DEC 13