Small Craft Advisory 77, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
105 PM AST MON JAN 28 2008

.ANALYSIS AND UPPER LEVELS...LONG-WAVE TROUGH IS CENTERED OVER THE
WESTERN BERING WITH MULTIPLE CLOSED LOWS EMBEDDED WITHIN. WATER VAPOR
IMAGERY SHOWS A HIGH AMPLITUDE LOW WAVELENGTH TROUGH EXTENDING FROM
THE BERING STRAIT REGION SOUTHEASTWARD ACROSS SOUTHWEST ALASKA AND
THE WESTERN GULF. THIS TROUGH HAS SMUSHED UP AGAINST A HIGH AMPLITUDE
RIDGE THAT HAD BEEN FIRMLY ENTRENCHED OVER MAINLAND ALASKA. THE RIDGE
HAS NOW BECOME ELONGATED AND SHIFTED A LITTLE BIT TO THE EAST. THE
RIDGE HAS CAUSED THE NORTHEAST PROGRESSION OF THE TROUGH TO SLOW TO
A CRAWL. AT THE SURFACE A TRIPLE POINT LOW FORMED LAST NIGHT JUST
EAST OF KODIAK ISLAND AND HAS NOW MOVED OUT INTO THE CENTRAL GULF. A
SURFACE TROUGH EXTENDS FROM THE LOW NORTHWESTWARD ACROSS SOUTHWEST
ALASKA. AREAS OF SNOW PERSIST AHEAD OF THE UPPER TROUGH ACROSS
INTERIOR SOUTHWEST ALASKA AND MUCH OF SOUTHCENTRAL. SNOW IS STEADIEST
ACROSS THE KUSKOKWIM VALLEY AND THE NORTHEAST INTERIOR OF THE BRISTOL
BAY ZONE. ELSEWHERE...SNOW IS GENERALLY VERY LIGHT WITH LITTLE OR NO
ACCUMULATION. A SECONDARY WEAKER SHORT-WAVE TROUGH IS CROSSING THE
EASTERN BERING/ALASKA PENINSULA AREA...RESULTING IN AN AREA OF SNOW
SHOWERS. COLD ADVECTION BEHIND THE MAIN UPPER TROUGH IS CONTRIBUTING
TO GUSTY WINDS FROM KODIAK ISLAND WESTWARD ACROSS THE BERING SEA AND
ALEUTIANS. FINALLY...SATELLITE SHOWS A DEVELOPING LOW 41N 179E ALONG
AN UPPER JET MAX TRACKING TO THE NORTHEAST TOWARD THE EASTERN
ALEUTIANS.

.MODEL DISCUSSION...MODELS ARE VERIFYING WELL WITH ONGOING WEATHER
OVER THE FORECAST AREA. LARGEST DIFFERENCES CONTINUE TO LIE WITH
DEVELOPING PACIFIC LOW. UNLIKE THE PAST FEW DAYS SOLUTIONS THE LATEST
MODEL RUNS ARE ALL BUNCHED IN THE SAME GENERAL AREA...SO CONFIDENCE
IS INCREASING. ECMWF AND UKMET CONTINUE TO BE FASTER AND WEAKER THAN
GFS WHILE THE NAM IS THE OUTLIER AMONG THE GROUP WITH A MORE
SOUTHERLY TRACK. FOR NOW WILL GO WITH A MIDDLE GROUND SOLUTION
BETWEEN THE GFS AND UKMET/ECMWF. BEYOND THIS SYSTEM MODELS DIVERGE
SIGNIFICANTLY SO WILL STICK CLOSE TO CURRENT FORECAST.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...A PIECE OF THE UPPER RIDGE WILL CUT OFF OVER
NORTHERN ALASKA AND THE TROUGH OVER SOUTHWEST ALASKA AND GULF WILL
UNDERCUT THIS RIDGE...MOVING ACROSS THE GULF AND INTO THE NORTHEAST
PACIFIC BY EARLY TUESDAY ALONG WITH THE SURFACE LOW. SNOW WILL
GRADUALLY TAPER OFF ACROSS SOUTHCENTRAL TONIGHT. THE DEVELOPING
PACIFIC SYSTEM LOOKS LIKE IT WILL TRACK FAR ENOUGH SOUTH OF
SOUTHCENTRAL TO MAINTAIN DRY CONDITIONS THROUGH THE WEST OF THE
SHORT-TERM. KODIAK ISLAND WILL LIKELY BE IMPACTED WITH SNOW AND
WIND TUESDAY NIGHT INTO WEDNESDAY...BUT WITH UNCERTAINTY IN TRACK
WILL KEEP WINDS AND SNOW CONSERVATIVE FOR NOW.

SOUTHWEST ALASKA...SNOW SHOWERS WILL PERSIST ACROSS SOUTHWEST ALASKA
THROUGH TONIGHT AND THEN END FROM COAST TO INTERIOR ON TUESDAY AS A
SHORT-WAVE RIDGE BUILDS IN AHEAD OF THE PACIFIC SYSTEM. THE ALASKA
PENINSULA PORTION OF THE BRISTOL BAY ZONE MAY BE IMPACTED BY MINOR
WINDS AND SNOW AS THE SYSTEM PASSES TO THE SOUTH TUESDAY NIGHT INTO
WEDNESDAY. THE REST OF SOUTHWEST ALASKA WILL STAY DRY.

BERING SEA/ALEUTIANS/ALASKA PENINSULA...SNOW SHOWERS AND GUSTY WINDS
WILL DIMINISH ACROSS THE REGION TONIGHT AS SURFACE PRESSURE GRADIENT
RELAXES AND COLD ADVECTION DIMINISHES. BLIZZARD WATCHES HAVE BEEN
ISSUED FOR ZONE 181 (ALASKA PENINSULA) AND 185 (EASTERN ALEUTIANS)
FOR TUESDAY MORNING THROUGH TUESDAY NIGHT. IF MODEL CONSENSUS OF
NORTHERLY TRACK IS CORRECT LOOKS GOOD FOR SNOW AND STRONG WINDS
THROUGH THIS REGION. WILL WAIT FOR 00Z MODEL CYCLE TO MAKE DECISION
ABOUT WHETHER TO UPGRADE TO BLIZZARD WARNINGS.

.LONG TERM FORECAST...MODELS CONTINUE TO INDICATE A FAIRLY FLAT
LONG-WAVE PATTERN THROUGH THE EXTENDED PERIOD WITH JET JUST SOUTH OF
THE FORECAST AREAS. DETAILS ARE NEARLY IMPOSSIBLE TO LOCK ON TO BUT
LOOK FOR CONTINUED ACTIVE WEATHER WITH SYSTEMS TRACKING NEAR THE
ALEUTIANS OVER TO THE GULF.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES...120 132 150 155 165 170 171 172 185.
         HEAVY FREEZING SPRAY...130.
FIRE WEATHER...NONE.

SEB JAN 08