Small Craft Advisory 108, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
342 AM AKST TUE FEB 4 2014

.ANALYSIS AND UPPER LEVELS...

NO DRAMATIC CHANGE IN THE UPPER AIR PATTERN SINCE YESTERDAY...WITH A
BROAD AND DISORGANIZED UPPER TROUGH OVER THE NORTH PACIFIC...AND HIGH
PRESSURE RIDGES OVER THE NORTHEAST PACIFIC AND THE NORTHWEST PACIFIC.
A CLOSED UPPER HIGH IS MIGRATING EAST OVER NORTHEAST ALASKA...WITH A
STRONG SHORTWAVE TROUGH TRANSLATING AROUND THE WESTERN BERING HIGH
NEAR KAMCHATKA. THE FLOW CONTINUES TO REMAIN WEAK AND CUTOFF FROM THE
POLAR JET STREAM OVER ALASKA...WITH A NUMBER OF WEAK MIGRATING UPPER
LEVEL VORTICIES OVER THE EASTERN BERING SEA. TWO WELL DEFINED UPPER
WAVE DISTURBANCES EMBEDDED WITHIN THE NORTH PACIFIC TROUGH CAN BE
SEEN ON WATER VAPOR...WITH THE FIRST LIFTING NORTH TOWARD THE ALASKA
PENINSULA. AN ASSOCIATED WARM FRONT IS LIFTING INTO BRISTOL
BAY...WITH RAIN AND SNOW IMPACTING SOUTHWEST ALASKA...AND A STEADY
STREAM OF CLOUDS MOVING OVER MUCH OF SOUTHCENTRAL ALASKA.

AT THE SURFACE...A VERY IMPRESSIVE 1054 MB SURFACE HIGH IS SITUATED
OVER THE YUKON...WITH A BROAD 992 MB SURFACE LOW IN THE NORTH
PACIFIC. THIS IS PROMOTING A GENERAL NORTHEAST TO SOUTHWEST ORIENTED
OFFSHORE PRESSURE GRADIENT...WITH COLDER AND DRIER AIR WORKING ITS
WAY INTO SOUTHCENTRAL. EVENTUALLY...THE STOUT HIGH OVER THE YUKON
WILL BUILD OVER ALL OF SOUTHERN ALASKA WEDNESDAY AND THURSDAY BEFORE
A POWERFUL NORTHERLY JET MAX/UPPER LEVEL POTENTIAL VORTICITY ANOMALY
TRACKS THROUGH ALASKA THURSDAY AND FRIDAY. EVENTUALLY...A RATHER
IMPRESSIVE 60-70 MB SURFACE PRESSURE DIFFERENCE WILL DEVELOP OVER THE
STATE OF ALASKA LATE FRIDAY.

.MODEL DISCUSSION...

THE NUMERICAL GUIDANCE IS IN SUPERB SYNOPTIC AGREEMENT DEEP INTO NEXT
WEEK. THE SMALLER DETAILS ARE SLIGHTLY UNCERTAIN STILL WITH RESPECT
TO A POWERFUL NORTHERLY JET STREAK/UPPER LEVEL POTENTIAL VORTICITY
ANOMALY EXPECTED TO TRACK INTO THE GULF FRIDAY...BUT OVERALL...THEY
ARE IN EXCELLENT AGREEMENT. CONFIDENCE IS VERY HIGH INTO THE WEEKEND.

THE ECMWF...GFS...NAM...AND CANADIAN GLOBAL DETERMINISTIC PREDICTION
SYSTEM WERE FAVORED FOR THIS FORECAST.

.SHORT TERM FORECAST...

SOUTHCENTRAL...
QUIESCENT WEATHER WILL CONTINUE THROUGH THE MIDDLE OF THE WEEK AS
HIGH PRESSURE BUILDS OVER THE REGION. RAIN WILL CONTINUE TO IMPACT
KODIAK ISLAND...WITH OTHERWISE DRY CONDITIONS ELSEWHERE. MID AND HIGH
CLOUDS OVER MAINLAND SOUTHCENTRAL WILL SLOWLY SCATTER OUT THIS
AFTERNOON...WITH PATCHY FOG IN THE BASIN DISSIPATING. BREEZY
NORTHEAST WINDS IN THE MATANUSKA VALLEY...WITH SOUTHEAST WINDS DOWN
TURNAGAIN ARM...WILL DIMINISH WEDNESDAY AS THE PRESSURE GRADIENT
SLACKENS.

THURSDAY EVENING...A STRONG JET STREAK WILL TRACK THROUGH
ALASKA...WITH A BRIEF SHOT OF SNOW...ESPECIALLY ACROSS PARTS OF THE
COPPER RIVER BASIN. THE BIGGER STORY WILL BE INCREASING NORTH TO
NORTHEAST WINDS FRIDAY AND SATURDAY...AND THE POTENTIAL FOR AREAS OF
BLOWING DUST AND SILT ACROSS THE MATANUSKA VALLEY SOUTH INTO
ANCHORAGE.

SOUTHWEST...
SNOW WILL CONTINUE TO IMPACT THE KUSKOKWIM DELTA THROUGH THE
DAY...WITH PERIODS OF RAIN MIXED IN THE AFTERNOON. COASTAL AREAS NEAR
BRISTOL BAY WILL ALSO SEE PERIODS OF RAIN...WITH SNOW IN THE AHKLUN
MOUNTAINS. MOST OF THE LOWER KUSKOKWIM DELTA AND LOCATIONS NEAR THE
ALASKA/ALEUTIAN RANGES WILL SEE STRONG DOWNSLOPE DRYING...WITH BREEZY
SOUTHEAST WINDS. THE FRONT WILL WEAKEN RAPIDLY BY WEDNESDAY
MORNING...WITH A FEW ISOLATED TO SCATTERED RAIN AND SNOW SHOWERS OVER
SOUTHWEST BEFORE DRYING OUT WEDNESDAY EVENING. A POWERFUL COLD FRONT
WILL SWEEP THROUGH THE AREA THURSDAY NIGHT AND FRI...WITH STRONG
NORTHEAST WINDS LASTING THROUGH THE WEEKEND.

BERING SEA/ALEUTIANS/ALASKA PENINSULA...

RAIN WILL IMPACT THE ENTIRE EASTERN BERING SEA AREA...ALASKA
PENINSULA...AND EASTERN ALEUTIANS INTO THIS EVENING BEFORE THE FRONT
FALLS APART AND WEAKENS. THE PRIBILOF ISLANDS WILL SEE SNOW SHOWERS
BEFORE TURNING TO RAIN AND SNOW SHOWERS TONIGHT. HIGH PRESSURE WILL
BUILD OVER THE REGION THURSDAY.

.LONG TERM FORECAST(SATURDAY 8TH - FRIDAY 14TH)...

BY SATURDAY...A DEEP UPPER LOW WILL BE DIVING SOUTHWEST INTO THE
NORTH PACIFIC SOUTH OF THE ALASKA PENINSULA...WITH NORTHERLY FLOW
ALOFT AS A VERY ANOMALOUSLY STRONG CLOSED BLOCKING HIGH OVER THE
BERING SEA EXERTS ITSELF. THE NET EFFECT FOR ALASKA WILL BE A COLD
NORTHEAST OFFSHORE FLOW PATTERN...WITH BREEZY MOUNTAIN GAP WINDS AND
SLOWLY COOLING TEMPERATURES. PRECIPITATION WILL BE RELEGATED TO
KODIAK ISLAND AND THE NORTH GULF COAST...MAINLY ALONG THE EASTERN
KENAI PENINSULA. INTERIOR SOUTHCENTRAL WILL LIKELY REMAIN DRY THROUGH
AT LEAST MONDAY AS DRY NORTHERLY FLOW ALOFT DOMINATES. BLOWING DUST
AND SILT WILL REMAIN A CONCERN THROUGH THE MATANUSKA VALLEY
SOUTH...AS WELL AS HEIGHTENED FIRE WEATHER CONCERNS DUE TO THE DRY
AIR AND BURNABLE FUELS IN THE MAT VALLEY.

MIDWEEK AND BEYOND...THE GFS ENSEMBLE...ECMWF ENSEMBLE...AND NORTH
AMERICAN ENSEMBLE FORECAST SYSTEM (NAEFS) IS STRONGLY HINTING AT A
RETROGRESSION OF THE BERING BLOCK...AND CONTINUED NORTHERLY
FLOW...EVENTUALLY LEADING TO A DEEP UPPER TROUGH OVER SOUTHWEST
ALASKA. SHOULD SUCH A PATTERN UNFOLD...PARTS OF SOUTHERN ALASKA WILL
BEGIN TO SEE INCREASING SNOW CHANCES BY LATE WEEK...WITH CONTINUED
BELOW NORMAL TEMPERATURES. IN ESSENCE...A RETURN TO MORE WINTERY
CONDITIONS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 132 138 150 160 165 170-177 179 180.
         HEAVY FREEZING SPRAY 127.
FIRE WEATHER...NONE.

AHSENMACHER FEB 14