Small Craft Advisory 109, NWS Anchorage, AK

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

.ANALYSIS AND UPPER LEVELS...
HIGH PRESSURE REMAINS SPRAWLED ACROSS NORTHWEST CANADA AND MUCH OF
INTERIOR ALASKA...LEADING TO SUNNY AND COLD CONDITIONS ACROSS MUCH OF
SOUTHCENTRAL AND POINTS NORTH OF THE ALASKA RANGE. ANOTHER STRONG
RIDGE IS BEGINNING TO BUILD OVER THE WESTERN BERING. BETWEEN THESE
SYSTEMS IS A BROAD AND DISORGANIZED UPPER TROUGH OVER THE NORTH
PACIFIC WITH DEEP MOISTURE AND PRECIPITATION OVER THE EASTERN
ALEUTIANS THAT IS ALSO BEING SQUEEZED NORTHWARD UP THE WEST COAST OF
ALASKA. THIS IS FALLING AS RAIN AT MOST LOCATIONS...WITH THE
EXCEPTION OF THE COAST OF THE KUSKOKWIM DELTA WHERE TEMPERATURES
REMAIN COLD ENOUGH FOR SNOW. SATELLITE IMAGERY SHOWS THIS AREA OF
UNSETTLED WEATHER ERODING FROM BOTH THE EAST AND THE WEST SIDES AS
THE AFOREMENTIONED HIGH PRESSURE CENTERS EXPAND TOWARD EACH OTHER. AT
THE SURFACE...GENERALLY LIGHT OFFSHORE WINDS CONTINUE ALONG THE GULF
COAST AS COLD AIR CONTINUES TO DRAIN OFF THE ALASKAN LANDMASS. OUT
WEST...WIDESPREAD MARINE FOG AND STRATUS CONTINUE ACROSS THE BERING
SEA UNDER NEUTRAL TEMPERATURE ADVECTION AND A LOW-LEVEL TEMPERATURE
INVERSION.

.MODEL DISCUSSION...
THE MODELS REMAIN IN VERY GOOD SYNOPTIC AGREEMENT THROUGH EARLY NEXT
WEEK AND PAINT A PICTURE OF HIGH PRESSURE STRENGTHENING NEAR THE
BERING STRAIT AND RESULTING COLD NORTHERLY FLOW ACROSS MAINLAND
ALASKA. THE BIGGEST ISSUE AMONG THE MODELS REMAIN THE DETAILS OF THE
UPPER LOW EXPECTED TO DROP DOWN THE FRONT OF THE LONGWAVE RIDGE
THURSDAY AFTERNOON. THE NAM AND EC ARE ON THE SAME PAGE IN CARRYING
THE UPPER WAVE INITIALLY JUST TO THE EAST OF THE ALCAN BORDER BEFORE
IT RAPIDLY REDEVELOPS IN THE WESTERN GULF. THE GFS HAS BEEN FAIRLY
CONSISTENTLY FURTHER WEST BOTH WITH THE UPPER LOW IN THE INTERIOR AS
WELL AS THE NEW LOW POSITION THAT WILL SPIN UP IN THE GULF. AT THIS
POINT THE PREFERENCE IS TOWARD THE EC/NAM FURTHER EAST
SOLUTION...THOUGH WOULD NOT BE SURPRISED IF THE FINAL SOLUTION IS A
TOUCH FURTHER WEST THAN THE CURRENT EC/NAM. THE BIGGEST IMPACT FROM
THIS EVOLUTION WILL BE AN ABRUPT MOVEMENT OF ARCTIC AIR DOWN INTO
SOUTHERN ALASKA FROM THE INTERIOR. THIS ALONE WILL SIGNIFICANTLY
INCREASE GAP WINDS AROUND THE GULF COAST REGION....WHICH WILL BE
PROLONGED AND ENHANCED EVEN MORE BY A TIGHTENING SURFACE PRESSURE
GRADIENT AS THE LOW IN THE GULF RAPIDLY INTENSIFIES ON FRIDAY.

.SHORT TERM FORECAST...
SOUTHCENTRAL...SUNNY SKIES ARE GRADUALLY SPREADING WESTWARD AS THE
AFOREMENTIONED UNSETTLED WEATHER OVER SOUTHWEST ALASKA IS SQUEEZED
OUT BY STRENGTHENING HIGH PRESSURE. KODIAK ISLAND WILL CONTINUE TO BE
THE ONLY LOCATION SEEING WINDS AND RAIN FROM THIS SYSTEM...AND EVEN
THERE CONDITIONS WILL IMPROVE MARKEDLY BY WEDNESDAY MORNING.
WEDNESDAY WILL BE ANOTHER BEAUTIFUL DAY ACROSS MUCH OF THE AREA...AS
LITTLE MORE THAN SOME MID AND HIGH-LEVEL CLOUDS MOVE IN FROM THE
NORTHWEST. BY THURSDAY AFTERNOON CLOUDS WILL THICKEN WITH A FEW
SNOWFLAKES POSSIBLE ACROSS THE REGION BEFORE SIGNIFICANTLY COLDER AND
DRIER AIR OVERTAKES THE REGION FROM THE NORTH THURSDAY NIGHT. AT THIS
POINT IT LOOKS LIKE STRONGEST WINDS WILL LIKELY BE FOUND IN THE
MATANUSKA VALLEY...WHERE GUSTY WINDS COUPLED WITH DRY CONDITIONS AND
LACK OF SNOWCOVER NOW LOOK INCREASINGLY LIKELY TO CREATE DANGEROUS
FIRE WEATHER CONDITIONS THURSDAY NIGHT AND FRIDAY. CONFIDENCE IS
LOWER THAT COASTAL SECTIONS OF THE WESTERN KENAI PENINSULA WILL SEE
STRONG WINDS...THOUGH THIS WILL NEED TO WATCHED VERY CLOSELY AS BARE
GROUND IN MANY AREAS COULD CREATE DANGEROUS FIRE WEATHER CONDITIONS
THERE AS WELL. WINDS WILL ALSO INCREASE THROUGH THOMPSON PASS AND
EVEN IN TOWN IN VALDEZ THURSDAY EVENING AS THE COLD AIR ARRIVES IN A
HURRY.

SOUTHWEST...RAIN AND SNOW ALONG THE COAST WILL GRADUALLY DIMINISH
THROUGH WEDNESDAY MORNING AS EVERY LAST DROP OF RAIN (OR SNOW ALONG
THE DELTA COAST) IS SQUEEZED OUT OF THE AIRMASS BY HIGH PRESSURE TO
THE WEST AND TO THE EAST. BY TOMORROW AFTERNOON INCREASING BREAKS OF
SUNSHINE WILL SPREAD THROUGH THE AREA AND PERSIST THROUGH THURSDAY.
OVERALL FLOW WILL BECOME DRIER AND OFFSHORE WEDNESDAY EVENING AND
THURSDAY BEFORE INTENSIFYING RAPIDLY THURSDAY EVENING AS THE
AFOREMENTIONED COLD AIR ARRIVES THURSDAY NIGHT. BY FRIDAY
MORNING...MUCH OF THE DELTA AND BRISTOL BAY ZONES WILL BE NEAR
STRONG-WIND THRESHOLDS AND BELOW-ZERO WINDCHILLS.

BERING SEA AND ALEUTIANS...WITH HIGH PRESSURE BUILDING INTO THE AREA
THROUGH THE WEEKEND CONDITIONS WILL REMAIN RELATIVELY BENIGN.
TEMPERATURES WILL REMAIN ABOVE NORMAL AND WIDESPREAD LOW CLOUDINESS
WILL CONTINUE THROUGH THE NEXT SEVERAL DAYS. COLD COMING OFF THE
ALASKAN LANDMASS WILL LEAD TO INCREASED SHOWER ACTIVITY AND GUSTY
WINDS OVER THE EASTERN BERING SEA BY THIS WEEKEND...WHILE THE REST OF
THE REGION REMAINS MOSTLY DRY WITH LIGHT WINDS.

.LONG TERM FORECAST FROM PREVIOUS DISCUSSION...

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 TYPICAL
WINTER CONDITIONS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 173 174 175 176 177
FIRE WEATHER...FIRE WEATHER WATCH 111 121

AMD/JA/MSO FEB 14