Gale Warning 909, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
549 AM AKST FRI DEC 18 2015

.ANALYSIS AND UPPER LEVELS...

PROGRESSIVE PATTERN PERSISTS THIS MORNING WITH AN UPPER LEVEL LOW
OVER THE EASTERN GULF AND THE WESTERN BERING...AND AN UPPER RIDGE
OVER THE AKPEN. AT THE SURFACE...A LOW IS SOUTHEAST OF THE GULF
OF AK WITH A VERY WEAK LOW NEAR THE KENAI PENINSULA AND A DEEP LOW
OVER THE WESTERN BERING. A RIDGE IS OVER SW AK AND THE AKPEN. A
STORM FORCE FRONT IS APPROACHING SW AK WITH SNOW AND BLOWING
SNOW. THE FRONT IS ALSO DRAPED ALONG THE ALEUTIANS WITH STORM
FORCE WINDS AND HURRICANE FORCE GUSTS.

&&

.MODEL DISCUSSION...

MODELS REMAIN IN DECENT AGREEMENT THROUGH SAT NIGHT. THE LOW IN
THE SE GULF CONTINUES TO PULL SOUTHEAST AND EXIT THE REGION. A
TRIPLE POINT LOW WILL DEVELOP LATER TONIGHT NEAR KODIAK AND THE
BARREN ISLANDS...WITH THE ASSOCIATED FRONT HEADED TO THE NORTHEAST
GULF COAST BY SAT NIGHT. WHILE THIS IS DEVELOPING...THE FRONT
ALONG THE SW AK COAST WILL DISSIPATE AS IT MOVES INLAND THROUGH
THIS EVENING. THE BERING LOW WILL RACE ACROSS THE BERING AND MOVE
INLAND NEAR NUNIVAK ISLAND SAT NIGHT. FILLING IN THE VOID BEHIND
THIS TRANSIT WILL BE THE NEXT NORTH PACIFIC LOW AND FRONT ENTERING
THE WESTERN BERING SAT NIGHT.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

AS A LOW IN THE GULF OF ALASKA CONTINUES TO DRIFT TO THE
SOUTHEAST...A NEW POTENT FRONTAL SYSTEM IS APPROACHING THE AREA
AND WILL BRING WIDESPREAD PRECIPITATION AND GUSTY WINDS TO
KODIAK BY THIS AFTERNOON...AND MAINLAND ALASKA BY THIS EVENING.
SATELLITE IMAGERY THIS MORNING CONFIRMS THAT THIS FRONTAL SYSTEM
IS STILL TAPPING INTO A RICH MOISTURE SUPPLY FROM THE NORTH PACIFIC
OCEAN. WHILE THE FRONT IS EXPECTED TO TRAVERSE QUICKLY ACROSS
KODIAK ISLAND...IT IS EXPECTED TO DEVELOP A TRIPLE POINT LOW AND
LINGER ALONG THE NORTH GULF COAST THROUGH SATURDAY. THE HEAVIEST
RAIN AND SNOW IS EXPECTED TO OCCUR ALONG THE EASTERN KENAI
PENINSULA DUE TO PERSISTENT ONSHORE FLOW. CURRENTLY AN OFFSHORE
PRESSURE GRADIENT IS EXPECTED TO BRING LOWER SNOW AMOUNTS ACROSS
VALDEZ...BUT ENOUGH SNOW WILL FALL ALONG WITH GUSTY WINDS FOR
BLOWING SNOW THROUGH THOMPSON PASS FRIDAY EVENING THROUGH SATURDAY.
THE PRESSURE GRADIENT WILL ALSO SUPPORT WIDESPREAD DOWNSLOPING AND
LIMIT SNOW ACROSS THE ANCHORAGE BOWL...MATANUSKA VALLEY AND THE
WESTERN KENAI PENINSULA.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A POTENT FRONT IS PUSHING ONSHORE THE MAINLAND EARLY THIS
MORNING...SPREADING SNOW FROM THE COAST TO INLAND AREAS. GUSTY
EASTERLY WINDS WITH THIS SNOW WILL BRING BLIZZARD CONDITIONS TO
THE COAST. WINDS WILL DROP OFF PRETTY QUICKLY THIS AFTERNOON AS
THE FRONT MOVES INLAND. BLIZZARD CONDITIONS WILL LAST THE LONGEST
ALONG THE NORTHERN COAST OF THE KUSKOKWIM DELTA THIS AFTERNOON.
THE SAME FRONT WILL BRING A LITTLE BIT MORE ACCUMULATING SNOW TO
THE GREATER BRISTOL BAY AREA...AREAS OF BLOWING SNOW ARE POSSIBLE
IN THIS AREA AS WELL...MAINLY FROM KOLIGANEK NORTHWARD THIS
AFTERNOON. SNOW WILL LINGER TONIGHT IN THE LOWER KUSKOKWIM VALLEY
AND FROM ILIAMNA NORTHWARD BEFORE THE FRONT WEAKENS AND MOVES OUT
OF THE AREA. THE ASSOCIATED LOW PRESSURE SYSTEM WILL SLOWLY MOVE
CLOSER TO THE MAINLAND AND KEEP A SHOWERY REGIME IN PLACE THROUGH
THE REMAINDER OF THE SHORT TERM FORECAST. EXPECT MODERATING
TEMPERATURES AND WINDS BEYOND TODAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE MOST IMPACTFUL WEATHER THIS MORNING ARE THE HIGH WINDS FOR
SHEMYA AND ADAK. CONTINUED COLD ADVECTION OVER THE WESTERN
ALEUTIANS/BERING SEA WILL DRIVE THESE WINDS IN ADDITION TO THE
DIRECTION BEING MORE FAVORABLE FOR CHANNELED WIND NEAR ADAK.
BEGINNING THIS AFTERNOON WINDS WILL SLOWLY DIMINISH OVER THE
WEEKEND AS THE RESPONSIBLE LOW PRESSURE WEAKENS OVER THE
NORTHERN/EASTERN BERING. OTHERWISE A SHOWERY REGIME WILL PERSIST
THROUGH SUNDAY BEFORE A NEW WEAKER FRONT ENTERS THE WESTERN BERING
SEA.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE BARREN ISLANDS WILL HAVE A TRIPLE POINT LOW DEVELOP ON
SATURDAY WITH AN ASSOCIATED WEATHER FRONT EXTENDING THROUGH THE
CENTRAL GULF. THIS SYSTEM WILL TRANSITION TO THE NORTHERN GULF
BEFORE BECOMING STATIONARY. AN UPSTREAM WEAK LOW PRESSURE SYSTEM
IN THE BRISTOL BAY AREA MOVES INTO THE GULF BY MONDAY. THESE TWO
SYNOPTIC FEATURES WILL PHASE INTO A BROAD AREA OF LOW PRESSURE
OVER THE NORTHERN GULF BEFORE GRADUALLY MOVING TO THE SOUTHEAST BY
MIDWEEK. THE MAJORITY OF THE PRECIPITATION WILL OCCUR ALONG THE
NORTHERN GULF COASTAL COMMUNITIES EXCEPT FOR A BRIEF PERIOD OF
SNOW AND RAIN UP THROUGH THE COOK INLET EXTENDING INTO THE LOWER
MATANUSKA VALLEY ON SATURDAY. THE SOUTHCENTRAL REGION WILL MAINLY
HAVE OFFSHORE WITH NORTHERLY WINDS BY EARLY NEXT WEEK AND
TEMPERATURES WILL BE COOLER WITH COLDER AIR FILTERING IN FROM THE
NORTH.

MEANWHILE THE CENTRAL TO NORTHERN BERING SEA WILL HAVE A STORM
FORCE LOW POSITIONED NORTH OF SAINT PAUL ON SATURDAY. THIS WILL
BRING WIDESPREAD WESTERLY GALE FORCE WINDS IN THE LOWER BERING SEA
SPREADING INTO THE ALEUTIAN CHAIN. BY SUNDAY THIS SYSTEM WILL BE
CROSSING THROUGH THE BRISTOL BAY REGION BEFORE ENTERING THE GULF.
WHILE A GALE FORCE LOW DROPS DOWN FROM THE KAMCHATKA PENINSULA
WITH A SECONDARY LOW FORMING OVER THE WESTERN BERING SEA. THIS
SYSTEM BECOMES ELONGATED ALONG THE ALEUTIANS PRODUCING SHOWERS AND
GUSTY WINDS ALONG THE CHAIN AND THE LOWER BERING SEA. THE MODELS
ARE STRUGGLING WITH THIS COMPLEX SYSTEM AND FORECAST CONFIDENCE IS
LOW GOING INTO THE EARLY PART OF NEXT WEEK. THE JET IS ZONAL
DURING THIS TIMEFRAME AND WILL MOVE THIS SYSTEM INTO THE NORTH
PACIFIC. BY WEDNESDAY AN UPPER LEVEL CLOSED LOW FORMS OVER WESTERN
ALEUTIANS. THE MODELS ARE HAVING DIFFICULTY WITH THE STRENGTH AND
PLACEMENT OF THIS DEVELOPING LOW BEFORE ENTERING THE BERING SEA BY
MIDWEEK.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...BLIZZARD WARNING 155
         HIGH WIND WARNING 187 191

MARINE...HEAVY FREEZING SPRAY 185
         STORM 173 175 176 177 178 179 185 411 412 413 414
         GALES 119 120 130 131 132 150 155 165 170 171 172
         174 180 181

&&

SYNOPSIS AND MODEL DISCUSSION...DS
SOUTHCENTRAL ALASKA...EN
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ML
LONG TERM...PD