Small Craft Advisory 996, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
549 AM AKST MON DEC 14 2015

.ANALYSIS AND UPPER LEVELS...

THE REMNANTS OF THE ONCE POWERFUL BERING SEA CYCLONE CONTINUES TO
FILL AND WEAKEN...WITH THE NOW 948 HPA STORM FORCE LOW NOW
CENTERED JUST WEST OF NUNIVAK ISLAND. STRONG WEST TO SOUTHWEST
WINDS ARE IMPACTING MUCH OF THE EASTERN BERING SEA/ALEUTIANS AS
WELL AS THE PRIBILOF ISLANDS AND SOUTHWEST COAST. WITH A LONG
SOUTHWEST FLOW FETCH...HIGHER SEAS WILL BRING IN SOME POTENTIAL
COASTAL FLOODING ACROSS PORTIONS OF THE SOUTHWEST COAST FROM CAPE
NEWENHAM TO SOUTH OF NUNIVAK ISLAND. THE ASSOCIATED GALE FORCE
OCCLUDED FRONT IS MOVING THROUGH THE NORTHERN GULF INTO PRINCE
WILLIAM SOUND THIS MORNING...AS INDICATED BY SURFACE OBS AND THE
MIDDLETON ISLAND RADAR. SNOW SHOWERS ARE ALSO FILLING IN ACROSS
NORTHERN COOK INLET INTO ANCHORAGE AS EVIDENCED BY THE KENAI
RADAR. THE EASTWARD FRONTAL PROGRESSION IS BEING DRIVEN BY THE
LEFT EXIT REGION OF A MUCH WEAKENED 120 KT POLAR JET STREAM WHICH
IS MOVING INTO THE YUKON THIS MORNING. FINALLY...A LOW AMPLITUDE
SHORTWAVE TROUGH IS FORMING ALONG THE PERIPHERY/BASE OF THE POLAR
JET SOUTH OF ADAK. THIS FEATURE WILL BE AN IMPORTANT WEATHER MAKER
AS IT MOVES FROM THE NORTH PACIFIC INTO BRISTOL BAY AND PARTS OF
COOK INLET TODAY AND TUESDAY.

&&

.MODEL DISCUSSION...

THE MODELS ARE IN EXCELLENT AGREEMENT WITH THE GENERAL SYNOPTIC
PATTERN HEADING INTO THE WEEKEND. THEY ARE IN OVERALL PRETTY GOOD
AGREEMENT WITH THE PATTERN AND DO NOT DIVERGE UNTIL A COMPACT LOW
RAPIDLY TRANSITS FROM THE NORTH PACIFIC THROUGH BRISTOL BAY AND
INTO SOUTHCENTRAL MONDAY EVENING THROUGH TUESDAY. THIS RAPIDLY
MOVING LOW WILL HAVE IMPACTS ACROSS THE REGIONS...WITH THE
POTENTIAL FOR A QUICK HITTING BURST OF MODERATE TO HEAVIER SNOW
ACROSS BRISTOL BAY. AS IT MOVES INLAND...THE LOW WILL WEAKEN...BUT
THE STREAM OF MOISTURE WILL IMPACT MANY LOCATIONS ACROSS COASTAL
SOUTHCENTRAL WITH THE POSSIBILITY OF ACCUMULATING SNOW...AS WELL
AS THE PRESSURE GRADIENT AND WINDS ACROSS COOK INLET. WITH SUCH AN
UNUSUAL LOW TRACK FROM BRISTOL BAY THROUGH THE LOWER KUSKOKWIM
VALLEY...THERE IS NOT MUCH "PATTERN RECOGNITION" TO SUPPORT SUCH
AN UNUSUAL SOLUTION. MOREOVER...THE MODELS DIFFER ON TIMING AND
STRENGTH OF THIS LOW...WITH THE NAM BEING A STRONGER AND SLOWER
SOLUTION COMPARED TO THE FAST ECMWF/GFS SOLUTIONS. FOR NOW...A
RATHER BROAD APPROACH FAVORING THE SLIGHTLY FASTER AND QUICKER
HITTING SOLUTIONS IS FAVORED.

&&

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

A FRONT THAT BROUGHT STRONG GALES ALONG THE EASTERN GULF OF
ALASKA THIS MORNING IS NOW DISSIPATING ALONG THE COAST AND WINDS
ARE SUBSIDING. SHOWERS ASSOCIATED WITH THIS FRONT CONTINUE TO
LINGER FROM THE GULF OF ALASKA TO THE ANCHORAGE BOWL...BUT THEY
ARE WEAKENING AS WELL. ANOTHER ROUND OF SNOW IS POSSIBLE THIS
EVENING AS AN UPPER LEVEL WAVE PROGRESSES QUICKLY NORTHWARD
ACROSS THE GULF OF ALASKA. FAVORABLE SOUTHWESTERLY SURFACE WINDS
SHOULD BE SUFFICIENT FOR A QUICK BURST OF SNOW...ALTHOUGH THE QUICK
PROGRESSION OF THIS SYSTEM WILL CAUSE ACCUMULATIONS TO REMAIN
LIGHT.

THE WEATHER PATTERN BECOMES MORE UNCERTAIN BEGINNING TUESDAY NIGHT
AS A SURFACE LOW PRESSURE SYSTEM TAKES AN UNUSUAL TRACK INTO THE
KUSKOKWIM VALLEY...AND A WEAKER LOW DEVELOPS IN COOK INLET. WHILE
MORE MOISTURE IS AVAILABLE WITH THIS SYSTEM...DOWNSLOPING IS ALSO
LIKELY TO LIMIT ACCUMULATIONS ACROSS THE ANCHORAGE
BOWL...MATANUSKA VALLEY...AND WESTERN KENAI PENINSULA.

&&

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

A LARGE BERING LOW CENTERED JUST WEST OF NUNIVAK ISLAND WILL
CONTINUE TO SPREAD RAIN AND SNOW SHOWERS ACROSS SOUTHWEST THROUGH
THE DAY TODAY...WITH A CHANGE TO MOSTLY ALL SNOW AS COLDER AIR
BEGINS TO MOVE IN TONIGHT. STRONG SOUTH TO SOUTHWEST WINDS WILL
DIMINISH GREATLY THIS EVENING AND TONIGHT AS THE PRESSURE GRADIENT
WEAKENS. A FAST MOVING COMPACT LOW WILL MOVE INTO BRISTOL BAY
AFTER MIDNIGHT TONIGHT THROUGH TUESDAY MORNING...SPREADING A
SWATH OF SNOW...HEAVY AT TIMES ACROSS THE BRISTOL BAY REGION. THIS
LOW WILL RAPIDLY TRACK INTO THE LOWER KUSKOKWIM VALLEY BY THE LATE
MORNING...THEN CLEARS OUT BY THE EVENING. ACCUMULATING SNOW
FALL IS LIKELY ACROSS BOTH REGIONS...WITH THE POSSIBILITY OF A
RATHER NARROW BUT HEAVY BAND OF SNOW ACROSS THE BRISTOL BAY
REGION. THERE WILL BE A REPRIEVE IN WEATHER TUE NIGHT AS HIGH
PRESSURE SETTLES IN BEHIND THE LOW MOVING OUT OF THE LOWER
KUSKOKWIM VALLEY.

THE LARGE SOUTHWESTERLY SWELL APPROACHING THE KUSKOKWIM DELTA
COAST TO CAPE NEWENHAM COAST WILL BRING HIGH SURF CONDITIONS AND
POSSIBLY SOME MINOR COASTAL FLOODING LATE THIS MORNING THROUGH
THIS EVENING WITH THE COMBINATION OF HIGH TIDES AND STORM SURGE
BRINGING COASTAL WATER LEVELS UP TO 4 TO 5 FEET ABOVE MAXIMUM
ASTRONOMICAL HIGH TIDE. THE VARIABLE ICE COVER ALONG THE COAST
WILL BRING BOTH INCREASED UNCERTAINTY IN THE MAGNITUDE OF THE
IMPACTS AS WELL AS THE POTENTIAL FOR ICE TO BE TOSSED UP ON
BEACHES AND INTO TO ADJACENT LOWLANDS.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

WITH THE GIANT LOW IN THE BERING CONTINUING TO FILL...THE STRONG
WESTERLY WINDS WILL GRADUALLY DIMINISH TODAY AND THEN DROP OFF
MORE RAPIDLY TONIGHT. A SERIES OF SMALLER SHORTWAVES WILL ROTATE
THROUGH THE BERING TUESDAY AND TUESDAY NIGHT KEEPING SHOWERS
ACTIVE BUT WINDS WILL REMAIN LIGHTER AND GENERALLY IN THE 20 TO
30 KT RANGE.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE BERING LOW WILL HAVE WEAKENED AND PUSHED OFF TO THE NORTH
HEADING INTO THE MID TERM LEAVING A SHOWERY PATTERN BEHIND IT. TWO
NEW SYSTEMS WILL APPROACH THE AREA MID TO LATE WEEK. THERE IS
DECENT AGREEMENT WITH THE WESTERN SYSTEM WHICH MOVES INTO THE
WESTERN BERING THURSDAY. THE EC IS A LITTLE BIT FASTER THAN THE
OTHERS BUT FROM AN IMPACTS STANDPOINT THEY ALL HAVE THE FRONT FROM
THIS SYSTEM MAKING IT TO THE WEST COAST FRIDAY. THERE IS MORE
DISAGREEMENT WITH THE LOW APPROACHING KODIAK WEDNESDAY. THE NAM
AND GEM TAKE THE LOW INTO SHELIKOF STRAIT WHILE THE GFS STAYS ON
THE SOUTHEASTERN SIDE OF THE ISLAND WITH THE EC EVEN FURTHER TO
THE SOUTH. THESE DIFFERENT SOLUTIONS OFFER A WIDE VARIATION ON
IMPACTS OF WINDS AND PRECIPITATION FOR THE GULF AND SOUTHCENTRAL
WHICH LEADS TO A LOW CONFIDENCE FORECAST BY LATE WEEK. AN
ENSEMBLE MEAN SOLUTION WAS CHOSEN WHICH HELPED GET A MIDDLE GROUND
SOLUTION THAT BRINGS THE LOW INTO THE SOUTHERN GULF WEDNESDAY
NIGHT.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...COASTAL FLOOD ADVISORY 155 161.
MARINE...STORM WARNING 179.
         HEAVY FREEZING SPRAY 185.
         GALE WARNING 119 120 130 131 132 138 139 150 155 160 165
                      171 172 173 174 175 180 181 185.
&&

SYNOPSIS AND MODEL DISCUSSION...JA
SOUTHCENTRAL ALASKA...EN
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
LONG TERM...DK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
733 AM AKST MON DEC 14 2015

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0732 AM     SNOW             8 NW HOMER              59.72N 151.68W
12/14/2015  M8.0 INCH                           AK   CO-OP OBSERVER

&&

LINGRAM