Small Craft Advisory 1025, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
514 PM AKST THU DEC 24 2015

.ANALYSIS AND UPPER LEVELS...

UPPER LEVELS...A HIGHLY AMPLIFIED PATTERN HAS DEVELOPED ACROSS
SOUTHERN ALASKA THIS AFTERNOON. A STRONG VERTICALLY STACKED LOW
OVER THE WEST CENTRAL BERING IS EVIDENT ON SATELLITE IMAGERY. THE
ASSOCIATED UPPER LEVEL LOW CURRENTLY EXTENDS SOUTHEAST AS AN UPPER
LEVEL TROUGH THAT IS BECOMING MORE NEGATIVELY TILTED. THE FRONT
IS ALSO CLEARLY EVIDENT ON SATELLITE IMAGERY AS THE TRANSITION
ZONE BETWEEN THE HIGH CLOUDS RAPIDLY MOVING NORTH AHEAD OF THE
FRONT TO RELATIVELY CLEAR SKIES WITH MORE CONVECTIVE CUMULUS
BEHIND IT. THIS FRONT EXTENDS SOUTH WELL INTO THE NORTH PACIFIC.
THE STRONG DIVERGENCE AHEAD OF THE FRONT IS CAUSING RAPID
CYCLOGENESIS JUST SOUTH OF THE EASTERN ALEUTIANS. THE MERGING OF
THE TWO LOWS TONIGHT HAS BEEN THE FORECAST CHALLENGE.

THE DIGGING TROUGH AND FRONT OVER THE BERING AND NORTH PACIFIC AND
THEIR ASSOCIATED LOWS HAVE BROUGHT A SLUG OF WARM AIR NORTH ON THE
STRONG SOUTHERLY WINDS...HELPING BUILD THE UPPER LEVEL RIDGE
NORTHWARD. ANCHORAGES 12Z SOUNDING HAD PEAK WINDS OF 140 KT AT 300
MB THIS MORNING...AS THE RIDGE PUSHED A DEVELOPING JET STREAK ON
THE EAST SIDE OF THE RIDGE NORTH ACROSS SOUTHCENTRAL ALASKA. THE
WARM AIR ALOFT ASSOCIATED WITH THE RIDGE HAS WARMED THE UPPER
LEVELS AT NEAR EXORBITANT RATES...AS BETWEEN ANCHORAGES 00Z AND
12Z SOUNDINGS...500 MB TEMPERATURES HAVE WARMED BY A FULL 8C.

SURFACE ANALYSIS...FOR SOUTHCENTRAL ALASKA...COLD POLAR AIR
REMAINS IN PLACE ACROSS THE ENTIRE AREA AS THE WARM AIR ALREADY
OVER THE ENTIRETY OF SOUTHCENTRAL HAS YET TO REACH THE SURFACE.
EVEN THE USUAL WARMER SPOTS LIKE KODIAK AND HOMER ARE BOTH BELOW
FREEZING. POLAR HIGH PRESSURE OVER THE INTERIOR IS THE
CULPRIT...KEEPING FRESH COLD AIR MOVING THROUGH ALL OF
SOUTHCENTRAL ON LIGHT NORTHERLY WINDS. THE LOW LEVELS OF THE
ATMOSPHERE REMAIN NEARLY SATURATED AROUND ANCHORAGE. DESPITE THE
VERY DRY LAYER OF AIR ABOVE THE INVERSION...THE MOISTURE HAS BEEN
CAUSING FLURRIES AROUND THE ANCHORAGE BOWL. DUE TO THE NEARLY SATURATED
AIR NEAR THE SURFACE BEING ONLY ABOUT 1500 FEET THICK...NOTHING
HEAVIER THAN THAT IS POSSIBLE.

OVER SOUTHWEST ALASKA...THE WARM AIR HAS BEEN STEADILY ADVANCING
NORTH INTO THE BRISTOL BAY AREA...SUCCESSFULLY SCOURING OUT THE
COLD AIR THAT WAS THERE AS RECENTLY AS A FEW HOURS AGO. THE STRONG
WIND AND SNOW PRODUCED BLIZZARD CONDITIONS ALONG THE THE COAST OF
THE KUSKOKWIM DELTA THROUGHOUT THIS MORNING INTO THIS AFTERNOON. STEADY
SNOW WAS FALLING IN BETHEL AND ANIAK AS THE WARM FRONT ASSOCIATED
WITH THE BERING STORM MOVED NORTH. FRICTION AND A WEAKENING PRESSURE
GRADIENT AS ONE GOES NORTH AND EAST ARE KEEPING THE STRONGER WINDS
TOWARDS COASTAL COMMUNITIES AND OUT OVER THE BERING.

OVER THE BERING...THE STORM THAT HAS BEEN IMPACTING THE BERING FOR
THE PAST FEW DAYS NOW CONTINUES TO DRIFT OVER THE WESTERN BERING.
WEST OF THE LOW...SHEMYA HAS BEEN REPORTING WIND GUSTS TO 70 MPH
WITH VISIBILITIES OCCASIONALLY DROPPING BELOW A MILE IN SNOW. EAST
OF THE STORM...GUSTS HAVE REACHED 40 TO 45 MPH. ALSO TEMPERATURES
HAVE WARMED INTO THE 30S AND 40S AS WARMER PACIFIC AIR IS DRAWN
NORTHWARD.

&&

.MODEL DISCUSSION...

A WIDE SPREAD IN THE MODEL SOLUTIONS REMAINS CONCERNING THE
EVENTUAL TRACK OF THE SECONDARY LOW HEADING FOR THE EASTERN
ALEUTIANS/SOUTHERN ALASKA PENINSULA. A NUMBER OF THE MODELS BRING
THE CENTER OF THE LOW NORTH OF THE ALASKA PENINSULA INTO THE
EASTERN BERING TOMORROW MORNING. WE WILL CONTINUE TO GO WITH THE
CENTER OF THE LOW REMAINING ALONG OR SOUTH OF THE ALASKA
PENINSULA...REMAINING CLOSER TO THE UPPER LEVEL FORCING AND
BAROCLINICITY ALONG WHICH THE LOW FORMED. THIS SOLUTION IS CLOSER
TO THE ENSEMBLE MEAN OF THE MODELS. THE MODEL SPREAD IS
CONSIDERABLY LESS OVER THE GULF...AS THE FRONT ASSOCIATED WITH THE
LOW TRACKS ACROSS THE GULF AND ONTO THE COAST...REGARDLESS OF THE
TRACK OF THE LOW CENTER. CONFIDENCE REMAINS SOMEWHAT BELOW NORMAL
REGARDING THE EVENTUAL TRACK OF THE LOW NEAR THE ALASKA
PENINSULA...BUT HIGHER OVER SOUTHCENTRAL ALASKA.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
A MUCH MORE ACTIVE WEATHER PATTERN WILL RETURN TO SOUTHCENTRAL
AK ON CHRISTMAS DAY AS A STRONG WARM FRONT ASSOCIATED WITH THE LOW
IN THE BERING SEA MOVES INTO THE GULF ACCOMPANIED BY STORM FORCE WINDS
AND HEAVY PRECIPITATION. THE MOST SIGNIFICANT IMPACTS FROM THIS
SYSTEM WILL BE FELT OVER PORTIONS OF WESTERN PRINCE WILLIAM SOUND
BEGINNING LATE FRIDAY MORNING AND LASTING THROUGH FRIDAY NIGHT AS
THE FRONT ARRIVES ALONG THE GULF COAST...BRINGING HEAVY SNOW TO
THE EASTERN KENAI PENINSULA. SNOW WILL BEGIN TO MIX WITH RAIN
DURING THE AFTERNOON ALONG THE COAST AS TEMPERATURES GRADUALLY
RISE ABOVE FREEZING...BUT INLAND LOCATIONS WILL CONTINUE TO SEE
ALL SNOW THROUGH FRIDAY NIGHT...WITH ACCUMULATIONS ON THE ORDER
OF 14-30 INCHES LIKELY BY EARLY SATURDAY MORNING. IN ADDITION TO
THE VISIBILITY REDUCTIONS THAT WILL LIKELY RESULT FROM HEAVY
FALLING SNOW...STRONG GAP WINDS WILL ALSO PRODUCE AREAS OF BLOWING
SNOW ACROSS THE PORTAGE VALLEY AND EASTERN TURNAGAIN ARM...FURTHER
REDUCING VISIBILITIES IN THESE AREAS. GIVEN THE SIGNIFICANT TRAVEL
IMPACTS THAT WILL ACCOMPANY THESE CONDITIONS...THE WINTER STORM
WATCH HAS BEEN UPGRADED TO A WINTER STORM WARNING WITH ISSUANCE OF
THE AFTERNOON FORECAST PACKAGE. MEANWHILE...THE IMPACTS OF THIS
SYSTEM WILL BE MUCH MORE MINIMAL ACROSS INTERIOR PORTIONS OF
SOUTHCENTRAL AK...WITH STRONG DOWNSLOPE FLOW KEEPING THE
ANCHORAGE BOWL AND THE MAT-SU REGION MOSTLY DRY THROUGH FRIDAY
NIGHT.

&&

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

A POTENT WARM FRONT CONTINUES TO PUSH ACROSS SOUTHWEST ALASKA THIS
AFTERNOON AS EVIDENT ON SURFACE OBSERVATIONS ACROSS THE BRISTOL
BAY AREA AND THE KUSKOKWIM DELTA. BLIZZARD CONDITIONS ACROSS THE
KUSKOKWIM DELTA HAVE TAPERED OFF AS TEMPERATURES HAVE BEGUN TO
WARM NEAR FREEZING AND PRECIPITATION INTENSITY BEGINS TO DECREASE.
THE SFC PRESSURE GRADIENT WILL REMAIN STRONG ACROSS SOUTHWEST
ALASKA AS HIGH PRESSURE CONTINUES TO BUILD ACROSS THE EASTERN HALF
OF ALASKA THROUGH FRIDAY. THIS WILL ALLOW FOR AREAS OF BLOWING
SNOW TO CONTINUE ALONG THE COAST OF THE KUSKOKWIM DELTA UNTIL
PRECIPITATION TAPERS OFF THIS EVENING. ANOTHER SHOT OF SNOW (MIXED
WITH RAIN SOUTH OF BETHEL) WILL BE SEEN ACROSS THE DELTA CHRISTMAS
DAY AND WILL BE ACCOMPANIED BY WIND OF 30 TO 45 MPH WITH SOME
STRONGER GUSTS. HOWEVER...WITH TEMPERATURES HOVERING NEAR
FREEZING...NEITHER BLOWING SNOW OR BLIZZARD CONDITIONS ARE EXPECTED
AT THIS TIME.

ATTENTION WILL TURN TO THE ALASKA PENINSULA AND BRISTOL BAY AREA
ON CHRISTMAS DAY AS A DEVELOPING LOW IN THE NORTH PACIFIC WILL ACT
TO TIGHTEN THE AFOREMENTIONED PRESSURE GRADIENT EVEN MORE. THE
GRADIENT WILL ALIGN ACROSS THE ALASKA PENINSULA IN A FAVORABLE
SOUTHEAST DIRECTION EARLY FRIDAY MORNING THAT WILL ALLOW WINDS TO
BLOWN STRONGLY THROUGH THE CHANNELED TERRAIN. THE TRACK OF THE LOW
BRINGS THE LOW NEAR COLD BAY...WHICH WOULD KEEP THE STRONGEST
WINDS EAST OF COLD BAY AND CLOSER TO THE SHUMAGIN ISLANDS AND
FURTHER EAST. BY LATE FRIDAY MORNING...THE FRONT ASSOCIATED WITH
THIS LOW WILL MOVE ACROSS THE BRISTOL BAY AREA AND PROVIDE THE
FAVORABLE EASTERLY DIRECTION TO LET WINDS BLOW THROUGH THE GAPS OF
THE ALEUTIAN RANGE. WIND GUSTS OF 70 TO 80 MPH WILL BE POSSIBLE
THROUGH CHANNELED TERRAIN EAST OF COLD BAY....THE GAPS OF THE
ALASKA RANGE AND THE WESTERN CAPES OF THE BRISTOL BAY ZONE.

CONDITIONS BEGIN TO IMPROVE HEADING INTO THE WEEKEND AS THE LOW
NEAR COLD BAY SHIFTS SOUTH AND EAST AND THE PRESSURE GRADIENT
RELAXES. TEMPERATURES WILL BEGIN TO COOL DOWN ON SATURDAY BUT
REMAIN ABOVE NORMAL.

&&

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

THE UNSETTLED WEATHER PATTERN ACROSS THE BERING SEA WILL CONTINUE
THROUGH CHRISTMAS. THE STORM FORCE LOW OVER THE WESTERN BERING SEA
WILL CONTINUE TO GRADUALLY WEAKEN THROUGH THE NIGHT BEFORE MERGING
WITH THE RAPIDLY DEVELOPING LOW IN THE NORTH PACIFIC. THIS INFLUX
OF ENERGY WILL CREATE A SWATH OF STORM FORCE WINDS NEAR THE CENTRAL
ALEUTIANS ON FRIDAY AND THE FRONT ASSOCIATED WITH THE DEVELOPING
LOW WILL BRING STORM FORCE WINDS TO THE COASTAL WATERS OF THE WEST
COAST. A LARGE SLUG OF WARM AIR WILL BE ADVECTED NORTHWARD LEAVING
MUCH OF THE BERING SEA TO SEE PERIODS OF MODERATE TO HEAVY
RAINFALL. THE WESTERN ALEUTIANS WILL REMAIN ON THE COLD SIDE OF
THE LOW WITH GOOD COLD AIR ADVECTION COMING FROM RUSSIA WHICH WILL
KEEP THE PRECIPITATION TYPE AS SNOW. AS THE LOW BEGINS TO DROP
SOUTH LATE FRIDAY...CONDITIONS WILL RAPIDLY IMPROVE ACROSS THE
BERING SEA AS WINDS TAPER OFF AND PRECIPITATION TRANSITIONS TO A
MORE SHOWERY REGIME.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
AN ACTIVE PATTERN IS EXPECTED TO CONTINUE INTO NEXT WEEK WITH
MULTIPLE LOWS COMING UP FROM THE SOUTH BRINGING WARMER CONDITIONS
TO THE STATE. TEMPERATURES OVER THE SOUTHERN MAINLAND AND
SOUTHWEST ALASKA LOOK TO BE AT OR ABOVE NORMALS FOR MUCH OF NEXT
WEEK. WITH THE MULTIPLE LOWS MOVING INTO THE AREA THERE IS
DISAGREEMENT AMONGST THE MODELS ON HOW THEY TRACK THROUGH THE AREA
AND HOW MUCH SNOW/RAIN THEY WILL BRING. BECAUSE OF THIS THE
ENSEMBLE MEANS WERE USED. THEY ARE MUCH CLOSER TOGETHER THAN THE
OPERATIONAL RUNS WITH THE LOW CENTERS SO EVEN THOUGH CONFIDENCE IS
LOW FOR SOME TIMING ISSUES WITH THE LOWS...THERE IS HIGHER
CONFIDENCE IN THE CONTINUING ACTIVE PATTERN.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WARNING...161 181
         WINTER STORM WARNING...125
MARINE...GALE...120 125 136 137 139 141 171 179 181 185 412
         STORM...119 130-132 138 150 155 160 165
                 170 172-178 180 351 352 411 413 414
         HVY FRZG SPRAY 181 185.

&&

SYNOPSIS AND MODEL DISCUSSION...JW
SOUTHCENTRAL ALASKA...CB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MC
LONG TERM...DK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
258 AM AKST FRI DEC 25 2015

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

0216 AM     NON-TSTM WND GST ADAK STATION            51.84N 176.64W
12/25/2015  M107 MPH                            AK   AWOS

&&

JAHSENMA

PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
307 AM AKST FRI DEC 25 2015

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

0206 AM     NON-TSTM WND GST PORT HEIDEN             56.96N 158.59W
12/25/2015  M72.00 MPH                          AK   AWOS

0216 AM     NON-TSTM WND GST ADAK STATION            51.84N 176.64W
12/25/2015  M107 MPH                            AK   AWOS

0258 AM     NON-TSTM WND GST PLATINUM                59.01N 161.81W
12/25/2015  M71.00 MPH                          AK   AWOS

&&

KUTZ

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
313 AM AKST FRI DEC 25 2015

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

0228 AM     NON-TSTM WND GST PORT HEIDEN             56.96N 158.59W
12/25/2015  M74 MPH                             AK   AWOS

0240 AM     NON-TSTM WND GST PLATINUM                59.01N 161.81W
12/25/2015  M74 MPH                             AK   AWOS

&&

KUTZ