Small Craft Advisory 1038, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
447 PM AKST MON DEC 28 2015

.ANALYSIS AND UPPER LEVELS...

A HIGHLY AMPLIFIED PATTERN IS IN PLACE ACROSS MAINLAND ALASKA WITH
STRONG SOUTHERLY FLOW BRINGING WARM AIR NORTHWARD INTO THE AREA.
AN IMPRESSIVELY STRONG FRONT IS AFFECTING SOUTHERN ALASKA...WITH
THE FRONTAL POSITION AT MIDDAY MONDAY STRETCHING FROM THE LOWER
KUSKOKWIM VALLEY ACROSS THE ALASKA RANGE TO ANCHORAGE AND NORTHERN
PRINCE WILLIAM SOUND. WARNING LEVEL WINDS HAVE BEEN OBSERVED ALONG
THE LENGTH OF TURNAGAIN ARM...WITH BLIZZARD CONDITIONS THROUGH
THOMPSON PASS AND HEAVY SNOW OVER PORTIONS OF THE SUSITNA VALLEY.
WARM AIR HAS CHANGED PRECIPITATION TO RAIN FROM THE MATANUSKA
VALLEY SOUTHWARD (INCLUDING ANCHORAGE) WITH GUSTY SOUTHERLY WINDS
AND TEMPERATURES SOARING INTO THE 40S IN MANY LOCATIONS.

WEST OF THE ALASKA RANGE...THE ENTIRE BERING AND ALEUTIAN REGION
ALONG WITH THE SOUTHWEST MAINLAND IS UNDER THE INFLUENCE OF A
SPRAWLING LOW PRESSURE SYSTEM ANCHORED IN THE SOUTHERN BERING.
THIS FEATURE HAS MULTIPLE VIGOROUS SHORTWAVES ALOFT SPINNING
AROUND IT...WITH MULTIPLE SURFACE CIRCULATION CENTERS AS WELL. AT
PRESENT...THE MOST IMPRESSIVE OF THESE IS SHORTWAVE/FRONT
AFFECTING THE EASTERN ALEUTIANS AND ALASKA PENINSULA WITH GALE
FORCE WINDS AND RAIN. OTHER LOCATIONS ARE SEEING MORE SHOWERY
CONDITIONS...MOSTLY IN THE FORM OF RAIN IN THE MARITIME AREAS AND
SNOW OVER INLAND PORTIONS OF SOUTHWEST ALASKA.

&&

.MODEL DISCUSSION...

MODELS ALL NOW DEPICT THE TRAILING SHORTWAVE THAT IS EXPECTED TO
MOVE THROUGH THE SUSITNA VALLEY TONIGHT...PROLONGING THE SNOW
EVENT THERE. MODEL DISAGREEMENT INCREASES BY TUESDAY
NIGHT/WEDNESDAY REGARDING THE NEXT STORM THAT WILL BE
STRENGTHENING AND MOVE NORTHWARD ALONG THE COAST OF THE SOUTHWEST
MAINLAND. THE NAM IS STILL THE FASTEST...BUT IS GRADUALLY SLOWING
DOWN WITH EACH SUCCESSIVE MODEL RUN. THE GFS IS STILL THE
STRONGEST/DEEPEST SOLUTION BY A WIDE MARGIN. THE 12Z ECMWF IS A
GOOD COMPROMISE BETWEEN THE TWO...WITH A POSITION FURTHER WEST
THAN THE NAM...WHICH MAKES SENSE BASED ON LONGWAVE TROUGH/ANCHOR
LOW POSITION IN THE BERING SEA...BUT A MORE MODERATE STRENGTH THAT
AT THIS TIME IS A BETTER TREND-FIT FOR THE FORECAST. IT IS WORTH
NOTING THAT ALL SOLUTIONS ARE SLOWLY TRENDING STRONGER WITH THIS
STORM...WHICH WILL LIKELY STILL BE STRENGTHENING AS IT AFFECTS THE
COMPLEX TERRAIN OF SOUTHERN ALASKA LATE TUESDAY NIGHT INTO
WEDNESDAY MORNING. OVERALL...THE ECMWF IS THE PREFERRED MODEL AND
IS BEING USED IN THE GENERATION OF THE AFTERNOON FORECASTS.

&&

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

AS THE FRONT CONTINUES MOVING INLAND TONIGHT IT WILL BRING RAIN
SHOWERS TO COASTAL LOCATIONS AND AS FAR NORTH AS TALKEETNA. NORTH
OF TALKEETNA WILL REMAIN SUFFICIENTLY COLD FOR SNOW...WHICH WILL
ALSO FALL JUST NORTH OF THE CHUGACH MOUNTAINS IN THE COPPER RIVER
BASIN. ON TUESDAY PRECIPITATION WILL BE LIMITED TO SNOW IN THE
MORNING OVER THE NORTHERN SUSITNA VALLEY WITH LINGERING SNOW
SHOWERS OVER PORTIONS OF THE CHUGACH AND WRANGELL MOUNTAINS. ON TUE
AFTERNOON THE NEXT FRONT ENTERS THE GULF AND THEN REACHES THE
NORTH GULF COAST BY WED AFTERNOON. IN THE PROCESS IT WILL CAUSE WINDS
TO INCREASE ALONG THE LENGTH OF TURNAGAIN ARM AND PORTAGE VALLEY.
HIGH WIND WATCHES HAVE BEEN ISSUED FOR POSSIBLY DANGEROUS WINDS
THROUGH THIS AREA TUE NIGHT THROUGH MIDDAY WED. OTHERWISE MUCH OF
THE PRECIPITATION ASSOCIATED WITH THIS SECOND FRONT WILL BE IN THE
FORM OF RAIN THROUGH WED AFTERNOON.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE FRONTAL SYSTEM OVER BRISTOL BAY WILL CONTINUE TO PUSH INLAND
THIS AFTERNOON AND EVENING QUICKLY REPLACING THE PREVIOUS FRONT
NOW LIFTING NORTH OUT OF SOUTHWEST ALASKA INTO INTERIOR ALASKA.
MOISTURE WILL REMAIN STRETCHED ACROSS SOUTHWEST ALASKA WITH A
DEFORMATION BAND OF ENHANCED PRECIPITATION STRETCHED ACROSS THE
AHKLUN...KILBUCK AND KUSKOKWIM MOUNTAINS THROUGH TUESDAY AS THE
FRONT IS SHEARED APART BY ITS PARENT LOW LIFTING NORTH AND A NEW
FRONTAL WAVE RAPIDLY DEEPENING TO THE SOUTH.

THE NEXT STRONG AREA OF LOW PRESSURE WILL LIFT UP FROM THE SOUTH
TUESDAY NIGHT...CROSSING THE ALASKA PENINSULA AND MOVING INTO
BRISTOL BAY WEDNESDAY MORNING. WHILE MODELS DIFFER ON THE PRECISE
TRACK OF THE LOW AND CENTRAL PRESSURE...ALL ARE STILL DEEPENING
THE LOW AS IT CROSSES BRISTOL BAY...WHICH GIVEN ITS TRACK FROM
ROUGHLY PORT MOLLER TO CAPE NEWENHAM MAKES HIGH WINDS A DEFINITE
CONCERN FOR THE BRISTOL BAY AREA. INITIALLY EAST WINDS ALONG THE
WESTERN SLOPES OF THE ALEUTIAN RANGE WILL BE FAVORED ESPECIALLY
NEAR GAPS AND PASSES. ONCE THE LOW PASSES BY...WINDS WILL RAPIDLY
SHIFT TO THE SOUTH TO SOUTHWEST WITH A TIGHT PRESSURE GRADIENT AND
STRONG PRESSURE RISES FAVORING THE STRONGEST WINDS TO OCCUR ALONG
AND NEAR THE NORTHERN BRISTOL BAY COAST. WHILE THE STRONGEST WINDS
WILL BE FAIRLY SHORT LIVED AT ANY GIVEN LOCATION...DUE TO THE
RAPID PROGRESS OF THE LOW THEY ARE EXPECTED TO IMPACT MOST ALL OF
THE BRISTOL BAY ZONES DURING SOME PORTION OF THE LOWS PASSAGE.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
INDIVIDUAL AREAS OF LOW PRESSURE CONTINUE TO ROTATE AROUND THE
LARGE UPPER LEVEL LOW CENTERED OVER THE BERING. THE LOW CURRENTLY
OVER THE CENTRAL ALEUTIANS WILL LIFT NORTH UP TOWARDS THE PRIBILOF
ISLANDS THROUGH TUESDAY MORNING...THEN CONTINUE TO FILL AND WEAKEN AS
IT TRACKS NORTHEAST TUESDAY AND TUESDAY NIGHT. ADDITIONAL COOL
SHOWERY TROUGHS WILL ROTATE ACROSS THE ALEUTIANS THROUGH MIDWEEK
BUT REMAIN LESS ORGANIZED.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

AN UNSEASONABLE WEATHER PATTERN LOOKS TO CONTINUE THROUGH THE
REMAINDER OF THE WEEK AS A HIGHLY AMPLIFIED TROUGH OVER THE BERING
SEA CONTINUES TO PUSH WARM SYSTEMS FROM THE SUBTROPICS UP TOWARD
THE ALASKA MAINLAND. THIS IS DUE IN LARGE PART TO MULTIPLE UPPER
LEVEL DISTURBANCES AND THEIR ASSOCIATED JET ENERGY COMING OFF THE
COAST OF RUSSIA AND WILL CONTINUE TO HELP DIG OUT THE TROUGH OVER
THE BERING SEA. WHILE A FEW SYSTEMS TRY TO FLATTEN AND WEAKEN THE
TROUGH...THE MERIDIONAL PATTERN IS JUST TOO STRONG. A COMPLEX AND
BROAD AREA OF LOW PRESSURE WILL ENCOMPASS MUCH OF THE BERING SEA
THROUGH THE WEEKEND AS ADDITIONAL WEAK LOW PRESSURE SYSTEMS
CONTINUE TO PHASE WITH THE BROAD LOW OVER THE BERING SEA. THIS
WILL KEEP SOUTHWEST AND SOUTHCENTRAL IN THE STORM TRACK LEADING TO
AN ACTIVE PERIOD OF WEATHER. HOWEVER...AS MENTIONED EARLIER THE
SYNOPTIC PATTERN WILL CONTINUE TO USHER WARMER AIR FROM THE
SUBTROPICS UP TOWARD THE MAINLAND. WHILE TEMPERATURES ARE NOT
EXPECTED TO REMAIN ABOVE FREEZING THROUGHOUT THE EXTENDED
FORECAST...PERIODS OF ABOVE FREEZING TEMPERATURES ARE LIKELY
ACROSS MUCH OF THE AREA. IT IS DIFFICULT TO DISCERN HOW WARM OR
COOL THE TEMPERATURES MAY BE AT THIS TIME...BUT THERE IS GREAT
CERTAINTY IN A PERIOD OF WELL ABOVE NORMAL TEMPERATURES.

ALL HOPE IS NOT LOST FOR SNOW HOWEVER AS THE ACTIVE STORM PATTERN
SHOULD BRING SEVERAL CHANCES OF SNOW TO SOUTHWEST AND SOUTHCENTRAL
ALASKA ON THURSDAY AND AGAIN OVER THE WEEKEND. HOWEVER...DOWNSLOPING
WILL ONCE AGAIN BE A BIG CONCERN AS LOWS WEST OF THE KENAI
PENINSULA OFTEN PUSH A WARM FRONT THAT KEEPS PORTIONS OF THE KENAI
PENINSULA...ANCHORAGE AND THE MATANUSKA VALLEY ON THE DRY SIDE
DUE TO CROSS BARRIER FLOW. HOWEVER...PATTERN RECOGNITION FAVORS
THAT AS THESE LOWS SHIFT EASTWARD TOWARD PRINCE WILLIAM SOUND THAT
UPPER LEVEL FLOW SHIFTS TO THE SOUTHWEST AND A SHOT OF SNOW WOULD
BE POSSIBLE. THIS SCENARIO EXISTS FOR BOTH THURSDAY AND SATURDAY
BUT IS HIGHLY DEPENDENT ON LOW TRACK. MODELS ARE STRUGGLING WITH
DEVELOPING THESE LOW PRESSURE SYSTEMS IN THE GULF OF ALASKA DUE TO
THE COMPLEX NATURE AND ATYPICAL SYNOPTIC PATTERN FOR THIS TIME OF
THE YEAR...SO THE CHANCES FOR SNOW COULD EITHER DECREASE OR
INCREASE IN THE COMING DAYS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WATCH...101 125 161.
		 WINTER WEATHER ADVISORY...145.
MARINE...STORMS...119 120 130 131 132 150 351 352.
		 GALES...125 128 136 137 138 139 141 155
				 160 165 170 171 172 174 176
				 177 180 181 185 411 412 414.
		 HEAVY FREEZING SPRAY...185.

&&

SYNOPSIS AND MODEL DISCUSSION...AMD
SOUTHCENTRAL ALASKA...DS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
LONG TERM...MC