Small Craft Advisory 1045, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
506 AM AKST THU DEC 31 2015

.ANALYSIS AND UPPER LEVELS...
THE OVERALL PATTERN OVER THE SOUTHERN MAINLAND REMAINS
ACTIVE...AS MULTIPLE WAVES ASSOCIATED WITH THE BROAD UPPER LOW
OVER THE BERING CONTINUE TO TRACK UP FROM THE NORTH PACIFIC AND
INTO THE SOUTHERN MAINLAND. THE UPPER LEVEL PATTERN REMAINS
DOMINATED BY A BROAD UPPER LEVEL TROUGH COVERING MUCH OF THE
BERING/ALEUTIANS AND NORTH PACIFIC...AND A STRONG BLOCKING RIDGE
TO THE EAST OVER WESTERN CANADA AND EASTERN ALASKA. A 120KT JET
STREAK IS CURRENTLY STRETCHING THROUGH THE GULF OF ALASKA FROM THE
NORTHEAST PACIFIC AND INTO SOUTHCENTRAL ALASKA. THIS MERIDIONAL
FLOW CONTINUES TO KEEP A DEEP MOISTURE FEED OVER THE GULF AND EASTERN
ALASKA...AS THE STRONG BLOCKING RIDGE REMAINS IN PLACE. AN UPPER
LOW IS CURRENTLY DEVELOPING ALONG THE BASE OF THE LONGWAVE TROUGH
OVER THE NORTH PACIFIC...WHICH WILL BE THE NEXT SYSTEM TO IMPACT
THE SOUTHERN MAINLAND BY THE END OF THE WEEK.

AT THE SURFACE...THE LOW THAT BROUGHT THE SOUTHERN MAINLAND SOME
VERY GUSTY WINDS YESTERDAY HAS NOW PUSHED WESTWARD OVER SAINT
MATTHEW ISLAND...WHILE WEAKENING AND BECOMING ABSORBED INTO A
LARGE AREA OF LOW PRESSURE OVER THE CENTRAL BERING. THERE ARE
SEVERAL WEAKER TROUGHS DEVELOPING ALONG THE WESTERN FLANK OF THE
RIDGE FROM THE NORTH PACIFIC...AND ARE EXPECTED TO REMAIN ALONG
THE SAME TRAJECTORY. OBSERVATIONS AND RADAR/SATELLITE IMAGERY
HAVE STARTED TO REPORT PRECIPITATION AND GUSTY WINDS OVER PARTS OF
THE SOUTHERN MAINLAND AS THIS NEXT WAVE BEGINS TO TRACK INTO THE
AREA. AS DEEP LAYER MOIST SOUTHERLY FLOW PERSISTS OVER THE GULF
AND SOUTHERN MAINLAND...THE WEATHER PATTERN WILL REMAIN ACTIVE FOR
MUCH OF THE FORECAST AREA.

&&

.MODEL DISCUSSION...
OVERALL THE MODELS REMAIN IN GOOD AGREEMENT WITH THE GENERAL
SYNOPTIC PATTERN THROUGH THE BEGINNING OF THE WEEKEND. THERE ARE
HOWEVER SOME MINOR TIMING AND STRENGTH DIFFERENCES WITH REGARDS
TO THE DEVELOPING SYSTEM OVER THE NORTH PACIFIC AS IT APPROACHES
THE ALASKA PENINSULA FRIDAY MORNING. CURRENTLY ANALYZED NEAR 962
MB...THIS SYSTEM WILL CONTINUE TO STRENGTHEN AS IT MOVES
NORTHEASTWARD BEFORE TURNING TOWARDS THE NORTH ON LATER TODAY. THE
MODEL SOLUTIONS BEGIN TO DIVERGE AS THE SYSTEM APPROACHES THE
ALASKA PENINSULA FRIDAY MORNING...WITH THE EC BEING THE
FASTER/WEAKER SOLUTION CROSSING INTO THE EASTERN BERING FRIDAY
NIGHT...AND THE GFS AND NAM BOTH SHOWING A STRONGER/SLOWER
SOLUTION. THE PREFERRED SOLUTION FOR THIS SYSTEM WAS MORE OF A
MIDDLE GROUND BETWEEN THE FASTER/WEAKER ECMWF SOLUTION AND THE
SLOWER/STRONGER GFS SOLUTION. HOWEVER WITH THE DISPARITY IN
SOLUTIONS...CONFIDENCE REGARDING THE TRACK/STRENGTH OF THIS SYSTEM
REMAINS LOW.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE LATEST IN THE SERIES OF FRONTS IS MOVING INTO SOUTHCENTRAL
ALASKA THIS MORNING. THIS IS CAUSING SOME HEAVY PRECIPITATION
ALONG THE GULF COAST LOCATIONS...MOSTLY IN THE FORM OF RAIN AT
LOWER ELEVATIONS. THERE IS SOME COLDER AIR ALOFT BEHIND THIS FRONT
WHICH WILL CAUSE SOME SNOW SHOWERS TO MIX IN WITH THE RAIN SHOWERS
THIS AFTERNOON. THE COPPER RIVER BASIN IS UNDER A WINTER WEATHER
ADVISORY FOR SNOW. UPSLOPE CONDITIONS OVER THE ALASKA RANGE AND
TALKEETNA MOUNTAINS WHICH STARTED THE SNOW OVERNIGHT ARE EXPECTED
TO CONTINUE THE SNOW THROUGH THE MORNING HOURS WITH TOTAL
ACCUMULATIONS IN THE 4 TO 8 INCH RANGE IN THESE AREAS. THERE IS
ALSO SOME AREAS OF FREEZING RAIN IN THE COPPER RIVER BASIN AT
LOWER ELEVATIONS. GLENNALLEN HAS REPORTED SOME OVERNIGHT AND THERE
WILL LIKELY BE AREAS THAT PERSIST THROUGH THE MORNING UNTIL THE
FRONT MOVES THROUGH THE AREA.

&&

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

AN UPPER LEVEL TROUGH WITH LOWER LEVEL COLD ADVECTION JUST AHEAD
OF IT WILL MOVE NORTH AND EAST THROUGH INLAND BRISTOL BAY AND THE
KUSKOKWIM VALLEY TODAY...BRINGING MINOR ACCUMULATING SNOW. BRIEF
DRYING WILL DEVELOP LATER TODAY INTO TONIGHT BEFORE ANOTHER FRONT
MOVES IN FRIDAY AFTERNOON AND EVENING...WITH INCREASING NORTHEAST
WINDS AND MORE PRECIPITATION CHANCES TO ALL OF SOUTHWEST ALASKA
THROUGH FRIDAY NIGHT.

&&

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

BROAD LOW PRESSURE WILL ENCOMPASS THE REGION THROUGH FRIDAY NIGHT...WITH
RAIN AND SNOW SHOWERS ROTATING THROUGH THE AREA...ESPECIALLY
ACROSS THE WESTERN BERING AND ALEUTIANS WHERE COLDER AIR WILL HELP
DESTABILIZE THE ATMOSPHERE. A NORTH PACIFIC LOW AND ASSOCIATED
FRONT WILL MOVE INTO THE EASTERN BERING ON FRIDAY...BRINGING
STRONGER EASTERLY WINDS AND RAIN AND SNOW. THE LATEST EC MODEL RUN
HAS SHIFTED A BIT WEST WITH THIS FEATURE...WITH THE BACK END OF
THIS STORM POTENTIALLY IMPACTING AS FAR WEST AS THE PRIBILOFS AND
EASTERN ALEUTIANS WITH SNOW AND RAIN ALONG WITH INCREASING
NORTHWEST WINDS LATE FRIDAY INTO FRIDAY NIGHT.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
AN ACTIVE WEATHER PATTERN CONTINUES THROUGH THE EXTENDED FORECAST
AS A BROAD UPPER TROUGH OVER THE BERING SLIDES FURTHER EAST
THROUGH THE MIDDLE OF NEXT WEEK. MODELS ARE IN GOOD GENERAL
AGREEMENT THAT THE UPPER RIDGE HOLDS OVER THE ALCAN BORDER WHICH
KEEPS THE LONGWAVE TROUGH CENTERED OVER THE BERING. THE LONG RANGE
FORECAST STARTING ON SATURDAY NIGHT BEGINS WITH A STORM SYSTEM
PUSHING A WARM FRONT INLAND ALONG THE SOUTHWEST BRINGING SCATTERED
RAIN AND SNOW SHOWERS INLAND ALONG WITH GUSTY CONDITIONS ALONG
THE BOUNDARY. A WEAKER WAVE FOLLOWS ON SUNDAY AND MOVES ACROSS THE
ALASKA PENINSULA AND WESTERN GULF...THIS WILL BRING ANOTHER ROUND
OF PRECIPITATION. THERE IS A BIT OF UNCERTAINTY ON THE NEXT STORM
SYSTEM THAT TRACKS SOUTH OF THE ALEUTIANS LATE SUNDAY INTO MONDAY.
THIS STORM SHOULD TAKE A NORTHWARD TURN...HOWEVER A DEVELOPING
WAVE LOOKS TO CLOSE OFF A NEW LOW CENTER IN THE EASTERN PACIFIC WHICH
WOULD SLOW THE TRACK OF THE FIRST SYSTEM AS RIDGING OVER THE ALCAN BUILDS
BACK OVER THE SOUTHEAST.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...SMALL STREAM FLOOD ADVISORY 121.
		 WINTER WEATHER ADVISORY FOR SNOW 141.
MARINE...GALE 119 120 125 130-138 150-165 172 180
		 HEAVY FREEZING SPRAY 185.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1057 AM AKST THU DEC 31 2015

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

1056 AM     HEAVY SNOW       THOMPSON PASS           61.14N 145.75W
12/31/2015  E30.0 INCH                          AK   DEPT OF HIGHWAYS

            TWO TO THREE FEET NEW SNOW HAS FALLEN TODAY IN THOMPSON
            PASS. ROAD IS CLOSED AND MOTORISTS ARE STUCK.

&&

RDUELL