Small Craft Advisory 148, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST SUN FEB 16 2014

.ANALYSIS AND UPPER LEVELS...
A LARGE UPPER LEVEL LOW IS CENTERED OVER SOUTHWEST ALASKA...WITH AN
AMPLIFYING RIDGE BUILDING JUST WEST OF ATTU AND A WEAKER RIDGE OVER
THE CANADIAN ROCKIES. MULTIPLE UPPER WAVES HAVE MOVED INLAND OVER THE
SOUTHCENTRAL AND SOUTHWEST MAINLAND...WITH A SHORTWAVE TROUGH MOVING
THROUGH THE WESTERN GULF AND INTO THE SOUTHERN KENAI PENINSULA. A
SERIES OF UPPER LEVEL WAVES ARE TRACKING ACROSS THE CENTRAL AND
EASTERN ALEUTIANS...BRINGING AREAS OF ENHANCED LIFT TO THE AREA.

AT THE SURFACE...A BROAD SURFACE LOW PERSISTS OVER THE NORTHWEST GULF
AND STRETCHES OVER MUCH OF THE REGION....WITH HIGH PRESSURE
STRETCHING FROM KAMCHATKA TO THE FAR WESTERN BERING. THE PRESSURE
GRADIENT BETWEEN THE ABOVE MENTIONED AIR MASSES CONTINUES TO
COMPRESS...CAUSING A STRONG AND COLD NORTHERLY FLOW ACROSS THE BERING
AND ALEUTIANS. CURRENT OBSERVATIONS SHOW COLDER AIR OVER MUCH OF THE
ALEUTIAN CHAIN AND BERING SEA...WITH GUSTY WINDS AND PERIODS OF
ENHANCED SNOW SHOWERS AS EMBEDDED WAVES MOVE THROUGH THE AREA.
CURRENT RADAR AND SURFACE OBSERVATIONS REPORT LIGHT SNOW SHOWERS
PERSISTING OVER THE NORTHERN GULF COAST. THE FORECAST CHALLENGE FOR
TODAY WAS HOMING IN ON A SOLUTION REGARDING THE TIMING AND STRENGTH
OF A SURFACE LOW FORMING AROUND THE SOUTHERN GULF. DIFFERENT MODEL
SOLUTIONS FOR THIS SINGLE FEATURE HAS HELPED KEEP SOME UNCERTAINTY IN
THE FORECAST REGARDING WINDS AND PRECIPITATION AMOUNTS ALONG THE
NORTHERN GULF COAST.

.MODEL DISCUSSION...
MODELS ARE IN GOOD SYNOPTIC AGREEMENT THROUGH MUCH OF THE SHORT
TERM...WITH SOME SMALLER FEATURES BEGINNING TO DIVERGE IN THEIR
SOLUTION REGARDING THE PLACEMENT AND STRENGTH OF A LOW FORMING OVER
THE SOUTHERN GULF OF ALASKA MONDAY AFTERNOON. OVERALL THE MODELS ARE
SHOWING A BROAD SURFACE LOW PERSISTING OVER MUCH OF THE MAINLAND AND
GULF THROUGH LATE MONDAY EVENING...WITH WEAK HIGH PRESSURE BUILDING
OVER THE WESTERN ALEUTIANS AND WESTERN BERING BY TUESDAY MORNING.

THE GFS AND EC REMAIN THE MOST CONSISTENT MODELS FROM RUN TO RUN
REGARDING THE LOW OVER THE NORTHWEST GULF...HOWEVER THE DIFFERENCES
IN THE OVERALL LOW PROGRESSION WITH TIME CONTINUES TO DIVERGE BETWEEN
THE MODELS. BEYOND 24 HOURS THE NAM BECOMES AN OUTLIER REGARDING THIS
FEATURE...FORMING A MUCH STRONGER LOW OVER THE CENTRAL GULF TUESDAY
MORNING. THE MODELS ALSO STRUGGLE WITH THE FORMATION OF A SURFACE LOW
SOUTH OF THE WESTERN ALEUTIANS TUESDAY MORNING...WITH THE EC BEING
THE ONLY MODEL TO CLOSE OFF THE SURFACE CIRCULATION SOUTHEAST OF
SHEMYA TUESDAY AFTERNOON. FOR THIS FORECAST PACKAGE THE NAM WAS USED
FOR THE FIRST 24 HOURS...THEN TRANSITIONED TO AN EC/GFS BLENDED
SOLUTION FOR THE REMAINDER OF THE SHORT TERM TO SHOW SOME UNCERTAINTY
DUE TO THE AFOREMENTIONED MODEL DISCREPANCIES.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...MULTIPLE WAVES PASSING OVER SOUTHCENTRAL WILL
CONTINUE TO PRODUCE SNOW SHOWERS OVER THE NORTHERN GULF COAST AND
AREAS AROUND THE COPPER RIVER BASIN AND SUSITNA VALLEY THROUGH
TOMORROW MORNING. CROSS BARRIER FLOW WILL BEGIN TO WEAKEN THIS
EVENING...OPENING UP THE CHANCE OF LIGHT SNOW SHOWERS TO DEVELOP OVER
THE WESTERN KENAI AND ANCHORAGE AREA AS THE SECOND WAVE MOVES THROUGH
THE AREA THIS EVENING. ONSHORE FLOW WILL CONTINUE TO ADVECT MOISTURE
OVER MUCH OF THE AREA...PROVIDING MOISTURE TO THE ABOVE MENTIONED
SNOW SHOWERS THROUGH TOMORROW AFTERNOON BEFORE DIMINISHING THAT
EVENING. STRONGER ONSHORE FLOW WILL BEGIN TO PICK UP AGAIN MONDAY
AFTERNOON AS A WEAK FRONTAL SYSTEM APPROACHES FROM THE SOUTH. THIS
WILL BRING ANOTHER WEAK ROUND OF LIGHT SNOW SHOWERS TO THE NORTHERN
GULF COAST THROUGH MIDWEEK.

SOUTHWEST ALASKA...COLDER THAN NORMAL TEMPERATURES ARE WIDESPREAD
OVER THE AREA WITH SOME LINGERING SNOW SHOWERS OVER THE LOWER
KUSKOKWIM DELTA. A SHORTWAVE TROUGH CURRENTLY OVER THE LOWER
KUSKOKWIM DELTA AND EXTENDING INTO THE CENTRAL BERING WILL BEGIN TO
PIVOT AROUND THE BACK END OF THE LOW...THEN BEGIN TO ELONGATE AND SET
UP OVER THE SOUTHWEST COAST AND AKPEN MONDAY AFTERNOON. PARTS OF THE
SOUTHWEST COAST AND SOUTHERN PORTION OF THE AKPEN WILL SEE SOME
SCATTERED SNOW SHOWERS AND BREEZY WINDS WITH THIS FEATURE...WHERE THE
INTERIOR OF THE SOUTHWEST MAINLAND WILL REMAIN MOSTLY DRY AND CALM
THROUGH MIDWEEK.

THE BERING SEA AND ALEUTIAN CHAIN...
SNOW SHOWERS WILL CONTINUE WITH NORTHERLY WINDS FOR MOST OF THE
BERING SEA. THE FLOW PATTERN AND TEMPERATURES ALOFT REMAIN
CONDUCIVE FOR INSTABILITY AND THEREFORE SHOWERS OVER THE BERING SEA
THROUGH MIDWEEK. WITH A TIGHTENING PRESSURE GRADIENT AND FAIR UPPER
LEVEL SUPPORT OVER THE CENTRAL BERING...GUSTY WINDS WILL PERSIST OVER
MUCH OF THE AREA THROUGH MONDAY AFTERNOON. A BLIZZARD WARNING FOR THE
PRIBILOF ISLANDS REMAINS IN EFFECT UNTIL MONDAY AFTERNOON. WINDS OVER
THE BERING SEA WILL BEGIN TO DIMINISH MONDAY EVENING...SLIGHTLY
IMPROVING CONDITIONS OVER THE CENTRAL BERING AND PRIBILOF ISLANDS
THROUGH MIDWEEK.

.LONG TERM FORECAST...
A PATTERN CHANGE STILL LOOKS IN ORDER AS THE CURRENT LOW PRESSURE
SYSTEM OVERHEAD WILL BREAK DOWN AND GET PUSHED OUT BY THE INCREASING
ZONAL FLOW. WHILE CONFIDENCE IS INCREASING IN A TRANSITION TO WARMER
CONDITIONS BY THE END OF THE WEEK...DETAILS ON STRENGTH AND TIMING OF
INDIVIDUAL EMBEDDED WAVES IN THE FLOW ARE STILL MUDDLED. OVERALL
EXPECT A SERIES OF FRONTS AND SYSTEMS TO MOVE INTO THE WESTERN GULF
OF ALASKA STARTING LATER THIS WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 195
MARINE...GALES 170 172-176 185 412 413
         HEAVY FREEZING SPRAY 165 170 173 179 185 411-414
FIRE WEATHER...NONE.

&&
TP

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1106 PM AKST SUN FEB 16 2014

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

1100 PM     SNOW             3 NW HOMER              59.66N 151.57W
02/16/2014  M9.0 INCH                           AK   PUBLIC

            SNOWFALL STARTED FRIDAY AFTERNOON AND 4 INCHES
            ACCUMULATION OVERNIGHT. ANOTHER 4 INCHES ACCUMULATION
            OVERNIGHT SATURDAY TO SUNDAY. TOTAL ACCUMULATION FROM
            FRIDAY AFTERNOON TO SUNDAY NIGHT IS 9 INCHES.

&&

DSTRICKL