Small Craft Advisory 121, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST SUN FEB 9 2014

.ANALYSIS AND UPPER LEVELS...THE UPPER LEVEL PATTERN HAS A LARGE
RIDGE OVER THE WESTERN BERING SEA INTO THE ARCTIC OCEAN WHILE AN
UPPER LEVEL LOW IS NEAR THE ALCAN BORDER IN THE COPPER RIVER. THE
TROUGH ASSOCIATED WITH THIS LOW EXTENDS THROUGH THE YUKON AND ACROSS
THE GULF OF ALASKA. THIS PATTERN IS BRINGING A STRONG NORTHERLY FLOW
ALOFT FROM THE CENTRAL BERING SEA THROUGH THE SOUTHWEST ALASKA COAST.
A WEAK SHORT WAVE CAN BE SEEN ON SATELLITE BETWEEN THE PRIBILOF
ISLANDS AND ST MATTHEW ISLAND.
AT THE SURFACE THERE IS A TROUGH ALONG THE NORTH GULF COAST WITH A
WEAK LOW THAT HAS DEVELOPED JUST SOUTH OF CORDOVA THIS AFTERNOON.
STRONG HIGH PRESSURE EXTENDS OVER THE NORTHERN PORTION OF THE STATE
INTO THE WESTERN BERING SEA. THIS PATTERN IS KEEPING THE GUSTY WINDS
ALONG THE COAST AND CHANNELED TERRAIN OVER SOUTHCENTRAL ALASKA
THROUGH SOUTHWEST ALASKA.

.MODEL DISCUSSION...MODELS ARE IN AGREEMENT WITH THE MAJOR FEATURES
OVER THE FORECAST AREA. THERE IS SOME DIFFERENCE IN THE WAY THE LOW
SOUTH OF THE GULF OF ALASKA WILL MOVE TOMORROW BUT IT WILL HAVE VERY
LITTLE IMPACT ON THE FORECASTS. A BIGGER QUESTION WILL BE HOW THE
COLD UPPER LEVEL LOW DESCENDS OUT OF THE ARCTIC AND INTO SOUTHWEST
ALASKA IN THE MIDDLE OF THE WEEK. THE SURFACE LOW THAT WILL DEVELOP
IN THE GULF ON WEDNESDAY WILL BE IMPACTED BY THIS FEATURE. A MORE
THROUGH LOOK INTO THIS IS IN THE LONG TERM DISCUSSION SECTION.

.SHORT TERM FORECAST...
SOUTHCENTRAL...THE UPPER LEVEL LOW NEAR THE ALCAN BORDER WILL MOVE
RAPIDLY SOUTHWEST OVERNIGHT AND TO THE ALASKA PENINSULA BY MONDAY
EVENING. WINDS WILL REMAIN GUSTY THROUGH MONDAY AFTERNOON AROUND THE
SOTUHCENTRAL REGION...ESPECIALLY THROUGH CHANNELED TERRAIN FACING
NORTHEAST. THESE WINDS COMBINED WITH LOW HUMIDITY AND A LACK OF SNOW
COVER HAVE CAUSED THE RED FLAG WARNING TO BE IN EFFECT FOR THE
MATANUSKA VALLEY THROUGH MONDAY AFTERNOON. THERE WILL BE SOME CLOUD
COVER AND SOME SNOW SHOWERS THAT MOVE THROUGH THE NORTH GULF COAST
OVERNIGHT IN CONJUNCTION WITH THIS UPPER LOW. THE KENAI PENINSULA AND
ANCHORAGE AREA WILL MOST LIKELY JUST SEE SOME CLOUDS MOVE THOUGH
OVERNIGHT INTO MONDAY AFTERNOON WITH THIS LOW...AND THEN RETURN TO
MOSTLY CLEAR SKIES.

SOUTHWEST...GUSTY NORTH OT NORTHEAST WINDS WILL CONTINUE THROUGH
MONDAY AFTERNOON AS THE PRESSURE GRADIENT REMAIN TIGHT AND THE UPPER
LEVEL LOW MOVING THROUGH THE AREA ENHANCES THE WIND. THE WIND WILL
THEN THEN BEGIN TO DIMINISH OVERNIGHT MONDAY NIGHT AS THE UPPER LEVEL
LOW MOVES SOUTHWEST OF THE AREA.
THERE SHOULD BE MUCH IN THE WAY OF CLOUD COVER IN SOUTHWEST MAINLAND
ALASKA THE NEXT DAY OR TWO. SOME AREAS ALONG THE BERING COAST FROM
SOUTHERN BRISTOL BAY THROUGH THE ALEUTIAN CHAIN WILL SEE SOME LOWER
CLOUDS BUT THE MAINLAND AREA WILL REMAIN MOSTLY CLEAR.

.LONG TERM FORECAST...
BY THURSDAY...A LARGE UPPER TROUGH WILL BE IN PLACE OVER ALASKA AND
THE BERING SEA...WITH A DEEP UPPER LEVEL CLOSED LOW IN THE VICINITY
OF KODIAK ISLAND AND SOUTHWEST ALASKA. THIS IS A CLASSIC MID WINTER
PATTERN FOR ALASKA...WITH COLD ARCTIC AIR WRAPPING AROUND THE LOW
ACROSS SOUTHWEST ALASKA WEST OF THE ALASKA/ALEUTIAN RANGES AND INTO
THE BERING SEA. A SURFACE LOW WILL FORM IN THE GULF OF ALASKA WITH
INCREASING SNOW CHANCES FOR LOCATIONS ALONG THE NORTHERN
GULF...PRINCE WILLIAM SOUND AND TURNAGAIN ARM...AND THE COPPER RIVER
BASIN. LOCATIONS WEST INCLUDING ANCHORAGE...THE MAT-SU VALLEYS...AND
THE EASTERN KENAI PENINSULA WILL ALSO SEE SNOW CHANCES
INCREASE...ALTHOUGH THOSE LOCATIONS WILL BE HIGHLY VARIABLE DEPENDING
UPON THE LOCATION OF THE UPPER TROUGH. THE ECWMF AND CANADIAN GLOBAL
DETERMINISTIC PREDICTION SYSTEM SUPPORT A FARTHER EAST SOLUTION WITH
THE UPPER LOW EVENTUALLY CENTERING ITSELF OVER THE GULF OF
ALASKA...WHILE THE GFS IS WEST OVER SOUTHWEST ALASKA AND KODIAK
ISLAND. THE LATTER WOULD BE A MUCH MORE FAVORABLE SNOW
PATTERN...WHILE THE FORMER SOLUTIONS WOULD MUCH DRIER FOR LOCATIONS
WEST OF THE CHUGACH. FOR THE TIME BEING...A MIDDLE GROUND SOLUTION IS
FAVORED...WHICH IS SUPPORTED BY THE GFS ENSEMBLE...WHICH SUPPORTS
INCREASING SNOW CHANCES THURSDAY AND FRIDAY ALBEIT MAINLY OVER THE
NORTH COAST INTO THE COPPER BASIN AND DOWN TURNAGAIN ARM.

THEREAFTER...UNCERTAINTY GROWS WITH THE DETAILS...BUT THE NORTH
AMERICAN ENSEMBLE FORECAST SYSTEM(NAEFS)...GFS ENSEMBLE...AND THE
NCEP CLIMATE FORECAST SYSTEM VERSION 2 (CFSV2) ALL FAVOR PERSISTENT
DEEP TROUGHING OVER ALASKA...WHICH WILL SUPPORT BELOW AVERAGE
TEMPERATURES AND A PERSISTENT NORTHERLY OFFSHORE FLOW REGIME WELL
INTO NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 119 120 127 128 130-132 138 139 170 172-174 176 179 180
         HEAVY FREEZING SPRAY 121 126-128 130 139-141 160 180-185.
FIRE WEATHER...RED FLAG WARNING 111.

EZ/AHSENMACHER FEB 14