Small Craft Advisory 124, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
145 PM AKST FRI FEB 8 2013

.ANALYSIS AND UPPER LEVELS...
THE OVERALL WEATHER PATTERN IS IN THE PROCESS OF AMPLIFYING AND
BECOME MORE ACTIVE. A DEEP LONGWAVE TROUGH IS DIGGING ACROSS THE
CENTRAL BERING SEA...OPENING THE DOOR FOR VERY COLD ARCTIC AIR TO
SPILL SOUTHWARD THROUGH THE BERING STRAIT. FURTHER TO THE EAST...A
NORTHEAST PACIFIC RIDGE IS RAPIDLY BUILDING ACROSS THE EASTERN GULF
OF ALASKA. BETWEEN THESE MAJOR FEATURES...A 140+ KT SOUTHERLY JET IS
TRANSPORTING LARGE AMOUNTS OF MOISTURE TOWARD ALASKA FROM LOWER
LATITUDES. A STRONG WAVE HAS DEVELOPED ALONG THIS BROAD BAROCLINIC
ZONE OVER THE NORTH PACIFIC. THE LOW WITH CENTRAL PRESSURE OF 967 MB
IS NOW LOCATED ABOUT 600 MILES SOUTH OF THE ALASKA PENINSULA AND IS
MOVING TO THE NORTH/NORTHEAST TOWARD MAINLAND ALASKA. WAY OUT
WEST...A SLOW-MOVING LOW NEAR THE SOUTHERN TIP OF THE KAMCHATKA
PENINSULA IS MAKING STEADY PROGRESS EASTWARD. AN ASSOCIATED FRONT IS
RACING WELL OUT AHEAD OF THE LOW AND WILL BE IMPACTING THE WESTERN
ALEUTIANS AFTER MIDNIGHT TONIGHT.

.MODEL DISCUSSION...
THE GLOBAL AND REGIONAL ATMOSPHERIC MODELS ARE IN ABOVE-AVERAGE
AGREEMENT WITH THE OVERALL EVOLUTION OF THE MAIN FEATURES OVER THE
NEXT SEVERAL DAYS. CONFIDENCE IS HIGH THAT THE AFOREMENTIONED NORTH
PACIFIC LOW WILL TRACK NORTHWARD AND MOVE INTO SOUTHWEST ALASKA BY
SATURDAY AFTERNOON. AN ASSOCIATED FRONT WILL BRING STRONG WINDS AND
HEAVY PRECIPITATION TO THE COASTLINES AROUND SOUTHCENTRAL ALASKA. THE
SAME FRONT WILL MOVE INTO SOUTHWEST ALASKA OVERNIGHT TONIGHT AND
INTERACT WITH COLDER AIR IN PLACE ACROSS THE REGION TO LIKELY PRODUCE
BLIZZARD CONDITIONS ACROSS PARTS OF THE BRISTOL BAY ZONE AND THE
KUSKOKWIM DELTA. BY SUNDAY MORNING...AS THE LOW CENTER TRACKS TOWARD
NOME...PRESSURE RISES WILL MOVE INTO SOUTHERN ALASKA FROM THE
SOUTHWEST AND BRING A SECONDARY PEAK TO PRESSURE GRADIENTS ACROSS THE
REGION.

.SHORT TERM FORECAST...
SOUTHCENTRAL...AS MENTIONED ABOVE...THE MAJORITY OF THE IMPACT
ASSOCIATED WITH THE STRONG WEATHER FRONT WILL BE CONFINED TO COASTAL
LOCATIONS. WITH STRONG AND MOIST SOUTHERLY FLOW ALOFT PRECIPITATION
TOTALS SHOULD BE SIGNIFICANT ACROSS THE PRINCE WILLIAM SOUND REGION.
THANKFULLY...MOST SEA-LEVEL LOCATIONS WILL BE WARM ENOUGH TO MIX WITH
OR CHANGE TO RAIN BY SATURDAY AFTERNOON. THE EXCEPTION WILL LIKELY BE
THE VALDEZ AREA WHERE TEMPERATURES EVEN IN TOWN WILL LIKELY STAY COLD
ENOUGH TO SUPPORT MOSTLY SNOWFALL THROUGH SUNDAY AFTERNOON.
ADDITIONALLY...WITH STRONG JET SUPPORT PROPELLING THE FRONT
INLAND...STRONG WINDS SHOULD COMBINE WITH THE HEAVY FALLING SNOW TO
PRODUCE BLIZZARD CONDITIONS THROUGH THOMPSON PASS. ADDITIONALLY...THE
FRONT WILL PRODUCE A VERY STRONG GRADIENT THROUGH BOTH EASTERN AND
WESTERN SECTIONS OF TURNAGAIN ARM AS WELL AS PORTAGE VALLEY...LEADING
TO WARNING LEVEL WINDS DURING THE DAY SATURDAY. BY SUNDAY...AS
MENTIONED ABOVE...THE LOW CENTER WILL CONTINUE TO MAKE NORTHWARD
PROGRESS TOWARD NOME. THIS WILL REVERSE THE COOK INLET GRADIENT AND
ALLOW RESIDUAL (BELOW WARNING LEVEL) WINDS IN TURNAGAIN ARM TO BEGIN
TO AFFECT THE ANCHORAGE AREA. ACCOMPANYING THESE WINDS WILL BE
COOLING TEMPERATURES AND THE LIKELIHOOD OF SNOW. AT THIS POINT IT
LOOKS LIKE SNOWFALL ACROSS THE REGION IN THIS SECOND PHASE OF THE
STORM WILL BE LIMITED TO AN INCH OR TWO AT MOST LOCATIONS...BUT THIS
WILL BE MONITORED IN SUBSEQUENT FORECAST CYCLES.

SOUTHWEST MAINLAND...NORTHEASTERLY WINDS ARE ALREADY BEGINNING TO
INCREASE ACROSS THE AREA IN ADVANCE OF THE STRONG LOW. AREAS OF
BLOWING SNOW ARE ALREADY REDUCING VISIBILITIES OVER PARTS OF THE
KUSKOKWIM DELTA...A CONDITION THAT WILL PERSIST BEFORE GETTING MUCH
WORSE AND MORE WIDESPREAD IN THE EARLY MORNING HOURS AS THE FRONT
APPROACHES. WITH THE LOW CENTER EXPECTED TO PASS JUST EAST OF BETHEL
SATURDAY EVENING...SECTIONS ALONG THE DELTA COAST WILL VERY LIKELY
SEE BLIZZARD CONDITIONS CONTINUE THROUGH EARLY SUNDAY MORNING AS
STRONG NORTHERLY WINDS AND HEAVY SNOW REMAIN IN THE AREA. ACROSS THE
BRISTOL BAY ZONE...CONDITIONS WILL GO STEADILY DOWNHILL TONIGHT AS
STRONG WINDS AND HEAVY SNOW ACCOMPANY THE ADVANCE OF THE WEATHER
FRONT. BLIZZARD CONDITIONS WILL DEVELOP NORTH AND WEST OF KING SALMON
AS NORTHEASTERLY WINDS KEEP TEMPERATURES IN THE UPPER 20S THROUGH
SATURDAY MORNING. A SECOND PUNCH COMES TO THE BRISTOL BAY ZONE
SATURDAY EVENING AS STRONG SOUTHWEST WINDS AND RAPIDLY DROPPING
TEMPERATURES WRAP AROUND THE BOTTOM OF THE LOW CENTER.

BERING SEA AND ALEUTIANS...TWO DIFFERENT STORMS WILL IMPACT OPPOSITE
SIDES OF THE BERING SEA OVER THE NEXT 36 HOURS. THE STRONG LOW
AFFECTING MAINLAND ALASKA WILL KEEP THE EASTERN BERING SEA IN GENERAL
NORTHERLY FLOW AND STRONG COLD AIR ADVECTION. THE INTERACTION OF TWO
UPPER LEVEL FEATURES IS BEGINNING TO DEVELOP A STRETCHING
AXIS/DEFORMATION BAND NEAR/OVER THE CENTRAL BERING. RESULTING LIGHT
TO MODERATE SNOWFALL WILL COMBINE WITH THE STRONG WINDS AND COLD
TEMPERATURES TO LIKELY PRODUCE BLIZZARD CONDITIONS ACROSS THE
PRIBILOFS BEGINNING THIS EVENING. WAY OUT WEST...A SEPARATE LOW SOUTH
OF THE KAMCHATKA PENINSULA WILL SEND A FRONT STRETCHING WELL TO THE
EAST OVER THE COMING DAYS. WITH NOTABLY COLD AIR IN PLACE ACROSS THE
REGION...TEMPERATURES SHOULD STAY BELOW FREEZING OVER THE WESTERN
ALEUTIANS AS THE REMNANTS OF THIS FRONT IMPACT THE AREA. AS A
RESULT...A BLIZZARD WARNING HAS BEEN ISSUED FOR THE WESTERN ALEUTIANS
BEGINNING LATE TONIGHT.

.LONG TERM FORECAST...
THE LONG-TERM MODELS CONTINUE TO SUGGEST A VERY ACTIVE PATTERN ACROSS
SOUTHERN ALASKA. THE OVERALL PATTERN WILL BE CHARACTERIZED BY A
PERSISTENT UPPER LOW SOUTH OF THE BERING STRAIT THROUGH THE MIDDLE OF
NEXT WEEK WITH SOUTHWESTERLY FLOW ALOFT WITH NUMEROUS EMBEDDED
DISTURBANCES. AS A RESULT...MUCH OF SOUTHERN ALASKA WILL SEE MULTIPLE
OPPORTUNITIES FOR ACCUMULATING SNOWFALL BEGINNING SUNDAY AND
CONTINUING THROUGH MUCH OF THE WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 131 155 161 191 195
         HIGH WIND WARNING 101 125
MARINE...STORM 120
         GALE 125 129 127 128 130 132 136 137 138 140 141 150 155 160
              165 170 171 172 175 176 179 180 185
         HEAVY FREEZING SPRAY 160 165 170 179 185
FIRE WEATHER...NONE

AMD FEB 13