Winter Weather Advisory 5, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
530 AM AKST SAT JAN 7 2012

.ANALYSIS AND UPPER LEVELS...
THE DOMINANT WEATHER FEATURE IS THE PACIFIC LOW 300 MILES SOUTHEAST
OF SAND POINT APPROACHING THE SOUTHERN GULF. WHILE IT'S 960 MB
CENTRAL PRESSURE IS NOT TERRIBLY DEEP...THERE IS A CONSIDERABLE
TEMPERATURE CONTRAST BETWEEN IT'S AIRMASS AND THE ARCTIC AIR
ESTABLISHED OVER THE SOUTHERN MAINLAND. THE PRESSURE GRADIENT BETWEEN
THE AIR MASSES IS REASONABLY STRONG AND PRODUCING WIDESPREAD GALE
FORCE WINDS FROM THE CENTRAL ALEUTIAN CHAIN EAST TOWARDS THE GULF OF
AK. GUSTY WINDS COUPLED WITH SNOW ARE PRODUCING BLIZZARD CONDITIONS
ALONG THE AKPEN AND KODIAK ISLAND. PERIPHERAL SNOW FROM THE LOW HAS
ARRIVED INTO THE SOUTHCENTRAL MAINLAND AS EVIDENCED BY RADAR. THE
SNOW IS APPRECIABLY DRY IN TEXTURE AND IS BEING EASILY BLOWN AROUND
EVEN WITH MODESTLY LIGHT WINDS. THE KUSKOKWIM VALLEY/DELTA WHILE
DRY...ARE EXPERIENCING CHILLY TEMPERATURES...WITH WIND CHILLS IN ZONE
THE DELTA 50 TO 65 BELOW ZERO. OVER THE BERING...THERE IS A WEAK
TROUGH OF LOW PRESSURE NEAR SAINT MATTHEW ISLAND SWINGING SOUTHEAST
TOWARDS THE PRIBILOF ISLANDS AND POINTS SOUTHEAST.

.MODEL DISCUSSION...
MODELS ARE IN DECENT AGREEMENT THIS MORNING AND CAPTURE THE SYNOPTIC
PICTURE WELL. THEY SHOW THE PACIFIC LOW MOVING UP THE GULF TONIGHT TO
PRINCE WILLIAM SOUND ON SUNDAY...THEN SLOWLY DRIFT IT EAST TOWARDS
CAPE SUCKLING ON MONDAY. THE NAM SEEMS TO SHEAR THIS SYSTEM OUT A BIT
TOO QUICKLY ONCE IT GETS TO PRINCE WILLIAM SOUND. AS A RESULT THE 00Z
AND 06Z RUNS DEPICT LESS QPF ON SUNDAY...ESPECIALLY FOR AREAS WEST OF
PRINCE WILLIAM SOUND. A SUPPORTING SHORTWAVE ALOFT DOES NOT SWING
THROUGH UNTIL SUNDAY AFTERNOON...AND TEND TO BELIEVE THERE IS A
THREAT OF SNOW UNTIL THESE DYNAMICS CLEAR THE REGION. SO WHILE THE
NAM HAS SOME UTILITY WITH GAP WINDS INITIALLY AS THE LOW MOVES
UP...HAVE TRENDED FORECASTS MORE TOWARDS THE GFS. OUT WEST...MODELS
REASONABLY SHOW A SERIES OF WEAK TROUGHS SWINGING THROUGH THE
PRIBILOFS TODAY AND SUNDAY. THE NEXT MORE SIGNIFICANT LOW MOVES UP TO
AROUND 250 MILES SOUTH OF DUTCH HARBOR MONDAY MORNING. THE NAM IS
SLOWEST WITH THIS DEVELOPMENT...AND ALSO TENDS TO CUT OFF THE SYSTEM
FROM THE MAIN UPPER-FLOW...TENDING TO KEEP THE LION'S SHARE OF ENERGY
JUST SOUTH OF THE AKPEN AND CHAIN. HAVE FAVORED THE GFS/ECMWF
SOLUTIONS OF KEEPING BULK OF MOISTURE A BIT FURTHER TO THE NORTH.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
BLIZZARD CONDITIONS OVER KODIAK ISLAND WILL IMPROVE AS THE ONSHORE
FLOW WEAKENS TODAY AND BECOMES A BIT MORE OFF-SHORE IN NATURE. WINDS
WILL REMAIN GUSTY HOWEVER AS THE LOW MOVES UP THE GULF AND THE
PRESSURE GRADIENT REMAINS SUBSTANTIALLY SQUEEZED. SNOW OVER THE
REMAINDER OF SOUTHCENTRAL WILL PERSIST TODAY AS AN INVERTED TROUGH
AXIS SETS UP FROM PRINCE WILLIAM SOUND UP TO THE MATANUSKA VALLEY.
THE GULF LOW WILL MOVE UP TO PRINCE WILLIAM SOUND ON SUNDAY...WITH
SNOWFALL HEAVIEST IN IT'S IMMEDIATE VICINITY. WEAK WARM ADVECTION
AHEAD OF IT MAY ALLOW SOME OF THE SNOW TO BECOME MIXED WITH RAIN AT
TIMES FOR AREAS SUCH AS CORDOVA THIS AFTERNOON AND EVENING. STRONGER
COLD-ADVECTION WRAPPING IN BEHIND THE LOW LATE TONIGHT WILL FILTER
ACROSS THE NORTHERN GULF AND ALLOW ALL PRECIPITATION TO END AS SNOW.
SNOW INTENSITY MAY BECOME A BIT HEAVIER THROUGH THE ANCHORAGE BOWL
AND MATANUSKA VALLEY ALONG THE LEADING EDGE OF THIS ADVECTION LATE
TONIGHT INTO EARLY SUNDAY MORNING. WE HAVE KEPT ACCUMULATIONS BELOW
ADVISORY CRITERIA...BUT THIS STILL LOOKS LIKE A MODEST SNOWFALL
EVENT. PRECIPITATION WILL TAPER OFF AS THE SUPPORTING SHORTWAVE
SWINGS THROUGH DURING THE DAY ON SUNDAY...THOUGH IN IT'S WAKE GUSTY
GAP WINDS WILL PERSIST INTO EARLY MONDAY UNTIL THE PRESSURE GRADIENT
RELAXES. WITH THE PASSAGE OF THE SHORTWAVE...LOOK FOR TEMPERATURES TO
BEGIN TO MODERATE A BIT AS SOME OF THE ARCTIC AIR IS DEFLECTED EAST.
A FRONT ASSOCIATED WITH ANOTHER PACIFIC LOW MOVES TOWARDS THE SW GULF
ON MONDAY.

SOUTHWEST...
WE EXPECT THE COLDEST WIND CHILLS BEING EXPERIENCED OVER THE
KUSKOKWIM DELTA TO BEGIN TO EBB BY THIS AFTERNOON. TEMPERATURES WILL
BEGIN TO REBOUND A BIT AS THE ARCTIC AIR SHIFTS EAST ON MONDAY.
FURTHER SOUTH...SNOW WILL BEGIN TAPERING TO SHOWERS ACROSS BRISTOL
BAY AS THE CRUX OF THE MOISTURE SWINGS EAST. GUSTY WINDS WILL STILL
PRODUCE AREAS OF BLOWING SNOW AND BLIZZARD CONDITIONS ALONG THE AKPEN
THROUGH THIS EVENING BEFORE WINDS FINALLY BEING TO DIMINISH A BIT.
THE LEADING EDGE OF MOISTURE FROM THE NEXT PACIFIC SYSTEM APPROACHES
ON MONDAY WITH MORE WIND AND PRECIPITATION.

BERING SEA/ALEUTIANS...
THE NEXT PACIFIC LOW MOVES UP TOWARDS DUTCH HARBOR ON MONDAY. LOOK
FOR ANOTHER ROUND OF GALES AND SNOW...THOUGH WARM AIR WITH THIS
SYSTEM MAY ALLOW FOR SOME MIXED PRECIPITATION.

.LONG TERM FORECAST...
CONDITIONS TO REMAIN VERY UNSETTLED OVER THE FORECAST AREA. STORM
TRACK SHIFTS A BIT FURTHER FROM THE EASTERN CHAIN UP THROUGH THE SW
MAINLAND. THIS WILL ALLOW SOME WARMER TEMPERATURES TO POKE UP TO THE
SOUTHERN MAINLAND. WITH ALL AREAS HAVING BEEN IN A PRETTY SUBSTANTIAL
FREEZE...THE INTRODUCTION OF WARM AIR WILL CREATE PRECIPITATION TYPE
FORECAST CHALLENGES.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING...161 171 181
         WIND CHILL WARNING...155
         WIND CHILL ADVISORY...161
MARINE...STORM...120 130 351
         GALE...129 132 138 140 150 155 160 165 170 352 414
         HEAVY FREEZING SPRAY...121 129 130 138 140 141 150 155 165
                                170 171 179 185 411 412 414
FIRE WEATHER...NONE

JAM JAN 12