Heavy Freezing Spray Warning 36, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKST FRI JAN 21 2011

.MODEL DISCUSSION...

MODELS ARE STRUGGLING IN DEPICTING THE MANY MID LEVEL SHORTWAVE
DISTURBANCES IN SOUTHWEST FLOW ALOFT...AS WELL AS IN THE SPEED AND
PLACEMENT WITH REGARDS TO SURFACE LOW MOVEMENT IN THE NORTHERN GULF
AND NORTH PACIFIC THROUGH TONIGHT. THE EUROPEAN MODEL (EC) IS
GENERALLY QUICKEST IN MOVING A DEVELOPING SURFACE LOW IN THE NORTH
PACIFIC NORTH AND EAST ACROSS THE WESTERN GULF TO NEAR PRINCE WILLIAM
SOUND...WITH THE NAM SLOWEST AND THE GFS DEPICTING SOMEWHAT OF A
MIDDLE GROUND. INITIALIZATIONS OF THE GFS AND EC MODEL RUNS INDICATE
THAT LOW MOVEMENT WILL FOLLOW SOMEWHAT OF A MIDDLE GROUND BETWEEN
THESE TWO MODELS. BASED ON THE INHERITED FORECAST THE GRIDS AND
ASSOCIATED TEXT FORECASTS LEANED TOWARDS THE LATEST GFS.

FOR THE EXTENDED TIME FRAME...A BLEND OF HPC GUIDANCE AND THE LATEST
EC MODEL WERE USED.

.ANALYSIS AND UPPER LEVELS...

WEAK DEFORMATION EXISTS ACROSS THE NORTH GULF COAST AS A SMALL UPPER
LEVEL LOW WEAKENS INTO A WAVE TODAY AS IT MOVES ALONG THE NORTH GULF
COAST AND TOWARDS WRANGELL-ST. ELIAS PARK. A WEAK SURFACE LOW WILL
REMAIN IN THE PRINCE WILLIAM SOUND AREA THIS MORNING INTO EARLY
AFTERNOON AS THE WAVE ALOFT APPROACHES BEFORE DISSIPATING OR MOVING
INLAND. THE NEXT WAVE APPROACHES THE GULF THIS AFTERNOON AND WILL
DRAG ANOTHER LOW INTO THE PRINCE WILLIAM SOUND VICINITY...BRINGING
ANOTHER ROUND OF SNOW TO SOUTHCENTRAL...WITH SOME RAIN MIXED ALONG
THE COAST. A THIRD DISTURBANCE IN WESTERLY FLOW OVER THE EASTERN
BERING CROSSES SOUTHWEST AND THEN SOUTHCENTRAL ALASKA DURING THE DAY
ON SATURDAY BEFORE TRANSITORY UPPER LEVEL RIDGING AHEAD OF A LARGE
AND DEEP LOW IN THE NORTH PACIFIC BEGINS TO APPROACH THE REGION FROM
THE SOUTH FOR LATE IN THE WEEKEND. THIS WILL PROVIDE A BRIEF PERIOD
OF MOSTLY DRY WEATHER FOR THE SOUTHERN MAINLAND SATURDAY EVENING
THROUGH SUNDAY MORNING.

OUT WEST...A WEATHER FRONT WILL REMAIN NEARLY STATIONARY FROM THE
WESTERN GULF AND EXTENDING WEST ACROSS THE SOUTHERN BERING SEA TO
WEST OF ATTU ISLAND...WHERE A STACKED LOW PRESSURE SYSTEM RESIDES. A
STRONG TRIPLE POINT LOW WILL STRENGTHEN TO AROUND 950 MB IN THE NORTH
PACIFIC TO THE SOUTH OF THE CENTRAL ALEUTIANS OVER THE NEXT 48 TO 60
HOURS AND THEN APPROACH THE EASTERN ALEUTIANS SUNDAY NIGHT. THIS
SYSTEM WILL USHER A SERIES OF FRONTS NORTH TOWARDS THE GULF...WITH
THE FIRST STRONG FRONT REACHING THE FAR SOUTHERN GULF DURING THE DAY
ON SUNDAY.

.SHORT TERM FORECAST...

SOUTHCENTRAL...

CURRENT SYSTEM AFFECTING SOUTHCENTRAL AND THE GULF COAST WILL MOVE
INLAND THROUGH THE DAY TODAY. LOCALLY HEAVY AMOUNTS OF SNOW MAY FALL
NORTH AND EAST OF VALDEZ TODAY...ESPECIALLY IN FAR SOUTHEASTERN
SECTIONS OF THE COPPER RIVER BASIN. A BRIEF RESPITE WILL OCCUR THIS
MORNING BEFORE THE NEXT SYSTEM APPROACHES THE REGION THIS EVENING AND
BRINGS ANOTHER ROUND OF SNOW...WITH RAIN MIXED ALONG THE IMMEDIATE
COAST. THIS SYSTEM WILL FEATURE A SLIGHTLY MORE IMPRESSIVE THERMAL
GRADIENT FOR SOUTHCENTRAL...ENOUGH SO THAT A COUPLE OF INCHES APPEAR
POSSIBLE FOR ANCHORAGE BEFORE IT DEPARTS THE AREA TO THE NORTH AND
EAST BY EARLY SATURDAY AFTERNOON. A BRIEF DRY PERIOD ENSUES AS UPPER
LEVEL RIDGING MOVES OVER THE REGION LATE SATURDAY THROUGH EARLY
SUNDAY AFTERNOON AS A STRONG MOISTURE-LADEN FRONT BEGINS TO MOVE
NORTH INTO THE GULF.

SOUTHWEST ALASKA...

UPPER LEVEL SYSTEM OVER THE ALEUTIAN RANGE ALONG THE ALASKA PENINSULA
WILL BRING PERIODS OF LIGHT SNOW THROUGH MID OR LATE MORNING TODAY
FROM THE NORTHERN AKPEN NORTH TO AROUND ILIAMNA...THEN BEGIN TO
DISSIPATE AS THE SYSTEM WEAKENS AND MOVES EAST BY THE AFTERNOON.
THERMAL PROFILES OVER PARTS OF THE BRISTOL BAY REGION INDICATE ENOUGH
DRYING IN THE DENDRITIC GROWTH LAYER ON THE PERIPHERY OF THE MAIN
PRECIPITATION SHIELD TO INDICATE THERE COULD BE POCKETS OF FREEZING
DRIZZLE ALONG WITH PATCHY FOG. ICE ACCRETIONS SHOULD BE MINIMAL. THE
NEXT COUPLE OF DISTURBANCES WILL BRING ANOTHER GLANCING SHOT OF SNOW
TO THE BRISTOL BAY AND KUSKOKWIM VALLEY ZONES TONIGHT AND AGAIN
SATURDAY MORNING BEFORE A DRYING TREND COMMENCES AHEAD OF THE NEXT
BIG LOW OUT OVER THE NORTH PACIFIC.

STIFF NORTHERLY WINDS 20 TO 30 MPH WITH TEMPERATURES 5 BELOW TO 10
BELOW HAVE PROMPTED THE ISSUANCE OF A WIND CHILL ADVISORY FOR THE
KUSKOKWIM DELTA ZONE...AND THIS WILL EXTEND OUT THROUGH SATURDAY
MORNING GIVEN LITTLE CHANGE IN TEMPERATURES OR WINDS EXPECTED UNTIL
LATE SATURDAY MORNING.

BERING SEA REGION...

A STATIONARY OCCLUDED FRONT WILL REMAIN SITUATED FROM SOUTHWEST OF
ATTU ISLAND ACROSS THE SOUTHERN BERING SEA TO THE WESTERN GULF.
EXPECT LOW CEILINGS AND DRIZZLE OR SHOWERS TO THE SOUTH OF THE
FRONT...WITH SNOW AND FREEZING DRIZZLE ON THE NORTH SIDE OF THE FRONT
ACROSS THE BERING THROUGH THE FIRST HALF OF SATURDAY. THIS FEATURE
THEN WEAKENS AS A STRONG LOW DEVELOPS IN THE NORTH PACIFIC SOUTH OF
THE ALEUTIAN CHAIN SATURDAY.

.LONG TERM FORECAST...

LONG RANGE MODELS ARE GENERALLY CONSISTENT IN DEPICTING THE MAIN
UPPER LOW PRESSURE SYSTEM REMAINING QUASI-STATIONARY OVER THE
SOUTHERN BERING SEA THROUGH MOST IF NOT ALL OF NEXT WEEK...WHICH WILL
ALLOW FOR MOIST SOUTHERLY FLOW TO CONTINUE TO MOVE NORTHWARD INTO THE
STATE FROM THE PACIFIC AS SYSTEMS ROTATE AROUND THIS FEATURE.
THUS...WARMER AND WETTER THAN NORMAL CONDITIONS ARE LIKELY FOR MOST
OF NEXT WEEK ACROSS THE SOUTHERN MAINLAND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...WIND CHILL ADVISORY...155
MARINE...GALES...130 132 155 170 172 179
         HVY FRZG SPRY...179 185
FIRE WEATHER...NONE.

CC JAN 11