Heavy Freezing Spray Warning 37, NWS Anchorage, AK

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

.ANALYSIS AND UPPER LEVELS...
MAIN UPPER LEVEL FEATURE THIS AFTERNOON IS A BROAD UPPER LEVEL LOW
CENTERED SEVERAL HUNDRED MILES SOUTHWEST OF SHEMYA BUT ENCOMPASSING
MUCH OF THE BERING SEA AND THE ALEUTIANS. A 120 KT JET...TRAPPED
BETWEEN THIS LOW AND A RIDGE TO THE SOUTH...FOLLOWS THE ALEUTIAN
ISLANDS AND THEN TURNS EASTWARD AND TRACKS THROUGH THE SOUTHERN GULF.
SEVERAL UPPER LEVEL SHORTWAVES EMBEDDED IN THIS SOUTHWESTERLY
FLOW...ONE OVER THE SOUTHEASTERN BERING AND ANOTHER SEVERAL HUNDRED
MILES SOUTH OF THE WESTERN ALEUTIANS....ARE QUICKLY TRACKING
NORTHEASTWARD TOWARDS THE WESTERN GULF.

AT THE SURFACE...A NUMBER OF WEATHER SYSTEMS RESIDE ACROSS THE AOR
THIS AFTERNOON. A DECAYING OCCLUDED LOW IS LOCATED IN THE SOUTHERN
COPPER RIVER BASIN AND BRINGING WIDESPREAD SNOW TO THE AREA. THIS
SYSTEM ALSO BROUGHT SOME LIGHT SNOW FROM THE KENAI PENINSULA
NORTHWARD TO THE SOUTHERN SUSITNA VALLEY THIS MORNING AS THE LOW
TRACKED JUST SOUTH OF THE PENINSULA. ONSHORE FLOW ON THE BACKSIDE OF
THE SYSTEM IS ALSO LEADING TO THE DEVELOPMENT OF CONVECTIVE SHOWERS
OVER THE NORTHERN GULF. A WEAK ZONALLY ORIENTED DEFORMATION
ZONE...THE REMNANTS OF THE OCCLUDED FRONT THAT PUSHED INLAND TWO DAYS
AGO...IS BRINGING SOME VERY LIGHT SNOW SHOWERS AND LOW CLOUDS TO MUCH
OF SOUTHWEST ALASKA. ANOTHER DEVELOPING LOW 200 MILES SOUTH OF KODIAK
IS RACING INTO THE WESTERN GULF. FINALLY...A LARGE COMPLEX 980 MB LOW
ENCOMPASSES MUCH OF THE NORTH PACIFIC A FEW HUNDRED MILES SOUTHWEST
OF THE ALEUTIANS.

.MODEL DISCUSSION...
THE MODELS ARE SLOWLY ADJUSTING TO OUR NEW WEATHER PATTERN AND COMING
INTO BETTER AGREEMENT...ESPECIALLY COMPARED TO YESTERDAY. THERE STILL
ARE SIGNIFICANT DIFFERENCES IN THE MODELS WITHIN THE FIRST 24 HOURS
OF THE FORECAST PERIOD WITH REGARDS TO THE LOW CURRENTLY POISED TO
ENTER THE GULF TONIGHT. THE NAM AND ECMWF ARE IN CLOSE PROXIMITY WITH
ONE ANOTHER WHILE THE GFS IS MUCH FARTHER SOUTH AND WEST. THIS IS
ALSO THE CASE WITH THE NEXT WEATHER SYSTEM THAT AFFECTS SOUTHERN
ALASKA THIS WEEKEND...WHERE THE ECMWF AND NAM ARE IN CLOSE AGREEMENT
AND THE GFS IS MUCH SLOWER. THE MODELS THEN DIVERGE SIGNIFICANTLY BY
MONDAY MORNING...BUT CONTINUE TO DEPICT AN ACTIVE WEATHER PATTERN
THROUGH NEXT WEEK. THIS AFTERNOON'S FORECAST USED PRIMARILY THE ECMWF
DUE TO ITS DECENT RUN TO RUN CONSISTENCY.

.SHORT TERM FORECAST...
.SOUTHCENTRAL ALASKA...THE DISSIPATING LOW OVER THE SOUTHERN COPPER
RIVER BASIN WILL PUSH NORTHEASTWARD INTO THE SOUTHERN YUKON TERRITORY
THIS EVENING...THOUGH ONSHORE FLOW ON THE BACKSIDE OF THE SYSTEM WILL
STILL LEAD TO THE DEVELOPMENT OF RAIN SHOWERS ALONG THE NORTH GULF
COAST. THE NEXT SYSTEM LOCATED 200 MILES SOUTH OF KODIAK TRACKS
ACROSS THE GULF TONIGHT BUT TAKES A MORE SOUTHERLY TRACK THAN ITS
PREDECESSOR...WHICH SHOULD LIMIT THE AMOUNT OF PRECIPITATION THAT
FALLS OVER SOUTHCENTRAL. THERE IS A CHANCE OF SNOW SHOWERS ACROSS THE
AREA ON SATURDAY DUE TO SEVERAL WEAK MID-LEVEL DISTURBANCES THAT PASS
THROUGH ON THE BACKSIDE OF THIS SYSTEM. A STRONG WEATHER FRONT SURGES
NORTH INTO THE GULF ON SUNDAY MORNING AND BRINGS A RENEWED CHANCE FOR
SIGNIFICANT PRECIPITATION ALONG THE COAST. TEMPERATURES WILL REMAIN
MODERATE GIVEN THE PERSISTENT CLOUD DECK AND ONSHORE FLOW.

.SOUTHWEST ALASKA...LIGHT SHOWERS ASSOCIATED WITH THE LOW SOUTH OF
KODIAK SHOULD LESSEN IN INTENSITY AND COVERAGE
TONIGHT...HOWEVER...SEVERAL WEAK DISTURBANCES MAY INSTIGATE A FEW
SNOW SHOWERS OVER THE REGION ON SATURDAY. A STRONG WEATHER FRONT
REACHES THE AKPEN SATURDAY NIGHT AND THE COAST OF SOUTHWEST ALASKA ON
SUNDAY MORNING. STIFF OFFSHORE WINDS WILL PERSIST INTO THE WEEKEND
AND INTENSIFY AS THE PRESSURE GRADIENT INCREASES DUE TO THE
APPROACHING FRONT. A WIND CHILL ADVISORY IS CURRENTLY IN EFFECT
THROUGH MUCH OF THE WEEKEND FOR THE KUSKOKWIM DELTA DUE TO THESE
WINDS AND A SHALLOW LAYER OF COLD ARCTIC AIR AT THE SURFACE.

.BERING SEA AND ALEUTIANS...A STORM FORCE LOW CURRENTLY DEVELOPING
SEVERAL HUNDRED MILES SOUTH OF THE WESTERN ALEUTIANS WILL QUICKLY
TRACK NORTH TONIGHT AND BEGIN IMPACTING THE ALEUTIANS TOMORROW
MORNING. THIS LOW WILL DRIFT EASTWARD JUST SOUTH OF THE ISLAND CHAIN
THROUGH MONDAY AND GRADUALLY WEAKEN AS IT OCCLUDES. STRONG
NORTHEASTERLY WINDS WILL SETUP OVER THE BERING ON SATURDAY AS THE LOW
DRAWS CLOSER TO ISLAND CHAIN. EXPOSED NORTHERN PORTS SUCH AS UNALASKA
BAY CAN EXPECT TO SEE GALE FORCE WINDS WITH THIS SYSTEM ON SATURDAY
AND SUNDAY.

.LONG TERM FORECAST...
A NEW STATIONARY UPPER LEVEL LOW DEVELOPS OVER THE WESTERN BERING
EARLY NEXT WEEK...WHICH WILL FACILITATE THE CONTINUED DEVELOPMENT OF
WEATHER SYSTEMS THAT WILL THEN TRACK INTO THE GULF OF ALASKA AND
AFFECT SOUTHERN ALASKA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...WIND CHILL ADVISORY...155.
MARINE...GALE WARNING...132 138 150 155 160 165 170 171 175 176 180
                        185 352 411 412.
         STORM WARNING...172 179 413 414.
         HEAVY FREEZING SPRAY WARNING...160 179 185 411 412 413 414.
FIRE WEATHER...NONE.

KS JAN 11