Wind Chill Advisory 20, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
625 AM AST WED DEC 19 2007

.ANALYSIS AND UPPER LEVELS...
A LARGE LOW PRESSURE SYSTEM IS DEEPENING OVER THE WESTERN ALEUTIANS
WHILE RELATIVELY TRANQUIL WEATHER IS IN PLACE OVER THE MAJORITY OF
THE STATE EARLY THIS MORNING. COLD CORE UPPER LOW TO THE NORTH NEAR
THE BROOKS RANGE MOVING VERY LITTLE WHICH IS KEEPING SURFACE LOWS
FROM TRACKING INLAND. AIR MASS COLDEST INLAND ALTHOUGH BELOW AVERAGE
TEMPERATURES CAN BE FOUND OVER THE ENTIRE DOMAIN. WEAK SURFACE LOW
LOCATED NEAR MIDDLETON ISLAND DRIFTING NORTHEAST. SNOW SHOWERS
ASSOCIATED WITH THIS FEATURE MOSTLY LIMITED TO OFFSHORE LOCATIONS
ALTHOUGH EXPECTING SOME IMPACT ON COASTAL AND INLAND AREAS LATER
TODAY AS IT APPROACHES CAPE SUCKLING.

.MODEL DISCUSSION...
MODELS CONTINUE TO HAVE A HARD TIME PAST 36 OR 48 HOURS. WE HAVE
RELATIVE CONFIDENCE THAT A WEAK TRIPLE POINT LOW WILL DEVELOP ON THE
PACIFIC SIDE OF THE AKPEN ALONG THE WEAKENING FRONTAL BOUNDARY. THIS
LOW WILL MOVE JUST EAST OF KODIAK THURSDAY AFTERNOON AND THEN MOVE
INTO THE NORTHERN GULF THURSDAY NIGHT. AFTER THIS...CONFIDENCE IS LOW
AS MODELS HAVE LARGE DIFFERENCES AS WELL AS VERY POOR RUN TO RUN
CONSISTENCY. AGREE WITH THE PREVIOUS FORECAST DISCUSSION THAT THE
UPPER LEVELS SHOW SOME CONTINUITY SO SYNOPTICALLY WE HAVE A GOOD IDEA
OF WHAT WILL BE HAPPENING BUT WITH SO MANY LARGE DIFFERENCES IN THE
SURFACE FEATURES...OPTED TO MAKE ONLY MINOR CHANGES IN THE MID AND
LONG RANGE FORECAST.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
COLD AIR MASS INLAND AND WARM OCEAN WATER TEMPERATURES RESULTING IN A
STRONG THERMAL GRADIENT. THE PRESSURE GRADIENT IS ALSO CAUSING SOME
STRONG WINDS THROUGH THE GAPS WITH 1012 MB NEAR BETHEL AND 990 MB
NEAR MIDDLETON ISLAND. TODAY...SCATTERED SNOW SHOWERS OVER KODIAK
WILL END WHILE ACTIVITY INCREASES AROUND PRINCE WILLIAM SOUND.
ELSEWHERE...MOSTLY CLEAR SKIES AND PATCHY FOG WILL PERSIST UNTIL THE
TRIPLE POINT LOW MOVES INTO THE NORTHERN GULF THURSDAY AFTERNOON. AT
THIS POINT...CONFIDENT THE COASTAL AREAS WILL SEE SNOW BUT NOT SURE
HOW FAR INLAND THE SNOW WILL MAKE IT. HAVE INCLUDED A CHANCE OF SNOW
FRIDAY FOR ANCHORAGE FOR THE POSSIBILITY THAT THE LOW MOVES INTO THE
FAVORABLE SNOW MAKING POSITION...KEEPING IN MIND THAT MODELS ARE IN
POOR AGREEMENT WITH SURFACE FEATURES AT THIS POINT.

SOUTHWEST MAINLAND...
LOW PRESSURE LOCATED OVER THE ALEUTIANS IS DRAWING ARCTIC AIR FROM
THE INTERIOR DOWN THE KUSKOKWIM VALLEY AND INTO BRISTOL BAY. MOST
STATIONS REPORTING ZERO TO 40 BELOW IN THESE THREE ZONES. WINDS WILL
INCREASE ALONG THE COAST AS THE FRONT APPROACHES THE AKPEN. THIS WILL
DROP WIND CHILL READINGS TO 20 BELOW TO 35 BELOW IN THIS AREA WHILE
FURTHER INLAND WILL REMAIN PARTLY CLOUDY...DRY...AND COLD. SNOW WILL
MAINLY FLY ALONG THE ALEUTIAN RANGE AND BRISTOL BAY STARTING EARLY
TOMORROW MORNING WITH THE POSSIBILITY OF BLOWING SNOW.

BERING SEA/ALEUTIANS...
A 976 MB LOW TO THE SOUTH OF THE ANDREANOF ISLANDS EARLY THIS MORNING
WILL CONTINUE TO MATURE TO 967 MB BY THIS AFTERNOON ON THE BERING SEA
SIDE OF THE ISLANDS. THE FRONT WILL BE THE MAIN WEATHER MAKER AS IT
SPREADS RAIN AND SNOW ALONG THE CHAIN. TEMPERATURES WILL REMAIN COLD
ENOUGH AT THE PRIBILOF ISLANDS TO WARRANT A BLIZZARD WARNING WITH
STRONG EASTERLY FLOW AHEAD OF THE FRONT AND ABUNDANT MOISTURE. THE
FRONT WILL STALL OUT JUST SOUTH OF THE PRIBILOFS WHICH WOULD KEEP
THEM IN AN AREA FAVORABLE FOR SNOW AND BLOWING SNOW FOR AN EXTENDED
AMOUNT OF TIME. HAVE PUT OUT THE WARNING TO REFLECT THIS SCENARIO.

.LONG TERM FORECAST...
TOO MUCH UNCERTAINTY.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 195.
MARINE...STORM WARNING ZONES 175.
         GALE WARNING ZONES 121 129 130 165 170 171 172 176 179 180
          185.
         HEAVY FREEZING SPRAY WARNING ZONES 121 125 129 130 138 140
          141 150 160 179 180 185
FIRE WEATHER...NONE.

AB DEC 07