Heavy Snow in Alaska, December 23, 2007

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
505 AM AST SUN DEC 23 2007

.ANALYSIS AND UPPER LEVELS...
THIS MORNING...THERE IS A STRONG SURFACE LOW IN THE EASTERN GULF OF
ALASKA MOVING NORTHEAST. A SURFACE TROUGH AXIS EXTENDS NORTHWEST
FROM THE LOW THROUGH KENNEDY ENTRANCE AND INTO THE KUSKOKWIM VALLEY.
PRECIPITATION IS PRESENT ALONG BOTH SIDES OF THIS TROUGH AXIS...WITH
SOME GUSTY WEST TO SOUTHWEST WINDS AND COLD ADVECTION ON THE BACK
SIDE OF THE TROUGH AXIS AS IT MOVES NORTHEAST AND UP COOK INLET
TODAY. OUT WEST...SHOWERY COLD NORTHWEST FLOW ENCOMPASSES THE
BERING. A SURFACE LOW PRESSURE IS TRACKING JUST SOUTH OF THE
ALEUTIAN CHAIN FROM WEST TO EAST TODAY...WITH THE NORTH SIDE OF THE
LOW BRINGING SNOW AND WINDS TO THE EASTERN ALEUTIANS TODAY.

.MODEL DISCUSSION...
MODELS OVERALL ARE DOING OKAY...BUT THEY HAVE NOT BEEN TERRIBLY
CONSISTENT RUN TO RUN WITH THE LOW TRACKING SOUTH OF THE ALEUTIANS
TODAY. LATEST MODEL RUNS ARE SHIFTING THE LOW TRACK A LITTLE FARTHER
SOUTH FOR TODAY AND THIS EVENING WHICH MAY MAKE IT TOUGH FOR THE
SNOW TO GET AS FAR NORTH AS DUTCH HARBOR TODAY AND COLD BAY TONIGHT.
STILL SOME INCONSISTENCIES FOR THE LOW TRACK AS WELL ONCE IN GETS
INTO THE NORTH/WEST GULF OF ALASKA MONDAY AND MONDAY NIGHT. STRONG
WINDS WITH THIS LOW PRESSURE ARE A CERTAINTY AND WE HAVE RAISED
WINDS OVER SOME AREAS...BUT THE UNCERTAINTY WITH THE TRACK WILL KEEP
US CONSERVATIVE FOR SNOWFALL TOTALS UNTIL WE GET A BETTER LOCK ONTO
THE LOW.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
FIRST ITEM OF CONCERN IS A SHARP TROUGH AXIS MOVING NORTHEAST
THROUGH THE FAR NORTHWEST GULF AND COOK INLET REGION TODAY.
EXPECTING GUSTY WEST TO SOUTHWEST WINDS ON THE BACK SIDE ALONG WITH
STRONG COLD ADVECTION. THIS IS EVIDENCED BY AUGUSTINE ISLAND WHICH
DROPPED 11 DEGREES WITHIN AN HOUR AS THE TROUGH AXIS MOVED THROUGH.
EXPECT A GOOD BUT QUICK SHOT OF SNOW TODAY INTO THIS EVENING AS THE
TROUGH AXIS MOVES UP COOK INLET. DO NOT EXPECT THE PRECIPITATION TO
LAST MUCH MORE THAN SIX HOURS ANYWHERE...WHICH SHOULD KEEP SNOW
AMOUNTS FROM REACHING ADVISORY CRITERIA. WILL HAVE TO WATCH FOR
BLOWING SNOW AROUND KACHEMAK BAY TODAY AS THE STRONG WESTERLY WINDS
KICK IN BY MIDDAY WITH THE SNOW. THERE WILL BE A VERY BRIEF BREAK IN
SYSTEMS THIS AFTERNOON/EVENING FOR KODIAK AND LATE TONIGHT FOR
SOUTHCENTRAL BEFORE A MAJOR LOW PRESSURE BRINGS BACK THE ACTION. DUE
TO UNCERTAINTY IN THE TRACK OF THE LOW...WE ARE NOT HITTING ANYTHING
TOO HARD AT THE MOMENT...BUT THERE IS THE POTENTIAL FOR SOME STRONG
WINDS AND HEAVY SNOW (AND RAIN) FOR QUITE A FEW AREAS WITH THIS LOW
DEPENDING ON ITS TRACK. THE BEST GUESS TRACK OF THE LOW IS FROM JUST
EAST OF KODIAK NORTHEAST INTO PRINCE WILLIAM SOUND. STORM FORCE
WINDS LOOK LIKELY OVER MANY MARINE AREAS. WITH VERY STRONG COLD
ADVECTION ON THE BACKSIDE OF THE LOW...ACCUMULATING SNOW IS A GOOD
POSSIBILITY FROM COOK INLET UP INTO THE SUSITNA VALLEY LATE MONDAY
INTO EARLY TUESDAY.

SOUTHWEST MAINLAND...
LIGHT SNOW WILL OCCUR OVER MUCH OF THE KUSKOKWIM VALLEY TODAY AS THE
ALREADY DISCUSSED TROUGH AXIS MOVES THROUGH. AFTER THIS...MOST OF
THE ACTIVE WEATHER (SNOW AND WIND) WILL BE ALONG THE ALEUTIAN AND
ALASKA RANGE ON THE WEST/NORTHWEST SIDE OF THE LOW TRACKING THROUGH
THE NORTH/WEST GULF OF ALASKA MONDAY AND MONDAY NIGHT.

BERING SEA/ALEUTIANS...
LOW PRESSURE PASSING SOUTH OF THE ALEUTIANS WILL SKIM THE EASTERN
ALEUTIANS AND ALASKA PENINSULA TODAY AND TONIGHT. NOT CONFIDENT THAT
A WHOLE LOT OF ACTUAL SNOW WILL REACH AS FAR NORTH AS DUTCH WITH
THIS SYSTEM...SO WE ARE OPTING WITH A BLOWING SNOW ADVISORY. ISSUING
A BLIZZARD WATCH FOR THE ALASKA PENINSULA THIS EVENING AS THE LOW
WILL TRACK A LITTLE CLOSER TO THEM BUT THEY WILL STILL BE ON THE
COLD SIDE OF THE LOW. A STRONGER LOW PRESSURE WILL THEN TAKE A TRACK
SIMILAR TO OR JUST NORTH OF ITS PREDECESSOR...TRACKING ALONG OR JUST
SOUTH OF THE ALEUTIANS/ALASKA PENINSULA TUESDAY THROUGH WEDNESDAY.

.LONG TERM FORECAST...
COLD SHOWERY NORTHWEST FLOW IS LIKELY TO PERSIST IN THE BERING
THROUGH LATE NEXT WEEK...WITH LOW PRESSURE OVER THE GULF OF ALASKA
AND SEASONABLY COLD AIR OVER THE MAINLAND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WATCH 181.
MARINE...STORM WARNING ZONES 120 130 132 140 351 352.
         GALE WARNING ZONES 125 138 141 150 155 160 165 170.
         HEAVY FREEZING SPRAY WARNING ZONES 130 138 140 150 155 160
          165 180 185 411 412 414.
FIRE WEATHER...NONE.

FOISY DEC 07