Gale Warning 1061, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTH CENTRAL AND SOUTHWEST ALASKA
500 PM AST THU DEC 28 2006

.DISCUSSION...THE ACTIVE WEATHER PATTERN CONTINUES FOR THE ENTIRE
FORECAST AREA. TODAY IS THE BREAK BETWEEN SYSTEMS FOR MOST OF
SOUTHERN ALASKA.

IN THE EAST...A LARGE LOW THAT IS VISIBLE ON SATELLITE JUST SOUTH OF
THE GULF OF ALASKA WILL MOVE INTO THE NORTH GULF OF ALASKA FRIDAY.
THIS STRONG SYSTEM HAS ALL THE INGREDIENTS TO MAKE THE FORECAST
PARTICULARLY CHALLENGING. THE WARM SECTOR IN THE SOUTHEAST PART OF
THE STORM IS MUCH WARMER THAN THE LAST COUPLE OF LOWS. THE LOW IS
EXPECTED TO GO INTO PRINCE WILLIAM SOUND FRIDAY EVENING BUT THE
IMPACT ON THE WEATHER IS NOT AS SIMPLE AS SOME LOWS. THE WARM AIR
WILL MOVE INTO THE SOUND WITH THE LOW AND BRING RAIN INTO A LOT OF
THE SOUND...ESPECIALLY IN EASTERN PARTS. THE PRECIPITATION TYPE IN
VALDEZ WILL BE A TOUGH CALL AS THE PROPENSITY FOR THE VALDEZ AREA TO
REMAIN SNOW EVEN WITH WARM AIR MOVING IN. ANOTHER CONSIDERATION FOR
THE VALDEZ AREA IS WHETHER THERE WILL BE BLOWING SNOW OR BLIZZARD
CONDITIONS THROUGH THOMPSON PASS. IF THE LOW REMAINS ON ITS FORECAST
TRACK IT WILL BRING SIGNIFICANT SNOWFALL TO THE COOK INLET AREAS AS
WELL AS THE HIGHER ELEVATIONS OF THE EASTERN KENAI PENINSULA. THE
REAL TRICKY PART IS EXACTLY WHERE THIS LOW TRACK WILL BE AND HOW MUCH
WARM AIR IS AROUND THE LOW BEFORE THE COLD AIR WRAPS AROUND THE LOW
AND PUSHES ALL LEVELS BELOW FREEZING. A HUNDRED MILE DIFFERENCE IN
WHERE THIS LOW MOVES INTO THE SOUND WILL MAKE A LARGE IMPACT IN THE
FORECASTS. AS THIS LOW MOVES INTO THE SOUND IT WILL MOVE VERY SLOWLY
AND WEAKEN. THIS WILL MAKE SNOW LIKELY OVER THE ENTIRE SOUTH CENTRAL
ALASKA REGION AS WELL AS PRINCE WILLIAM SOUND AREAS...EVEN AREAS THAT
INITIALLY GET RAIN. THE EXCEPTION TO ALL THIS WILL BE KODIAK WHICH
SHOULD REMAIN OUTSIDE MOST OF THE PRECIPITATION WITH THIS STORM AND
WILL LIKELY ONLY SEE GUSTY NORTHWEST WINDS OUT OF IT.

MODELS...THE GFS MODEL HAS BEEN VERY CONSISTENT THE LAST NUMBER OF
RUNS WITH BRINGING THE LOW INTO THE MIDDLE OF THE SOUND. IF THIS
OCCURS WITH THE WARM AIR REMAINING MOSTLY EAST IT WILL BRING A
SIGNIFICANT SNOWFALL TO THE COOK INLET AREA AND EASTERN KENAI
PENINSULA. A CONSIDERATION FOR THE ANCHORAGE AREA IS THE POSSIBILITY
OF SOME FREEZING RAIN IF ENOUGH OF THE WARM AIR ALOFT AROUND THIS LOW
OVERRIDES THE COLD SURFACE AIR OVER ANCHORAGE AND TURNAGAIN ARM.
THE NAM IS SIMILAR TO THE GFS OVERALL. HOWEVER ONE DIFFERENCE BETWEEN
THE TWO THAT COULD HAVE AN IMPACT IS THE WAY THE NAM WANTS TO DEVELOP
A LOW AHEAD OF THE MAIN LOW AS IT MOVES THROUGH THE GULF. WE WILL
WANT TO WATCH THIS SYSTEM OVERNIGHT AND SEE IF A SPLIT IN THIS LOW
INTO TWO LOWS OCCURS. IF SO IT WILL LIKELY BRING SOME OF THE WARM AIR
FURTHER WEST AND INCREASE THE PROBABLY OF RAIN MAKING IT INTO THE
EASTERN KENAI AND EVEN COOK INLET AREA. RIGHT NOW THE MODELS ARE
INDICATING THE PRECIPITATION IN THESE AREAS TO REMAIN SNOW. THE BIG
CONCERN ABOUT THIS RIGHT NOW IS THAT THE MODELS HAVE BEEN RUNNING A
LITTLE COOL WITH WARMER AIR IN THE SYSTEMS THAN THE MODELS ARE
INDICATING. THAT IS WHY THERE IS STILL SOME CONCERN ABOUT RAIN OR
FREEZING RAIN IN THE COOK INLET AREA AND EASTERN KENAI PENINSULA.

IN THE WEST...NUMEROUS AREAS OF BLOWING SNOW PERSIST AS THE OLD LOW
JUST SOUTHEAST OF COLD BAY CONTINUES TO CHURN. THIS LOW SHOULD
FINALLY DISSIPATE OVERNIGHT AND HELP DIMINISH THE WINDS AND BLOWING
SNOW AREAS. IT WILL REMAIN BREEZY IN THE SOUTHWEST ALASKA MAINLAND AS
THE LOW IN MOVING INTO THE GULF OF ALASKA KEEP THE PRESSURE GRADIENT
FROM RELAXING ENTIRELY. A COMPLEX LOW AND ASSOCIATED FRONT SOUTHWEST
OF ATTU WILL MOVE SOUTH OF THE ALEUTIAN CHAIN OVERNIGHT AND
STRENGTHEN AS IT MOVES EASTWARD. IT WILL CREATE A LARGE AREA OF
STRONG WINDS OVER THE ENTIRE ALEUTIAN CHAIN BY SATURDAY AFTERNOON.
SNOW AND BLOWING SNOW ARE LIKELY IN THESE AREAS AT THAT TIME.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM 120 172 175 350. GALE 125 130 132 150 176 410 .
FIRE WEATHER...NONE.

DEC 06