Gale Warning 112, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKST SAT FEB 27 2010

.ANALYSIS AND UPPER LEVELS...
AMPLIFIED PATTERN TAPPING INTO A VERY COLD ARCTIC AIR MASS. AIDED BY
A 180 KT JET CORE ROTATING AROUND THE BASE OF THE TROUGH...AN
IMPRESSIVE 963 MB LOW HAS DEVELOPED AND REACH MATURITY IN THE NORTH
PACIFIC. THE MATURE SYSTEM IS OCCLUDING AS THE ENERGY MOVES NORTH
INTO THE GULF OF ALASKA. HIGH PRESSURE CENTERED OVER EASTERN SIBERIA
LOSING GROUND AS A POTENT SHORTWAVE UNDERCUTS THE RIDGE OFF OF THE
KAMCHATKA PENINSULA.

.MODEL DISCUSSION...
SUBTLE DIFFERENCES IN THE MODELS THAT WILL HAVE LARGE IMPACTS ON THE
FORECAST. THE CHALLENGE HAS BEEN TO PICK THE RIGHT TRACK OF THE
OCCLUDED LOW AS IT WEAKENS AND MOVES NORTH TOWARD THE NORTHWESTERN
GULF TONIGHT AND SUNDAY. THE NAM CONTINUES TO HOLD ON TO A EASTERN
TRACK. IT IS THE OUTLIER AND HAS BEEN DISREGARDED. THE
GFS...UKMET...AND ECMWF ARE IN BETTER AGREEMENT TAKING THE LOW JUST
EAST OF KODIAK ISLAND. THE MEMBERS OF THE GFS ENSEMBLE ARE IN
RELATIVELY GOOD AGREEMENT WITH THIS TRACK AS WELL.

.SOUTHCENTRAL ALASKA...THE CHALLENGE OF THIS FORECAST PACKAGE WILL BE
NAILING DOWN THE AFFECTS OF THE APPROACHING LOW INCLUDING THE AMOUNT
OF OVERRUNNING MOISTURE VS THE DOWNSLOPING EFFECT. FURTHER
COMPLICATING MATTERS IS THE WARM AIR WRAPPING AROUND THE OCCLUSION
THAT COULD ALSO LIMIT SNOWFALL TOTALS ALONG COASTAL SECTIONS. AN
INITIAL SHORTWAVE IS SPREADING RAIN AND SNOW TOWARD WESTERN PRINCE
WILLIAM SOUND AND EASTERN KENAI PENINSULA. EXPECT SNOW TO SPREAD INTO
THE ANCHORAGE BOWL TONIGHT WITH THE FIRST WAVE AND ASSOCIATED
OVERRUNNING MOISTURE. THERE SHOULD BE A BREAK IN THE PRECIPITATION AS
SOUTHEASTERLY WINDS INCREASE AND DOWNSLOPE THE AREA...RESULTING IN
FLURRIES OR EVEN A BREAK IN THE ACTION BEFORE THE LOW APPROACHES THE
SOUTHERN KENAI SUNDAY AFTERNOON. PRECIP WILL AGAIN INCREASE IN
INTENSITY AND COULD MIX WITH RAIN OR EVEN FREEZING RAIN SUNDAY NIGHT
AND MONDAY.

THE LOW DISSIPATES DURING THAT TIME FRAME BUT AN INVERTED SURFACE
TROUGH REMAINS IN THE REGION THROUGH AT LEAST TUESDAY. THIS COULD
RESULT IN A PROLONGED PERIOD OF PRECIPITATION...WITH THE POSSIBILITY
OF HEAVY PRECIPITATION AS THE EMBEDDED UPPER LEVEL SHORTWAVES ROTATE
AROUND THE EASTERN PERIPHERY OF THE UPPER TROF.

SOUTHWEST ALASKA...SOUTHWEST INTERIOR IS RELATIVELY QUIET COMPARED TO
THE OTHER REGIONS IN ALASKA. THE EXCEPTION IS THE EXTREME COLD AIR
MASS COUPLED WITH GUSTY WINDS RESULTING IN WIND CHILLS REACHING
ADVISORY CRITERIA...SPECIFICALLY AROUND THE KUSKOKWIM DELTA. SOME
LIGHT OVERRUNNING MOISTURE IS CROSSING THE ALEUTIAN RANGE ALONG THE
ALASKA PENINSULA RESULTING IN LIGHT SNOW SHOWERS NEAR KING SALMON.
THIS AREA OF LIGHT SNOW WILL SPREAD NORTH ALONG THE RANGE BUT
OTHERWISE SOUTHWEST ALASKA WILL REMAIN MOSTLY DRY...ESPECIALLY UP
NEAR THE KUSKOKWIM VALLEY.

ALEUTIANS/BERING SEA...COLD ADVECTION SHOWERS AND BLOWING SNOW
AFFECTING THE WESTERN ALASKA PENINSULA AND EASTERN ALEUTIANS. ON THE
WESTERN SIDE OF THE EASTERN BERING SEA HIGH IS A WEAKENING FRONTAL
BOUNDARY STRETCHING OUT OF EASTERN SIBERIA. THE FRONT WILL FALL APART
AS IT REACHES THE CENTRAL ALEUTIANS SUNDAY BUT A MUCH MORE POWERFUL
LOW WILL DEVELOP SOUTH OF THE CHAIN MONDAY MORNING AND DEEPEN RAPIDLY

INTO A STORM FORCE SYSTEM WITH POSSIBLE HURRICANE FORCE GUSTS. THIS
SAME SYSTEM WILL SLIDE EAST AND POSSIBLY BRING BLIZZARD CONDITIONS TO
THE PRIBILOFS AS THE COLD AIR AND WINDS MEET IN THAT REGION.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING ZONES 120132 138 150 155 160 165 170 171 172
       175 176 185
FIRE WEATHER...NONE.

AB FEB 10