Avalanche in Alaska, February 9, 2006

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM AST THU FEB 9 2006

.DISCUSSION...

UPPER LEVELS...TWO MAIN FEATURES ANCHORING THE 500MB PATTERN FOR THE FORECAST
AREA ARE A RIDGE EXTENDING NEARLY ALL THE WAY UP THE WEST COAST OF NORTH
AMERICA FROM BAJA CALIFORNIA THROUGH INTERIOR ALASKA TO THE ARCTIC OCEAN AND A
BROAD ANCHOR LOW CENTERED OVER THE SEA OF OKHOTSK. A STRONG AND MOBILE UPPER
LOW SOUTH OF THE ANDREANOF ISLANDS IS BETWEEN THE TWO FEATURES. THIS LOW WILL
MOVE EAST TO UNALASKA BY THU EVENING AND STALL OUT AS IT RUNS INTO RUN INTO THE
RIDGE. THE LOW WILL THEN RIDE NORTHWEST ACROSS THE BERING SEA ALONG THE WESTERN
EDGE OF THE RIDGE BEFORE BEING ABSORBED INTO ANOTHER TROUGH EXTENDING ACROSS
NORTHERN KAMCHATKA FROM THE ANCHOR LOW OVER THE SEA OF OKHOTSK FRI NIGHT. AS
THE LOW MOVES ACROSS THE BERING SEA...A STRONG VORTMAX WILL ROTATE AROUND THE
LOW AND ACROSS SOUTHCENTRAL FRI MORNING AND TO THE SEWARD PENINSULA BY EARLY
SAT MORNING. ANOTHER VORTMAX EMBEDDED IN THE WESTERLIES AROUND 45N WILL AMPLIFY
SOUTH OF THE AK PEN AND DEVELOP INTO A CLOSED LOW FRI NIGHT AS IT DIGS INTO THE
RIDGE AND MOVES OVER SOUTHWEST AK BY SUN AFTERNOON.

SURFACE EAST...THE SURFACE LOW THAT HAS BEEN DEVELOPING OVERNIGHT HAS MATURED
AND IS PUSHING A STRONG FRONT ONTO THE NORTHERN GULF COAST. THE TIGHT PRESSURE
GRADIENT COUPLED WITH THE DEVELOPMENT OF A BARRIER JET ALONG THE NORTHEAST GULF
COAST WILL ALLOW FOR VERY STRONG WINDS TO DEVELOP OVER THE NORTHERN GULF WITH
HURRICANE FORCE WINDS POSSIBLE ACROSS MARINE ZONE 120. A HIGH WIND WARNING IS
ALSO IN EFFECT FOR PUBLIC ZONES 135 121 AND 101. PRECIP IMMEDIATELY ALONG THE
COAST SHOULD CHANGE FROM SNOW OVER TO RAIN OVER THE NEXT FEW HOURS AS THE WARM
AIR MOVES IN. AMPLE MOISTURE STREAMING NORTH FROM THE SUBTROPICS WILL SPILL
OVER THE CHUGACH MOUNTAINS AND ALLOW FOR DECENT SNOWFALL TOTALS IN THE COPPER
RIVER BASIN...PARTICULARLY IN THE UPSLOPE AREAS WEST OF THE COPPER RIVER. THE
ANCHORAGE BOWL AND MATSU VALLEY SHOULD SEE LITTLE TO NO SNOW ACCUMULATION DUE
TO STRONG DOWNSLOPING.

THE FRONTAL PASSAGE LATER TODAY WILL USHER IN A SIGNIFICANT WARMING TREND FOR
MUCH OF THE SOUTHERN PART OF THE STATE. A STRONG SURFACE LOW NEAR THE AK PEN
WILL MOVE INTO THE BERING SEA FRI NIGHT AS ANOTHER VIGOROUS LOW DEVELOPS IN THE
WESTERLIES AND MOVES RAPIDLY EAST AND THEN NORTH TO THE AK PEN SAT. IN SHORT
THIS ADDS UP TO MOIST SOUTHERLY FLOW PERSISTING THROUGH THE WEEKEND WITH
TEMPERATURES APPROACHING THE 40 DEGREE MARK ACROSS SOUTHCENTRAL WITH RAIN
LIKELY IN THE FORECAST ALONG THE COAST AND ACROSS UPSLOPE AREAS. DOWNSLOPING
SHOULD KEEP ANCHORAGE LIMITED TO CHANCE POPS THROUGH THE WEEKEND HOWEVER. THE
COPPER RIVER BASIN WILL WARM UP AS WELL...BUT THE COLDER AIR THERE IS SLOWER TO
ERODE AND TEMPS WILL STAY BELOW OR CLOSE TO FREEZING THROUGH THE WEEKEND.

ACROSS THE WEST...THE LARGE SURFACE LOW ADVERTISED OVER THE LAST SEVERAL DAYS
WILL CONTINUE TO MOVE SOUTH OF THE ALEUTIANS WITH A BROAD SHIELD OF
PRECIPITATION SWEEPING ACROSS THE EASTERN ALEUTIANS...AK PEN...AND BERING SEA.
PRECIP STAY AS SNOW EXCEPT FOR ALONG THE AK PEN WHERE 850 TEMPS WARM ENOUGH TO
MIX RAIN TODAY. AS THE LOW TURNS NORTH...THE MAIN PRECIP SHIELD SHOULD REMAIN
FAR ENOUGH AWAY FROM THE COAST TO KEEP THE LOWER YUKON-KUSKOKWIM VALLEYS IN
ONLY CHANCE POPS TODAY. BEHIND THE LOW OVER THE WESTERN AND CENTRAL
ALEUTIANS...COLD ADVECTION BRINGS SNOW SHOWERS. BY FRIDAY NIGHT THE COLD
ADVECTION AND SNOW SHOWERS MAKE THEIR ACROSS THE EASTERN ALEUTIANS AND TO THE
AK PEN WHILE ANOTHER LOW MOVES INTO THE BERING SEA NORTH OF SHEMYA WHILE
SWEEPING A FRONT THROUGH FAR WESTERN ALEUTIANS SAT NIGHT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 101 125 135
MARINE...HURRICANE FORCE 120
         STORM 125 129 130 132 138 140 150 171
         GALE 141 155 160 165 170 172 176 179
FIRE WEATHER...NONE

WOOD FEB 06