Wind Chill Advisory 10, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM AST TUE FEB 5 2008

.MODEL DISCUSSION...MODELS IN REASONABLY GOOD AGREEMENT THROUGH THE
SHORT TERM. GFS STILL THE PREFERRED MODEL FOR OPERATIONS. HOWEVER 00Z
TUE GFS RUN IS MARKEDLY DIFFERENT THAN PREVIOUS RUNS BEGINNING AT
AROUND 18Z FRI. NEW RUN RECOGNIZES A LOW CENTER NEAR 50N 155W TO BE A
FULL 30 MB DEEPER THAN 12Z MON RUN. SINCE THIS RAPID DEEPENING IS
ANAMOLOUS TO THE 00Z RUN WE HAVE CHOSEN TO MAKE ONLY MINIMAL CHANGES
TO THE FORECAST PACKAGE FRIDAY ONWARD.

.SURFACE FEATURES...
STRONG HIGH PRESSURE HOLDS FIRMLY OVER INTERIOR ALASKA.
A TROUGH OF LOW PRESSURE WILL PERSIST ALONG THE GULF COAST.
A MODERATE LOW WILL DEVELOP JUST SOUTH OF THE GULF OF ALASKA WED
MORNING THEN TRACK DUE EASTWARD INTO INTERIOR BRITISH COLUMBIA BY THU
MORNING.
A LARGE 960 MB NORTH PACIFIC LOW CENTERED NEAR 48N 179E WILL WEAKEN
TO 975 MB JUST SOUTH OF THE CENTRAL ALEUTIANS NEAR 52N 171W TUE NIGHT
THEN DISSIPATE JUST SOUTH OF THE ALASKA PENINSULA NEAR 54N 160W WED
NIGHT.
MEANWHILE A SECONDARY LOW DEVELOPS NEAR ADAK TUE NIGHT. THE LOW
RAPIDLY DEEPENS TO 990 MB AS IT MOVES TO NEAR SEGUAM ISLAND THU
MORNING.

.UPPER LEVELS...
UPPER LEVEL BLOCKING HIGH WILL REMAIN ANCHORED IN THE VICINITY OF THE
CHUKOTSK AND SEWARD PENINSULAS THROUGH AT LEAST THE NEXT FOUR DAYS.
IT IS THEN FORECAST TO RETREAT BACK INTO CENTRAL SIBERIA BY SUNDAY
AFTERNOON.
LONG WAVE TROUGH ALOFT HAS STALLED OUT OVER EASTERN ALASKA. THE
TROUGH LINE NOW EXTENDS ALONG A INUVIK TO MIDDLETON ISLAND LINE. IT
WILL WEAKEN AND DRIFT EASTWARD DURING THE DAY TODAY ULTIMATELY
DISINTEGRATING OVER WESTERN CANADA THURSDAY MORNING.
A SERIES OF WEAK UPPER LEVEL DISTURBANCES WILL TRACK ALONG THE
ALEUTIAN CHAIN BUT NONE ARE EXPECTED TO BE LONG LIVED.
THE JET STREAM WILL REMAIN WELL SOUTH OF BOTH MAINLAND ALASKA AND THE
ALEUTIAN CHAIN THROUGH THE WEEKEND.

.SOUTHCENTRAL AND SOUTHWESTERN ALASKA...
COLD ARCTIC AIR WILL REMAIN ENTRENCHED OVER SOUTHCENTRAL ALASKA AND
INTERIOR SOUTHWEST ALASKA THROUGH THE WEEK. THE TIGHT PRESSURE
GRADIENT ALONG THE GULF COAST WILL RELAX ONLY SLIGHTLY BETWEEN NOW
AND THURSDAY. SUBZERO TEMPERATURES AND PERIODS OF DANGEROUSLY LOW
WIND CHILLS WILL REMAIN AN ISSUE THROUGH AT LEAST THURSDAY. HIGH
WINDS WILL DEVELOP THIS MORNING ALONG THE COPPER RIVER
DELTA...THROUGH THOMPSON PASS...AND POSSIBLY PORT VALDEZ AS WELL.
NORTHEAST WINDS ARE ALREADY GUSTING TO 51 KT AT THE THOMPSON PASS
RWIS STATION AND SHOULD INCREASE FURTHER WHEN THE TROUGH ALOFT MOVES
OFF TO THE EAST LATER THIS MORNING.

.ALASKA PENINSULA...BERING SEA...AND ALEUTIAN CHAIN...
STRONG STORM SYSTEMS TRACKING JUST SOUTH OF THE CHAIN WILL PRODUCE A
30 TO 50 KT SWATH OF COLD EASTERLIES ACROSS THE SOUTHERN BERING SEA
AND PORTIONS OF THE ALEUTIAN CHAIN BY THIS AFTERNOON. ASSOCIATED
PRECIPITATION SPREAD ACROSS THE ALEUTIAN CHAIN THIS MORNING THEN
ACROSS THE ALASKA PENINSULA TONIGHT.
PORTIONS OF THE ALEUTIAN CHAIN WILL CREEP ABOVE FREEZING DURING THE
DAYTIME HOURS BUT THE PRIBILOFS AND ALASKA PENINSULA WILL REMAIN
SUBFREEZING.

.LONG RANGE FORECAST...
UPPER LEVEL STEERING FLOW IS CONDUCIVE TO CONTINUED COLD HIGH
PRESSURE OVER INTERIOR ALASKA AND TRANSIENT LOWS SKIMMING THE
ALEUTIAN CHAIN. THIS PATTERN SHOULD PERSIST THROUGH THE WEEKEND.
LITTLE CONFIDENCE IN PROGS BEYOND 120 HOURS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND 131 135
MARINE...GALE  121 129 130 155 160 165 171 175 176 179 185
         STORM 170 172
         HEAVY SPRAY 120 121 125 129 130 132 138 140 141 160 179 185
FIRE WEATHER...NONE

ASB FEB 08