Small Craft Advisory 844, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
100 PM ADT THU OCT 11 2007

.MODEL DISCUSSION...
THE MODELS HAVE SURPRISINGLY BEEN STRUGGLING WITH THE CURRENT
PATTERN. PLACEMENT AND DEPTH OF SURFACE LOWS AS WELL AS THE TIMING
AND TYPE OF PRECIP...THESE ARE IMPORTANT FEATURES IN THE FORECAST
FOR THE NEXT FEW DAY AND THE MODELS ARE NOW ONLY SLOWLY COMING INTO
SOME KIND OF AGREEMENT. FORECAST PACKAGE LEANS TOWARD THE GFS AS IT
HAS SOME AGREEMENT WITH THE UKMET AND THE ECMWF...WHEREAS THE NAM
SEEMS TO BE SINGING TO ITS OWN TUNE.

.ANALYSIS AND UPPER LEVELS...
THERE IS A STEERING LOW CENTERED OVER THE SEWARD PENINSULA AND A
PROGRESSIVE BUT FULLY STACKED LOW OVER THE CENTRAL BERING SEA. THE
SUBTROPICAL JET STREAM EXITS ASIA/JAPAN AT ABOUT 35 DEGREES NORTH
LATITUDE...MOVES EAST TO ABOUT THE DATE LINE...THEN NORTHEAST TO
NEAR JUNEAU. THE POLAR JET IS ALMOST TOO WEAK TO MENTION...MOVING
STRAIT SOUTH ALONG THE DATE LINE TO THE ALEUTIANS THEN BECOMING
INCOHERENT.

.SHORT TERM FORECAST...
PLENTY OF CHALLENGES IN THE FORECAST THROUGH THE WEEKEND. A WEAK
OCCLUDED FRONTAL BAND OVER THE NORTHERN GULF WILL MOVE ONSHORE LATE
TONIGHT AND STALL OVER SOUTH CENTRAL ALASKA ON FRIDAY. RAIN VS SNOW
WILL BE A CHALLENGE...AS WELL AS IF ANY PRECIP WILL MAKE IT AS FAR
WEST AS THE ANCHORAGE BOWL. ENOUGH WARM AIR WITH THIS SYSTEM THAT
GULF COAST AND PRINCE WILLIAM SOUND AREAS SHOULD CHANGE TO RAIN BY
FRIDAY AFTERNOON...IF NOT SOONER. CURRENT THINKING IS TO CONTINUE
SLIGHT CHANCE TO CHANCE POPS FOR THE ANCHORAGE BOWL THROUGH FRIDAY.

THE NEXT SYSTEM IS CURRENTLY DEVELOPING UNDER THE JET AT ABOUT 50
DEGREES NORTH LATITUDE AND 160 DEGREES WEST LONGITUDE. CLOSE
INSPECTION OF WATER VAPOR IMAGERY SHOWS THE POSSIBLE BEGINNINGS OF A
BAROCLINIC LEAF...THOUGH THIS COULD BE A TRICK OF THE EYES. LEAF OR
NOT...THIS SYSTEM WILL SPIN UP INTO A DEEP STORM FORCE LOW BY LATE
FRIDAY IN THE NORTHERN GULF. AS MENTIONED ABOVE...MODELS STRUGGLING
WITH THIS...BUT SEEM TO BE ON TO SOME KIND OF CONSENSUS FOR THE LOW
TO BE AT ITS DEEPEST FRIDAY AFTERNOON NEAR 58 NORTH 147 WEST (MINUS
THE ROGUE NAM). THE LOW WILL THEN CURL NORTHWEST TO THE KENAI
PENINSULA. BETTER CHANCES OF PRECIPITATION FOR THE ANCHORAGE BOWL
WITH THIS SYSTEM FRIDAY NIGHT...SATURDAY AND POSSIBLY SUNDAY.
PRECIPITATION MAY START AS RAIN...BUT SHOULD SWITCH TO SNOW BEFORE
SUNDAY MORNING AS THERE WILL BE DECENT COLD ADVECTION.

.LONG TERM FORECAST...
UNCERTAINTY IS FAIRLY HIGH ON THE DAY TO DAY WEATHER...BUT THE MEAN
TROUGH POSITION WILL LIKELY BE ALONG THE WEST COAST OF ALASKA
KEEPING THE AREA IN MOIST CYCLONIC FLOW.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING 120.
         GALE WARNING 170 172 175 176.
FIRE WEATHER...NONE.

LUDWIG OCT 07