Small Craft Advisory 170, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
1235 PM AST SAT FEB 17 2007

.DISCUSSION...

ANALYSIS...MOST OF THE SOUTHERN MAINLAND IS UNDER CLOUDY SKIES THIS
MORNING...THE REMNANT MOISTURE FROM THE WEAK UPPER TROUGHS THAT
AFFECTED THE REGION THE LAST COUPLE DAYS. NOW CAUGHT IN A COL...IT
IS GOING TO BE HARD TO SCOUR ALL OF THESE CLOUDS OUT. BUT VISIBLE
SATELLITE IS SHOWING SOME DISSIPATION OF THESE CLOUDS AS THE DAY
WEARS ON. SO EXPECT SLOWLY IMPROVING CONDITIONS (MORE SUN BREAKING
THROUGH) FOR THE REST OF TODAY.

LOW OVER SOUTHCENTRAL BERING SEA IS NOW STARTING TO FILL. THE FRONT
EXTENDS FROM THE LOW EASTWARD ACROSS THE BERING SEA AND
THE AKPENN INTO THE NORTH PACIFIC. THIS FRONT IS REALLY BEGINNING TO
STRETCH OUT DUE TO THE FACT THE BERING LOW IS NEARLY STATIONARY...THE
PORTION OF THE FRONT OVER THE BERING IS BARELY MOVING WHILE THE
SOUTHERN PORTION NEAR THE AKPENN IS BEING DRIVEN EASTWARD BY THE JET.
THIS WILL HELP TEAR THE FRONT APART TONIGHT SO THAT INLAND PORTIONS
OF SOUTHWEST ALASKA AND MOST OF SOUTHCENTRAL ALASKA WILL NOT BE
IMPACTED BY THE FRONT. THE TRIPLE POINT IS LOCATED SOUTH OF CHIGNIK
AND HEADED FRO KODIAK ISLAND. EXPECT A WEAK LOW TO DEVELOP BY THIS
EVENING.

A DEVELOPING LOW NEAR 42N 180 IS RIDING THE UPPER JET NORTHEASTWARD
TOWARD KODIAK ISLAND. DOWNSTREAM FROM THIS A LOW OVER THE EASTERN
GULF AND ASSOCIATED UPPER TROUGH ARE PROGRESSING EASTWARD TOWARD
BRITISH COLUMBIA. AS THEY DO SO THE JET WILL BEND EASTWARD AND DRIVE
THE DEVELOPING PACIFIC LOW EASTWARD ACROSS THE SOUTHERN GULF TOWARD
SOUTHEAST ALASKA.

MODEL DISCUSSION...MODELS SHOW DECENT AGREEMENT WITH MAJOR SYNOPTIC
FEATURES. THE LARGEST DIFFERENCES LIE WITH THE DEVELOPING PACIFIC
LOW HEADED TOWARD KODIAK ISLAND. THE GFS CONTINUES TO BE THE DEEPEST
WITH THIS LOW. THE OTHER MODELS TRENDED TOWARD THE GFS THE PAST
COUPLE RUNS. SO PREFER THE STRONGER SOLUTION...PERHAPS A COUPLE
MILLIBARS WEAKER THAN THE GFS...MORE IN LINE WITH THE GFS ENSEMBLE
MEAN. THE MODELS BEGIN TO DIVERGE WITH THE TRACK OF THIS LOW AS IT
REACHES THE EASTERN GULF...BUT THIS WILL NOT IMPACT THE ANCHORAGE
FORECAST AREA.

BERING SEA/ALEUTIANS/AKPENN FORECAST...AS THE LOW SITS OVER THE
BERING SEA MODERATE COLD ADVECTION WILL CONTINUE ACROSS THE
SOUTHERN BERING...ALEUTIANS...AND NORTH PACIFIC. THEREFORE...EXPECT
COLD ADVECTION GENERATED SNOW SHOWERS AND GUSTY GALE FORCE WINDS
TO CONTINUE THROUGH MONDAY...WITH IMPROVEMENT FROM WEST TO EAST AS
A SHORT-WAVE RIDGE BUILDS OVER THE WESTERN BERING SEA ON MONDAY.
THE DEVELOPING LOW TRACKING TOWARD KODIAK ISLAND WILL BRIEFLY IMPACT
THE AKPENN WITH SNOW AND SOME WIND LATE SUNDAY AND THEN QUICKLY MOVE
OFF TO THE EAST. THE NEXT MAJOR SYSTEM DEVELOPING OVER THE WEST
PACIFIC WILL HELP AMPLIFY THIS RIDGE EVEN MORE AND HOLD IT OVER THE
WESTERN BERING. AT THIS POINT LOOKS LIKE THE FRONT ASSOCIATED WITH
THIS NEXT SYSTEM WILL MOVE TO THE WESTERN ALEUTIANS MONDAY NIGHT.
WITH A DEEP SURFACE LOW AND FAIRLY STRONG RIDGE TO THE EAST THE
PRESSURE GRADIENT WILL BE VERY TIGHT AND STORM FORCE WINDS ARE
LIKELY.

SOUTHERN MAINLAND FORECAST...AS MENTIONED EARLIER APPROACHING FRONT
WILL SHEAR APART AS TONIGHT. THEREFORE...WILL SEE SNOW FROM THE
KUSKOKWIM DELTA TO BRISTOL BAY TO KODIAK ISLAND AND JUST A FEW
CLOUDS FARTHER INLAND AND OVER SOUTHCENTRAL. TRIPLE POINT LOW WILL
FORM EAST OF KODIAK ISLAND THIS EVENING BUT WILL BE FORCED EASTWARD
ACROSS THE GULF WITH LITTLE IMPACT FOR SOUTHCENTRAL. MEANWHILE...THE
FIRST OF SEVERAL SHORT-WAVES WILL BEGIN DROPPING SOUTHWARD ACROSS
THE STATE...AND COLDER AIR WILL BEGIN TO FILTER INTO SOUTHCENTRAL.
THE DEVELOPING PACIFIC LOW WILL BRING A BIT OF SNOW AND WIND TO
KODIAK ISLAND SUNDAY NIGHT AND THEN QUICKLY BE PUSHED EASTWARD
ACROSS THE GULF TOWARD SOUTHEAST ALASKA. AFTER THIS POINT A NEW
PATTERN REALLY BEGINS TO TAKE SHAPE. A RIDGE BUILDS OUT WEST WHILE
A TROUGH SETS UP OVER ALASKA. BEGINNING MONDAY SIGNIFICANT COLD AIR
TRANSPORT FROM THE POLAR REGION DOWN TO THE GULF OF ALASKA WILL
BEGIN. CONFIDENCE IN THIS FORECAST SOLUTION IS INCREASING...SO
FORECASTS WILL REFLECT THIS THROUGH STRONGER WINDS AND COLDER
TEMPERATURES. AS WE GET CLOSER WILL NEED TO TAKE A CLOSER LOOK AT
POTENTIAL FOR REACHING HIGH WIND WARNING THRESHOLDS. RIGHT NOW IT
APPEARS THAT INITIALLY THERE WILL NOT BE A LOT OF UPPER SUPPORT...IN
OTHER WORDS THE WINDS ALOFT WILL NOT BE VERY STRONG. HOWEVER...THE
AIR LOOKS TO BE SO COLD (850 TEMPS OF -30 AND 500 TEMPS OF -40
DROPPING INTO THE SOUTHERN MAINLAND) THAT DOWNWARD MOMENTUM OF
THIS DENSE AIR WILL BE ENOUGH TO CREATE VERY STRONG WINDS AT THE
SURFACE.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES 132 150 155 170 171 172 175 176 185.

SEB FEB 07