Small Craft Advisory 991, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTH CENTRAL AND SOUTHWEST ALASKA
200 PM AST SAT NOV 26 2005

.DISCUSSION...
.ANALYSIS...THE LOW IN THE GULF OF ALASKA CONTINUES CIRCULATING BANDS
OF SNOW SHOWERS ACROSS SOUTHERN AND WESTERN PRINCE WILLIAM SOUND.
THESE SNOW SHOWERS HAVE DUMPED UP TO 3 INCHES AN HOUR IN CORDOVA AS
REPORTED FROM LOCAL SPOTTERS. WE EXPECT THE SNOW SHOWERS TO CONTINUE
THROUGH THE REGION THROUGH THIS AFTERNOON WITH ADDITIONAL
ACCUMULATIONS UP TO 5 INCHES IN THE SHOWERS AND POSSIBLY MORE IN THE
MOUNTAINS ON THE KENAI PENINSULA. THE CURRENT SATELLITE AND RADAR
INFORMATION INDICATES A BAND OF SNOW SHOWERS MOVING INTO THE NORTHERN
SOUND THAT SHOULD REMAIN SOUTH OF VALDEZ. NORTHWEST FLOW ACROSS
KODIAK ISLAND IS DIMINISHING. ISOLATED SNOW SHOWERS ARE OCCURRING
OVER THE ISLAND. PATCHY FOG AND LOW STRATUS IS MORE COMMON IN THE
COPPER RIVER BASIN TO NORTHERN COOK INLET DUE TO THE STRONG LOW LEVEL
INVERSIONS. THE PRESSURE GRADIENT OVER COOK INLET IS KEEPING
CONDITIONS MIXED ENOUGH TO KEEP THE FOG AND STRATUS FROM FORMING. THE
NORTHWEST FLOW IS PRODUCING A LAKE EFFECT TYPE OF ENVIRONMENT IN THE
HOMER AREA RESULTING IN LIGHT SNOW SHOWERS.

OVER SOUTHWEST ALASKA AND THE ALASKA PENINSULA SNOW SHOWERS PERSIST
IN THE NORTHWEST FLOW MAINLY ALONG THE OROGRAPHIC LIFT REGIONS OF THE
ALEUTIAN MOUNTAINS.

FURTHER WEST A LARGE INTENSE LOW IN THE WESTERN BERING SEA HAS A
FRONT EXTENDING THROUGH THE ADAK AREA TO A DEVELOPING LOW 400 NM
SOUTH OF ADAK. THE STRONG GRADIENT IN ADVANCE OF THE LOW IS PRODUCING
NEAR STORM FORCE WIND OVER THE CENTRAL ALEUTIANS.

.MODEL COMPARISON...ALL MODELS IN RELATIVELY GOOD AGREEMENT WITH THE
EXCEPTION OF THE ETA MODEL. THE ETA MODEL IS A BIT FAST INITIALLY
WITH THE LOW SOUTH OF THE ALEUTIANS AND TENDS TO MOVE IT TO FAST THEN
WEAKEN QUICKER THAN THE GFS AND UKMET. SO WE ARE USING THE GFS FOR
THE BERING SEA AND THE ETA/GFS FOR THE MAINLAND AND GULF.

.SHORT-TERM FORECAST...THE LOW IN THE NORTHERN GULF MOVES SOUTHEAST.
THIS WILL PULL THE SHOWER ACTIVITY SOUTH OUT OF THE SOUND OVERNIGHT.
THIS SHOULD ALSO RESULT IN AN INCREASE IN THE NORTHERLY GRADIENT IN
THE NORTHERN AND WESTERN SOUND AS THE HIGH BUILDS OVER THE INTERIOR.
SHOULD SEE THE TYPICAL WHITTIER WIND AND POSSIBLY SEE SOME NORTH WIND
IN THE THOMPSON PASS TO VALDEZ REGION AND TO THE COPPER RIVER DELTA
TONIGHT AND SUNDAY.

A WEAKER PRESSURE GRADIENT WITH LESS CLOUD COVER AS THE RIDGE BUILDS
IN FROM THE EASTERN BERING SEA WILL INCREASE THE LIKELYHOOD OF FOG
OVER THE SOUTH CENTRAL REGION TONIGHT THROUGH SUNDAY NIGHT.

TEMPERATURES OVER THE WESTERN INTERIOR ARE SUBSTANTIALLY COLDER THAN
THE CURRENT FORECASTS AND WE WILL BE MAKING THE NECESSARY CHANGES TO
REFLECT TEMPERATURES IN THE 30 BELOW RANGE OVER THE KUSKOKWIM VALLEY
FOR TONIGHT.

THE LOW NOW SOUTH OF ADAK WILL MOVE NORTH INTO THE CENTRAL BERING SEA
THROUGH SUNDAY. EXPECT AN INTENSE PRESSURE GRADIENT IN ADVANCE OF THE
FRONT TO CONTINUE TO PRODUCE NEAR STORM FORCE WIND OVER THE CENTRAL
ALEUTIANS THAT SHOULD SPREAD TO THE EASTERN ALEUTIANS TONIGHT AND
SUNDAY. A STRONG PUSH OF WARMER AIR OVER THE WARM OCEAN WILL KEEP THE
PRECIPITATION OVER THE CENTRAL ALEUTIANS TO THE PRIBILOF ISLANDS
RAIN.

AS THIS FRONT PUSHES EAST, THE SURFACE AND UPPER LEVEL RIDGE OVER
WESTERN ALASKA WILL HOLD IT OVER THE EASTERN BERING SEA THROUGH THE
WEEKEND. WE PREFER A MIX OF THE ETA AND GFS...ETA OVER THE MAINLAND
FOR THE DETAILS AND THE GFS FOR THE BERING SEA AS THE TIMING AND
INTENSITY OF THIS SYSTEM IS ALREADY BEING HANDLED BETTER BY THE GFS
THAN THE ETA.

.EXTENDED FORECAST...BY MID WEEK A STRONG BLOCKING RIDGE OF HIGH
PRESSURE WILL EXTEND FROM THE ARCTIC INTO THE ALASKA PENINSULA TO THE
NORTH PACIFIC. THE MODEL SOLUTION BEYOND DAY FIVE IS HIGHLY SUSPECT
AT THIS POINT. THE MODEL WANTS TO FORCE THE LOW IN THE NORTH BERING
THROUGH THE RIDGE INTO NORTON SOUND THEN DIVE ACROSS THE MAINLAND
INTO THE NORTHERN GULF OF ALASKA. WE WILL MAINTAIN A SOLUTIONS ALONG
THE LINES OF THE PREVIOUS GRID FORECASTS AT THIS TIME WITH MINOR
ADJUSTMENTS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...HEAVY FREEZING SPRAY 130 138 140 180 185.
         STORM 172.
         GALE 150 170 171 175 176 179 180 185.
FIRE WEATHER...DONE.

SAM NOV 05