Small Craft Advisory 339, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
630 AM ADT WED APR 16 2008

.ANALYSIS AND UPPER LEVELS...
A VERY AMPLIFIED UPPER LEVEL PATTERN THIS MORNING WITH TROF AXIS
EXTENDING FROM THE NORTHERN YUKON TERRITORY TO THE NORTHERN GULF AND
THEN SOUTHWEST ALL THE WAY 40N 170W. THE BASE OF THE TROF IS IN THE
PROCESS OF BECOMING A LARGE CUTOFF LOW IN THE SUBTROPICS...MORE ON
THIS LATER. TO THE WEST OF THE TROF IS A HIGH AMPLITUDE RIDGE OVER
THE CENTRAL ALEUTIANS AND THEN ANOTHER DEEP TROF IS LOCATED NEAR THE
KAMCHATKA PENINSULA.

THE SURFACE FEATURES INCLUDE A WEAK LOW NEAR CORDOVA AND ITS
ASSOCIATED COLD FRONT EXTENDING SOUTHWEST...PARALLELING THE UPPER
TROF. HIGH PRESSURE QUICKLY BUILT IN OVER THE CENTRAL ALEUTIANS WHERE
WINDS HAVE ALREADY BECOME SOUTHWESTERLY ACROSS THE PRIBILOFS...THIS
TIME YESTERDAY THE PRIBILOFS WERE EXPERIENCING BLIZZARD CONDITIONS
WITH 40 KT NORTHWESTERLY WINDS.

.MODEL DISCUSSION...
MODELS REMAIN CONSISTENT AND IN GOOD AGREEMENT. THE HIGH RESOLUTION
OF THE NAM IS HANDLING THE PRECIPITATION AND LOCAL STRONG WINDS
BETTER IN THE SHORT TERM. FOR THIS REASON...PREFER THE NAM SOLUTION
IN THE NORTHEASTERN GULF AS THE LOW SLOWLY DISSIPATES NEAR YAKUTAT
TODAY. BEYOND 36 HOURS...HAVE BLENDED IN THE LATEST RUN OF THE GFS.

.SHORT TERM FORECAST...
SOUTH AND EAST OF THE ALASKA RANGE...
THE MAJOR STORY THESE LAST SEVERAL DAYS HAS BEEN THE COLD FRONT
PUSHING THROUGH OUR FORECAST DOMAIN. ALTHOUGH THE UPPER TROF WAS A
LITTLE SLOWER THAN EXPECTED...OTHERWISE MODELS HAVE HANDLED THIS
SYSTEM ADMIRABLY. OVERNIGHT ISSUED A SNOW ADVISORY FOR THE COPPER
RIVER BASIN AS INGREDIENTS HAVE COME TOGETHER NICELY IN THE AREA. THE
RIGHT FRONT QUADRANT OF THE JET IS POSITIONED OVER THE EASTERN HALF
OF THE COPPER RIVER BASIN. OVERNIGHT A SHORTWAVE MOVED OVER THE
REGION FURTHER ENHANCING THE DYNAMICS. THIS COUPLED WITH LOW LEVEL
FORCING IN THE FORM OF THE STRONG COLD FRONT WAS MORE THAN ENOUGH TO
SUSTAIN MODERATE TO HEAVY SNOW ACROSS THE REGION. SNOW WILL LINGER IN
THE AREA TODAY BEFORE FINALLY TAPERING OFF NORTHWEST TO SOUTHEAST BY
THE AFTERNOON. STORM TOTALS OF 5 TO 11 INCHES ARE LIKELY IN THE
ADVISED AREA.

ELSEWHERE...GAP WINDS ARE THE ONLY OTHER MAIN CONCERN IN THE EASTERN
DOMAIN. THE POTENTIAL FOR BLIZZARD CONDITIONS EXISTS THROUGH THOMPSON
PASS WHERE HEAVY SNOW FELL FOR SOME PERIOD OVERNIGHT AND NOW POST
FRONTAL COLD AIR ADVECTION WINDS HAVE INCREASED. WORDED THE FORECAST
STRONGLY BUT HELD OFF ISSUING A BLIZZARD WARNING UNTIL WE CAN GET
CONFIRMATION FROM DOT.

BESIDES THOMPSON PASS...WHITTIER AND SEWARD WILL SEE THE STRONGEST
WINDS AROUND PRINCE WILLIAM SOUND. STORM FORCE WINDS ARE OCCURRING
THROUGH THE BARREN ISLANDS WITH THE POTENTIAL FOR HURRICANE FORCE
GUSTS. THIS WILL CONTINUE TODAY AND DIMINISH EARLY THURSDAY.

HIGH PRESSURE BUILDS FROM THE WEST QUICKLY TODAY AND REMAINS IN THE
AREA THROUGH THE WEEKEND. THE LATEST EXTENDED GFS IS STRENGTHENING
THE UPPER LEVEL RIDGE OVER THE NORTHERN GULF AND EASTERN MAINLAND
ALASKA...TRANSLATING TO WARM SPRING LIKE TEMPERATURES OVER
SOUTHCENTRAL THROUGH THE WEEKEND.

SOUTHWEST MAINLAND AND BERING SEA FORECAST...
STRONG NORTHWESTERLY FLOW WILL QUICKLY DIMINISH TODAY AS A SURFACE
TROF MOVES ACROSS THE NORTHERN BERING AND ONSHORE ACROSS THE YUKON
AND KUSKOKWIM VALLEYS THIS AFTERNOON. WINDS WILL BECOME SOUTHWESTERLY
AND CLOUDS WILL BE ON THE INCREASE. WIDESPREAD LIGHT SNOW WILL RESUME
BY THIS EVENING ACROSS THE KUSKOKWIM VALLEY. BRISTOL BAY WILL REMAIN
DRY WHILE HIGH PRESSURE STRENGTHENS OVER THE AREA.

THE AFOREMENTIONED DEVELOPING CUTOFF LOW NEAR 40N WILL RETURN TO THE
PICTURE OVER THE WEEKEND. THE LOW WILL GATHER STRENGTH AND MOISTURE
DURING THE WEEK AS IT MEANDERS ABOUT 35N AND THEN GETS CAUGHT UP IN
THE DEEPENING TROF TO THE WEST LATER IN THE WEEK...SENDING THE
MOISTURE NORTHWARD TOWARD THE ALASKA PENINSULA. THE JOURNEY TO THE
SOUTH HELP THE SYSTEM GATHER ABUNDANT SUBTROPICAL MOISTURE AND WARMTH
BEFORE RETURNING BACK TO ALASKA FOR THE WEEKEND...FURTHER REINFORCING
THE IDEA THAT SPRING LIKE WEATHER IS ON ITS WAY.

FURTHER OUT WEST...A STORM FORCE FRONT IS APPROACHING THE WESTERN
ALEUTIANS TODAY. THE WATER VAPOR IMAGERY SHOWS A LONG FETCH OF
TROPICAL MOISTURE ASSOCIATED WITH THIS SYSTEM. THE FRONT WILL WEAKEN
TOMORROW AS IT ENCOUNTERS HIGH PRESSURE OVER THE CENTRAL BERING BUT
WILL BECOME THE CATALYST TO BRINGING THE AFOREMENTIONED CUTOFF LOW
BACK NORTH AND THEN RE-ENERGIZING OVER THE WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM 130 176
         GALE 120 121 129 132 138 150 155 172 175
         HEAVY FREEZING SPRAY 130 140.
FIRE WEATHER...NONE.

AB APR 08