Small Craft Advisory 130, NWS Anchorage, AK

AREA FORECAST DISCUSSION SOUTHWEST ALASKA
100 PM AST WED FEB 9 2005

.DISCUSSION...
.500 MB...4830M VORTEX NEAR SAINT LAWRENCE ISLAND HOLDS POSITION AND
SLOWLY WEAKENS. ASSOCIATED TROUGH DIGS SE TOWARD THE GULF OF ALASKA
TONIGHT. TROUGH THEN ELONGATES AND MOVES TO THE SOUTHERN
INTERIOR/WESTERN CANADA LATE THU NIGHT. FLOW SHIFTS WEST TO SW OVER
MUCH OF THE SOUTHCENTRAL AND WESTERN MAINLAND FRI. A 5060M VORTEX
OVER THE SEA OF OKHOTSK INTENSIFIES AS IT MOVES SE OF THE KAMCHATKA
PEN FRI. A WEAK RIDGE OVER THE EASTERN ALEUTIANS IN ADVANCE OF THIS
CENTER FRI MORNING.

.SURFACE...THE MAJOR WEATHER CONCERN OVER THE NEXT 24 TO 36 HOURS
HOURS WILL BE THE EVOLUTION OF THE STORM COMPLEX MOVING INTO THE
NORTHERN GULF OF ALASKA TODAY. SAT AND BUOY DATA PLACED CENTER NEAR
56N 150W AT 18Z. THIS POSITION IS IN FAIR AGREEMENT WITH NCEP
MODELS(GFS/ETA/MESO ETA) 6 HOUR FORECASTS. HOWEVER...MODEL PRESSURES
ARE SEVERAL MBS HIGHER THEN ESTIMATED 970 MB CENTER. SAT PIX SHOWS
OPEN/CLOSED CELL CU ASSOCIATED WITH COLD ADVECTION OVER THE EASTERN
BERING SEA AND SOUTH OF THE AK PEN. THE ARCTIC FRONT THIS MORNING
EXTENDED FROM SOUTHERN KODIAK ISLAND...TO THE NORTHERN KENAI
PEN...AND INTO THE INTERIOR. FAIRLY WARM AIR IS EVIDENT ALONG THE
NORTH GULF COAST AND THE SOUTHERN AND EASTERN KENAI PENINSULA.

MODEL FORECAST ARE STILL CONSISTENT WITH DEEPENING GULF CENTER AND
MOVING IT TO WESTERN PRINCE WILLIAM SOUND(PWS) EARLY THURSDAY
MORNING. THIS TRACK STILL APPEARS TO BE REASONABLE. HOWEVER...AS
CENTER CONTINUES TO DEVELOP IT MAY MOVE FURTHER WEST OF TRACK THEN
ORIGINAL THINKING AND MAY REQUIRE SHORT FUSE ADJUSTMENTS IN INITIAL
FORECAST PERIODS. COLD ADVECTION...EVIDENT BY SAT PIX WILL MOVE OVER
THE KENAI PEN/NORTHERN COOK INLET EARLY THU. THIS COMBINED WITH
STRONG NEG TILTED 500 MB TROUGH AND PRINCE WILLIAM SOUND MOISTURE
SOURCE WILL MAKE FOR SIGNIFICANT SNOWFALL POTENTIAL OVER SOUTHCENTRAL
ALASKA...PARTICULARLY THE ANCHORAGE BOWL AND NORTHERN KENAI PEN. WARM
AIR TO EAST WILL KEEP PRECIPITATION MAINLY AS RAIN OR MIXED ALONG THE
GULF TONIGHT. COLD ADVECTION SPREADS ACROSS THE NORTHERN GULF
THU...SO PRECIPITATION SHOULD CHANGE OVER TO SNOW.

GALE AND STORM FORCE WINDS WILL BE TO RULE IN ADVANCE AND ON THE
BACKSIDE OF LOW CENTER AS IT MOVES INTO THE NORTHERN GULF TONIGHT.
EAST STORMS OVER THE NORTH GULF THIS AFTERNOON WILL DIMINISH LATE
TONIGHT AS FRONT MAKES LANDFALL. NW STORMS WILL BE SLOW TO DIMINISH
OVER THE WESTERN GULF AS COLD ADVECTION WILL HOLD WEAKENING LOW NEAR
PRINCE WILLIAM SOUND THU.

OUT WEST...SAT PIX SHOWS WHAT APPEARS TO BE A POLAR LOW NEAR 56N 172W
THIS AFTERNOON. THE GFS AND MESO ETA PICK UP ON THIS CENTER. THE GFS
WHICH APPEARS TO HANDLE THE MOVEMENT BETTER MOVES CENTER TO OVER
WESTERN BRISTOL BAY TONIGHT. CENTRAL PRESSURE HARD TO GAUGE AT THIS
POINT AS CENTER IS IN A DATA VOID...BUT THE GFS PRESSURE IN THE MID
TO UPPER 990S SEEMS REASONABLE. SNOW OVER SW AK THIS AFTERNOON WILL
DIMINISH AS COLD DRY AIR MOVES IN THIS EVENING. SAT PIC SHOWS
EXTENSIVE OPEN/CLOSED CELL CU OVER MUCH OF THE AK PEN AND ALEUTIAN
CHAIN TODAY. DEVELOPING LOW NEAR JAPAN WILL MOVE SE OF THE KAMCHATKA
IN THE 950S THU NIGHT AND BECOME QSTRNY. ASSOCIATED FRONTAL BOUNDARY
ELONGATES AND SPREADS TO THE CENTRAL ALEUTIANS FRI AFTERNOON.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...WINTER STORM WATCH 101. WIND WARNINGS 135 AND 171.
MARINE...STORMS: 2B,3A,3B,3C, AND 5A. . GALES: 2B1,2C,4, AND 4A.

RMC FEB 05