Small Craft Advisory 971, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
140 PM ADT SUN OCT 22 2006

.DISCUSSION...

ANALYSIS...A NEAR ZONAL UPPER LEVEL JET EXTENDS FROM KOREA TO THE
GULF OF ALASKA BETWEEN 45 TO 55 DEGREES NORTH. A HIGH AMPLITUDE
RIDGE SITS TO THE EAST OVER WESTERN CANADA AND THE WESTERN U.S.
(APPROXIMATELY ALONG 115W LONGITUDE). THE JET IS DRIVING SYSTEMS
QUICKLY EASTWARD ALONG THE SOUTHERN PORTION OF THE ANCHORAGE FORECAST
AREA FROM THE ALEUTIANS TO THE GULF...RESULTING IN RAPIDLY CHANGING
WEATHER. THESE SYSTEMS ARE HELPING TO BREAK DOWN THE CANADIAN RIDGE
AND SHOVE IT EASTWARD. THIS IS LEADING TO A PATTERN CHANGE FOR AT
LEAST THE NEXT WEEK.

AT THE SURFACE...THERE IS A VIGOROUS LOW NORTHEAST OF KODIAK ISLAND
SPREADING PRECIPITATION ACROSS PRINCE WILLIAM SOUND...IN THE FORM OF
RAIN NEAR SEA LEVEL AND SNOW AT HIGHER ELEVATIONS. RADAR SHOWS SOME
ECHOES WRAPPING AROUND INTO COOK INLET BUT WITH DRY LOW LEVELS AND
NORTHERLY FLOW TO MAINTAIN DRY LOW LEVELS THE PRECIP IS EVAPORATING
BEFORE REACHING THE GROUND. GUSTY SOUTHEAST WIND ARE FOUND AHEAD OF
THE OCCLUSION WHICH IS JUST WEST OF MIDDLETON ISLAND AND GUSTY
SOUTHWEST WINDS BEHIND THE OCCLUSION. RIDGING AHEAD OF THE LOW
OVER THE COPPER RIVER BASIN IS ALSO PRODUCING GUSTY SOUTHEAST WINDS.
THERE IS ALSO A WEAK LOW SOUTH OF THE AKPENN RIDING THE JET
EAST-NORTHEASTWARD. SOUTHWEST ALASKA IS IN A COL...SO WINDS ARE
LIGHT AND THERE ARE AREAS OF LOW CLOUDS AND FOG...MAINLY IN THE
KUSKOKWIM VALLEY. THESE WILL REMAIN IN PLACE UNTIL WE GET ENOUGH
WIND IN THERE TO MIX THINGS OUT. A TRANSIENT HIGH IS MOVING ACROSS
THE CENTRAL ALEUTIANS WITH JUST SOME CLOUDS AND SHOWERS ACROSS THE
REGION. SEVERAL LOWS ARE SPINNING SOUTH OF THE KAMCHATKA PENINSULA.
SATELLITE IMAGERY/SURFACE OBSERVATIONS SHOWS LOTS OF COLD AIR
DROPPING OUT OF RUSSIA AND FEEDING INTO THESE LOWS. THIS WILL LIKELY
LEAD TO MORE TRIPLE POINT DEVELOPMENT WHICH THE MODELS SOMETIMES ARE
LATE TO PICK UP ON.

MODEL DISCUSSION...MODELS ARE A LITTLE WEAK WITH NORTHERN GULF LOW.
NAM WAS ALSO A BIT SLOW WITH PROGRESSION OF OCCLUSION AND ASSOCIATED
PRECIP. MODELS ARE ALL A BIT OFF ON LOCATIONS OF SURFACE LOWS NEAR
THE SOUTHERN KAMCHATKA PENINSULA. WITH THESE DEFICIENCIES NOTED...GFS
IS THE MOST CONSISTENT MODEL. IT HAS EXCELLENT RUN-TO-RUN CONSISTENCY
THROUGH ABOUT 54 HOURS AS LOW COMPLEX TRACKS ACROSS THE BERING SEA.
BEYOND THAT IS QUESTIONABLE AS MODELS DIVERGE AND THERE IS POOR
RUN-TO-RUN CONSISTENCY. DO LIKE THE IDEA OF THE GFS SOLUTION WHICH
DEVELOPS A TRIPLE POINT LOW OVER THE GULF TUESDAY NIGHT AND WEAKENS
THE EASTERN BERING LOW. SO HAVE TRENDED TOWARD THE NEW GFS SOLUTION.

SOUTHCENTRAL FORECAST...THE NORTHERN GULF LOW WILL GRADUALLY
DISSIPATE TONIGHT AS THE UPPER SHORT-WAVE MOVES EASTWARD INTO
CANADA. COLD ADVECTION WILL ENSUE BEHIND THE SYSTEM DOWN THE FRONT
OF THE CENTRAL BERING SHORT-WAVE RIDGE. THIS WILL HELP DEVELOP THE
LOW SOUTH OF THE AKPENN AS IT TRACKS EASTWARD ACROSS THE SOUTHERN
GULF TONIGHT AND MONDAY. COLD ADVECTION PLUS TIGHTER PRESSURE
GRADIENT WILL PRODUCE GUSTY NORTH TO WEST WINDS ACROSS SOUTHCENTRAL
AND THE GULF WATERS LATE TONIGHT THROUGH MONDAY. WITH THE MEAN UPPER
TROUGH POSITION MOVING EASTWARD THE NEXT LOW MOVING IN FROM THE
BERING LOOKS TO STAY DOWN OVER THE GULF AND TRACK EASTWARD TO
SOUTHEAST ALASKA. SO EVEN WITH UNCERTAINTY IN THE EXACT EVOLUTION
OF THE FORECAST TUESDAY AND WEDNESDAY...BEST LIKELIHOOD OF PRECIP
AND WINDS IS ALONG THE COAST WITH INLAND AREAS REMAINING DRY. WITH
UPPER TROUGH PROGRESSING EASTWARD TO MAINLAND ALASKA/GULF BY THE END
OF NEXT WEEK LOOK FOR THE COLDEST AIR OF THE SEASON ACROSS MAINLAND
ALASKA.

SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...EASTERN BERING AND AKPENN
CAN EXPECT GUSTY NORTHWEST WINDS TONIGHT IN COLD ADVECTION. STRATUS
IN THE KUSKOKWIM HAS A CHANCE TO MIX OUT AS LOW LEVEL WINDS PICK UP
A BIT ON MONDAY IN COLD ADVECTION...BUT IF IT SURVIVES THAT THAN IT
MAY SIT IN THE VALLEYS FOR THE NEXT FEW DAYS. THE LOW COMPLEX NEAR
THE KAMCHATKA PENINSULA WILL MOVE ACROSS THE WESTERN ALEUTIANS
TONIGHT AND TRACK EASTWARD ACROSS THE SOUTHERN BERING MONDAY AND
MONDAY THROUGH TUESDAY. BASED ON STRENGTH OF COLD ADVECTION AND
PRESENCE OF MULTIPLE SHORT-WAVES EMBEDDED IN THE UPPER FLOW...EXPECT
THERE WILL BE SEVERAL TRIPLE POINT DEVELOPERS AS THE SYSTEM MOVES
ACROSS THE BERING AND INTO THE GULF. LOOK FOR POSSIBLE STORMS ON THE
BACK SIDE OF THE SYSTEM IN COLD ADVECTION ALONG WITH LOTS OF STRATOCU
AND SHOWERS. CONDITIONS WILL IMPROVE AS HEAD INTO LATE WEEK WITH
RIDGE BUILDING OVER THE BERING. WITH MEAN TROUGH POSITIONED OVER THE
MAINLAND/GULF BY THE END OF THE WEEK LOOK FOR FUTURE SYSTEMS TO
COME OUT OF RUSSIA AND BRING A NEW SUPPLY OF COLD AIR.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES 130 132 150 155 160 165 170 171 172 175 176 180 185.

SEB OCT 06