Small Craft Advisory 1044, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AST SAT NOV 11 2006

.DISCUSSION...

WE ARE IN A VERY STABLE PATTERN WITH A BLOCKING RIDGE OVER THE
WESTERN BERING SEA AND TROUGH CENTERED OVER THE GULF. LOOK FOR
PERSISTENT CONDITIONS AT THE SURFACE...NAMELY COLD NORTHERLY FLOW
OVER THE MAINLAND AND EASTERN BERING. THE PAST COUPLE WEEKS THE
UPPER JET HAS BEEN SPLIT WITH NUMEROUS SHORT-WAVES MOVING SOUTHWARD
ACROSS THE STATE...SO COLD ADVECTION EVENTS HAVE HAD LITTLE UPPER
SUPPORT. LOOK FOR THIS TO CHANGE SUNDAY AS BLOCKING HIGH BUILDS AND
AMPLIFIES AND UPPER TROUGH BECOMES NEUTRALLY TILTED. THIS WILL SET
UP A NORTH-SOUTH JET OVER WESTERN ALASKA/EASTERN BERING WHICH WILL
TRANSPORT ARCTIC AIR (COLDEST OF THE SEASON THUS FAR) FROM THE POLE
SOUTHWARD ACROSS ALASKA. THE MAIN FORECAST CHALLENGE IS TO IDENTIFY
LOCATIONS WHERE THE STRONGEST WINDS WILL OCCUR.

MODELS SHOW GOOD RUN-TO-RUN CONSISTENCY. THERE IS A DIFFERENCE IN
THE HANDLING OF SHORT-WAVE EMBEDDED IN NORTHERLY FLOW THAT DROPS
DOWN ACROSS WESTERN ALASKA/EASTERN BERING SUNDAY NIGHT AND MONDAY.
PREFER THE GFS/UKMET SOLUTION WHICH IS THE MOST CONSISTENT. DPROG/DT
SHOWS A SLIGHT TREND WESTWARD WITH THIS FEATURE WHICH MEANS THE
STRONGEST WINDS WOULD OCCUR OVER THE EASTERN BERING AND AKPENN.

SOUTHCENTRAL ALASKA FORECAST...GULF LOW THAT BROUGHT SNOW TO COASTAL
REGIONS THURSDAY NIGHT AND FRIDAY IS TRACKING EASTWARD TOWARD THE
QUEEN CHARLOTTE ISLANDS SO WINDS AND SEAS WILL CONTINUE TO DIMINISH
TONIGHT ACROSS THE GULF WATERS. AN UPPER SHORT-WAVE WHICH IS
CURRENTLY PRODUCING A FEW CIRRUS CLOUDS OVER SOUTHCENTRAL/SOUTHWEST
ALASKA WILL MOVE THROUGH TONIGHT AND WEAK TO MODERATE COLD ADVECTION
WILL BEGIN TO KICK UP THE WINDS BY SUNDAY MORNING. THE NEXT
SHORT-WAVE DROPPING DOWN IS MUCH MORE SIGNIFICANT. IT WILL DROP DOWN
ACROSS EASTERN ALASKA SUNDAY AND AID IN DEVELOPMENT OF A SURFACE LOW
OVER THE NORTHEAST GULF SUNDAY NIGHT. STRONG COLD ADVECTION WILL
ENSUE BEHIND THIS TROUGH WHICH WILL PRODUCE SOME GUSTY WINDS ACROSS
ALL OF SOUTHCENTRAL ALASKA SUNDAY NIGHT THROUGH MONDAY NIGHT. SURFACE
LOW OVER NORTHEASTERN GULF WILL REALLY TIGHTEN UP PREESSURE GRADIENT
FROM COPPER RIVER BASIN TO THE GULF. ALTHOUGH UPPER JET WILL BE OVER
WESTERN ALASKA THERE WILL BE ENOUGH UPPER SUPPORT AND STRONG ENOUGH
SURFACE PRESSURE GRADIENT/COLD ADVECTION TO WARRANT A HIGH WIND
WARNING FOR THE COPPER RIVER DELTA. VALDEZ TO THOMPSON PASS WILL
ALSO SEE SOME VERY STRONG WINDS BUT THEY SHOULD REMAIN BELOW WARNING
LEVELS. LOOKS LIKE COLD ADVECTION WILL WEAKEN BY MONDAY NIGHT SO
WINDS WILL BEGIN TO LET UP. HOWEVER...MODELS INDICATE ANOTHER
SHORT-WAVE EMBEDDED IN NORTHERLY FLOW MOVING THROUGH WITH EVEN COLDER
AIR BEHIND IT...SO LOOK FOR WINDY CONDITIONS TO CONTINUE THROUGH THE
WEEK.

SOUTHWEST ALASKA/EASTERN BERING SEA/AKPENN FORECAST...COLD ADVECTION
AND WINDS WILL GRADUALLY INCREASE TONIGHT AND SUNDAY. A STEEP
INVERSION IN THE INLAND VALLEYS WILL MAINTAIN LIGHT WINDS IN THOSE
LOCATIONS. AN UPPER LEVEL SHORT-WAVE WILL BRING SNOW TO THE KUSKOKWIM
DELTA SUNDAY NIGHT AND TO BRISTOL BAY AND THE AKPENN ON MONDAY.
THERE WILL LIKELY BE SOME BLOWING SNOW ALONG THE KUSKOKWIM DELTA
COAST LATE SUNDAY NIGHT AND MONDAY...HOWEVER AT THIS POINT STRONGEST
WINDS SHOULD BE OFFSHORE SO DO NOT THINK WILL REACH BLOWING
SNOW/BLIZZARD CRITERIA. THIS IS WORTH KEEPING AN EYE ON THOUGH. IT
DOES LOOK LIKE THE AKPENN WILL GET 40 TO 50 KT OF WIND COMBINED WITH
PRECIPITATION ON MONDAY. INITIALLY IT LOOKS WARM ENOUGH ALOFT TO
START PRECIP ALONG AKPENN IN FORM OF RAIN...BUT WITH COLD AIR COMING
IN FAST IT MAY END AS SNOW. THE AKPENN WILL GET CLOBBERED WITH
40 TO 50 KT WINDS SO IF PRECIP DOES CHANGE TO SNOW THERE COULD BE
SOME LOW VISIBILITIES. WILL REFINE THIS FORECAST AS WE GET CLOSER.
STRONG COLD ADVECTION BEHIND THE UPPER SHORT-WAVE WILL PRODUCE STRONG
WINDS ACROSS SOUTHWEST ALASKA MONDAY AND ONWARD. WITH THE UPPER JET
SETTING UP RIGHT OVER THE REGION EXPECT SOME STRONGER WINDS TO MIX
DOWN...EVEN INTO THE VALLEYS. OUTFLOW GUSTS ON THE SOUTH SIDE OF THE
AKPENN WILL LIKELY REACH STORM FORCE BY TUESDAY.

WESTERN TO CENTRAL BERING AND ALEUTIANS...AS UPPER RIDGE STRENGTHENS
LOOK FOR INVERSION TO DEEPEN AND LOWER. THIS WILL FORM AREAS OF FOG.
OTHERWISE DRY WITH LOTS OF STRATUS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING ZONE 135 COPPER RIVER DELTA SUNDAY EVENING
         THROUGH MONDAY NIGHT.
MARINE...GALES 121 180.

SEB