Small Craft Advisory 977, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM ADT MON OCT 23 2006

.DISCUSSION...

ANALYSIS...IN THE UPPER LEVELS THERE IS LONG-WAVE TROUGH COVERING THE
ENTIRE ANCHORAGE FORECAST AREA WITH A NEAR ZONAL JET EXTENDING ACROSS
THE PACIFIC BETWEEN 45 AND 55 DEGREES NORTH LATITUDE. A WEAK
SHORT-WAVE MOVING ACROSS SOUTHCENTRAL PRODUCED A BIT OF LIGHT SNOW
ON THE WEST SIDE OF THE CHUGACH THIS MORNING INCLUDING ANCHORAGE.
NOW ALL THAT IS LEFT IS SOME CLOUDS OVER THE MOUNTAINS AND INTO THE
COPPER RIVER BASIN. AT THE SURFACE THERE IS A DEEPENING LOW OVER THE
FAR SOUTHEASTERN GULF HEADING EASTWARD TOWARD THE QUEEN CHARLOTTE
ISLANDS. THERE IS A RIDGE OF HIGH PRESSURE OVER THE EASTERN
BERING/SOUTHERN AKPENN WITH COLD ADVECTION DOWN THE FRONT SIDE OF
THE RIDGE. THE COMBINATION OF THE GULF LOW AND COLD ADVECTION IS
SERVING TO TIGHTEN THE PRESSURE GRADIENT AND INCREASE WINDS ACROSS
THE GULF WATERS. ANOTHER SURFACE LOW IS LOCATED OUT OVER THE SOUTHERN
BERING NORTH OF ADAK WITH OCCLUSION EXTENDING EASTWARD ACROSS THE
CENTRAL BERING JUST SOUTH OF THE PRIBILOFS TO A TRIPLE POINT THAT
IS SHOWING A LITTLE BIT OF ROTATION. WITH LOTS OF COLD AIR FEEDING
OUT OF RUSSIA ACROSS THE WESTERN BERING AND INTO THIS SYSTEM AS WELL
AS GOOD UPPER LEVEL SUPPORT EXPECT A TRIPLE POINT LOW TO DEVELOP
OVER THE NEXT 6 TO 12 HOURS.

MODEL DISCUSSION...12Z MODELS WERE A BIT TOO WEAK WITH GULF LOW AND
LATEST SATELLITE IMAGERY SHOWS THAT THEY TRACK IT TOO FAR NORTH. ALL
MODELS ARE REASONABLY CLOSE WITH THE LOW OUT WEST. MODELS ARE SHOWING
FAIRLY GOOD RUN-TO-RUN CONSISTENCY THE PAST FEW RUNS AND THE IDEA OF
DEVELOPING MULTIPLE TRIPLE POINT LOWS AS THE WHOLE LOW COMPLEX HEADS
EASTWARD. FORECAST IS BASED OFF A BLEND OF NAM/GFS...TAKING ADVANTAGE
OF THE NAMS HIGHER RESOLUTION AND BETTER DEPICTION OF TRIPLE POINT
LOWS. HAVING SAID THAT...MODELS USUALLY DONT HANDLE THE EXACT
POSITION AND STRENGTHS OF TRIPLE POINT LOWS IN RELATION TO
ORIGINATING LOW...SO WILL CLOSELY MONITOR SYSTEM EVOLUTION VIA
SATELLITE IMAGERY.

BERING SEA/ALEUTIANS FORECAST...WITH THE NEAR ZONAL JET THE LOW
COMPLEX WILL TRACK ALMOST DUE EASTWARD ACROSS THE SOUTHERN BERING
SEA TONIGHT...BRISTOL BAY MONDAY...AND INTO THE GULF TUESDAY. WITH
VERY COLD AIR FEEDING IN BEHIND THE LOW EXPECT WIDESPREAD STRATOCU
AND SHOWERS OVER THE WARMER WATERS AND PRECIPITATION TO CHANGE TO
MAINLY SNOW BY TUESDAY NIGHT. COLD ADVECTION WILL ALSO PRODUCE SOME
GUSTY WINDS ON THE BACK SIDE OF THE SYSTEM TONIGHT THROUGH TUESDAY
NIGHT. AS A RIDGE OF HIGH PRESSURE BUILDS INTO THE WESTERN BERING
WEDNESDAY EVEN COLDER AIR WILL BE TRANSPORTED SOUTHWARD ACROSS THE
CENTRAL AND EASTERN BERING AND GUSTY NORTHERLIES WILL CONTINUE.
THIS WILL END FROM WEST TO EAST AS WE REACH THE END OF THE WEEK
AND ANOTHER STORM SYSTEM COMES INTO THE PICTURE.

SOUTHWEST ALASKA FORECAST...VERY WEAK FLOW OVER THE KUSKOKWIM HAS
MAINTAINED A LAYER OF STRATUS OVER THE KUSKOKWIM VALLEY THE PAST
COUPLE DAYS. LOOKS LIKE THIS WILL HANG IN THERE UNTIL WE GET ENOUGH
MIXING WHICH SHOULD OCCUR AS THE LOW COMPLEX MOVES INTO BRISTOL BAY
TUESDAY. THE FORECAST FOR SOUTHWEST ALASKA IS HEAVILY DEPENDENT ON
WHERE THE TRIPLE POINT LOWS DEVELOP AND HOW STRONG THEY ARE. AS IT
LOOKS NOW...PRECIP WILL MAKE IT UP TO THE SOUTHERN KUSKOKWIM VALLEY
AND KUSKOKWIM DELTA TUESDAY IN THE FORM OF SNOW. WITH FLOW OFF THE
WARM WATERS OF BRISTOL BAY PRECIPITATION IN THAT REGION WILL BE
MAINLY RAIN. AS THE SYSTEM TRANSITIONS TO THE GULF TUESDAY NIGHT
CONDITIONS WILL DRY OUT FROM NORTH TO SOUTH AND MUCH COLDER AIR WILL
MOVE IN...CREATING SOME GUSTY WINDS...ESPECIALLY THROUGH CHANNELED
AREAS AND AT HIGHER ELEVATIONS.

SOUTHCENTRAL ALASKA...SURFACE RIDGE BUILDING INTO SOUTHCENTRAL
TONIGHT WITH SURFACE TROUGH REMAINING ALONG GULF COAST WILL GENERATE
SOME GUSTY NORTH WINDS ALONG THE NORTH GULF COAST. MOST AREAS WILL
CLEAR OUT...BUT SOME STRATUS MAY REMAIN IN THE COPPER RIVER BASIN
WITH GENERALLY WEAK FLOW THERE. OCCLUDED FRONT FROM BERING LOW
COMPLEX WILL REACH THE WESTERN GULF BY TUESDAY MORNING SO CONDITIONS
WILL QUICKLY HEAD DOWNHILL FOR KODIAK ISLAND TUESDAY MORNING AND
SPREAD TO THE GULF COAST TUESDAY NIGHT. MULTIPLE TRIPLE POINT
DEVELOPMENT WILL MEAN QUICKLY CHANGING WIND DIRECTIONS OVER THE
GULF WATERS. IT WILL ALSO MAINTAIN MAINLY OFFSHORE FLOW IN THE LOW
LEVELS ACROSS SOUTHCENTRAL. THEREFORE..DO NOT EXPECT PRECIP TO
PENETRATE INLAND. IT SHOULD HOLD RIGHT ALONG THE GULF COAST. WITH
MULTIPLE UPPER LEVEL SHORT-WAVES IT WILL TAKE A WHILE BEFORE UPPER
TROUGH MOVES THROUGH SOUTHCENTRAL. SO A SURFACE LOW WILL REMAIN OVER
THE NORTHERN GULF/PRINCE WILLIAM SOUND REGION THROUGH THE END OF THE
WEEK. THERE MAY BE A CHANCE THAT A BIT OF MOISTURE MAKES IT INLAND
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...BUT IF SO IT SHOULD BE LIGHT
AND BRIEF. STRONG COLD ADVECTION WILL THEN CLEAR THINGS OUT AND COOL
DOWN TEMPS AS WE HEAD TOWARD THE WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES 130 150 155 165 170 171 172

SEB OCT 06