Small Craft Advisory 768, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
158 PM AKDT THU OCT 2 2014

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL PATTERN KEEPS A STRONG RIDGE OVER THE BERING SEA
WITH A HIGH AMPLITUDE TROUGH DIGGING OUT OF THE ARCTIC ACROSS THE
INTERIOR OF THE STATE. THIS COLD UPPER LEVEL TROUGH WILL CONTINUE
TO MOVE SOUTHWARD AND BRING COLDER AIR WITH IT. A UPPER LEVEL LOW
IN THE GULF OF ALASKA WILL MOVE NORTHWARD AND GET ABSORBED INTO
THE TROUGH OVERNIGHT TONIGHT.
THE STRONG SURFACE LOW IN THE SOUTHERN GULF IS MOVING NORTHWARD
AND IS EVERY BIT AS STRONG AS EXPECTED. THE HIGH PRESSURE OVER
THE BERING SEA WILL PERSIST THROUGH THE REMAINDER OF THE WEEK.
&&

.MODEL DISCUSSION...
MODELS HAVE COME INTO VERY GOOD AGREEMENT WITH THE LARGE LOW IN
THE GULF OF ALASKA. PART OF THIS GOOD AGREEMENT IS THAT THE MODELS
ARE BRINING THE MOISTURE FARTHER WEST WHICH MEANS THAT THERE WILL
BE PRECIPITATION MOVING INTO THE AREA FROM THE NORTHERN KENAI
PENINSULA NORTHWARD THROUGH ANCHORAGE AND THE MAT-SU VALLEY
TOMORROW AND TOMORROW NIGHT.
MODELS ARE ALL KEEPING THE LARGE BERING SEA RIDGE IN PACE THROUGH
SATURDAY AND THEN PUSHING IT SLOWLY EASTWARD AS THE NEXT LOW AND
FRONT MOVE INTO THE BERING SEA FROM THE WEST.
&&

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
THE STRONG LOW IN THE GULF WILL BRING CLOUD COVER INTO
SOUTHCENTRAL OVERNIGHT WITH RAIN SPREADING ALONG THE NORTH GULF
COAST. AT THIS TIME IT LOOKS LIKE THE COPPER RIVER BASIN WILL SEE
SNOW DEVELOP FROM SOUTH TO NORTH OVERNIGHT. THE SNOW SHOULD MIX
WITH OR TURN TO RAIN AT LOWER ELEVATIONS OF THE BASIN TOMORROW.
HOWEVER THE PASSES SUCH AS CHICKALOON PASS ON THE GLENN HIGHWAY
AND MACLAREN PASS ON THE DENALI HIGHWAY WILL LIKELY STAY SNOW AND
COULD SEE A FEW INCHES OF ACCUMULATION.
ANCHORAGE AND THE MATANUSKA VALLEY WILL SEE RAIN DEVELOP TOMORROW.
THE HIGHER ELEVATIONS WILL SEE THE RAIN TURN TO SNOW TOMORROW
EVENING AND THERE IS A POSSIBILITY THE SNOW WILL MAKE IT INTO THE
ANCHORAGE BOWL AND PALMER-WASILLA AREA FRIDAY NIGHT INTO SATURDAY
MORNING.

SOUTHWEST ALASKA...
STRONG HIGH PRESSURE OVER THE BERING SEA WILL PERSIST THROUGH
SATURDAY. THE UPPER LEVEL TROUGH MOVING FROM THE INTERIOR THROUGH
THE AREA WILL BRING SOME PASSING CLOUDS OVERNIGHT AND THE LOW IN
THE GULF WILL BRING SOME CLOUD COVER INTO AREAS NEAR THE ALASKA
RANGE FRIDAY NIGHT INTO SATURDAY. OTHERWISE THE GUSTY NORTHERLY
WINDS WILL KEEP MOSTLY CLEAR SKIES OVER THE REGION THROUGH THE
REMAINDER OF THE WEEK.

BERING SEA/ALEUTIANS...
THE EASTERN BERING SEA AS WELL AS THE ALASKA PENINSULA AND
EASTERN ALEUTIANS ARE UNDER A FAIRLY TIGHT NORTH TO NORTHEASTERLY
FLOW WHICH CONTINUES TO BRING IN DRY AIR AND MOSTLY CLEAR SKIES.
THE WESTERN ALEUTIANS ARE SEEING SOME CLOUDS AND AREAS OF RAIN
FROM A WEAKENING FRONT THAT IS IN THE AREA. A STRONGER FRONT WILL
MOVE INTO THE REGION SATURDAY AND SATURDAY NIGHT BRINGING IN
STRONG WINDS AND RAIN.

&&

.LONG TERM FORECAST...
MODELS HAVE CHANGED QUITE A BIT IN THE PAST 24 HOURS FOR NEXT
WEEK. YESTERDAY...THE MODELS WERE HINTING AT A LONGWAVE TROUGH
EXTENDING ACROSS THE BERING SEA AND INTO THE ALASKA MAINLAND WHICH
WOULD HAVE RESULTED IN A COLD PERIOD WITH MULTIPLE DISTURBANCES
IMPACTING SOUTHCENTRAL ALASKA. THAT LOOK UNLIKELY NOW. THE FIRST
NOTICEABLE CHANGE WILL BE ACROSS THE WESTERN HALF OF THE BERING
SEA WHERE AN AMPLIFYING TROUGH WILL BE HALTED WITH RIDGING
BUILDING ACROSS THE CENTRAL AND EASTERN BERING SEA. A SURFACE LOW
TRAPPED IN THIS TROUGHING WILL SLOWLY WEAKEN THROUGH TUESDAY
MORNING AS IT DROPS SOUTH. AS THE LOW WEAKENS...THE REMNANTS OF
TYPHOON PHANFONE...WHICH IS CURRENTLY SOUTHEAST OF JAPAN...WILL
PUSH INTO THE NORTH PACIFIC AND PHASE WITH THIS WEAKENING LOW.
MODELS HAVE THE REMNANTS OF TYPHOON PHANFONE UNDERGOING RAPID
CYCLOGENESIS SOUTH OF THE ALEUTIAN CHAIN. ALTHOUGH MODELS DIFFER
ON THE OVERALL DEEPENING OF THE LOW...THE CLUSTER OF THE
DETERMINISTIC AND ENSEMBLE MEMBERS GIVES GOOD CONFIDENCE TO THIS
SOLUTION.

WHAT THIS WILL ALL MEAN OVER SOUTHWEST AND SOUTHCENTRAL
ALASKA...HIGH PRESSURE WILL BUILD ACROSS THE INTERIOR OF ALASKA
WHICH WILL BRING THE RETURN OF NORTHERLY FLOW ALOFT...CLEARER
SKIES AND COLDER TEMPERATURES. A WEAK SURFACE LOW OVER THE
NORTHERN GULF WILL MOVE INLAND OVER THE NORTHEASTERN GULF OF
ALASKA AND BRING A PERIOD OF RAIN ACROSS THE NORTHERN GULF
COAST...WITH A PERIOD OF SNOW IN THE COPPER RIVER BASIN. CLOUD
COVER AND WARMER TEMPERATURES WILL BE ON THE RETURN WEDNESDAY
AFTERNOON AND EVENING AS THE AFOREMENTIONED LOW SOUTH OF THE
ALEUTIAN ISLANDS SLOWLY PUSHES EASTWARD.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 119 120 131-136 138 150 155.
FIRE WEATHER...NONE.
&&

OCT 14