Small Craft Advisory 663, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
150 PM AKDT TUE SEP 2 2014

.ANALYSIS AND UPPER LEVELS...
THE COLD UPPER LEVEL LOW ALONG THE ARCTIC COAST IS PUSHING ANOTHER
FRONT THROUGH SOUTHWEST AND SOUTH CENTRAL ALASKA. THE RIDGE OF
HIGH PRESSURE SOUTH OF THE REGION COMBINED WITH THE LOW PRESSURE
TO THE NORTH IS PRODUCING A LARGE AREA OF ZONAL FLOW OVER MOST OF
THE SOUTHERN PORTION OF THE STATE.
&&

.MODEL DISCUSSION...
MODELS REMAIN IN GOOD SYNOPTIC AGREEMENT THROUGH THE WEEKEND BUT
THERE ARE SOME DETAILS WITH THE DEVELOPMENT OF A COMPLEX LOW SOUTH
OF THE ALASKA PENINSULA THURSDAY THROUGH FRIDAY THAT ARE NOT
RESOLVED CONSISTENTLY BETWEEN MODELS. THE MAIN ISSUE IS THE WAY
THE MAIN LOW MOVES NORTHWARD TOWARD THE ALASKA PENINSULA AND THEN
DEVELOPS A TRIPLE POINT LOW SOUTH OF KODIAK WHICH WILL PROBABLY
OCCUR THURSDAY NIGHT. THIS NEW TRIPLE POINT LOW WILL THEN BECOME
THE MAIN LOW AS IT MOVES INTO THE GULF OF ALASKA AFTER THAT. THE
MODELS ARE ALL SHOWING THIS BASIC DEVELOPMENT AND MOVEMENT BUT
DIFFER ON HOW LOW THE ORIGINAL LOW PERSISTS AND WHEN THE SECONDARY
LOW DEVELOPS. AT THIS TIME THE DEVELOPMENT SOUTH OF KODIAK
THURSDAY NIGHT AND MOVEMENT INTO THE GULF FRIDAY LOOKS THE MOST
LIKELY.
&&

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
MOST OF THE ENERGY WITH THE FRONT IS IN THE NORTHERN PART OF THE
AREA. THIS WILL RELEGATE THE BULK OF THE RAINFALL OVERNIGHT TO
ANCHORAGE NORTHWARD. THE COPPER RIVER BASIN WILL ALSO SEE SOME
RAIN MOVE INTO THE AREA OVERNIGHT. AHEAD OF THIS FRONT THERE IS A
FAIRLY TIGHT PRESSURE GRADIENT BRINGING IN GUSTY SOUTHERLY WINDS
TO COOK INLET AND THE COPPER RIVER BASIN. THIS GRADIENT WILL
WEAKEN THIS EVENING AND WINDS WILL THEN QUICKLY DIMINISH.

SOUTHWEST ALASKA...
CLOUD COVER SHOULD PERSIST OVERNIGHT OVER MUCH OF THE REGION AND
THEN DIMINISH SOME TOMORROW AS THE FRONT MOVES THROUGH THE AREA
AND THE WESTERLY SURFACE FLOW OFF THE BERING SEA WEAKENS. THIS
WILL ALSO END THE PRECIPITATION FOR INLAND AREAS. A WEAK FRONT
WILL MOVE TO THE EASTERN ALEUTIANS AND ALASKA PENINSULA THURSDAY
AND FRIDAY WHICH WILL BRING SOME MORE RAINFALL TO THESE AREAS AT
THAT TIME.

BERING SEA/ALEUTIANS...
WESTERLY ZONAL FLOW OVER THE BERING SEA WILL BEGIN TO WEAKEN
TOMORROW AS THE RIDGE OF HIGH PRESSURE MOVES SLOWLY WESTWARD OVER
THE NEXT FEW DAYS. WHILE PRECIPITATION WILL BE MINIMAL THERE WILL
BE LARGE AREAS OF LOW CLOUDS AND STRATUS OVER THE REGION.
&&

.LONG TERM FORECAST...
THE NORTHERN GULF WILL HAVE A NORTH PACIFIC LOW BY SATURDAY
MORNING. THIS WILL BRING STRATUS AND RAIN TO THE NORTHERN GULF
COASTLINE SPREADING INTO THE INTERIOR SOUTHCENTRAL MAINLAND
THROUGH NEXT WEEKEND. BY LATE SUNDAY SOUTHCENTRAL ALASKA WILL SEE
AN INCREASE IN CLOUDS AND PRECIPITATION FROM THE NEXT SYSTEM
TRACKING INTO THE SOUTHWEST ALASKA REGION. FOR THE BERING SEA AND
ALEUTIANS...A NORTH PACIFIC LOW WILL APPROACH THE ALEUTIAN CHAIN
BY SATURDAY WITH A FRONTAL BOUNDARY ASSOCIATED WITH THIS SYSTEM
POSITIONED THROUGH THE CENTRAL ALEUTIANS. THIS NORTH PACIFIC LOW
WILL TRACK ACROSS THE ALEUTIAN CHAIN AND MOVE NEAR THE PRIBILOF
ISLANDS BY TUESDAY. THIS SYSTEM WILL BRING ABUNDANT MOISTURE AND
PRECIPITATION WITH GUSTY WINDS FOR THE ALEUTIANS AND THE BERING
SEA BEFORE SPREADING INTO THE SOUTHWEST ALASKA REGION BY SUNDAY
THROUGH THE EARLY PARTS OF NEXT WEEK.
&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.
&&

SEP 14