Small Craft Advisory 476, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
533 AM AKDT THU JUN 4 2015

.ANALYSIS AND UPPER LEVELS...

THE REGION CONTINUES TO REMAIN UNDER THE INFLUENCE OF A POLAR
TROUGH STRETCHING FROM THE BEAUFORT SEA TO NORTHWEST ALASKA...WITH
A BROAD TROUGH OVER THE NORTHCENTRAL PACIFIC OCEAN. THE NORTH
PACIFIC TROUGH IS TAPPING INTO A SUBTROPICAL MOISTURE STREAM IN
THE VICINITY OF 40N. THIS WARM AIRSTREAM IS INTERACTING WITH A
CLOSED UPPER LOW JUST SOUTHWEST OF KODIAK ISLAND...WITH A POWERFUL
(FOR THIS TIME OF YEAR) SURFACE LOW AND ASSOCIATED STORM FORCE
FRONTAL ZONE IMPACTING THE NORTHERN GULF COAST OF ALASKA AND
PRINCE WILLIAM SOUND. A PLUME OF RISING AIR CAN BE SEEN ON WATER
VAPOR SATELLITE IMAGERY IN THE FORM OF COOLING CLOUD TOPS...WITH A
BROAD REGION OF RAIN HAMMERING PORTIONS OF THE NORTHERN GULF
COAST...AS DEPICTED BY MIDDLETON ISLAND RADAR (AND 1-2" 12 HOUR
RAINFALL MEASUREMENTS ACROSS CERTAIN COASTAL LOCATIONS). THE
STRONG GULF LOW WILL MOVE INLAND TODAY AND RAPIDLY WEAKEN...BUT
NOT BEFORE SPREADING MORE PRECIPITATION INLAND...WITH GUSTY
AFTERNOON WINDS ACROSS MOST OF SOUTHERN ALASKA. A CLOUDY...SLIGHTLY
COOLER...AND SHOWERY PATTERN WILL REMAIN OVER MOST OF SOUTHERN
ALASKA THROUGH SATURDAY.

&&

.MODEL DISCUSSION...

THE MODELS ARE IN EXCELLENT AGREEMENT WITH ALL THE MAJOR LARGE
SCALE FEATURES THROUGH THE SHORT TERM FORECAST. THE ONE AREA OF
DISAGREEMENT IS OVER THE GULF OF ALASKA ON SATURDAY AS A NORTH
PACIFIC LOW MOVES INTO THAT AREA. THE GFS HAS BEEN THE MOST
BULLISH IN DEPICTING A VERY STRONG LOW IN THAT AREA...BUT RECENT
GFS MODEL SIMULATIONS ARE BACKING OFF AND ARE MORE INLINE WITH
THE REST OF THE GLOBAL MODEL SUITE...WITH THAT LOW TRACKING
FARTHER EAST TOWARD THE PANHANDLE. THEREAFTER...THEY REMAIN IN
GOOD AGREEMENT WITH THE GENERAL PATTERN OVER THE REGION INTO THE
MIDDLE OF NEXT WEEK AS THE WETTER PATTERN RESUMES OVER SOUTHERN
ALASKA AFTER A BRIEF REPRIEVE SUNDAY AND EARLY MONDAY. FORECAST
CONFIDENCE IS HIGH.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

THE SURFACE LOW JUST TO THE EAST OF THE BARREN ISLANDS WILL TRACK
NORTHWEST ACROSS THE TIP OF THE KENAI PENINSULA THIS MORNING...CROSS
INTO COOK INLET LATE MORNING THEN RAPIDLY LIFT NORTH AND INLAND
THROUGH THE AFTERNOON. IN ADDITION TO THE STRONG EAST WINDS IN THE
NORTHERN GULF AND PRINCE WILLIAM SOUND TAPERING OFF AS THE BARRIER
JET WEAKENS THROUGH THE MORNING...SOME OF THE MAIN IMPACTS OF THIS
LOW TRACK WILL BE A RATHER RAPID TRANSITION FROM NORTHERLY WINDS
OF 30 TO 35 KT DOWN COOK INLET TO SOUTHERLY WINDS AROUND 25 KT
SUPPORTED BY STRONG PRESSURE RISES BEHIND THE LOW. RESURRECTION
BAY WILL ALSO LIKELY SEE A GOOD PUSH OF SOUTHERLY SCA WINDS IN THE
AFTERNOON AS PRESSURE RISES ALSO SURGE AGAINST THE SOUTHEAST SIDE
OF THE KENAI PENINSULA. FURTHER NORTH AND INLAND SOUTHEASTERLY GAP
WINDS WILL ALSO INCREASE AGAIN SUBSTANTIALLY IN THE AFTERNOON AND
EVENING THROUGH TURNAGAIN ARM...THE KNIK VALLEY AND IN THE COPPER
BASIN SUPPORTED BY PRESSURE RISES IN THE GULF AND DROPS INLAND.
ADDITIONALLY ONCE THE LOW GOES PAST AND COOK INLET WINDS TURN
SOUTHERLY...THE STRENGTHENING TURNAGAIN ARM WINDS WILL BE PUSHED
NORTH TO WRAP INTO SOUTH AND WEST ANCHORAGE LATE AFTERNOON AND
EARLY EVENING.

A DEEP UPPER LEVEL TROUGH PERSISTING OVER THE ALASKA PENINSULA AND
KODIAK ISLAND WILL KEEP THE GULF AND SOUTHCENTRAL ALASKA IN COOL
MOIST SOUTH TO SOUTH WEST FLOW FRIDAY AND FRIDAY NIGHT. IN GENERAL
THIS WILL CONTINUE TO BRING RAIN TO THE COAST AND SHOWERS INLAND
THOUGH INDIVIDUAL SMALL WAVES MOVING THROUGH THE FLOW WILL
DETERMINE WHEN DOWNSLOPING WILL WIN OUT AND WHEN PRECIPITATION
WILL BE MORE WIDESPREAD...BUT OVERALL THE FORECAST FOR THE NEXT
COUPLE DAYS LOOKS COOL...CLOUDY AND DAMP.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...

THE WET PATTERN WILL CONTINUE FOR MOST OF SOUTHWEST ALASKA
THROUGH THE END OF THE WORK WEEK AS THE LOW IN THE NORTHERN GULF
OF ALASKA MOVES INLAND TODAY AND INTERACTS WITH THE UPPER LEVEL
TROUGH CENTERED OVER THE NORTHWEST ALASKA COAST. RAIN SHOWERS WILL
TAPER OFF TODAY OVER THE KUSKOKWIM DELTA AS THE AXIS OF THE UPPER
TROUGH SHIFTS EASTWARD...BRINGING DRIER AND MORE STABLE AIR
SOUTHWARD. SHOWERS AND ISOLATED AFTERNOON/EVENING THUNDERSTORMS
ARE EXPECTED THIS TODAY MAINLY BETWEEN THE KILBUCK MOUNTAINS AND
THE ALASKA/ALEUTIAN RANGE AS THIS AREA WILL HAVE THE BEST UPPER
LEVEL FORCING AND DIURNALLY DRIVEN INSTABILITY TO SUPPORT
CONVECTION. TOMORROW...THE FAVORABLE AREA FOR ISOLATED
THUNDERSTORMS WILL BE LIMITED TO MAINLY THE KUSKOKWIM VALLEY AND
THE INTERIOR PORTIONS OF THE BRISTOL BAY REGION.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

HIGH PRESSURE WILL CONTINUE TO DOMINATE THE BERING SEA AND
ALEUTIANS THROUGH FRIDAY. WINDS WILL PEAK NEAR 30 KNOTS TODAY OVER
MUCH OF THE EASTERN BERING SEA AND THE PRIBILOF ISLANDS AS THE
PRESSURE GRADIENT TIGHTENS BETWEEN THE RIDGE AND THE LOW MOVING
INLAND OVER SOUTH CENTRAL ALASKA BEFORE DIMINISHING AFTER MIDNIGHT
TONIGHT. A WEAK SURFACE TROUGH WILL PUSH SOUTHWARD THROUGH THE
ALEUTIANS AND ALASKA PENINSULA TODAY WHICH WILL PRODUCE SHOWERS
FROM DUTCH HARBOR EASTWARD. ELSEWHERE...MARINE STRATUS AND AREAS
OF FOG WILL CONTINUE.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

A LONGWAVE TROUGH WILL REMAIN OVER MUCH OF THE SOUTHERN MAINLAND
THROUGH SATURDAY AFTERNOON...KEEPING ONSHORE FLOW AND SHOWERY
CONDITIONS OVER THE AREA INTO THE WEEKEND. A RIDGE OF HIGH
PRESSURE FROM OVER THE WESTERN BERING/ALEUTIANS WILL PUSH FURTHER
EASTWARD THIS WEEKEND...EVENTUALLY SPLITTING THE TROUGH INTO AN
UPPER LOW THAT STAYS QUASI-STATIONARY NEAR EASTERN SIBERIA AND AN
UPPER LOW OVER THE GULF. THIS WILL ESSENTIALLY END THE SHOWERY
CONDITIONS OVER THE SOUTHWEST MAINLAND...AND KEEP SOME SHOWERY
CONDITIONS OVER SOUTHCENTRAL THROUGH MONDAY. THE RIDGE WILL THEN
AMPLIFY OVER THE GULF AND SOUTHCENTRAL THROUGH THE EARLY PORTION
OF NEXT WEEK...REDUCING SOME OF THE SHOWERY CONDITIONS OVER
SOUTHCENTRAL THROUGH MONDAY. FURTHER WEST...ANOTHER SYSTEM WILL
DEVELOP JUST SOUTH OF THE WESTERN ALEUTIANS SATURDAY...AND DEEPEN
AS IT TRACKS EASTWARD OVER THE CENTRAL ALEUTIANS/BERING SUNDAY
INTO MONDAY. THIS SPREAD WET AND WINDY WEATHER FROM WEST TO EAST
THROUGH THE ALEUTIANS AND BERING THROUGH EARLY NEXT WEEK. AS THIS
SYSTEM WEAKENS AND COMBINES WITH ANOTHER SYSTEM OFF EASTERN
SIBERIA TUESDAY...BROAD CYCLONIC FLOW WILL BLANKET MUCH OF THE
BERING THROUGH WEDNESDAY MORNING.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 119 125 130 139.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...JA
SOUTHCENTRAL ALASKA...JER
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...RF
LONG TERM...JA/TP