Small Craft Advisory 350, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
605 PM AKDT FRI APR 22 2016

.ANALYSIS AND UPPER LEVELS...
ALTHOUGH THE LARGER SCALE PATTERN REMAINS THE SAME...THERE ARE A
COUPLE DEEPENING SYSTEMS ACROSS THE NORTH PACIFIC WHICH WILL HELP
CONSOLIDATE ENERGY INTO TWO DISTINCT LOWS OVER THE NEXT 24
HOURS...ONE IN THE GULF OF ALASKA AND ONE ALONG THE CENTRAL
ALEUTIANS. IN THE MEANTIME THE FOCUS OF RAIN AND WINDS REMAINS
IN THE AREA SOUTH OF KODIAK ISLAND NORTHWESTWARD ACROSS THE
SOUTHERN ALASKA PENINSULA AND EASTERN ALEUTIANS ON UP TO THE
PRIBILOF ISLANDS. OUT AHEAD OF THIS A WEAK AND DIFFUSE SHORT-WAVE
IS TRACKING INLAND ACROSS SOUTHCENTRAL ALASKA. THE BULK OF RAIN
IS FALLING ALONG THE GULF COAST/PRINCE WILLIAM SOUND WHILE DRY
LOW LEVEL AIR IN THE LEE OF THE MOUNTAINS AND OVERALL WEAK
VERTICAL MOTION IS PRODUCING NO MORE THAN SOME SPRINKLES INLAND.

&&

.MODEL DISCUSSION...
NUMERICAL GUIDANCE IS IN GOOD AGREEMENT WITH LARGE SCALE FEATURES
OVER THE NEXT COUPLE DAYS. THE 12Z NAM WAS AN OUTLIER WITH SYSTEM
OVER THE GULF...BUT THE 18Z RUN HAS NOW COME IN LINE. THE MAIN
FEATURE OF CONCERN IS AN EASTERLY WAVE MOVING INTO THE COPPER
RIVER BASIN SATURDAY NIGHT/SUNDAY TIME FRAME. THE NAM WAS THE
FIRST MODEL TO PICK UP ON THIS YESTERDAY. ALL MODELS NOW HAVE SOME
INDICATION OF A WAVE...BUT VARY IN TIMING AND STRENGTH. HAVE THE
CONFIDENCE TO TREND TOWARD A COOLER WETTER FORECAST FOR THE
COPPER RIVER BASIN...BUT WILL WAIT AND OBSERVE NEXT COUPLE MODEL
CYCLES TO SEE IF GUIDANCE COMES INTO AGREEMENT ON WHETHER THIS
WAVE WILL BRING RAIN TO AREAS FARTHER WEST....INCLUDING ANCHORAGE
AND THE MAT VALLEY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THERE WILL BE A BRIEF BREAK IN STEADY RAIN ALONG THE GULF COAST
THIS EVENING AS UPPER LEVEL SHORTWAVE EXITS TO THE NORTH AND WEST.
RAIN WILL THEN SPREAD NORTH AND WEST ACROSS THE GULF OVERNIGHT
TONIGHT THROUGH SATURDAY MORNING AS A STORM SYSTEM MAKES ITS WAY
INTO THE SOUTHERN GULF. THE LOW WILL STALL OVER THE SOUTHERN GULF
SO THE OCCLUDED FRONT WILL QUICKLY ELONGATE AND WEAKEN AS IT
REACHES THE GULF COAST...KEEPING INLAND AREAS MOSTLY DRY. A
SURFACE RIDGE WILL BUILD IN ALONG THE NORTH GULF COAST BEHIND
THE OCCLUDED FRONT LEADING TO LOCALLY GUSTY GAP WINDS (TURNAGAIN
ARM/KNIK ARM/COPPER RIVER) SATURDAY AFTERNOON AND EVENING.

THERE IS A HIGH LEVEL OF UNCERTAINTY IN THE FORECAST FOR SATURDAY
NIGHT AND SUNDAY...WITH QUESTIONS ABOUT THE TRACK AND STRENGTH OF
AN UPPER LEVEL WAVE MOVING IN FROM THE YUKON. ITS LOOKING MORE AND
MORE LIKELY THAT THE COPPER RIVER BASIN WILL SEE SOME STEADY RAIN
OUT OF THIS. THERE IS POTENTIAL THIS RAIN COULD SPREAD SOUTH AND
WEST AND AFFECT PORTIONS OF PRINCE WILLIAM SOUND...ANCHORAGE...AND
THE MATANUSKA VALLEY. FOR NOW WILL STICK WITH A BROAD BRUSH
CHANCE OF RAIN. AT A MINIMUM...EVEN IF IT DOES NOT RAIN IN ALL OF
THESE AREAS SUNDAY WILL LIKELY BE MOSTLY CLOUDY.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
AN UPPER LEVEL RIDGE CONTINUES TO BUILD INTO THE SOUTHWESTERN REGION
RESULTING IN MOSTLY DRIER AND MILD CONDITIONS HEADING INTO THE
WEEKEND. THE WESTERN GULF WILL HAVE SHORTWAVES MOVING THROUGH
RESULTING IN SOME MOISTURE SPILLING OVER THE ALASKA PENINSULA AND
THE ALEUTIAN RANGE. THE BULK OF THE PRECIPITATION WILL BE OVER THE
BRISTOL BAY COMMUNITIES AND THE ALASKA PENINSULA. WHILE THE
INTERIOR WILL HAVE DOWNSLOPING CONDITIONS RESULTING IN LESS
MOISTURE THROUGH THE WEEKEND.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE BERING SEA WILL REMAIN UNDER THE INFLUENCE OF AN UPPER LEVEL
CLOSED LOW POSITIONED OVER THE WESTERN ALEUTIANS. AS THIS SYSTEM
DEVELOPS AT THE SURFACE INTO A BROAD AREA OF LOW PRESSURE THIS
WILL BRING A CONTINUED SHOWERY WEATHER REGIME THROUGH THE WEEKEND.
THERE WILL BE SHORTWAVES ROTATING AROUND THE CLOSED UPPER LOW
WHICH WILL FURTHER ENHANCE THE SHOWERY REGIME IN THE BERING AND
ALONG THE ALEUTIAN CHAIN. AS THIS SURFACE LOW TRACKS SOUTH OF THE
CENTRAL ALEUTIANS THIS WILL PRODUCE EASTERLY TO NORTHEASTERLY
WINDS THROUGH THE BERING/ALEUTIANS. THE STRONGEST WINDS WILL BE ON
THE PACIFIC SIDE RESULTING IN GALE FORCE WINDS ALONG THE EASTERN
ALEUTIANS BY SUNDAY MORNING THROUGH EARLY MONDAY MORNING.

&&

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

BEGINNING THE EXTENDED PERIOD SUNDAY EVENING...THE REGION WILL BE
UNDER THE INFLUENCE OF A DEEP NORTH PACIFIC LOW CENTERED SOUTH OF
THE ALASKA PENINSULA. A WEAKENING LOW IN THE GULF OF ALASKA WILL
EVENTUALLY MERGE WITH THE WARM FRONT ASSOCIATED WITH THE
AFOREMENTIONED NPAC LOW. EASTERLY FLOW ALOFT AND A REGION OF
MOISTURE ORIGINATING FROM THE YUKON WILL SPREAD CLOUDS AND
PRECIPITATION ACROSS SOUTHCENTRAL...WITH MORE SHOWERY ACTIVITY
INTO SOUTHWEST. BY MONDAY AFTERNOON...THE MAIN LOW CENTER WILL
MOVE TOWARD KODIAK...WITH STRONG SOUTHEAST FLOW FOCUSING MOST OF
THE PRECIPITATION ALONG THE NORTH COAST INTO SOUTHWEST...WITH
TYPICAL DOWNSLOPE DRYING KEEPING MOST OF INLAND SOUTHCENTRAL ON
THE DRIER SIDE.

BY MIDWEEK...THE PATTERN WILL GO BACK TO REPEAT WITH A WESTERN
BERING TROUGH SLOWLY MOVING EAST INTO THE GULF OF ALASKA BY NEXT
WEEKEND. THIS WILL KEEP SHOWERY CONDITIONS ACROSS MOST OF
SOUTHERN ALASKA WITH MOST PRECIPITATION ALONG THE COAST.
TEMPERATURES WILL REMAIN ABOVE AVERAGE THROUGH NEXT WEEK EVEN IN
THE MIDST OF INCREASED CLOUD COVER.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...SB
SOUTHCENTRAL ALASKA...SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PD
LONG TERM...JA