Small Craft Advisory 688, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
146 PM AKDT TUE SEP 9 2014

.ANALYSIS AND UPPER LEVELS...
AN UPPER-LVL RIDGE OVER THE E COPPER RIVER BASIN/GULF OF AK IS
AMPLIFYING A BIT AS IT SLIDES EAST. A NEARLY STATIONARY UPPER-LOW
AROUND 250 MI W OF THE PRIBILOFS IS BECOMING ABSORBED BY ANOTHER
UPPER-LOW THAT PUSHED DOWN FROM E RUSSIA AND IS NOW NEARING ATTU.
SHORTWAVE TROUGHS PINWHEELING AROUND THE BROAD BERING LOW BRUSH THE
CHAIN AND SW MAINLAND WITH PASSING RAIN SHOWERS. NESTLED IN
BETWEEN THE E GULF RIDGE AND BERING LOW/TROUGH A NEAR STATIONARY
FRONT DRAPES THE WESTERN GULF OF AK WITH SURFACE WAVES DEVELOPING
ALONG IT'S AXIS BEGINNING TO DRAG IT TO THE NE. AN ASSOCIATED RAIN
SHIELD HAS ADVANCED TO THE KENAI PEN EARLY THIS AFTERNOON...WHICH
IS A LITTLE BEHIND EARLIER MODEL PROJECTIONS. WAY OUT WEST...
TROPICAL STORM FENGSHEN CONTINUES TO PUSH AWAY FROM JAPAN INTO THE
N PACIFIC.

&&

.MODEL DISCUSSION...
MODELS CONTINUE TO STRUGGLE WITH SYNOPTIC FEATURES IN THE LATTER
PART OF THE SHORT TERM...THU AND FRI. FORECASTS THROUGH WED ARE
SIMILAR AND REASONABLE WITH A FRONTAL WAVE TRACKING NORTH IN THE
GULF TODAY AND UPPER TROUGH MOVING INTO SOUTHCENTRAL WED AND
ENHANCING THE PRECIPITATION. PROBLEMS ARISE ON THU AND FRI AS
MODEL DIFFERENCES OCCUR DUE TO THE HANDLING OF THE REMNANTS OF
TROPICAL STORM FENGSHEN. THE ECMWF WHICH HAS HAD DRAMATIC FLIP
FLOPS IN THE LAST COUPLE OF DAYS HAS NOW HAD TWO RUNS WITH
SIMILAR SOLUTIONS (00Z-12Z). IT CONTINUES TO BE THE ONLY SOLUTION
WHICH BRINGS A DEEP LOW CENTER INTO THE EASTERN BRISTOL BAY ON
FRI. THE NAM/GEM/GFS ALL HAVE SOLUTIONS WITH DIFFER SIGNIFICANTLY
ON THIS FEATURE WITH WEAK LOW CENTERS FROM SOUTH OF THE AK PEN TO
OVER EASTERN BRISTOL BAY. NEEDLESS TO SAY...CONFIDENCE IS FAIRLY
LOW. THE MAIN DIFFERENCE IS THE DEGREE OR LACK OF DIGGING OF THE
UPPER TROUGH OVER THE NORTH PACIFIC. THE ECMWF SHOWS A MORE
AMPLIFIED 500 MB PATTERN AS IT DRAWS COLD OUT OF THE BERING SEA
AND SHARPENS THE NORTH PACIFIC TROUGH. THE RESULT IS THE
DEVELOPMENT OF A STRONGER SWLY NORTH PACIFIC JET WHICH ENHANCES
VERTICAL MOTION AS IT INTERACTS WITH THE REMNANTS OF FENGSHEN. THE
OTHER AFOREMENTIONED MODELS ARE NOT AS AMPLIFIED AND AS SUCH HAVE
HAVE GENERALLY WEAKER SOLUTIONS. FOR NOW WILL CONTINUE WITH A GFS
MIDDLE GROUND SOLUTION UNTIL WE GET ANOTHER MODEL RUN UNDER OUR
BELT. REGARDLESS OF THE SCENARIO...MODELS ALL TAP INTO THE
TROPICAL MOISTURE AND BRING SIGNIFICANT RAINS TO THE NORTH GULF
COAST/KENAI PEN THU NIGHT THROUGH FRI.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
SOUTHCENTRAL ALASKA/GULF...
KODIAK...LIKELY WILL SEE SOME BREAKS IN RAIN AS THE FRONTAL ZONES
MOVES NORTH AND EAST SOME THIS EVENING. THE NEXT SHOT AT RAIN HITS
KODIAK THU AFTERNOON.

WET WEATHER IS EXPECTED TO CONTINUE ACROSS MUCH OF SOUTHCENTRAL
MAINLAND THROUGH  THE LATTER PART OF THIS WEEK. MOISTURE WITH
FRONTAL TROUGHS WILL SPREAD NORTH ACROSS SOUTHCENTRAL THROUGH
TONIGHT. THE HEAVIER RAINS ARE EXPECTED TO BE CONFINED INITIALLY
TO THE COASTS AND SE EXPOSURES TONIGHT. RAIN WILL BECOME MORE
WIDESPREAD WED AS THE SE CROSS BARRIER FLOW WEAKENS AND THE UPPER
TROUGH APPROACHING FROM THE WEST PROVIDES ADDITIONAL LIFT AND
FURTHER ENHANCES RAIN ACROSS THE REGION. THERE WILL LIKELY BE A
BRIEF BREAK IN ORGANIZED PRECIPITATION THU UNTIL THE INFLUX OF
TROPICAL MOISTURE THU NIGHT AND INTO FRI. THE GULF COAST AND
EASTERN KENAI SHOULD SEE A SIGNIFICANT AMOUNTS OF RAIN WITH THIS
MOISTURE LADEN AIRMASS THU NIGHT THROUGH FRI. RIVERS AND SMALL
STREAMS ACROSS THE GULF AND KENAI SHOULD EXPERIENCE RISES IN
WATER LEVELS INTO THE WEEKEND.

SOUTHWEST ALASKA...GENERALLY CLOUDY AND SHOWERY CONDITIONS WILL
PERSIST THROUGH THURSDAY MORNING FOR MUCH OF THE AREA. WHILE THERE
STILL REMAINS SIGNIFICANT MODEL DISAGREEMENT WITH THE REMNANTS OF
TROPICAL STORM FENGSHEN...IT LOOKS LIKE THE SYSTEM WILL SPREAD
WIDESPREAD RAIN AND GUSTY EASTERLY WINDS STARTING SOMETIME LATE
THURSDAY AND CONTINUING AT LEAST INTO THE WEEKEND.

BERING SEA/ALEUTIANS...THE BERING LOW CURRENTLY PASSING TO THE
NORTH OF SHEMYA WILL BRING ANOTHER ROUND OF RAIN AND GUSTY
SOUTHWESTERLY WINDS TO THE THE WESTERN AND CENTRAL ALEUTIANS
THROUGH WEDNESDAY. THIS LOW WILL THEN BECOMING REINVIGORATED BY AN
APPROACHING LOW FROM THE SOUTH...KEEPING THE AREA CLOUDY AND WET
THROUGH THIS WEEKEND.

&&

.LONG TERM FORECAST...
THE FOCUS AND PRIMARY CONCERN IN THE LONG TERM FORECAST REMAINS
CENTERED AROUND HOW THE REMNANTS OF TROPICAL STORM FENGSHEN WILL
INTERACT WITH AN APPROACHING BERING LOW ON SATURDAY. THE MODELS
HAVE STRUGGLED WITH THE PROGRESSION OF THESE FEATURES OVER THE
LAST FEW DAYS...WITH LARGE RUN TO RUN INCONSISTENCIES (ESPECIALLY
FROM THE EC). THEY ARE FORTUNATELY STARTING TO COME INTO BETTER
GENERAL AGREEMENT WITH THE 12Z EC. IT NOW APPEARS THAT A CONSOLIDATED
LOW AROUND 980 MB WILL DEVELOP OVER THE CENTRAL BERING ON
SATURDAY...AND SLOWLY DRIFT EASTWARD THROUGH EARLY NEXT WEEK.
THIS FORECAST IS VERY CLOSE TO THIS MORNINGS WPC GUIDANCE...WHICH
WAS USED HEAVILY FOR THE AFTERNOON FORECAST PACKAGE.

IN GENERAL...THIS SETUP WILL LEAD TO CONTINUED CLOUDY AND WET
CONDITIONS FOR MUCH OF THE SOUTHERN MAINLAND FROM THIS WEEKEND
INTO EARLY NEXT WEEK...ESPECIALLY FOR THE GULF COAST. WHAT
REMAINS VERY UNCERTAIN AT THIS POINT IS HOW MUCH WIND AROUND
SOUTHCENTRAL WILL ACCOMPANY THE RAIN. THE 12Z GFS CAME IN WITH A
MUCH STRONGER LOW OVER THE SOUTHWEST MAINLAND ON SATURDAY...LEADING
TO MUCH STRONGER WINDS OVER SOUTHCENTRAL FOR THE WEEKEND. THIS
SOLUTION HOWEVER IS A DISTINCT OUTLIER AND WAS THROWN OUT FOR NOW.
THERE IS A GOOD CHANCE THAT GUSTY WINDS WILL DEVELOP THROUGH WIND
PRONE AREAS SUCH AS TURNAGAIN WITH THIS SETUP...HOWEVER EXACTLY
WHEN AND HOW STRONG REMAINS TO BE SEEN.

&&

AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING 119.
FIRE WEATHER...NONE.

&&

RMC/DEK SEP 14