Gale Warning 523, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
153 PM AKDT WED SEP 10 2014

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL PATTERN HAS A STRONG LOW OVER THE WESTERN BERING
SEA WITH A TRANSITORY RIDGE OVER SOUTHWEST ALASKA AND A WEAKER
UPPER LEVEL LOW OVER THE KENAI PENINSULA. THE JET STREAM AT 250 MB IS
RUNNING JUST SOUTH OF THE ALEUTIAN ISLANDS AROUND THE BERING SEA
LOW AT AROUND 150 KT.
THE SURFACE LOW IN THE BERING SEA IS SEEN CLEARLY ON SATELLITE
IMAGERY AND ITS STRUCTURE DRAWS A CONTRAST WITH THE EXTRA-
TROPICAL CYCLONE TO ITS SOUTH WHICH WILL BE A BIG WEATHER FEATURE
THE NEXT FEW DAYS.
&&

.MODEL DISCUSSION...
WHILE NO MODEL IS COMPLETELY LOCKED ONTO WHAT THE APPROACHING
EXTRA-TROPICAL SYSTEM WILL DO THEY ARE STARTING TO CONVERGE
TOWARD A SOLUTION THAT WE CAN WORK WITH. THE MODELS ARE SHOWING A
SITUATION WHERE THE EXTRA-TROPICAL SYSTEM MOVES INTO THE EASTERN
BERING SEA AND MERGES WITH THE LOW CURRENTLY IN THE BERING SEA.
THIS WILL RAPIDLY DEEPEN THE BERING SEA LOW AND INCREASE WINDS
ACROSS MOST OF SOUTHERN ALASKA. AT THIS TIME IT LOOKS LIKE THESE
SYSTEMS WILL MERGE IN THE EASTERN BERING SEA LATE THURSDAY NIGHT
INTO FRIDAY MORNING AND THEN RETROGRADE WESTWARD INTO THE CENTRAL
BERING SEA FRIDAY AFTERNOON.
THE LOW CENTER IS NOT THE ONLY KEY FEATURE WITH THIS SYSTEM. THE
FRONT ASSOCIATED WITH THE BERING SEA LOW WILL BE THE TRACK THE
MAJORITY OF THE MOISTURE ASSOCIATED WITH THAT SYSTEM TAKES. AS THE
EXTRA-TROPICAL SYSTEM MOVES EASTWARD THE FRONT THAT IS CURRENTLY
ASSOCIATED WITH THE BERING SEA LOW WILL STRENGTHEN AS THE EXTRA-
TROPICAL SYSTEM INTERACTS WITH IT. THE RESULT WILL BE THE MOISTURE FROM
THE EXTRA-TROPICAL SYSTEM WILL GET ENTRAINED WITH THE FRONT AND
MOVE INTO SOUTHCENTRAL ALASKA AND ALONG THE NORTH GULF COAST. &&

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
THE DISTURBANCE IN THE NORTH GULF COAST AND SOUTH CENTRAL ALASKA
THAT HAS BEEN BRINGING RAINFALL TODAY WILL CONTINUE TO MOVE
NORTHWARD AND WEAKEN OVERNIGHT...BRINGING AN END TO THIS BATCH OF
RAIN. THE MORE SIGNIFICANT RAINFALL ASSOCIATED WITH THE EXTRA-
TROPICAL MOISTURE WILL REACH KODIAK THURSDAY EVENING AND TO THE
NORTH GULF COAST AND KENAI PENINSULA OVERNIGHT THURSDAY NIGHT. THE
DUE SOUTH ORIENTATION OF THE UPPER LEVEL FLOW AT THAT TIME WILL
ALSO BRING SOME DECENT RAINFALL AMOUNTS TO THE SUSITNA VALLEY AND
RAIN WILL ALSO OCCUR IN SOME OF THE MORE RAIN SHADOWED AREAS SUCH
AS ANCHORAGE. THE BACK OF THE FRONT SHOULD MOVE THROUGH THE KENAI
PENINSULA FROM SOUTH TO NORTH EARLY SATURDAY MORNING TO SATURDAY
AFTERNOON. THIS WILL SHIFT THE HEAVIEST RAINFALL FATHER EASTWARD
AT THAT TIME TO THE EASTERN PORTIONS OF PRINCE WILLIAM SOUND.
WINDS WILL ALSO BE A FACTOR IN SOME AREAS WITH THIS SYSTEM. AN
IMPORTANT PART OF THE MAIN LOW CENTER MOVING FARTHER WEST IN THE
BERING SEA WILL BE TO MINIMIZE THE AMOUNT OF WIND THAT WILL MAKE
IT INTO THE ANCHORAGE BOWL. TURNAGAIN ARM AND THE HIGHER
ELEVATIONS WILL SEE STRONG WINDS BUT IT CURRENTLY LOOKS LIKE THE
MAJORITY OF ANCHORAGE WILL NOT SEE OVERLY STRONG WINDS.

SOUTHWEST ALASKA...
RAINFALL FROM THE CURRENT BERING SEA SYSTEM WILL MOVE INTO THE
REGION AFTER MIDNIGHT TONIGHT AND PERSIST AS THE SYSTEMS MERGE.
THIS DURATION OF RAINFALL WILL INCREASE WATER LEVELS OF THE
STREAMS AND RIVERS BUT THERE IS NOT ANY FLOODING CONCERNS AT THIS
TIME. THE WINDS MAY BECOME MORE OF A FACTOR BY FRIDAY AS STRONG
EAST TO SOUTHEAST WINDS WILL DEVELOP OVER THE AREA WITH THE
STRENGTHENING LOW.

BERING SEA/ALEUTIANS...
THE BERING SEA REGION WILL SEE A LOT OF WHAT IT HAS BEEN SEEING
WITH THE LARGE LOW LOCATED THERE...WINDS AND RAINFALL WILL
INCREASE WITH THE INFLUX OF ENERGY FROM THE EXTRA- TROPICAL
SYSTEM. THIS WILL BE THE STRONGEST SYSTEM TO MOVE THROUGH THE
REGION THIS FALL SEASON.
&&

.LONG TERM FORECAST...
NOW THAT THE OVERNIGHT MODELS HAVE COME INTO MUCH BETTER
AGREEMENT WITH THE TRACK AND INTENSITY OF THE LOW OVER THE BERING
BY EARLY THIS WEEKEND...THE LONG TERM FOCUS HAS NOW SHIFTED TO THE
TRACK OF THIS LOW THROUGH EARLY NEXT WEEK. THE GEM AND EC HAVE
CONSISTENTLY BROUGHT THIS SYSTEM ASHORE OVER THE SOUTHWEST
MAINLAND BY LATE SUNDAY...WHILE THE GFS HAS BEEN EQUALLY
CONSISTENT IN BRINGING THIS LOW ACROSS THE AKPENN AND INTO THE
SOUTHWESTERN GULF. FOR NOW THE FORECAST RELIES HEAVILY ON WPC
GUIDANCE BEYOND SUNDAY...WHICH IS CLOSEST TO THE CURRENT FORECAST
AND THE FURTHER SOUTH GFS SOLUTION. REGARDLESS OF THE EXACT LOW
TRACK HOWEVER THE LONG TERM FORECAST FOR SOUTHCENTRAL REMAINS
CLOUDY AND WET THROUGH EARLY NEXT WEEK. THE GULF COAST WILL
RECEIVE ONLY SHORT LIVED BREAKS IN THE OTHERWISE STEADY AND
POTENTIALLY HEAVY RAIN THROUGH THIS WEEKEND...AS PERSISTENT
RIDGING OVER THE SOUTH PANHANDLE WILL KEEP THE AREA EXPOSED TO
DEEP AND MOIST SOUTHERLY FLOW. THE FORECAST FOR THE SOUTHWEST
MAINLAND AND EASTERN ALEUTIANS HOWEVER REMAINS MUCH UNCERTAIN...AS
IT WILL BE HEAVILY DEPENDENT ON THE TRACK OF THE BERING LOW. &&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 119 172 177 178 180.
FIRE WEATHER...NONE.
&&

SEP 14