Small Craft Advisory 737, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
225 PM AKDT WED SEP 24 2014

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL PATTERN SHOWS A LONG WAVE TROUGH RUNNING OUT OF
THE ARCTIC AND DOWN THE ALCAN BORDER AND FAR TO THE SOUTH OFF THE
COAST OF CALIFORNIA. AN UPPER LEVEL LOW CENTERED IN THE WESTERN
BERING SEA HAS A TROUGH EXTENDING TO THE SOUTH WITH THE UPPER
LEVEL RIDGE OVER SOUTHWEST ALASKA. THE RIDGE IS NOT AS STRONG AS
IT LOOKED LIKE IT WOULD BE AS IT HAS BEEN FLATTENED OUT BY THE
POLAR JET WHICH IS RUNNING WEST TO EAST ACROSS THE NORTHERN PART
OF THE STATE. A SHORTWAVE TROUGH HAS MOVED INTO THE KUSKOKWIM
VALLEY AND ALONG THE ALASKA RANGE BRINGING SOME CLOUDS WITH IT.
THE SUBTROPICAL JET IS MUCH STRONGER AND IS RUNNING SOUTH OF THE
UPPER LEVEL LOWS. THIS PATTERN IS CONDUCIVE FOR THE STRENGTHENING
OF THE SURFACE LOW THAT IS SOUTH OF THE ALEUTIANS. ANOTHER SURFACE
LOW IS IN THE BERING SEA AND IS REMAINING NEARLY STATIONARY. THE
SURFACE RIDGE IS OVER THE EASTERN BERING SEA THROUGH THE INTERIOR
OF THE STATE. A TROUGH ALONG THE NORTH GULF COAST IS KEEPING THE
FLOW NORTHERLY OVER SOUTHCENTRAL ALASKA.

&&

.MODEL DISCUSSION...
MODELS ARE DOING WELL OVERALL BUT ARE ALL MOVING THE LOW THAT IS
CURRENTLY SOUTH OF THE ALEUTIANS ALONG A LITTLE MORE SOUTHERLY
TRACK AS IT MOVES TOWARD THE GULF. THEY ARE ALSO BACK TO HAVING
SOME STRUGGLES WITH THE STRUCTURE OF THE LOW AS IT MOVES INTO THE
GULF. WHILE THERE IS A 150 MILE DIFFERENCE IN THE LOW CENTER
POSITION BETWEEN THE NAM AND ECMWF ON FRI AFTERNOON THIS WILL
LIKELY RESOLVE ITSELF ON LATER MODEL RUNS. THE BIGGER ISSUE IS THE
WAY A TRIPLE POINT LOW DEVELOPS SOUTH OF THE GULF LATE FRIDAY AND
MOVES NORTHWARD INTO THE GULF BY SATURDAY MORNING. THE ECMWF
FAVORS A STRONGER LOW TO THE NORTH WHICH WOULD BRING IN MORE
CLOUDS AND RAIN TO THE NORTH GULF COAST AND EVEN INLAND INTO PARTS
OF SOUTHCENTRAL. THIS SOLUTION LOOKS LESS LIKELY DUE TO THE
LOCATION OF THE JET STREAM BUT THE NAM AND GFS ALSO BRING IN A
CHANCE OF RAIN INTO THE REGION AS WELL DUE TO A DISTURBANCE ALOFT
AND A WEAKER LOW AT THE SURFACE. IT IS PROBABLY FAIR OT SAY THAT
THIS SITUATION IS STILL UNRESOLVED AND WILL NEED TO BE WATCHED AS
IT DEVELOPS. THE DEVELOPMENT OF THE GULF LOW WILL ALSO BE
INFLUENCED BY THE STRENGTH OF THE RIDGE OVER THE MAINLAND PART OF
THE STATE. THE LATEST MODEL RUNS ON THE GFS AND ECMWF ARE ALSO
BREAKING DOWN THE RIDGE LATE THIS WEEKEND AS AN UPPER LEVEL LOW
BUILDS INTO THE STATE FROM THE NORTHWEST.

&&

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
CLEAR SKIES WILL CONTINUE OVER MOST OF SOUTHCENTRAL ALASKA THROUGH
THURSDAY. A FEW CLOUDS MAY MAKE IT OVER THE ALASKA RANGE INTO THE
SUSITNA VALLEY AND THERE IS A CONTINUED RISK OF EARLY MORNING FOG
TOMORROW MORNING AROUND COOK INLET...BUT OTHERWISE IT SHOULD BE
CLEAR. THE GUSTY WINDS ALONG THE NORTH GULF COAST AND OTHER
CHANNELED TERRAIN WILL BE STRONGEST TODAY AND THEN SLOWLY
WEAKENING THROUGH THURSDAY AS THE TROUGH DISSIPATES AND THE
SURFACE RIDGE BUILDS INTO THE GULF.

SOUTHWEST ALASKA...
THE SHORTWAVE TROUGH IN THE NORTHERN PART OF THE AREA IS BRINGING
SOME CLOUDINESS AND A FEW SHOWERS. THIS AREA SHOULD CLEAR OUT
THURSDAY AS THE WAVE DISSIPATES AND THE RIDGE REMAINS OVER THE
AREA. PATCHY FOG IS LIKELY IN LOW LYING AREAS AGAIN TONIGHT.

BERING SEA/ALEUTIANS...
THE MODELS MORE SOUTHERLY TRACK OF THE LOW WILL MEAN THAT THERE
WILL BE LESS WIND AND RAIN IN THE EASTERN AND CENTRAL ALEUTIANS AS
IT PASSES BY THE AREA. THE ALASKA PENINSULA WILL STILL LIKELY SEE
STEADY RAIN AND GUSTY WINDS WITH THIS LOW. THE OLD LOW IN THE
WESTERN BERING SEA WILL STILL BRING SOME SHOWERS TO THE WESTERN
ALEUTIANS BUT THEY WILL TAPER OFF AS THAT LOW DISSIPATES THURSDAY
NIGHT.

&&

.LONG TERM FORECAST...
THE CURRENT BERING LOW WILL BRING ANOTHER CHANCE FOR RAIN TO
MAINLY COASTAL PORTIONS OF SOUTHCENTRAL ALASKA THIS WEEKEND AS IT
TRACKS EASTWARD ACROSS THE GULF...ALTHOUGH FORECAST CONFIDENCE
REMAINS LOW WITH THIS FEATURE AS MENTIONED ABOVE. ONCE THAT
SYSTEM DEPARTS...A PERIOD OF DRY AND SEASONABLY COOL WEATHER
APPEARS TO BE IN STORE FOR MUCH OF THE SOUTHERN MAINLAND THROUGH
LATE NEXT WEEK. MODELS HAVE BEEN MORE AGGRESSIVE OVER THE PAST 24
HOURS IN BRINGING AN UPPER TROUGH OVER THE NORTHERN MAINLAND FROM
THE NORTHWEST...WHICH HAS HAD THE EFFECT OF FLATTENING THE RIDGE
WHICH WAS BEING DEPICTED OVER THE GULF AND SOUTHERN MAINLAND EARLY
NEXT WEEK. HOWEVER...SENSIBLE WEATHER IMPACTS WILL REMAIN MUCH THE
SAME AS NORTHWESTERLY FLOW YIELDS DRY CONDITIONS AND COOLER
TEMPERATURES AS A COLDER AIRMASS FILTERS IN FROM THE NORTH. MODELS
HAVE ALSO BEEN LESS CONSISTENT WITH THE TRACK OF THE NEXT LOW
ACROSS THE BERING NEXT WEEK...BUT GENERALLY RAINY AND GUSTY
CONDITIONS CAN BE EXPECTED ALONG THE ALEUTIANS DURING THAT TIME
PERIOD.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING 155 172.
FIRE WEATHER...NONE.

&&

EZ/CB SEP 14