Small Craft Advisory 624, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
135 PM AKDT SUN AUG 17 2014

.ANALYSIS AND UPPER LEVELS...
.SURFACE...
A WAVE AND ASSOCIATED OCCLUDED FRONT MOVED TO THE NORTHERN GULF
THIS MORNING. MODERATE RAIN FELL ACROSS THE NORTH GULF COAST WITH
LIGHTER INTENSITIES OVER THE COPPER RIVER BASIN AND WEST OF THE
CHUGACH AND TALKEETNA RANGES. WEAK BARRIER JET CONDITIONS ALONG
THE GULF COAST WITH GUSTS TO GALE STRENGTH HAVE SINCE DIMINISHED.

OUT WEST... THE COLD UPPER TROUGH CONTINUED UNSTABLE CONDITIONS
ACROSS THE SW MAINLAND WITH MORNING SOUNDING SHOWING A FAIR AMOUNT
OF POTENTIAL INSTABILITY. LOW CLOUDS WERE EVIDENT ALONG THE SW
COASTS AND THE AK PEN AND THE MAJORITY OF THE ALEUTIANS AND BERING
SEA.

UPPER LEVELS...
THE UPPER TROUGH OVER THE WESTERN MAINLAND MOVES NORTH AND EAST
MON AS A WEAK RIDGE MOVES OVER THE CENTRAL MAINLAND. MINOR WAVES
ARE STILL EXPECTED TO RIPPLE THROUGH THE FLOW INTO TUE WITH A
MORE SIGNIFICANT WAVE MOVING TO THE SW COAST TUE AFTERNOON. 500 MB TEMPS
WILL WARM A LITTLE ACROSS BRISTOL BAY...COOK INLET..AND THE NORTH
GULF BY TUE BUT SHOULD REMAIN IN THE -20C RANGE ELSEWHERE OVER
THE MAINLAND. 850 MB TEMPS GENERALLY COOL OVER THE SW MAINLAND
THROUGH TUE...THOUGH IT DOES RECOVER SOME OVER THE INTERIOR SW
TUE. IN THE EAST...THE THERMAL TROUGH WILL REBOUND ACROSS
SOUTHCENTRAL MON AND TUE.

&&

.MODEL DISCUSSION...
MODELS ARE IN GENERAL AGREEMENT THROUGH THE SHORT TERM. AFTERNOON
PACKAGES WILL MAKE UPDATES USING A GENERAL BLEND OF THE NAM AND
GEM WITH A LITTLE EC THROWN IN.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
RAIN SHOULD CONTINUE TO DIMINISH ACROSS THE NORTH GULF AND COPPER
RIVER BASIN TONIGHT AS THE FRONT AND LOW EXIT THE AREA. PRESSURE
RISES TO THE LEE OFF THIS FEATURE INCREASE GAP FLOWS AND SOUTHERLY
WINDS ACROSS THE COPPER RIVER...SHELIKOF STRAIT...AND COOK INLET
THROUGH TONIGHT. MON AND TUE WILL BRING MORE CLOUDY BREAKS...AFTERNOON
AND EVENING SEABREEZES...AND SHOWERY CONDITIONS. THE COLD AIR
ALOFT AND STRENGTHENING THERMAL TROUGH MON AND TUE INDICATE
STABILITY INDICES MARGINALLY SUPPORTIVE OF ISOLATED THUNDERSTORM
ACTIVITY.

.SOUTHWEST ALASKA...
MORNING SOUNDINGS AND COLD AIR ALOFT POINT TO A FAIRLY ACTIVE
AFTERNOON AND EVENING FOR THUNDERSTORMS ACROSS THE SW MAINLAND.
CONDITIONS BECOME SOMEWHAT MORE STABLE MON AND TUE ACROSS MUCH OF
THE AREA AS TEMPS COOL IN THE LOWER LEVELS WITH INCREASED ON SHORE
FLOW. THE ONLY EXCEPTION IS OVER THE INTERIOR SW TUE AFTERNOON AS
THE THERMAL TROUGH NOSES IN FROM THE EAST AND AN UPPER LEVEL
SHORT WAVE APPROACHES FROM THE WEST. STRATUS AND FOG WILL CONTINUE
TO ENCROACH ON THE DELTA/BRISTOL BAY ZONES THROUGH TUE AS HIGH
PRESSURE BUILDS OVER THE EASTERN BERING SEA.

BERING SEA/ALEUTIANS...
EXCEPT FOR SOME SPRINKLES OVER THE EASTERN ALEUTIANS TODAY...LOW
CLOUDS AND FOG WILL SPREAD ACROSS THE REGION THROUGH WED. THE
APPROACHING LOW FROM KAMCHATKA WILL BRING SOME RAIN TO THE WESTERN
HALF OF THE REGION MON NIGHT THROUGH WED.

&&

.LONG TERM FORECAST...

OPERATIONAL MODEL PERFORMANCE IN THE LONG TERM FORECAST PERIOD HAS
LEFT MUCH TO BE DESIRED WITH LITTLE AGREEMENT AND BELOW AVERAGE RUN
TO RUN CONSISTENCY. WHAT CAN BE GLEANED AT THIS JUNCTURE IS THAT AN
UPPER-LVL LOW CENTERED OVER THE WESTERN BERING SEA EARLY THU LOOKS TO
DRIFT EASTWARD TO NEAR THE AK PEN BY NEXT WEEKEND. SHORTWAVE
ENERGY EJECTING OFF OF THE ASIAN MAINLAND AND ROTATING UP FROM THE
NORTH CENTRAL PACIFIC STILL LOOK TO INTERACT WITH THE LARGE
FEATURE AND HELP FORM SOME SURFACE LOW PRESSURE SYSTEMS THAT TRACK
INTO THE GULF OR TOWARDS THE SOUTHERN MAINLAND. THE COMPLEXITY OF
THE PARENT UPPER-LOW DUE OF THE NUMEROUS LOBES OF ENERGY
INTERACTING WITH IT MAKE PLACEMENT AND TIMING OF THESE SURFACE
LOWS (AND THUS THEIR ASSOCIATED WEATHER) VERY DIFFICULT TO
PROG...AND THIS IS BEING REFLECTED IN THE POOR MODEL CONSENSUS.
THE JET STREAM WHICH WILL LARGELY BE WEAK OVER THE AOR EARLY IN
THE WEEK DOES TREND STRONGER WITH TIME AS THE PARENT UPPER-LOW
NEARS THE SW MAINLAND. AVERAGE FORECAST CONFIDENCE MID WEEK TRENDS
TO LOW FRI NIGHT AND BEYOND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.
&&

RMC/JAM AUG 14