Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 182142
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
142 PM AKDT THU SEP 18 2014

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL PATTERN IS FAIRLY BASIC TODAY WITH A RIDGE OVER
THE WESTERN BERING SEA AND LONGWAVE TROUGH OVER THE WEST COAST OF
THE STATE. ANOTHER UPPER LEVEL RIDGE EXTENDS OUT OF NORTHWEST
CANADA TO THE ALCAN BORDER. THE MAIN JET STREAM IS RUNNING SOUTH
OF THE AREA WITH A FEW JET STREAKS AROUND THE BERING SEA RIDGE. AT
THE SURFACE THERE IS A DOUBLE CENTERED LOW WITH ONE CENTER ALONG
THE NORTH GULF COAST AND THE OTHER IN THE CENTRAL GULF. THIS
SECOND LOW WILL GET ABSORBED INTO THE FIRST ONE OVERNIGHT. THERE
IS ALSO A FAIRLY STRONG RIDGE IN THE WESTERN BERING SEA.

&&

.MODEL DISCUSSION...
THE MODELS ARE DOING WELL FOR THE SHORT TERM BUT A FEATURE MOVING
INTO THE GULF OF ALASKA LATE THIS WEEKEND IS GIVING THEM TROUBLE.
THE MODELS ALL HAVE A LOW THAT STRENGTHENS AS IT MOVES FROM AN
AREA NEAR 50N 140W SATURDAY EVENING INTO THE EASTERN GULF LATE
SUNDAY. THE GOOD NEWS IS THAT THE MODELS ARE BEGINNING TO CONVERGE
TOWARD A COMMON SOLUTION...BUT THEY ARE NOT QUITE THERE YET. THE
GFS IS THE FASTEST OF THE BUNCH AND THE NAM IS NOT FAR BEHIND. THE
ECMWF WAS VASTLY DIFFERENT FROM THE MODELS RUN FROM YESTERDAY
AFTERNOON AND HAD MOVED MUCH CLOSER TO THE NAM...GFS...AND GEM
SOLUTIONS. THE ECMWF DOES APPEAR TO BE IN CATCH-UP MODE AS IT WAS
SO DIFFERENT FROM THE REST AND IS STILL 200 MILES FARTHER SOUTH
THAN THE GFS POSITION SUNDAY NIGHT. THE STRENGTH ON ALL THE
SOLUTIONS IS IN THE UPPER 970S TO LOWER 980S SO THE ARE ALL
SHOWING A FAIRLY STRONG LOW DEVELOPING. A STRONG LOW DEVELOPING
NEAR THE SOUTHERN TIP OF KAMCHATKA TOMORROW WILL MOVE EASTWARD
THROUGH THE WEEKEND AND INTO THE WESTERN BERING SEA. THE MODELS
ARE ALL SHOWING A DOUBLE CENTER. THE NAM AND GFS SHOW THE LOW
STRONGER TO THE EAST WITH A WEAKER TROUGH TOWARD THE WEST...WHILE
THE ECMWF REVERSES THIS ORIENTATION.

&&

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
THE FRONT MOVING THROUGH SOUTHCENTRAL ALASKA WILL BRING RAINFALL
TO MOST OF THE AREA OVERNIGHT. THE HEAVIEST RAINFALL WILL BE OVER
THE EASTERN KENAI PENINSULA AND NORTHWEST PRINCE WILLIAM SOUND.
HOWEVER IT DOES NOT LOOK LIKE IT WILL BE ENOUGH TO CAUSE ANY
FLOODING CONCERNS. THERE LOOKS TO BE A BRIEF PERIOD OF GUSTY WINDS
LATE TOMORROW AFTERNOON INTO FRIDAY EVENING THROUGH THE CORDOVA
AREA AS WELL AS TURNAGAIN ARM AND ALONG THE COPPER RIVER.
PRESSURE RISES BEHIND THE LOW MOVING ON SHORE TOMORROW AFTERNOON
IN NORTHERN PRINCE WILLIAM SOUND WILL CAUSE THESE GUSTY WINDS. AS
THE RIDGE BUILDS IN BEHIND THE LOW.

SOUTHWEST ALASKA...
WITH THE UPPER LEVEL LOW MOVING OUT OF SOUTHWEST ALASKA THE
MAJORITY OF THE RAINFALL HAS ENDED WITH JUST A FEW LINGERING
SHOWERS HERE AND THERE. THE EXCEPTION WILL BE IN THE KUSKOKWIM VALLEY
WHERE THE FRONT MOVING THROUGH SOUTHCENTRAL ALASKA WILL BRING SOME
RAINFALL OVERNIGHT IN THAT AREA AS WELL. THERE WILL BE SOME MORE
AREAS OF FOG THAT DEVELOP OVERNIGHT OVER MUCH OF THE REGION WITH
THE RECENT RAINFALL AND COOL TEMPERATURES. BREEZY NORTH TO
NORTHWEST WINDS WILL PERSIST OVER THE KUSKOKWIM DELTA WITH THE
STRONGEST OCCURRING ALONG THE COAST. THESE WINDS SHOULD DIMINISH
OVERNIGHT FRIDAY NIGHT AS THE PRESSURE GRADIENT WEAKENS.

BERING SEA/ALEUTIANS...
THE RIDGE IN THE WESTERN BERING SEA IS COMBINING WITH THE LOW IN
THE GULF TO PRODUCE GOOD NORTH TO NORTHWEST FLOW OVER THE CENTRAL
AND EASTERN BERING SEA. THIS IS PRODUCING SOME SHOWERS OVER THE
REGION...ESPECIALLY OVER THE TERRAIN ON THE ALEUTIAN ISLANDS.
THE STRENGTH OF THE RIDGE HAS CLEARED OUT A GOOD PORTION OF THE
WESTERN BERING SEA.

&&

.LONG TERM FORECAST...
ON MONDAY...A STOUT UPPER LEVEL BLOCKING HIGH WILL EXIST OVER THE
BERING...WITH A TROUGH OVER THE GULF OF ALASKA AND NORTH PACIFIC.
ALONG THE POLEWARD JET EXTENDING INTO THE EASTERN GULF OF
ALASKA...A STRONG LOW WILL BE IN THE PROCESS OF TRACKING INTO THE
COPPER BASIN. EXACTLY HOW FAR WEST THE PRECIPITATION SHIELD
STRETCHES REMAINS UNCERTAIN...BUT LOCATIONS EAST OF THE CHUGACH
AND TALKEETNA MOUNTAINS WILL LIKELY SEE PERIODS OF RAIN INTO
TUESDAY. WESTERN ALASKA WEST OF THE ALASKA RANGE WILL BE DRY AS
OFFSHORE FLOW INCREASES IN RESPONSE TO THE LOW ACROSS THE GULF.
LATE TUESDAY THROUGH THURSDAY WILL GRADUALLY DRY OUT ACROSS THE
COPPER BASIN...WITH LARGELY DRY CONDITIONS DEVELOPING ACROSS MOST
OF SOUTHERN ALASKA AS THE STORM TRACK SHIFTS SOUTH ACROSS THE
NORTH PACIFIC.

&&

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

$$

SEP 14



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