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FXAK68 PAFC 010036
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
436 PM AKDT FRI JUL 31 2015

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL PATTERN SHOWS THE UPPER LEVEL RIDGE OVER THE
BERING SEA AND BUILDING OVER THE INTERIOR OF THE STATE. THE MAIN
UPPER LEVEL LOW IS NOW SOUTH OF THE MAINLAND IN THE GULF OF
ALASKA. THE RIDGE WILL BUILD IN OVER THE MAINLAND PART OF THE
STATE OVER THE COURSE OF THE WEEKEND. THE ATMOSPHERE OVER
SOUTHCENTRAL ALASKA AND NEAR THE BRISTOL BAY REGION WILL BE
UNSTABLE THIS AFTERNOON AND EVENING.

&&

.MODEL DISCUSSION...
MODELS ARE IN GOOD ENOUGH AGREEMENT TO GIVE A HIGH AMOUNT OF
CONFIDENCE IN THE FORECAST THROUGH THE WEEKEND OVER MOST OF THE
AREA. THE MOST SIGNIFICANT DIFFERENCE IN MODELS IS SOUTH OF
ALASKA PENINSULA AND KODIAK ISLAND SUNDAY INTO TUESDAY WHERE
THERE IS A BIT OF DISAGREEMENT BETWEEN MODELS AS TO HOW FAST A 
LOW FROM THE NORTH PACIFIC WILL TRACK TOWARD THE GULF. THE GFS
WAS A BIT OF AN OUTLIER FROM THE 12Z SUITE OF MODELS HAVING A
SOLUTION MUCH FASTER THAN THE ECMWF NAM OR GEM. HOWEVER THE 18Z
NAM JUMPED FORWARD TOWARD THE FASTER GFS SOLUTION. IT WILL BE
INTERESTING TO SEE IF THE MODELS START TO SHIFT TOWARD THIS FASTER
SOLUTION OR HOLD FARTHER BACK. THE PLACES THIS WILL IMPACT THE
MOST WILL BE THE ALASKA PENINSULA ON MONDAY AND THEN THE GULF OF
ALASKA REGION BY LATE TUESDAY. INLAND AREAS WILL NOT BE IMPACTED
AS MUCH DUE TO THE TRACK REMAINING IN THE FAR SOUTHERN PART OF 
THE FORECAST AREA REGARDLESS OF THE TIMING.

&&

.FIRE WEATHER...
THE EARLY PART OF NEXT WEEK WILL SEE SOME WARMER TEMPERATURES AND
LOWER RH VALUES IN CONJUNCTION WITH THE UPPER LEVEL HIGH PRESSURE
OVER SOUTHERN ALASKA. HOWEVER THESE RH VALUES ARE NOT EXPECTED TO
BE UNUSUALLY LOW WITH LOWEST VALUES IN THE MID TO UPPER 20S IN
INTERIOR PARTS OF SOUTHCENTRAL ALASKA. HUMIDITY WILL BE HIGHER
WEST OF THE ALASKA RANGE AS LOW LEVEL MOISTURE OFF BRISTOL BAY
HEADS INLAND.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
CONDITIONS OVER SOUTHCENTRAL ALASKA WILL CONTINUE TO DRY OUT AND
WARM UP AS THE RIDGE BEGINS TO SETTLE IN OVER THE AREA THROUGH
SUNDAY. THE BEST CHANCES FOR SHOWERS WILL BE THIS EVENING AS THERE
WILL BE ENOUGH WIDESPREAD MOISTURE AND INSTABILITY TO GENERATE
SHOWERS AND ISOLATED THUNDERSTORMS...MAINLY OVER THE SUSITNA
VALLEY AND THE COPPER RIVER BASIN. ALTHOUGH CONDITIONS ARE
EXPECTED TO STABILIZE AS THE RIDGE BUILDS IN ON SATURDAY...AN
UPPER LEVEL SHORTWAVE MOVING AHEAD OF THE RIDGE AXIS WILL PROVIDE
ENOUGH INSTABILITY FOR SOME CONVECTIVE POTENTIAL...MAINLY ALONG
MOUNTAIN AREAS WHERE THERE WILL BE SUFFICIENT MOISTURE FOR
SHOWERS. 

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA...
HIGH PRESSURE IS BUILDING IN OVER THE BERING WITH ASSOCIATED
RIDGING MOVING IN OVER THE SOUTHWEST. THIS IS CLEARING OUT THE
SKIES IN THE AREA BUT FOR THIS EVENING THE UPPER LEVELS WILL
REMAIN COLD ENOUGH FOR UNSTABLE CONDITIONS TO CONTINUE AROUND
BRISTOL BAY. THIS WILL RESULT IN THUNDERSTORM DEVELOPMENT IN 
THE BRISTOL BAY AREA THAT WILL EXTEND UP INTO THE ALASKA RANGE.
OVERNIGHT THE RIDGING WILL BUILD IN MORE BRINGING IN MORE WARM 
AIR ALOFT WHICH WILL PROVIDE A MORE STABLE ATMOSPHERE AND
SUBSEQUENTLY LESS CLOUD COVER. WITH THE HIGH IN PLACE FOG
DEVELOPMENT IS LIKELY...ESPECIALLY ALONG THE COAST. WITH WESTERLY
FLOW OFF THE BERING NEAR THE KUSKOKWIM DELTA FOG WILL LIKELY BE
ADVECTED INLAND.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS...
WITH HIGH PRESSURE OVER THE BERING STRATUS AND FOG WILL REMAIN
ABUNDANT THROUGH THE WEEKEND. WAY OUT WEST NEAR THE WESTERN
ALEUTIANS A WEAK TROUGH WILL MOVE IN AND STALL OUT THERE SATURDAY
BRINGING IN SOME LIGHTER RAIN TO THE ISLANDS. THEN ON SUNDAY
EVENING A NORTH PACIFIC LOW WILL APPROACH THE ALASKA PENINSULA
BRINGING SOME MORE STEADY RAIN TO THE AREA.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
GENERALLY PLEASANT CONDITIONS MARKED BY ABUNDANT SUNSHINE AND
WARMER TEMPERATURES WILL SETTLE OVER THE REGION THROUGH THE MIDDLE
OF NEXT WEEK AS HIGH PRESSURE REMAINS OVER THE BERING SEA AND
EXTENDS EASTWARD OVER THE MAINLAND. A SLIGHT COMPLICATING FACTOR
WILL BE THE EVOLUTION OF A CUTOFF LOW THAT DEVELOPS OVER THE NORTH
PACIFIC THIS WEEKEND IN RESPONSE TO THE BUILDING RIDGE OVER THE
BERING. MODEL SPREAD HAS INCREASED OVER THE PAST 24 HOURS WITH
RESPECT TO THIS FEATURE...WITH THE 12Z GFS AND 18Z NAM DEPICTING A
DRAMATIC EASTWARD SHIFT THAT WOULD BRING THE LOW AND AN ASSOCIATED
FRONT MUCH CLOSER TO THE WESTERN GULF AND THUS INCREASE
PRECIPITATION CHANCES OVER KODIAK ISLAND BY EARLY NEXT WEEK. THE
EC/GEM KEEP THE LOW FARTHER TO THE WEST WITH IMPACTS MAINLY
CONFINED TO THE AKPEN/EASTERN ALEUTIANS BEFORE BEGINNING TO
APPROACH THE BRISTOL BAY REGION BY WEDNESDAY. PREFERRED TO STAY
CLOSER TO THE WESTERN SOLUTION FOR NOW AS IT HAS BEEN THE MOST
CONSISTENT OVER THE PAST FEW DAYS. REGARDLESS...THE BULK OF THE
IMPACTS FROM THIS SYSTEM ARE EXPECTED TO REMAIN SOUTH OF THE
MAINLAND THROUGH MIDWEEK BEFORE PRECIPITATION CHANCES BEGIN TO
INCREASE AS HIGH PRESSURE GRADUALLY WEAKENS.

&&


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

&&

$$

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...RF
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DK
LONG TERM...CB

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