Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 271257
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
457 AM AKDT SAT JUN 27 2015

.ANALYSIS AND UPPER LEVELS...

THE DOPPLER RADARS ACROSS MUCH OF ALASKA ARE QUITE BUSY THIS
MORNING AS MULTIPLE LARGE SCALE SYSTEMS ARE IMPACTING THE WESTERN
COAST AND THE NORTHERN GULF COAST OF ALASKA. A LARGE SWATH OF
RAIN EXTENDS FROM NORTON SOUND EXTENDING SOUTH TOWARD THE
KUSKOKWIM DELTA...WHERE BETHEL HAS ALREADY BEGUN TO PARTAKE IN THE
RAINFALL. THIS RAIN IS ASSOCIATED WITH THE ARCTIC TROUGH THAT
DROPPED SOUTH FROM SIBERIA SEVERAL DAYS AGO. IN ADDITION TO THE
RAIN OVER THE KUSKOKWIM DELTA...A LEE SIDE LOW HAS DEVELOPED
ACROSS THE BRISTOL BAY AREA OVERNIGHT AND HAS HELPED RE-INVIGORATE
SHOWERS ACROSS THE LOWER KUSKOKWIM DELTA AND BRISTOL BAY AREA
OVERNIGHT. THE INTERACTION BETWEEN THE TWO AFOREMENTIONED SYSTEM
WILL SET UP A DEFORMATION ZONE NEAR DILLINGHAM AND EXTEND NORTH
TOWARD ANIAK. THIS SHOULD HELP BRING SOME MUCH NEEDED RAINFALL TO
SOUTHWEST ALASKA AND PARTS OF THE INTERIOR WHERE WILDFIRES HAVE
BEEN VERY ACTIVE.

HEADING OVER TOWARD THE NORTHERN GULF COAST...AN AREA OF LOW
PRESSURE SOUTHEAST OF KODIAK ISLAND HAS PUSHED MULTIPLE WAVES OF
PRECIPITATION ACROSS THE NORTHERN GULF COAST...WHICH HAS SEEN
PRETTY DECENT RAIN AMOUNTS OVERNIGHT. AN UPPER LEVEL LOW IS
STACKED ON TOP OF THE SURFACE LOW WHICH HAS HAD SEVERAL EASTERLY
WAVES TRACK ACROSS THE GULF COAST WHICH HAS HELPED BRING PERIODS
OF HEAVIER RAINFALL. THIS UPPER LEVEL LOW HAS BEGUN TO PHASE WITH
THE ARCTIC TROUGH OVER SOUTHWEST ALASKA AND WILL KEEP A GOOD
PORTION OF SOUTHWEST AND SOUTHCENTRAL ALASKA ON THE WET SIDE OVER
THE WEEKEND.

&&

.MODEL DISCUSSION...

MODELS ARE IN VERY GOOD AGREEMENT WITH THE PHASING OF THE SYNOPTIC
SYSTEMS ACROSS SOUTHWEST ALASKA (ARCTIC TROUGH AND LOW SOUTHEAST
OF KODIAK ISLANDS). IT APPEARS LIKELY...ESPECIALLY BASED OFF RADAR
TRENDS THIS MORNING...THAT A DEFORMATION ZONE WILL SET UP NEAR
DILLINGHAM AND EXTEND NORTH TOWARD THE CROOKED CREEK/ANIAK AREA
AND LIKELY BRING SOME DECENT RAINFALL. MODELS HINTED AT A
SIGNIFICANT WEAKENING OF THE THERMAL TROUGH WITH THE ARCTIC TROUGH
MOVING OVER SOUTHWEST ALASKA...BUT NEWEST GUIDANCE SUGGESTS THE
WEAKENING WAS NOT AS PROFOUND AS EXPECTED. EVEN WITH THIS PATTERN
SHIFT IN FULL SWING...THE THERMAL TROUGH LOOKS TO NUDGE ACROSS
SOUTHWEST ALASKA AGAIN THIS AFTERNOON WITH SOME ISOLATED
THUNDERSTORMS OVER THE LOWER KUSKOKWIM VALLEY AND SCATTERED
THUNDERSTORMS ALONG THE TERRAIN OF THE ALASKA RANGE AND TALKEETNA
MOUNTAINS. THUNDERSTORMS APPEAR TO BE SLIGHTLY MORE WIDESPREAD
HEADING INTO SUNDAY AS THE THERMAL TROUGH BEGINS TO STRENGTHEN AND
THE ATMOSPHERE BECOMES A BIT MORE UNSTABLE. IN ADDITION...A SHORTWAVE
WILL PUSH ACROSS SOUTHWEST ALASKA AND BRING ANOTHER GOOD SHOT OF
RAINFALL. MODELS ARE IN RELATIVELY GOOD AGREEMENT WITH THE PLACEMENT
OF THIS WAVE BUT THERE ARE STILL SOME NOTICEABLE DIFFERENCE WITH
HOW FAR NORTH PRECIPITATION SPREADS ACROSS THE LOWER KUSKOKWIM
VALLEY. THUNDERSTORM ACTIVITY ACROSS SOUTHWEST ALASKA LOOKS TO BE
ENHANCED WITH THE POSITIVE VORTICITY ADVECTION ASSOCIATED WITH THE
WAVE.

&&

.FIRE WEATHER...

SOUTHCENTRAL ALASKA...THE GULF COAST AND KENAI PENINSULA WILL
GENERALLY REMAIN ON THE COOL AND WET SIDE. THE WESTERN KENAI WILL
REMAIN DRIER...BUT ANY SHOWERS THAT DO SURVIVE THE TRIP ACROSS THE
KENAI MOUNTAINS COULD PRODUCE ISOLATED AREAS OF MODERATE RAIN OVER
THE NEXT COUPLE DAYS. MARGINALLY DRIER AND WARMER CONDITIONS WILL
DOMINATE AS YOU HEAD NORTH AND EAST TO INTERIOR SOUTHCENTRAL. THE
COPPER RIVER BASIN WILL BE FARTHEST FROM THE UPPER LOW OVER THE
GULF AND WILL SEE THE MOST SUNSHINE OVER THE NEXT COUPLE DAYS.
THERE IS SOME POTENTIAL THAT CONDITIONS MAY APPROACH RED FLAG
THRESHOLDS FOR STRONG WIND ON SUNDAY...BUT AT THIS POINT IT LOOKS
LIKE RELATIVE HUMIDITIES WILL REMAIN JUST ABOVE THE 30 PERCENT
THRESHOLD.

SOUTHWEST ALASKA...FIRE WEATHER CONDITIONS WILL CONTINUE TO IMPROVE
OVER THE REGION THROUGH SUNDAY AS THE REGION ENTERS A WET PATTERN
WITH WIDESPREAD WETTING RAINS EXPECTED OVER MOST OF SOUTHWEST
ALASKA THROUGH SUNDAY. THERE IS A CHANCE TODAY FOR ISOLATED WET
THUNDERSTORMS OVER THE MIDDLE KUSKOKWIM VALLEY AND BRISTOL BAY
REGION WITH SCATTERED WET THUNDERSTORMS EXPECTED FROM SLEETMUTE
EAST THIS AFTERNOON/EVENING. AN UPPER LEVEL DISTURBANCE WILL MOVE
WESTWARD THROUGH THE AREA ON SUNDAY PRODUCING A SECOND ROUND OF
WIDESPREAD WETTING RAINS WITH ISOLATED WET THUNDERSTORMS...MAINLY
FROM BETHEL TO SLEETMUTE. MINIMUM RH VALUES ARE EXPECTED TO REACH
THE LOW 40S TODAY AND UPPER 30S ON SUNDAY WITH EXCELLENT OVERNIGHT
RECOVERIES.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

AN UPPER LOW WILL DRIFT NORTHWARD ACROSS THE WESTERN GULF THROUGH
TONIGHT THEN WILL BE ABSORBED BY ANOTHER LOW CURRENTLY DROPPING
SOUTHWARD ALONG THE SOUTHWEST COAST OF ALASKA. THIS NEW LOW WILL
SETTLE IN SOUTH OF KODIAK ISLAND AND THE ALASKA PENINSULA. THIS
WILL PRODUCE A VERY PERSISTENT PATTERN WITH UPPER LEVEL
DISTURBANCES TRACKING ACROSS THE WESTERN GULF AND KENAI PENINSULA.
EXPECT COOL AND WET CONDITIONS THROUGH THE WEEKEND FROM KODIAK
ISLAND UP TO WESTERN PRINCE WILLIAM SOUND/EASTERN KENAI PENINSULA.
EASTERLY FLOW ACROSS THE KENAI MOUNTAINS WILL KEEP THE WESTERN
KENAI DRIER...THOUGH SHOWERS WILL PERIODICALLY MAKE IT OVER THE
MOUNTAINS AS EACH UPPER DISTURBANCE MOVES THROUGH.

CONDITIONS ON THE NORTHERN AND EASTERN PERIPHERY OF THE UPPER LOW
WILL BE MUCH DRIER WITH PRIMARILY DIURNALLY DRIVEN CONVECTION. THE
DISTURBANCE APPROACHING THE GULF COAST THIS MORNING WILL HEAD
INLAND THIS AFTERNOON...SO SHOWERS WILL BE MORE NUMEROUS OVER THE
TALKEETNA MOUNTAINS AND NORTHERN SUSITNA VALLEY. WITH LOW PRESSURE
OVER THE WESTERN GULF AND OVER INTERIOR ALASKA SURFACE RIDGING
WILL PERSIST IN BETWEEN ALONG THE NORTH GULF COAST AND INTO
SOUTHCENTRAL. THIS WILL PRODUCE AFTERNOON AND EVENING GAP WINDS
THROUGH THE COASTAL RANGE WITH THE MOST WIDESPREAD WINDS THROUGH
THE HEART OF THE COPPER BASIN. THESE WINDS WILL PROVIDE A BIT OF
DOWNSLOPING ALONG THE CHUGACH WHICH WILL ALLOW SOME SUN TO PEAK
THROUGH EACH AFTERNOON AND EVENING. INSTABILITY LOOKS MARGINAL FOR
THUNDERSTORMS. THE BEST CHANCE WILL BE FOR ISOLATED THUNDERSTORMS
OVER INTERIOR MOUNTAINS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...

THE WIDESPREAD WET PATTERN HAS BEGUN IN EARNEST OVER SOUTHWEST
ALASKA AS THE LOW AND ITS ASSOCIATED FRONT MOVING SOUTH OUT OF
THE BERING STRAIGHT HAS MOVED ONSHORE OVERNIGHT. RADAR AND
SATELLITE IMAGERY THIS MORNING IS SHOWING WIDESPREAD AREAS OF RAIN
AND SHOWERS OVER SOUTHWEST ALASKA WITH 00-12Z RAINFALL TOTALS OF
UP TO 0.25 INCH FROM THE CENTRAL BRISTOL BAY REGION NORTHWARD
THROUGH THE MIDDLE KUSKOKWIM VALLEY. THE FRONT WILL CONTINUE TO
PUSH SOUTHWESTWARD TODAY WITH RAIN TAPERING OFF THIS EVENING OVER
MOST AREAS EXCEPT THE ALASKA/ALEUTIAN RANGE. ISOLATED TO SCATTERED
THUNDERSTORMS ARE EXPECTED AGAIN TODAY MAINLY OVER THE MIDDLE
KUSKOKWIM VALLEY AND THE INTERIOR SECTIONS OF BRISTOL BAY.

AS THE LOW MERGES WITH THE LOW CURRENTLY SOUTH OF KODIAK...A
SHORTWAVE WILL ROTATE WESTWARD THROUGH SOUTHWEST ALASKA. WITH
ABUNDANT MOISTURE IN PLACE...THIS SHORTWAVE WILL SERVE AS THE
FOCUS FOR A SECOND ROUND OF SHOWERS OVER THE REGION WITH
NUMEROUS SHOWERS EAST OF THE KILBUCK/AHKLUN MOUNTAINS. ISOLATED
THUNDERSTORMS ARE EXPECTED AGAIN WITH THIS WAVE WITH THE BEST AREA
FOR DEVELOPMENT BETWEEN BETHEL AND SLEETMUTE. AT THIS TIME
COVERAGE LOOKS TO BE ISOLATED...HOWEVER IF THERE ARE ENOUGH
BREAKS IN CLOUD COVER AHEAD OF THE SHORTWAVE TO PROVIDE SUFFICIENT
DAYTIME HEATING COVERAGE COULD BE MORE WIDESPREAD.

AREAS OF SMOKE ARE EXPECTED TO CONTINUE THROUGH TOMORROW AS
MORNING/EVENING INVERSIONS WILL LIMIT DISPERSION OF SMOKE NEAR THE
SURFACE...ESPECIALLY IN VALLEY LOCATIONS. THIS SHOULD IMPROVE
THROUGH SUNDAY AS THE ATMOSPHERE WILL BE MIXED SUFFICIENTLY TO
ALLOW FOR IMPROVED VENTILATION.

WINDS WILL BEGIN TO INCREASE THIS AFTERNOON AND REMAIN ELEVATED
OVER THE INTERIOR SECTIONS OF BRISTOL BAY THROUGH THE WEEKEND AS
STRONG SOUTHEAST TO EASTERLY WINDS FROM THE LOW SOUTH OF KODIAK
WILL PUSH THROUGH KAMISHAK GAP AND INTO THE SOUTHWEST MAINLAND.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

HIGH PRESSURE WILL CONTINUE TO WEAKEN OVER THE BERING SEA AS THE
LOW CURRENTLY MOVING SOUTHWARD THROUGH THE FAR EASTERN BERING
MERGES WITH A LOW SOUTH OF KODIAK ISLAND AND A SECOND LOW AND
FRONT MOVES THROUGH THE WESTERN ALEUTIANS. EXPECT NUMEROUS SHOWERS
TODAY AS THE FRONT PUSHES SOUTH FROM THE PRIBILOF ISLANDS AND INTO
THE EASTERN ALEUTIANS/ALASKA PENINSULA TODAY. AS THE FRONT
CLEARS...SCATTERED TO ISOLATED SHOWERS WILL REMAIN ALONG THE
ALASKA PENINSULA IN THE NORTHERLY FLOW. RAIN CHANCES WILL INCREASE
FROM ADAK WEST SUNDAY MORNING AS THE FRONT MOVES INTO THE REGION.
EXPECT WINDS TO INCREASE TO NEAR GALE FORCE FROM ADAK WEST ON
SUNDAY...BUT SHOULD BEGIN TO DIMINISH LATE SUNDAY NIGHT AS THE
FRONT WEAKENS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

BEGINNING THE EXTENDED PERIOD FORECAST SUNDAY NIGHT...A CLOSED
UPPER LEVEL LOW IN THE VICINITY OF KODIAK ISLAND WILL BE THE MAIN
IMPACTFUL FEATURE OF INTEREST FOR THE REGION. THIS LOW WILL KEEP
MOISTURE...CLOUDS...AND COOLER WEATHER OVER MUCH OF THE REGION
THROUGH THE DAY TUESDAY. PRECIPITATION WILL GENERALLY BE IN THE
FORM OF SHOWERS WITH PERIODS OF LIGHTER RAIN ALONG THE NORTHERN
GULF COAST. DIFFICULTY IN ASCERTAINING WEAK EMBEDDED SHORTWAVE TROUGHS
WITHIN THE CLOSED LOW MEANS THAT DIURNAL HEATING AND INSTABILITY
WILL BE DIFFICULT TO DIAGNOSE AT THIS TIME...BUT THERE MAY BE
ENOUGH HEATING FOR ISOLATED THUNDERSTORMS ACROSS THE MORE
FAVORABLE LOCATIONS ALONG THE TALKEETNA MOUNTAINS AND PORTIONS OF
THE ALASKA RANGE. UNCERTAINTY QUICKLY RISES LATE TUESDAY AS A
CENTRAL PACIFIC LOW...WITH AN ASSOCIATED SUBTROPICAL WARM
FRONT...MERGES WITH THE LEFTOVER REMNANT UPPER LOW NEAR KODIAK
ISLAND. HOWEVER...THE LATEST SUITE OF GLOBAL NUMERICAL GUIDANCE
HAS CLUSTERED AROUND A GENERAL SOLUTION WHICH PHASES THE PACIFIC
LOW WITH THE KODIAK LOW...EVENTUALLY DRIVING A STOUT WARM FRONT
INTO THE GULF OF ALASKA WEDNESDAY AND THURSDAY. SHOULD THIS
PATTERN EMERGE AS CURRENTLY PROGGED...ESPECIALLY BY THE 12Z AND
18Z GFS SOLUTIONS...A STRONG GALE FORCE FRONT MAY MOVE UP TOWARD
THE NORTH GULF COAST...WITH AN IMPRESSIVE SLUG OF PRECIPITATION
IMPACTING COASTAL AND INLAND LOCATIONS. HOWEVER...DUE TO THE POOR
MODEL RUN CONSISTENCY WITH LARGE DEVIATIONS NOTED WITHIN THE
ENSEMBLE GUIDANCE...A VERY GENERALIZED WPC BLEND WAS FAVORED FOR
THE TIME BEING. UNCERTAINTY CONTINUES TOWARD THE END OF THE
WEEK...BUT THE GENERAL PATTERN LOOKS TO FAVOR TROUGHING OVER THE
EASTERN BERING SEA...AND SOUTH TO SOUTHWEST FLOW OVER MOST OF
SOUTHERN ALASKA...KEEPING A SLIGHTLY COOLER...POSSIBLY WETTER...AND
CLOUDIER PATTERN IN PLACE. OF COURSE...BY THAT FAR OUT...THERE
TENDS TO BE INTERMITTENT DRIER AND NICER DAYS IN BETWEEN...BUT
THAT IS DIFFICULT IF NOT IMPOSSIBLE TO FORECAST IN THESE PATTERNS
AT THAT TIME RANGE.

&&


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

&&

$$

SYNOPSIS AND MODEL DISCUSSION...MMC
SOUTHCENTRAL ALASKA...SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...RF
LONG TERM...JA



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