Gale Warning 514, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
411 PM AKDT THU AUG 20 2015

.ANALYSIS AND UPPER LEVELS...

THE MAIN WEATHER FEATURE ON THE MORNING SATELLITE IS AN UPPER LOW
OVER THE NORTHERN BERING THAT IS MOVING STEADILY TO THE SOUTHEAST.
SOUTHERLY FLOW AHEAD OF THE STORM IS PUSHING SUBSTANTIAL MARINE
STRATUS ONSHORE THE KUSKOKWIM DELTA AND PORTIONS OF THE BRISTOL
BAY ZONE. EAST OF THE ALASKA RANGE...RIDGING AHEAD OF THE BERING
SEA SYSTEM IS PRODUCING A VERY NICE DAY WITH MOSTLY SUNNY
CONDITIONS AT MOST AREAS. A WEAK SHORTWAVE IS MOVING THROUGH THE
RIDGING...WITH SOME MID AND HIGH CLOUDS AROUND UPPER COOK INLET
AND THE MAT-SU VALLEYS. THERE IS NO PRECIP ASSOCIATED WITH THIS
SHORTWAVE...BUT IT WILL MOVE THROUGH THE COPPER RIVER BASIN NEAR
PEAK-HEATING THIS AFTERNOON AND IS EXPECTED TO KICK OFF A FEW
THUNDERSTORMS THIS AFTERNOON ALONG AND EAST OF THE TALKEETNA
MOUNTAINS. AT THE SURFACE...OUTFLOW WINDS ARE WINDING DOWN ALONG
THE NORTH AND WEST GULF COAST AS THE PRESSURE GRADIENT HAS GONE
SLACK AND IS RE-ORIENTING AS THE BERING COMPLEX MAKES STEADY
PROGRESS TOWARD THE GULF.

&&

.MODEL DISCUSSION...

THE MODELS ARE ALL IN PRETTY GOOD AGREEMENT...ESPECIALLY ON THE
SYNOPTIC SCALE...FOR THE FIRST FEW DAYS OF THE FORECAST. THE
SURFACE LOW WIDELY ANTICIPATED TO DEVELOP IN THE GULF NOW APPEARS
THAT IT WILL STAY FAR ENOUGH OUT TO SEA THAT EVEN THE EASTERN
KENAI PENINSULA WILL STAY MOSTLY OR TOTALLY DRY ON FRIDAY NIGHT
AND SATURDAY. STEADY RAINFALL NOW LOOKS LIKE IT WILL NOT MAKE IT
ANY FURTHER EAST THAN CORDOVA AND THE EASTERN COPPER RIVER BASIN
THROUGH THE START OF THE WEEKEND. THE GFS IS THE OVERALL PREFERRED
MODEL TODAY...THOUGH NO HUGE OUTLIERS WERE PRESENT.

&&

.FIRE WEATHER...

WITH A FURTHER SOUTH AND EAST TRACK OF THE LOW IN THE GULF
TOMORROW AND SATURDAY THE INLAND AREAS OF SOUTHCENTRAL WILL STAY
DRY AND RH VALUES WILL LIKELY DROP INTO THE 30S. GUSTY NORTH TO
WEST WINDS WILL DEVELOP...BUT CONDITIONS ARE EXPECTED TO REMAIN
ABOVE CRITICAL THRESHOLDS DUE TO RECENT WIDESPREAD RAINFALL.

&&

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

WHILE CLEAR SKIES WERE OBSERVED THIS MORNING...AN UPPER LEVEL
DISTURBANCE NEAR THE ALASKA RANGE HAS BROUGHT HIGH CLOUDS TO PART
OF SOUTHCENTRAL ALASKA THIS AFTERNOON. HOWEVER...THE LOWER LEVELS
OF THE ATMOSPHERE HAVE CONTINUED TO DESTABILIZE UNDER ABUNDANT
SUNSHINE...WITH THE GREATEST INSTABILITY DEVELOPING ACROSS THE
TALKEETNA MOUNTAINS AND INTO THE COPPER RIVER BASIN. AS THIS WAVE
CONTINUES TO PUSH EAST THIS AFTERNOON AND EVENING...ISOLATED
SHOWERS AND THUNDERSTORMS ARE ANTICIPATED TO DEVELOP ALONG THE
TALKEETNA MOUNTAINS AND PARTS OF THE MAT-SU VALLEYS AS WELL AS THE
COPPER RIVER BASIN. ANY SHOWERS OR THUNDERSTORMS THAT DO DEVELOP
WILL BE SHORT LIVED AS THE ATMOSPHERE STABILIZES AGAIN THIS EVENING.

ON FRIDAY...AN AREA OF LOW PRESSURE WILL DEVELOP SOUTH OF KODIAK
ISLAND AND TRACK ACROSS THE SOUTHERN GULF OF ALASKA. MUCH OF THE
RAINFALL WILL STAY SOUTH OF THE AREA...WITH SOME LOCATIONS OF THE
NORTHERN GULF COAST SEEING A FEW SHOWERS. INLAND...INSTABILITY
APPEARS TO BE MORE FAVORABLE THAN THAT SEEN TODAY WHICH WILL
LIKELY LEAD TO LITTLE GREATER COVERAGE IN BOTH SHOWERS AND
THUNDERSTORMS. THESE SHOWERS AND THUNDERSTORMS WILL LIKELY REMAIN
ACROSS THE SUSITNA VALLEY AND COPPER RIVER BASIN AS A WEAK WAVE
MOVING ACROSS THE AREA IN THE MORNING WILL LIKELY CREATE SOME
CLOUD COVER WHICH WILL SLOW DOWN DIURNAL HEATING ACROSS
ANCHORAGE...THE MATANUSKA VALLEY AND KENAI PENINSULA.

STRONG OUTFLOW WINDS WILL BE SEEN SATURDAY MORNING AND CONTINUE
THROUGH THE DAY SATURDAY AND POSSIBLY INTO SUNDAY AS THE SURFACE
LOW SHIFTS INTO THE EASTERN GULF AND A TIGHT GRADIENT OF PRESSURE
RISES DEVELOPS ACROSS THE AREA. THE STRONGEST WINDS WILL LIKELY BE
OBSERVED NEAR WHITTIER WHERE WIND GUSTS UP TO 45 MPH MAY BE SEEN.
OTHER LOCATIONS SUCH AS THOMPSON PASS SHOULD PEAK IN THE 25 TO 35
MPH RANGE.

&&

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

SHOWERS ARE EXPECTED THROUGH SATURDAY. AS THE UPPER LOW MOVES
FROM THE BERING TO THE GULF OF AK...THE THERMAL TROUGH WILL SET UP
ALONG THE ALASKA AND ALEUTIAN RANGES FRI AND FRI NIGHT. WEAK
IMPULSES MOVING THROUGH THIS AREA WILL PROVIDE ENOUGH FOCUSED
LIFT FOR A SLIGHT CHANCE OF THUNDERSTORMS FRI EVENING ALONG THE
WEST SIDE OF THE MOUNTAINS. WHILE THE LOW IS CROSSING INTO THE
GULF...GUSTY WINDS CAN BE EXPECTED ALONG THE ALASKA PENINSULA
SOUTH OF KING SALMON THROUGH SAT.

&&

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

RIDGE BUILDING OVER THE BERING AND A LOW MOVING INTO THE GULF WILL
TIGHTEN THE PRESSURE GRADIENT ACROSS THE EASTERN AND CENTRAL ALEUTIANS.
THIS WILL ALLOW FOR SOME SMALL CRAFT WINDS THROUGH FRI. FOR THE
REST OF THE CHAIN...HIGH PRESSURE WILL BRING IN LIGHT WINDS AND
AREAS OF FOG THAT PERSIST THROUGH THE WEEKEND.

&&

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

A LOW PRESSURE SYSTEM EXITING THE GULF THIS WEEKEND WILL RESULT IN
SHOWERY CONDITIONS ALONG THE NORTHERN GULF COAST AND EASTERN
COPPER RIVER BASIN THROUGH SUNDAY. RIDGING WILL START TO BUILD IN
FROM THE NORTH PACIFIC/EASTERN BERING...BRINGING SOME FAIRLY GUSTY
NORTHWEST FLOW THROUGH FAVORED AREAS SUCH AS WHITTIER AND KAMISHAK
GAP THROUGH THE END OF THE WEEKEND. THAT NORTHWEST FLOW WILL ALSO
USHER IN SOME DRIER AIR ACROSS MUCH OF THE MAINLAND. THE EXCEPTION
TO THIS WILL BE A FEW WEAK WAVES COMING ACROSS THE ALASKA RANGE
WHICH COULD TRIGGER SOME AFTERNOON-EVENING SHOWERS ALONG HIGHER
TERRAIN. WINDS SHOULD START TO RELAX SLOWLY ON SUNDAY AND MOSTLY
DRY CONDITIONS WILL PERSIST TROUGH EARLY NEXT WEEK...WHICH IS WHEN
MODELS BEGIN TO STRUGGLE WITH THE UPCOMING PATTERN.

EVEN THOUGH MODELS ARE IN SLIGHTLY BETTER AGREEMENT TODAY...THEY
CONTINUE TO STRUGGLE WITH FINDING A COMMON SOLUTION REGARDING HOW
FAR NORTH THE UPPER LEVEL RIDGE BUILDS OVER THE BERING SEA...AND
THE PROGRESSION OF THE NORTHERN ENERGY STREAM. THE MAJORITY OF
RECENT MODEL RUNS NOW SHOW THE RIDGE FLATTENING OUT MORE AND THE
NORTHERN ENERGY STREAM TRACKING FURTHER SOUTH OVER THE MAINLAND
MON INTO TUE. THERE ARE STILL QUITE A FEW DIFFERENCES BETWEEN THE
MODELS REGARDING THE STRENGTH AND TIMING OF MULTIPLE SHORT-WAVES
TRACKING THROUGH THE MAINLAND THROUGH MIDWEEK. HOWEVER...DESPITE
THESE DIFFERENCES...IT DOES LOOK LIKE MUCH OF THE MAINLAND WILL
SEE A BROAD WARM FRONT MOVE THROUGH MIDWEEK AS FLOW SWITCHES TO
SOUTHWESTERLY. THE PATTERN CONTINUES TO SHOW AMPLIFICATION THROUGH
THE END OF NEXT WEEK. MODELS CONTINUE TO STRUGGLE WITH THE DETAILS
REGARDING THE REMNANTS OF TYPHOON ATSANI...AS IT APPROACHES THE
WESTERN ALEUTIANS AND DEEPENS AS AN EXTRA-TROPICAL SYSTEM BY THE
END OF NEXT WEEK.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...119.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...AD
SOUTHCENTRAL ALASKA...MC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DS
LONG TERM...TP