High Wind Watch 11, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT SUN SEP 1 2013

.ANALYSIS AND UPPER LEVELS...
A STRONG VERTICALLY STACKED 978 MB LOW OVER THE WESTERN ALEUTIANS IS
THE PRIMARY WEATHER-MAKER ACROSS THE REGION TODAY. THE ZONAL FLOW OF
THE LAST SEVERAL DAYS HAS BECOME MORE AMPLIFIED AND PROGRESSIVE AS
THIS BERING LOW HAS DEVELOPED. A WARM FRONT STRETCHES EASTWARD ACROSS
PARTS OF SOUTHWEST ALASKA WITH OVERRUNNING PRECIPITATION NOW MOVING
INTO SOUTHCENTRAL ALASKA AS NOTED ON THE KENAI NEXRAD. MODEST
RAINFALL AMOUNTS AND MILD TEMPERATURES ARE THE MAIN IMPACTS OF THIS
FRONT...WITH TEMPERATURES EARLY THIS MORNING AT DUTCH HARBOR REACHING
INTO THE UPPER 60S. THE COLD FRONT ASSOCIATED WITH THIS STORM IS
LOCATED OVER THE EASTERN ALEUTIANS...AND IS PUSHING ANOTHER ROUND OF
RAIN EASTWARD ACROSS THE REGION AND TOWARD THE MAINLAND.
MEANWHILE...AN UPPER LEVEL DISTURBANCE WELL AHEAD OF THE COLD FRONT
IS DRIFTING NORTHEASTWARD...AND WILL CONTINUE TO FRAGMENT AS IT HEADS
TOWARD SOUTHCENTRAL ALASKA OVERNIGHT. AT THE SURFACE...RIDGING IS
BUILDING IN THE GULF AHEAD OF THE BERING STORM AND IS ALLOWING
PRESSURE GRADIENTS TO BEGIN TO TIGHTEN THROUGH TURNAGAIN ARM AND
OTHER GAPS AROUND SOUTHCENTRAL ALASKA.

.MODEL DISCUSSION...
MODELS REMAIN IN GOOD SYNOPTIC AGREEMENT THAT THE LARGE LOW NEAR ADAK
WILL BECOME A COMPLEX LOW WITH MULTIPLE CENTERS AS THE WHOLE
CIRCULATION SLIDES INTO THE EASTERN BERING BY MONDAY MORNING AND THEN
TAKES A TURN NORTHWARD DURING THE AFTERNOON AND HEADS TOWARD THE
BERING STRAIT. THERE CONTINUES TO BE A DIFFERENCE AMONG SOME OF THE
MODELS CONCERNING HOW FAST THE COMPLEX TAKES THAT NORTHWARD
TURN...WITH THE GFS TRYING TO KEEP THE LOW NEAR BRISTOL BAY THROUGH
TOMORROW NIGHT...WHILE THE NAM/EC/UKMET/GEM ARE A BIT FURTHER NORTH
WITH THE LOW APPROACHING NUNIVAK ISLAND. IN THE GRAND SCHEME OF
THINGS THIS IS NOT A HUGE DIFFERENCE...HOWEVER THE EXACT POSITION OF
THE LOW AS THE ASSOCIATED FRONT COMES THROUGH SOUTHCENTRAL WILL BE
KEY TO WHETHER STRONG WINDS FROM TURNAGAIN ARM MOVE INTO THE LOWER
ELEVATIONS OF ANCHORAGE (OR NOT). A FURTHER NORTH SOLUTION WOULD
BRING GUSTY WINDS INTO SOUTH AND WEST ANCHORAGE...WHILE THE SOUTHERLY
GFS SOLUTION WOULD LIKELY KEEP LOWER ELEVATIONS OF ANCHORAGE FAIRLY
LIGHT. THE 12Z GFS TRENDED SLIGHTLY NORTHWARD...AND THE 12Z NAM
TRENDED SLIGHTLY SOUTHWARD WITH THE LOW POSITION. MEANWHILE THE EC
WAS NEARLY UNCHANGED WITH THE FURTHEST NORTH POSITION. WILL PRETTY
MUCH KEEP THE INHERITED FORECAST AS-IS...WITH ONLY A VERY SLIGHT
SOUTHWARD JOG IN THE LOW POSITION BASED ON THE FACT THAT EVEN THE
ECMWF AGREES THAT THE UPPER LOW WILL REMAIN SOUTH OF NUNIVAK ISLAND
TOMORROW NIGHT AND SURFACE CIRCULATIONS TEND TO FAVOR REMAINING IN
THE VICINITY OF THE SUPPORTING UPPER FEATURE.

.SHORT TERM FORECAST...
SOUTHCENTRAL...LIGHT OVERRUNNING PRECIP CURRENTLY MOVING INTO COOK
INLET FROM THE WEST WILL CONTINUE AND INTENSIFY THROUGH THE EARLY
EVENING HOURS. THERE MAY BE A SHORT BREAK OVERNIGHT AS THE WARM FRONT
PASSES THROUGH BEFORE RAIN FILLS BACK IN AHEAD OF THE UPPER
DISTURBANCE MENTIONED EARLIER. WITH A VERY WARM AND MOIST AIRMASS THE
MODELS ARE ACTUALLY DROPPING QUITE A BIT OF RAINFALL LATE TONIGHT
AROUND COOK INLET...AND SMALLER STREAMS AND RIVERS THAT RESPOND
QUICKLY TO RAIN MAY SEE A QUICK RISE (AND THEN FALL) INTO THE MORNING
HOURS TOMORROW. MEANWHILE...WINDS THROUGH TURNAGAIN ARM WILL INCREASE
DRAMATICALLY TOMORROW MORNING AHEAD OF THE FRONT. THERE IS NO
SIGNIFICANT CHANGE IN EXPECTED WIND SPEEDS WITH THE AFTERNOON
FORECAST. HOWEVER...WITH THIS BEING THE FIRST HIGH WIND EVENT IN A
WHILE AND ELEVATED LEVELS OF RECREATIONAL TRAFFIC ALONG THE
HIGHWAY...HAVE DECIDED TO ISSUE A HIGH WIND WATCH FOR WESTERN
TURNAGAIN ARM. BY TUESDAY...LOW PRESSURE WILL BE HEADED INTO THE
INTERIOR OF THE STATE...WITH A WIDESPREAD AREA OF MODERATE PRESSURE
RISES LIKELY BRINGING ANOTHER PERIOD OF GUSTY SOUTHERLY WIND TO MOST
AREAS.

SOUTHWEST...WIDESPREAD RAIN WILL CONTINUE ACROSS THE KUSKOKWIM VALLEY
AND DELTA ZONES UNTIL THE FRONT PASSES TO THE EAST ON MONDAY
AFTERNOON. THE BRISTOL BAY ZONE WILL SEE MORE OF A BREAK OVERNIGHT
WITH MORE SEPARATION BETWEEN THE WARM AND COLD FRONTAL
PASSAGES...HOWEVER COPIOUS WARM AIR OVER THE RELATIVELY COLDER WATERS
WILL CONTINUE TO DEVELOP SIGNIFICANT AREAS OF FOG ALONG THE
COASTLINES. SIGNIFICANT WINDS WILL NOT BE WIDESPREAD WITH THIS
STORM...AND WILL BE LARGELY CONFINED TO COASTAL AREAS. BEYOND
MONDAY...SHOWERS AND ONSHORE FLOW ASSOCIATED WITH THE LOW ITSELF WILL
LINGER THROUGH MIDWEEK.

BERING SEA AND ALEUTIANS...WIND AND RAIN AND OVERALL ACTIVE WEATHER
WILL SHIFT FROM THE WESTERN TO THE EASTERN BERING FOR THE START OF
THE WEEK. THE LOW PRESSURE CENTER BOTTOMED OUT SOMEWHERE IN THE MID
970S EARLY THIS MORNING AND HAS BEGUN TO SLOWLY WEAKEN. AS THE LOW
CONTINUES TO SLIDE TO THE EAST AN EARLY-SEASON SHOT OF COLD AIR WILL
COME DOWN FROM THE NORTH FOR THE REMAINDER OF THE WEEK...AND MAY EVEN
BE COLD ENOUGH ALOFT TO DEVELOP SOME INSTABILITY RAIN SHOWERS
EMBEDDED IN THE NORTHERLY FLOW.

.LONG TERM FORECAST...
THE LONGWAVE TROUGH LOOKS LIKE IT WILL ANCHOR OVER THE EASTERN BERING
THROUGH NEXT WEEKEND. THIS WILL SET THE MAINLAND UP UNDER GENERAL
SOUTHWESTERLY FLOW...WHICH MEANS A CONTINUATION OF THE CLOUDY AND WET
CONDITIONS FOR MANY LOCATIONS. MEANWHILE...THE WESTERN HALF OF THE
BERING WILL SEE CALMER WEATHER MOVE BACK IN FOR THE REMAINDER OF THE
WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WATCH 101
MARINE...GALE 120 125 130 132 150 155 160 165 170 172 175 176 180 185

FIRE WEATHER...NONE

DIXON SEP 13

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
100 PM AKDT SUN SEP 1 2013

AKZ181-020300

...MINOR ASH FALL REMAINS POSSIBLE NEAR CHIGNIK AND ALONG THE...

SATELLITE IMAGERY AND INSTRUMENTATION NEAR VENIAMINOF VOLCANO
CONTINUE TO INDICATE ELEVATED LEVELS OF ACTIVITY AT THE VOLCANO.
WINDS ARE EXPECTED TO TRANSPORT THE ASH TO THE NORTHEAST WHICH COULD
STILL BRING SOME VERY LIGHT ASHFALL TO AREAS ALONG THE ALASKA
PENINSULA NEAR CHIGNIK AND TO THE NORTH ALONG THE ALEUTIAN RANGE
THROUGH EARLY THIS EVENING.

THIS STATEMENT WILL BE UPDATED AT 700 PM AKDT TODAY OR SOONER IF
CONDITIONS WARRANT.

SPECIAL WEATHER STATEMENT...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
100 PM AKDT SUN SEP 1 2013

AKZ181-020300

...MINOR ASH FALL REMAINS POSSIBLE NEAR CHIGNIK AND ALONG THE
ALEUTIAN RANGE...

SATELLITE IMAGERY AND INSTRUMENTATION NEAR VENIAMINOF VOLCANO
CONTINUE TO INDICATE ELEVATED LEVELS OF ACTIVITY AT THE VOLCANO.
WINDS ARE EXPECTED TO TRANSPORT THE ASH TO THE NORTHEAST WHICH COULD
STILL BRING SOME VERY LIGHT ASHFALL TO AREAS ALONG THE ALASKA
PENINSULA NEAR CHIGNIK AND TO THE NORTH ALONG THE ALEUTIAN RANGE
THROUGH EARLY THIS EVENING.

THIS STATEMENT WILL BE UPDATED AT 700 PM AKDT TODAY OR SOONER IF
CONDITIONS WARRANT.