High Wind Watch 10, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
442 PM AKST SAT DEC 26 2015

.ANALYSIS AND UPPER LEVELS...

A BLOCKED WEATHER PATTERN REMAINS IN PLACE ACROSS SOUTHERN ALASKA
THIS AFTERNOON. THE STORM THAT HAS BEEN SLAMMING THE BERING FOR
MUCH OF THE PAST WEEK REMAINS NEARLY STATIONARY JUST WEST OF
BRISTOL BAY. THE STORM...WHICH BECAME VERTICALLY STACKED LAST WEEK
IS KEEPING THE UPPER LEVEL TROUGH OF COLD AIR ALSO RELATIVELY
STATIONARY. THIS BROAD UPPER LEVEL TROUGH IS KEEPING MOST OF THE
JET ENERGY SOUTH OF THE AREA ACROSS THE NORTHERN PACIFIC.
HOWEVER...NUMEROUS WAVES OF ENERGY TRAVELING IN THE MEAN UPPER
FLOW WILL CONTINUE ROTATING AROUND THE RELATIVELY STATIONARY UPPER
TROUGH. THUS WITH A BROAD TROUGH WEST OF MAINLAND ALASKA AND
RIDGING OVER EASTERN ALASKA...THIS SETUP IS MAKING FOR CONTINUED
WARMING AND A MORE ACTIVE WEATHER PATTERN FOR MAINLAND SOUTHERN
ALASKA.

SCATTERED SHOWER ACTIVITY CONTINUES ALONG MUCH OF THE GULF COAST
THIS AFTERNOON. THE SHOWERS ARE BEING CAUSED BY A SERIES OF FRONTS
AND UPPER LEVEL DISTURBANCES ROTATING AROUND THE NEARLY STATIONARY
LOW IN THE BERING. BROAD SOUTHEAST FLOW THROUGH MUCH OF THE
ATMOSPHERE IS EVIDENCED ON THE ANCHORAGE 12Z SOUNDING. WHILE THIS
IS A MOIST FLOW FOR COASTAL REGIONS...THE MOUNTAINS ARE
EFFECTIVELY WRINGING OUT THE MOISTURE BEFORE IT CAN EVER REACH
INLAND LOCALES. WARMING TEMPERATURES ARE THE OTHER WEATHER STORY
ALL OVER SOUTHERN ALASKA. THE SOUTHEAST WINDS ARE BEGINNING TO
SCOUR OUT THE COLD AIR THAT HAS BEEN IN PLACE FOR THE LAST
WEEK...WITH THE FREEZING LINE APPROACHING THE KUSKOKWIM RIVER IN
SOUTHWEST ALASKA...AND EXTENDING ALONG THE KENAI PENINSULA AND
PRINCE WILLIAM SOUND. TEMPERATURES HAVE WARMED INTO THE 20S FOR
MUCH OF THE REST OF SOUTHCENTRAL.

THE FIZZLING STORM OVER THE EASTERN BERING RECENTLY LOST ITS
DISTINCTION AS THE STRONGEST LOW PRESSURE AREA IN THE BERING. A
STRONGER LOW IS PUSHING INTO THE WESTERN AND CENTRAL ALEUTIANS
THIS AFTERNOON. THIS LOW IS CAUSING SNOWFALL IN THE WESTERN
ALEUTIANS...WHILE PRECIPITATION HAS NOT YET BEEN REPORTED AT ADAK.
THIS LOW WILL EVENTUALLY ABSORB THE EASTERN BERING LOW...THEN
REPLACE IT AS THE NEW COMBINED LOW TRACKS INTO THE EASTERN BERING.
THE MERGING OF THE TWO LOWS IS THE MAIN FORECAST CHALLENGE THIS
AFTERNOON.

&&

.MODEL DISCUSSION...

THE PRIMARY FORECAST CHALLENGE IN THE MODELS CONCERNS THE MERGER
OF THE TWO LOWS IN THE BERING. ALL OF THE MODELS AGREE THAT THE
LOW OVER THE WESTERN AND CENTRAL ALEUTIANS WILL QUICKLY BECOME
DOMINANT...BUT THE DIFFERENCES ARE HOW QUICKLY THE TWO LOWS
MERGE...AND WHERE THE COMBINED LOW MOVES AFTER THE MERGER IS
COMPLETE. THE GFS AND NAM WERE CHOSEN BECAUSE THEIR SOLUTION IS A
BIT SLOWER WITH THE MERGER...AND KEEP THE RESULTING LOW FURTHER
SOUTH AND CLOSER TO THE ALEUTIANS. THE SLOWER...SOUTHERN SOLUTION
WAS PREFERRED AS IT KEEPS THE LOW BEING SUPPORTED BY THE UPPER
LEVEL DYNAMICS FOR A LONGER PERIOD. FORECAST CONFIDENCE IS
AVERAGE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
WITH MODELS IN FAIRLY GOOD AGREEMENT THROUGH THE SHORT TERM...FEW
CHANGES WERE MADE IN THE FORECAST FROM THE MORNING PACKAGE. TWO
SYSTEMS ARE EXPECTED TO IMPACT SOUTHCENTRAL ALASKA OVER THE NEXT
48 HOURS. AN UPPER TROUGH ASSOCIATED WITH THE VERTICALLY STACKED
LOW CENTERED OVER BRISTOL BAY WILL MOVE THROUGH THE REGION
OVERNIGHT TONIGHT...BRINGING WITH IT WIDESPREAD PRECIPITATION TO
THE GULF COAST...PRINCE WILLIAM SOUND...AND THE SOUTHERN PORTIONS
OF COOK INLET. THE ANCHORAGE BOWL WILL SEE MINIMAL PRECIPITATION
AS THE REGION SHOULD REMAIN DOWNSLOPED. THE PRECIPITATION TYPE
WITH THIS FIRST SYSTEM SHOULD REMAIN RAIN ALONG MOST AREAS
IMMEDIATELY ALONG THE COAST CHANGING TO SNOW FURTHER INLAND. AS
THE TROUGH ROTATES TO THE NORTHEAST...AN UPPER LEVEL RIDGE WILL
BUILD ALONG 140W AHEAD OF THE NEXT TROUGH.

THE NEXT TROUGH IS EXPECTED TO BE MORE VIGOROUS THAN THE FIRST
WITH A WEAK SURFACE LOW FORMING ALONG THE SOUTHERN SIDE OF THE
ALASKA PENINSULA AND MOVING UP SHELIKOF STRAIT SUNDAY NIGHT AND
INTO UPPER COOK INLET BY MONDAY MORNING. WITH THE STRONG
MERIDIONAL ORIENTATION OF THE TROUGH...A SOUTHERLY PUSH OF WARM
AND MOIST AIR IS EXPECTED INTO THE SYSTEM. WITH THE LOWER LEVEL
WINDS EXPECTED TO BE EASTERLY...PRECIPITATION ALONG THE GULF COAST
AND PRINCE WILLIAM SOUND MAY BE HEAVY AT TIMES MONDAY AFTERNOON.
THE ANCHORAGE BOWL WILL BEGIN AS DOWNSLOPED BUT AS THE WEAK LOW
MOVES UP COOK INLET...PRECIPITATION CHANCES WILL INCREASE. AS THE
RIDGE BUILDS AND THE LOW BEGINS ITS NORTHWARD MOVEMENT...WINDS ARE
EXPECTED TO INCREASE OVER MUCH OF SOUTHCENTRAL ALASKA STARTING
SUNDAY MORNING. THE STRONGEST WINDS ARE EXPECTED ALONG TURNAGAIN
ARM AND HIGHER ELEVATIONS SUNDAY NIGHT THROUGH MONDAY WITH STRONG
WINDS THROUGH THE MATANUSKA VALLEY AS WELL AS THE PORTAGE VALLEY
FOR THE SAME TIME FRAME.

PRECIPITATION TYPE FOR THE SECOND SYSTEM WILL BEGIN MUCH THE SAME
AS THE SYSTEM OVERNIGHT TONIGHT...HOWEVER WITH THE WARM SOUTHERLY
PUSH...SNOW IS EXPECTED TO CHANGE OVER TO RAIN IN THE ANCHORAGE
AREA AND ALONG MOST COASTAL LOCATIONS. PRECIPITATION SHOULD REMAIN
AS ALL SNOW THROUGH THE SUSITNA AND COPPER RIVER BASINS THROUGH
MONDAY AFTERNOON.

&&

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

A WEAKENING AREA OF LOW PRESSURE IN THE VICINITY OF BRISTOL BAY
WILL PUSH ANOTHER FRONT ACROSS THE BRISTOL BAY REGION TONIGHT.
THIS WILL INCREASE RAIN CHANCES ACROSS THE BRISTOL BAY COAST THIS
EVENING...WHILE INTERIOR LOCATIONS REMAIN LARGELY ON THE DRY SIDE
AS DOWNSLOPING CONDITIONS WILL BE OBSERVED WITH 30 TO 40 KT OF
CROSS BARRIER FLOW AT 850 MB TO 700 MB. THESE DOWNSLOPING
CONDITIONS WILL ALSO KEEP TEMPERATURES QUITE WARM THROUGH THE
BRISTOL BAY REGION...WITH TEMPERATURES REMAINING ABOVE FREEZING
THROUGH THE OVERNIGHT PERIOD TONIGHT FOR SOME LOCATIONS. WITH THE
STRONG CROSS BARRIER FLOW...SOME GUSTY WINDS WILL BE OBSERVED
THROUGH THE GAPS AND PASSES THROUGH THE ALEUTIAN RANGE...MAINLY
NORTH OF KING SALMON TOWARD LAKE ILIAMNA AND LAKE CLARK. WIND
GUSTS THROUGH THESE PASSES WITH LIKELY RANGE FROM 35 TO 50 MPH
WHILE THE REST OF THE ZONE WILL SEE WINDS CLOSER TO 25 TO 35 MPH.
ANOTHER FRONT WILL MOVE ACROSS THE SAME LOCATIONS LATE SUNDAY WITH
SIMILAR WIND GUSTS OBSERVED THROUGH THE GAPS AND PASSES OF THE
ALEUTIAN RANGE. HOWEVER...DOWNSLOPING ENDS PRIOR TO AN UPPER LEVEL
DISTURBANCE PUSHING THROUGH THE REGION...SO INLAND LOCATIONS
SHOULD OBSERVE A DECENT PERIOD OF STEADY RAINFALL INSTEAD OF A FEW
SHOWERS MOVING FROM THE MOUNTAINS. PRECIPITATION CHANCES THEN
TAPER OFF ON MONDAY AS THE LOW IN BRISTOL BAY DISSIPATES. ABOVE
NORMAL TEMPERATURES ARE EXPECTED TO CONTINUE THROUGH AT LEAST
TUESDAY.

LOOKING TOWARD BRISTOL BAY...CONDITIONS WILL BE FAIRLY BENIGN
COMPARED TO THE CONDITIONS OBSERVED THE PAST FEW DAYS. SCATTERED
SNOW SHOWERS (MIXED WITH RAIN AT TIMES IN THE AFTERNOON) WILL RE-
DEVELOP SUNDAY EARLY AFTERNOON AS A WARM FRONT TRAVERSES THE
REGION. BLOWING SNOW CONDITIONS DO NOT LOOK TO POSE A THREAT AS
TEMPERATURES WILL BE NEAR OR ABOVE FREEZING WITH WINDS IN THE 20
TO 30 MPH RANGE. THE LOWER KUSKOKWIM VALLEY WILL REMAIN LARGELY
DOWNSLOPED THANKS TO THE ALASKA RANGE THROUGH MUCH OF THE PERIOD
BUT THE WEAK WAVE MENTIONED PASSING THROUGH THE BRISTOL BAY REGION
LATE SUNDAY WILL MOVE INTO THE VALLEY MONDAY MORNING AND BRING A
QUICK 1 TO 3 INCHES OF SNOWFALL ON MONDAY.

&&

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

THE SHORT-TERM FORECAST IS QUITE COMPLICATED AS MULTIPLE LOW
CENTERS COME TOGETHER TO REINFORCE A COMPLEX LOW SET TO DEVELOP
OVER THE CENTRAL BERING SEA ON SUNDAY. THE MOST POTENT OF THESE
LOWS IS THE LOW CURRENTLY LOCATED SOUTHWEST OF ADAK. THIS WILL
WILL BRING STORM FORCE WINDS ALONG THE PACIFIC COASTAL WATERS OF
THE CENTRAL ALEUTIANS TONIGHT AND EASTERN ALEUTIANS TOMORROW
AFTERNOON. THE STRONGEST WINDS SHOULD PASS OVER THE WATER...SO NO
SIGNIFICANT IMPACTS FROM WINDS ARE EXPECTED. THIS LOW WILL PHASE
WITH THE COMPLEX LOW IN THE BERING LATE SUNDAY WHICH WILL HELP
REINFORCE THE LONGWAVE TROUGH OVER THE BERING. THIS WILL LEAD TO
SMALL CRAFT TO GALE FORCE WINDS RESIDING IN PROXIMITY OF THE LOW
AS WELL AS RAIN/SNOW SHOWERS THROUGH AT LEAST MONDAY NIGHT.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE TREND FOR THE WEEK WILL BE MULTIPLE LOWS MOVING INTO THE
BERING FROM THE SOUTH ONE AFTER THE OTHER. THESE LOWS WILL BRING
WARMER AIR UP FROM THE SOUTH KEEPING TEMPERATURES IN MOST PLACES
IN SOUTHERN MAINLAND ALASKA AND SOUTHWEST ALASKA AT OR ABOVE
NORMALS FOR THE WEEK. THEY WILL ALSO BRING RAIN AND SNOW TO THE
AREA WITH THE MAJORITY OF IT BEING AROUND THE
ALEUTIANS...SOUTHWEST ALASKA AND THE NORTH GULF COAST. THE LOWS
ARE ALSO EXPECTED TO BRING STRONGER WINDS TO THESE SAME AREAS.
GUIDANCE IS INDICATING THAT THERE WILL BE SHORT BREAKS IN BETWEEN
THESE SYSTEMS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM 172 174 176 177.
		 GALE 119 120 125 130-132 139 140 150 155 165-171
173 175 178 180 185.
		 HEAVY FREEZING SPRAY 181 185.

&&

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

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
329 AM AKST SUN DEC 27 2015

AKZ101-281230-
ANCHORAGE-
INCLUDING THE CITIES OF...ANCHORAGE...EAGLE RIVER...INDIAN...
EKLUTNA
329 AM AKST SUN DEC 27 2015

...CHANGE IN THE WEATHER PATTERN EXPECTED FOR MUCH OF
SOUTHCENTRAL BEGINNING MONDAY AS A SERIES OF WARM STORMS IMPACTS
THE REGION...

A WARM FRONT MOVING INTO SOUTHERN ALASKA SUNDAY NIGHT AND MONDAY
WILL SPREAD WARMER NORTH PACIFIC AIR INLAND...ALLOWING FOR
TEMPERATURES TO RISE ABOVE FREEZING ACROSS MANY INLAND LOCATIONS
BY MONDAY. IN ADDITION...STRONG EAST TO SOUTHEAST WINDS WILL
IMPACT MANY COASTAL LOCATIONS INCLUDING ANCHORAGE MONDAY...WHICH
WILL ALLOW FOR TEMPERATURES TO RISE INTO THE 40S ACROSS THE
ANCHORAGE BOWL AND THE MATANUSKA VALLEY. THE POSSIBILITY FOR RAIN
(MIXED WITH SNOW AT TIMES) WILL ALSO ACCOMPANY THIS FRONT...WHICH
MAY HAVE AN IMPACT ON AREA ROADWAYS WHICH HAVE BEEN BELOW FREEZING
FOR AN EXTENDED PERIOD OF TIME.

A POTENTIALLY STRONGER AND MORE SIGNIFICANT STORM WILL BRING
ANOTHER SHOT OF WARM PACIFIC AIR AND STRONG SOUTHEAST WINDS AGAIN
ON TUESDAY NIGHT INTO WEDNESDAY. THEREAFTER...THE WARMER AND
ACTIVE PATTERN LOOKS TO PERSIST INTO THE WEEKEND AND POSSIBLY
LONGER...KEEPING TEMPERATURES ABOVE AVERAGE ACROSS MUCH OF
SOUTHERN ALASKA.