Gale Warning 713, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
516 AM AKST MON NOV 16 2015

.ANALYSIS AND UPPER LEVELS...

UPPER LEVEL LOW PRESSURE CONTINUES TO GRADUALLY DEEPEN OVER THE
SOUTHERN INTERIOR OF THE STATE...WITH A STRONG JET STREAM SOUTH OF
THE GULF PUSHING A STRENGTHENING SURFACE LOW INTO THE FAR SOUTHERN
MAINLAND AND BRITISH COLUMBIA. A RESIDUAL LOW PRESSURE TROUGH IS
JUST STARTING TO SHOW SIGNS OF DEVELOPING AHEAD OF THE UPPER LEVEL
TROUGH AXIS ALONG THE NORTH GULF COAST...WHICH WILL INCREASE THE
PRESSURE GRADIENT AND COLD ADVECTION THROUGH TERRAIN GAPS INTO THE
GULF AND PRINCE WILLIAM SOUND THROUGH THIS MORNING...AND SHOULD
HELP CLEAR OUT THE PATCHY FOG AND LOW STRATUS OBSERVED OVER PARTS
OF SOUTHCENTRAL ALASKA OVERNIGHT. MEANWHILE...A WELL-DEVELOPED LOW
PRESSURE SYSTEM NEAR THE ALASKA PENINSULA CONTINUES TO WEAKEN AND
WILL DISSIPATE OVER THE NORTH PACIFIC LATER TODAY. TO THE NORTH
AND WEST OVER FAR EASTERN RUSSIA...A POTENT UPPER LEVEL
DISTURBANCE WITH A STRONG FRONT IS DROPPING SOUTH AND EAST INTO
THE NORTHERN BERING FROM FAR EASTERN RUSSIA CURRENTLY. THE NEXT
SYSTEM THAT WILL INITIATE A PATTERN CHANGE TOWARD WARMER
CONDITIONS IS SITUATED WELL SOUTHWEST OF THE BERING AND WESTERN
ALEUTIANS.

&&

.MODEL DISCUSSION...
MODELS ARE IN RELATIVELY GOOD AGREEMENT SYNOPTICALLY UNTIL ABOUT
MID-WEEK...WHEN SUBTLE DIFFERENCES IN THE HANDLING OF THE BERING
SEA WEATHER SYSTEMS ENDS UP YIELDING GREATER DISCREPANCIES TOWARD
THE WEEKEND DOWNSTREAM OVER THE ALASKA MAINLAND.

THE BROAD TROUGH FORMING OVER THE NORTHERN GULF CURRENTLY WILL
SLOWLY WEAKEN THROUGH MID-WEEK. THE SHARP UPPER LEVEL TROUGH
DROPPING SOUTH AND EAST THROUGH THE EASTERN BERING WILL PUSH
RAPIDLY INTO THE WESTERN GULF TONIGHT AND BRING A SHARP INCREASE
IN WINDS BEHIND IT WITH STRONG COLD ADVECTION.

A GALE-FORCE WEATHER FRONT WITH EMBEDDED SURFACE LOWS CURRENTLY
SOUTHWEST OF THE BERING SEA WILL TRACK INTO THE BERING AND
ELONGATE WEST TO EAST ACROSS THE CENTRAL BERING. THIS ELONGATED
SURFACE FRONT WILL SERVE AS THE FOCUS FOR ADDITIONAL QUICK-MOVING
LOW PRESSURE SYSTEMS TO TRAVEL ALONG IT TOWARD THE NORTHERN GULF
AND SOUTHERN MAINLAND THROUGH THE REMAINDER OF THE WEEK. THERE
ARE DIFFERENCES IN HOW FAR NORTH THIS FRONT EXTENDS INTO THE
MAINLAND THAT WILL PLAY A LARGE ROLE IN THE TYPE OF HAZARDOUS
WEATHER TO IMPACT THE STATE LATE WEEK INTO THE WEEKEND.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
ANOTHER COLD ADVECTION BORA WIND EVENT WILL RAMP UP TODAY ALONG
THE GULF COAST. THE KEY FEATURES AT PLAY ARE A COLD UPPER LOW
CURRENTLY MAKING ITS WAY INTO THE SUSITNA VALLEY FROM INTERIOR
ALASKA WITH TRAILING TROUGH TO THE SOUTHWEST...AND A SHORT-WAVE
TROUGH DROPPING THROUGH SOUTHWEST ALASKA. AS THESE FEATURES
PROGRESS EASTWARD ARCTIC AIR WILL ADVECT SOUTH AND EASTWARD
ACROSS SOUTHCENTRAL AND THE GULF.

THE ADVECTION WILL BE STRONGEST FROM SOUTHWEST ALASKA ACROSS THE
ALASKA PENINSULA INTO THE WESTERN GULF. WINDS WILL PEAK TONIGHT
AS THE SHORT-WAVE MOVES THROUGH...AIDED BY STRONG SYNOPTIC SCALE
SUBSIDENCE AND MIXING DOWN OF STRONGER WINDS FROM ALOFT. COLD
ADVECTION WILL BE WEAKER FROM INTERIOR ALASKA INTO THE HEART OF
SOUTHCENTRAL...SO EXPECT WINDS TO BE WEAKER. ALSO WITH STRONG
SURFACE-BASED INVERSIONS IN MANY OF THE INLAND VALLEYS IT WILL BE
HARD FOR THE WINDS TO ERODE THE INVERSIONS. THE FAVORED AREAS FOR
STRONGER WINDS WILL BE OUT OF GAPS ALONG THE ALASKA RANGE...ALONG
COOK INLET...AND AT HIGHER ELEVATIONS. FOR THE NORTH GULF COAST
AND PRINCE WILLIAM SOUND IT WILL BE ANOTHER STRONG WIND EVENT. THE
COMBINATION OF A DEEP LOW MOVING TO SOUTHEAST ALASKA THIS MORNING
AND COLD AIR POURING OFF THE COASTAL MOUNTAINS INTO THE GULF WILL
LEAD TO FALLING PRESSURE OVER THE NORTHERN GULF AND TIGHTENING
PRESSURE GRADIENTS REGION-WIDE. THIS WILL ENHANCE WINDS THROUGH
ALL OF THE MOUNTAIN GAPS AND BAYS.

WITH TEMPERATURES ALREADY QUITE COLD ACROSS THE REGION THE
ADDITION OF WIND WILL CREATE SOME VERY LOW WIND CHILLS. AT THIS
POINT IN TIME DO NOT EXPECT TO REACH WIND CHILL CRITERIA EXCEPT
FOR POSSIBLY A FEW ISOLATED (LARGELY UNINHABITED) LOCATIONS ALONG
THE ALASKA RANGE. THIS LATEST WIND EVENT WILL DIE DOWN TUESDAY
FOR MOST OF SOUTHCENTRAL...SO TUESDAY NIGHT COULD BE THE COLDEST
NIGHT SO FAR THIS YEAR FOR MANY AREAS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
DRY WEATHER WILL CONTINUE THROUGH MONDAY NIGHT AS A COLD AIR MASS
LIES OVER THE AREA ALONG WITH NORTHWESTERLY FLOW ALOFT. ON
TUESDAY THE FLOW ALOFT BECOMES MORE WESTERLY AS THE UPPER LOW OVER
SOUTHERN ALASKA WEAKENS AND MOVES FURTHER EAST. THIS WILL ALLOW
SOME MOISTURE TO BEGIN PUSHING INTO THE WESTERN COAST AND ALONG
THE ALASKA PENINSULA TUESDAY. A FRONTAL SYSTEM ASSOCIATED WITH A
SURFACE LOW TRACKING THROUGH THE CENTRAL BERING WILL BEGIN TO
INLAND OVER THE SOUTHWEST MAINLAND WEDNESDAY MORNING...BRINGING
SOME SLIGHTLY WARMER TEMPERATURES AND STEADIER PRECIPITATION TO
THE AREA.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
STRONG WINDS AND SHOWERY CONDITIONS OVER THE EASTERN ALEUTIANS
WILL CONTINUE TO DIMINISH THROUGH THE MORNING PERIOD...AS THE LOW
CENTERED JUST EAST OF UNALASKA CONTINUES TO WEAKEN AND TRACK
SOUTH INTO THE NORTH PACIFIC THIS MORNING. A STRONG SYSTEM WILL
PUSH INTO THE WESTERN BERING/ALEUTIANS TONIGHT FROM THE
SOUTHWEST...BRINGING MOSTLY RAIN AND GUSTY SOUTHERLY WINDS TO THE
AREA THROUGH TUESDAY MORNING. THIS SYSTEM WILL THEN TRACK INTO
THE CENTRAL BERING/ALEUTIANS BY TUESDAY AFTERNOON...BRINGING
ANOTHER ROUND OF WET AND WINDY CONDITIONS TO THE CENTRAL AND
EASTERN ALEUTIANS TUESDAY. ANOTHER SYSTEM WILL DEVELOP OFF THE
SOUTHERN KAMCHATKA PENINSULA AND APPROACH THE WESTERN ALEUTIANS
LATE TUESDAY NIGHT.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE MIDDLE OF THE WEEK WILL FEATURE A TRANSITION FROM THE CURRENT
PATTERN DOMINATED BY COLD TEMPERATURES AND OUTFLOW WINDS TO MORE
MODERATE TEMPERATURES AND INCREASING CHANCES FOR PRECIPITATION.
HOWEVER ASIDE FROM THESE BASIC DETAILS...OVERALL FORECAST
CONFIDENCE REMAINS LOW AS MODEL GUIDANCE CONTINUES TO OFFER VASTLY
DIFFERENT SOLUTIONS WITH RESPECT TO THE EVOLUTION OF THE PATTERN
DURING THE LATTER HALF OF THE WEEK. THESE DIFFERENCES WILL HAVE A
LARGE IMPACT ON THE DEGREE OF WARMING AND ALSO PRECIPITATION
TYPE. THE FIRST IN A SERIES OF SYSTEMS POISED TO TRAVERSE THE
BERING SEA DURING THE UPCOMING WEEK LOOKS TO BEGIN IMPACTING THE
SOUTHWEST MAINLAND LATE TUESDAY OR WEDNESDAY WITH PRECIPITATION
THEN SPREADING TO SOUTHCENTRAL AK IN THE WEDNESDAY OR THURSDAY
TIME FRAME. NUMERICAL GUIDANCE HAS BEEN FLIPPING BACK AND FORTH
FROM RUN TO RUN WITH THE AMOUNT OF WARM AIR THAT WILL BE ADVECT
INLAND THROUGH THE SECOND HALF OF THIS WEEK. HOWEVER...AN OVERALL
COLDER TREND HAS BEEN OBSERVED WITH MUCH OF THE GUIDANCE WHICH
TENDS TO FAVOR THE UPCOMING PRECIPITATION EVENTS TO BE MAINLY SNOW
EVENTS. THERE IS STILL A LOT OF UNCERTAINTY AS MODELS POORLY
HANDLE THE ENERGY IN THE JET STREAM AND HOW IT AMPLIFIES THE UPPER
LEVEL TROUGH. ANY WARMER SOLUTION WOULD FAVOR A FREEZING RAIN
EVENT IF THE COLDER AIR MASS REMAINS IN PLACE NEAR THE SURFACE.
WILL CONTINUE TO MONITOR MODEL TRENDS OVER THE COMING DAYS TO
NARROW DOWN THE SPECIFIC DETAILS OF THE FORECAST.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...HEAVY FREEZING SPRAY...130 138.
         GALE...121 127 129 130-132 137 138 150 170-179

&&

SYNOPSIS AND MODEL DISCUSSION...CC
SOUTHCENTRAL ALASKA...SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TP
LONG TERM...CB/MMC