Gale Warning 805, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
506 PM AKST MON NOV 23 2015

.ANALYSIS AND UPPER LEVELS...

THE SINGULAR DOMINANT WEATHER FEATURE AFFECTING THE ALASKAN DOMAIN
THIS AFTERNOON IS A MATURE STORM OVER THE NORTHERN BERING SEA. THE
ASSOCIATED FRONT WITH IMPRESSIVE JET SUPPORT AND A LOW-LATITUDE
MOISTURE FEED IS ORIENTED GENERALLY SOUTHWEST TO NORTHEAST ACROSS
SOUTHERN ALASKA. THIS STORM IS STRONG ENOUGH THAT A FAIRLY
IMPRESSIVE SURGE OF WARM AIR IS BEING PULLED NORTHWARD INTO THE
MAINLAND...WITH ALL PARTS OF THE BRISTOL BAY ZONE NOW CHANGED OVER
TO RAIN. THIS WARM AIR IS STARTING TO SLOWLY WORK ITS WAY UP COOK
INLET...WITH TEMPERATURES AROUND KACHEMAK BAY ALREADY CLIMBING
INTO THE 40S. WARM AIR ALOFT IS ALREADY SURGING NORTHWARD OVER
ANCHORAGE AND THE MAT-SU VALLEYS...WITH WIDESPREAD LIGHT SNOW
QUICKLY BREAKING OUT ACROSS MOST OF THE AREA. A SHALLOW LAYER OF
NORTHERLY WINDS IS KEEPING TEMPERATURES IN THE 20S AROUND UPPER
COOK INLET...BUT THIS WILL CONTINUE TO SLOWLY ERODE THROUGHOUT THE
AFTERNOON AND EVENING IN THE FACE OF THE TIDE OF INCOMING
SOUTHERLY FLOW.

&&

.MODEL DISCUSSION...

THE MODELS ARE IN EXCELLENT SYNOPTIC AGREEMENT WITH THE CURRENT
STORM. THE FRONT WILL STALL THIS EVENING OVER THE FAR WESTERN
SUSITNA VALLEY AND ALASKA RANGE...SETTING UP A LONG-DURATION
PRECIPITATION EVENT OVER THE EASTERN KUSKOKWIM VALLEY AND SUSITNA
VALLEY. ALL MODELS DEVELOP SOME FORM OF WAVE ALONG THE
STALLED/STATIONARY BOUNDARY TUESDAY NIGHT INTO WEDNESDAY THAT
MOVES UP TOWARD KODIAK ISLAND. THE GFS AND GEM ARE SIGNIFICANT
OUTLIERS KEEPING THIS WAVE TOO FAR EAST AND SOUTH RESPECTIVELY. AS
THE NAM AND ECMWF ARE IN MUCH BETTER AGREEMENT...AND WILL BE
UTILIZED IN THE AFTERNOON FORECAST CYCLE TODAY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE MAIN FOCUS OF THE FORECAST IS A FRONTAL BOUNDARY APPROACHING
THE GULF COAST TONIGHT AND AN ACTIVE SOUTHWESTERLY JET STREAM
PARKING OVER THE AREA. THE FRONT WILL CONTINUE TO SPREAD LIGHT
SNOW OVER MUCH OF THE COOK INLET AREA NORTHWARD. AS THE FRONT
PASSES THIS EVENING AREAS ALONG THE INLET FROM SOUTH TO NORTH WILL
SWITCH TO SOUTHERLY FLOW...WARMING UP SURFACE TEMPERATURES INTO
THE 30S AND CHANGING PRECIPITATION OVER TO RAIN IN MOST AREAS.
THE FRONTAL BOUNDARY FOLLOWED BY PERSISTENT UP-VALLEY FLOW WILL
BRING COPIOUS AMOUNTS OF MOISTURE INTO THE SUSITNA VALLEY. THE
WINTER WEATHER ADVISORY HAS BEEN UPGRADED TO A WINTER STORM
WARNING. THE HEAVIEST SNOW AND ACCUMULATIONS WILL REMAIN NORTH OF
TALKEETNA AND TOWARD THE PARK.

A STRONG PRESSURE GRADIENT ALONG THE NORTH GULF COAST WILL PEAK
EARLY THIS EVENING THEN RELAX OVERNIGHT INTO TUESDAY. THE
CHALLENGE WITH THE FORECAST INVOLVES BOTH WINDS AND TEMPERATURES
IN RELATION TO PRECIPITATION TYPE. AS THE SOUTHERLY WINDS PROGRESS
FROM COOK INLET/TURNAGAIN ARM...WARMER AIR WILL INTRUDE AT THE
SURFACE CHANGING SNOW TO RAIN. THIS WILL TAKE PLACE EARLY TONIGHT
FOR SOUTHERN COOK INLET...OVERNIGHT FOR THE ANCHORAGE AREA...AND
TUESDAY MORNING INTO THE AFTERNOON FOR THE SUSITNA VALLEY. SNOW
COULD HANG ON INTO TUESDAY EVENING BEFORE CHANGING OVER TO RAIN
FOR AREAS NORTH OF TALKEETNA TOWARD THE PARK.

ANOTHER FRONT AND UPPER LEVEL DISTURBANCE PUSHES INTO THE GULF ON
WEDNESDAY BRINGING ANOTHER ROUND OF RAIN AND WIND TO THE AREA.

&&

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

THE WEATHER FRONT BISECTING THE BRISTOL BAY AND THE KUSKOKWIM
VALLEY ZONES WILL REMAIN NEARLY STATIONARY THROUGH AT LEAST
WEDNESDAY. HOWEVER...THIS FRONT WILL SHARPEN AS LOW PRESSURE MOVES
NORTH ALONG THE FRONT FROM THE NORTH PACIFIC AND MOVES TOWARD THE
BRISTOL BAY AREA LATE TUESDAY INTO WEDNESDAY. AS THE FRONT
SHARPENS...A SHARP TEMPERATURE GRADIENT WILL DEVELOP...WITH
TEMPERATURES ON THE WEST SIDE OF THE FRONT BECOMING COLD ENOUGH
FOR SNOW WHILE THE EAST SIDE WILL CONTINUE TO SUPPORT RAIN. WITH A
STATIONARY FRONT OVER THE AREA AND SIGNIFICANT MOISTURE MOVING
INTO THE REGION...A SIGNIFICANT POTENTIAL IS POSSIBLE OVER THE
WESTERN HALF OF THESE ZONES LATE TUESDAY AND PERSISTING THROUGH
WEDNESDAY (AND PERHAPS BEYOND).

MEANWHILE...STRONG SOUTH TO SOUTHWESTERLY WINDS PARTICULARLY
COASTAL LOCATIONS OF THE KUSKOKWIM DELTA REGION THROUGH TUESDAY
MORNING.

&&

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

THE POWERFUL BERING SEA STORM CONTINUES TO SLOWLY WEAKEN AS IT
MOVES NORTH TOWARD THE BERING STRAIT. THE PRIMARY WIND IMPACTS
WILL BE FROM THE PRIBILOFS NORTH AND EAST TOWARD THE WESTERN
ALASKA COAST. SCATTERED TO NUMEROUS SNOW AND RAIN SHOWERS WILL
CONTINUE TO MOVE WEST TO EAST ACROSS THE REGION THROUGH TUESDAY.
MEANWHILE...THE NEXT POWERFUL WEATHER SYSTEM MOVES INTO THE
WESTERN ALEUTIANS LATE TUESDAY NIGHT INTO WEDNESDAY. THIS LOW WILL
TAKE MORE OF AN EAST TRACK JUST TO THE SOUTH OF THE ALEUTIANS.
THIS WILL MEAN STRONG STORM-FORCE WINDS WILL BE POSSIBLE FOR THE
WESTERN AND CENTRAL ALEUTIANS LATE TUESDAY NIGHT THROUGH
WEDNESDAY.

&&

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

BY WED EVENING A LOW MOVING INTO THE AKPEN WILL BE DIRECTING A
SURGE OF WARM AIR INTO THE NORTH GULF COAST...WHILE THE
EXTRATROPICAL REMNANT OF IN-FA WILL BE NEAR THE CENTRAL ALEUTIANS
ON ITS EASTWARD TRANSIT. MODELS ARE IN EXCELLENT AGREEMENT
BRINGING THE INITIAL LOW INTO SW AK WHERE IT DECAYS ON THU...AND
THE FORMER IN-FA TO THE EASTERN ALEUTIANS ON FRI. AT THIS POINT
MODEL AGREEMENT DIVERGES WITH IN-FA MOVING INTO THE EASTERN
BERING....AND THE BERING THEN BECOMING POPULATED BY SURFACE WAVES
BENEATH AN AMORPHOUS UPPER LOW. WPC ONCE AGAIN APPLIES ITS
ENSEMBLE APPROACH AND BRINGS IN-FA TO THE WEST COAST OF AK WHERE
IT DISSIPATES LATE ON SAT...AND A SECOND LOW TRANSITS THE ENTIRE
ALEUTIAN CHAIN SAT THROUGH MON BEFORE REACHING BRISTOL BAY ON TUE.
THE FORECAST UTILIZES THIS SOLUTION WITH DECREASING CONFIDENCE
OVER TIME AS THE ENSEMBLE SOLUTION BECOMES DOMINANT.

IN THE EAST...WARM ONSHORE FLOW WILL PERSIST INTO EARLY NEXT WEEK
WITH RAIN ALONG THE COAST...CROSSING THE KENAI AND REACHING AT
LEAST INTO THE SOUTHERN SUSITNA VALLEY. COOLER TEMPERATURES NEAR
THE ALASKA RANGE NORTH OF TALKEETNA MAY BE SUFFICIENT TO KEEP
PRECIPITATION ALL SNOW IN THAT AREA THROUGH THE WEEKEND...BUT THE
COPPER RIVER BASIN WILL REMAIN COLD ENOUGH FOR SNOW.

IN THE WEST...RAIN WITH GALES AND STORMS WILL ACCOMPANY THE LOW
FORMERLY KNOWN AS IN-FA AS IT MOVES TO THE EASTERN BERING.
LOCATIONS ALONG THE BACKSIDE OF THE LOW WILL CONTINUE TO
EXPERIENCE WINDY CONDITIONS...BUT THERE WILL BE A MIX OF RAIN AND
SNOW THU AND FRI. AS THE SECOND LOW BEGINS ITS TRANSIT...WIND AND
RAIN WILL AGAIN AFFECT THE CHAIN SAT THROUGH TUE...WITH RAIN
MIXING WITH SNOW ON THE WESTERN FLANK AS IT CROSSES THE ISLANDS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WSW HEAVY SNOW 145. COASTAL FLOOD/HIGH SURF ADVISORY 155
AND 161.

MARINE...STORMS 170 173 177 178 180 412 413 414.
GALES 130 132 138 139 150 155 160 165 172 174 175 176 350 411.

&&

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

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
303 AM AKST TUE NOV 24 2015

AKZ101-111-250015-
ANCHORAGE-MATANUSKA VALLEY-
INCLUDING THE CITIES OF...ANCHORAGE...EAGLE RIVER...INDIAN...
EKLUTNA...PALMER...WASILLA...SUTTON...CHICKALOON
303 AM AKST TUE NOV 24 2015

...EXPECT SLICK ROADS TODAY AS LIGHT RAIN COATS SNOW COVERED
ROADS...

USE CAUTION ON THE ROADS AND SURFACES THIS MORNING. LIGHT SNOW
YESTERDAY EVENING QUICKLY TURNED TO LIGHT RAIN OVERNIGHT IN
ANCHORAGE AS TEMPERATURES WARMED TO ABOVE FREEZING IN THE EARLY
MORNING HOURS. THE LAYER OF RAIN ON TOP OF SNOW AND ICE COVERED
ROADS WILL CREATE SLIPPERY DRIVING CONDITIONS TODAY OVER THE
ANCHORAGE BOWL AND THE MATANUSKA VALLEY. ADDITIONALLY...POCKETS OF
FREEZING RAIN ARE POSSIBLE THIS MORNING ON THE GLENN HIGHWAY FROM
PALMER TOWARDS CHICKALOON.

THE WARMUP OVER SOUTHCENTRAL WAS CAUSED BY A WEATHER FRONT THAT
MOVED WARM AIR NORTHWARD OVERNIGHT RESULTING IN A SOUTH TO NORTH
CHANGEOVER FROM SNOW TO RAIN. TEMPERATURES IN THE ANCHORAGE BOWL
TODAY WILL REMAIN ABOVE FREEZING WITH SCATTERED RAIN SHOWERS.
TEMPERATURES IN THE MATANUSKA VALLEY WILL WARM TO ABOVE FREEZING
LATER THIS MORNING WITH ANY MIX OF RAIN AND SNOW IN THE MORNING
CHANGING TO ALL RAIN BY THE AFTERNOON.

CHECK THE LATEST FORECAST FOR YOUR EXACT LOCATION AT
WWW.WEATHER.GOV/ANCHORAGE