Heavy Freezing Spray Warning 4, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
255 PM AKST SUN JAN 8 2012

.ANALYSIS AND UPPER LEVELS...THE LONG WAVE PATTERN CONTINUES TO
INCLUDE AN UPPER LEVEL TROUGH OVER THE BERING SEA AND WESTERN ALASKA
WITH A BLOCKING UPPER LEVEL RIDGE OVER THE PACIFIC NORTHWEST. A WAVES
IN THE UPPER LEVEL PATTERN ARE LOCATED OVER SOUTHCENTRAL ALASKA AND A
SECOND MORE SIGNIFICANT WAVE IS LOCATED SOUTH OF THE ALEUTIANS.

VERY STRONG COLD ADVECTION ON THE BACKSIDE OF THE INITIAL SHORTWAVE
WITH 60 KNOT WINDS BLASTING THROUGH THE BARREN ISLANDS. THE TROUGH
AXIS IS LINGERING OVER THE KENAI PENINSULA RESULTING IN WIDESPREAD
LIGHT SNOW CONTINUING FROM COOK INLET UP TO THE SUSITNA VALLEY.
SHOWERS ARE DEVELOPING OVER THE NORTHERN GULF AS A RESIDUAL SURFACE
LOW BECOMES ESTABLISHED OVER PRINCE WILLIAM SOUND. THIS IS A RESULT
OF THE COLD AIR ADVECTION AND OVERALL CYCLONIC NATURE OF THE UPPER
LEVELS.

FURTHER WEST...A VERY POWERFUL STORM DEVELOPING SOUTH OF THE
ALEUTIANS WILL BE A GAME CHANGER. THIS SYSTEM WILL AFFECT THE
SOUTHERN HALF OF THE STATE THIS WEEK...BEFORE EVENTUALLY HELPING
SHIFT THE LONG WAVE PATTERN TO THE EAST SETTING UP A HIGH AMPLITUDE
RIDGE OVER WESTERN ALASKA.

.MODEL DISCUSSION...THE MODELS ARE ALL PAINTING A VERY SIMILAR
PICTURE THROUGH THE REST OF THE WEEK. THE DIFFERENCES MAINLY SURROUND
THE TIMING OF THE LARGE LOW AS IT MOVES TOWARD THE ALASKA PENINSULA.
THEN THERE IS GREATER DISCREPANCY IN THE MID TERM AS THE LOW OCCLUDES
AND WEAKENS IN THE GULF MID TO LATE THIS WEEK. FOR THE AFTERNOON
FORECAST PACKAGE...WE LEANED HEAVILY TOWARD THE 12Z GFS WHICH IS NOT
TOO DISSIMILAR FROM THE PREVIOUS MODEL RUNS AND WITH THE EC. THE NAM
CONTINUES TO BE A BIT OF AN OUTLIER.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...AFTER THE LINGERING LIGHT SNOW TAPERS OFF THIS
EVENING...OUR FOCUS QUICKLY TURNS TOWARD THE DEVELOPING STORM SOUTH
OF THE ALEUTIANS. SEVERAL WATCHES WILL BE ISSUED WITH THE AFTERNOON
PACKAGE WHICH ARE VERY TYPICAL FOR THIS TYPE OF STORM TRACK. THE
PRESSURE GRADIENT AROUND PRINCE WILLIAM SOUND WILL BE VERY STRONG
RESULTING IN BLIZZARD CONDITIONS WHERE IT STAYS COLD ENOUGH AND HIGH
WIND WARNING CRITERIA ALONG TURNAGAIN ARM AND THE HIGHER ELEVATIONS
ABOVE ANCHORAGE.

UNLIKE THE DECEMBER CHINOOK EVENTS...THIS APPEARS TO BE A MUCH MORE
TYPICAL WINTER STORM WHERE THE COLD AIR WILL PROTECT THE LOWER
ELEVATIONS FROM THE STRONG WINDS. A TRIPLE POINT WILL DEVELOP NEAR
KODIAK ISLAND RESULTING IN A DOWN INLET GRADIENT...A KEY COMPONENT TO
INSURING THAT WINDS DO NOT MIX DOWN TO SEA LEVEL ACROSS ANCHORAGE.

THE SUBTROPICAL FETCH ASSOCIATED WITH THIS SYSTEM WILL BE IMPRESSIVE
BRINGING THE GULF COAST SIGNIFICANT MOISTURE. INITIALLY...MUCH OF THE
PRECIPITATION WILL FALL IN THE FORM OF SNOW BEFORE TRANSITIONING TO
RAIN TUESDAY EVENING. COASTAL COMMUNITIES THAT HAVE BEEN HAMMERED
RECENTLY INCLUDING CORDOVA WILL SEE SIGNIFICANT PRECIPITATION OUT OF
THIS SYSTEM TUESDAY THROUGH TUESDAY NIGHT. ALL INTERESTED PARTIES IN
THE COASTAL COMMUNITIES WILL NEED TO BE AWARE OF THE IMPENDING EVENT
36 TO 60 HOURS FROM NOW.

THE GOOD NEWS FOR THESE LOCATIONS IS THAT HIGH PRESSURE WILL
EVENTUALLY BUILD OVER SOUTHWEST ALASKA SHIFTING THE UPPER TROF AND
SUBSQUENTLY THE ACTIVE WEATHER TO THE EAST. IT APPEARS BY THE WEEKEND
THAT MUCH OF MAINLAND ALASKA WILL SEE A SIGNIFICANT AND POSSIBLY LONG
LIVED DRY SPELL.

SOUTHWEST ALASKA...BLIZZARD WATCHES AND WARNINGS WILL BE POSTED FOR
MOST OF THE WESTERN PUBLIC ZONES WITH THIS AFTERNOON FORECAST
PACKAGE. THE TRACK OF THE LOW AND THE ASSOCIATED OCCLUSION WILL TRACK
INITIALLY JUST SOUTH OF THE CHAIN. THIS TRACK WILL MEAN THAT
OVERRUNNING MOISTURE IN THE FORM OF SNOW WILL FALL AS THE WINDS
INCREASE. AT TIMES...BLIZZARD CONDITIONS ARE LIKELY FROM THE CENTRAL
ALEUTIANS ALL THE WAY UP THROUGH THE KUSKOKWIM DELTA OVER THE NEXT 36
HOURS.

THE OCCLUSION MOVES JUST NORTH OF THE EASTERN ALEUTIANS AND ALASKA
PENINSULA BRINGING AN END TO THE BLIZZARD CONDITIONS...POSSIBLY
MIXING WITH RAIN DURING THE AFTERNOON MONDAY. THIS WARM AIR INTRUSION
WILL BE SHORT LIVED AS COLD AIR WRAPPING BACK AROUND THE LOW WILL
DROP SOUTH AGAIN BRINGING TYPICAL COLD AIR ADVECTION SHOWERS ACROSS
THE EASTERN BERING THROUGH MID WEEK. HIGH PRESSURE EVENTUALLY BUILDS
BY THURSDAY RESULTING IN COLD BUT RELATIVELY CALM CONDITIONS FOR THE
BERING THROUGH THE WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNINGS 181 185 187
         BLIZZARD WATCHES 125 131 155 161 195
         HIGH WIND WATCH 101
MARINE...STORM WARNING...130 150 172 175
         GALE WARNING...120 121 125 129 132 138 140 155 160 165 170
                        171 179 180.
         HEAVY FREEZING SPRAY WARNING...121 129 130 138 140 141
                                        179 185.
FIRE WEATHER...NONE.

AB JAN 12

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
215 PM AKST SUN JAN 8 2012

AKZ101-111-090300-

...VERY HAZARDOUS DRIVING CONDITIONS ALONG THE GLENN HIGHWAY...

THE RECENT STORM HAS RESULTED IN 7 TO 12 INCHES OF FRESH SNOW AROUND
TOWN TODAY. PASSING VEHICLES ARE EASILY PICKING UP THE SNOW ON THE
ROAD RESULTING IN LIMITED VISIBILITY. VERY HAZARDOUS DRIVING
CONDITIONS ARE BEING REPORTED ALONG THE GLENN HIGHWAY WITH PERIODIC
ROAD CLOSURES TO DUE THE RESTRICTED VISIBILITY.

PLEASE USE CAUTION WHEN TRAVELING TODAY AS POOR VISIBILITY IS LIKELY
ALONG THE MAIN ROADS.

AB 2012

SPECIAL WEATHER STATEMENT...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
215 PM AKST SUN JAN 8 2012

AKZ101-111-090300-

...VERY HAZARDOUS DRIVING CONDITIONS ALONG THE GLENN HIGHWAY...

THE RECENT STORM HAS RESULTED IN 7 TO 12 INCHES OF FRESH SNOW AROUND
TOWN TODAY. PASSING VEHICLES ARE EASILY PICKING UP THE SNOW ON THE
ROAD RESULTING IN LIMITED VISIBILITY. VERY HAZARDOUS DRIVING
CONDITIONS ARE BEING REPORTED ALONG THE GLENN HIGHWAY WITH PERIODIC
ROAD CLOSURES DUE TO THE RESTRICTED VISIBILITY.

PLEASE USE CAUTION WHEN TRAVELING TODAY AS POOR VISIBILITY IS LIKELY
ALONG THE MAIN ROADS.

AB 2012