Heavy Freezing Spray Warning 36, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
506 AM AKST WED FEB 17 2016

.ANALYSIS AND UPPER LEVELS...

A BROAD AND DEEP LOW PRESSURE SYSTEM OVER THE NORTHERN BERING
CONTINUES TO DOMINATE THE WEATHER MAP THROUGHOUT THE BERING SEA
AND WEST MAINLAND. SNOWFALL AND STRONG WINDS FROM THE ASSOCIATED
FRONT BROUGHT BLIZZARD CONDITIONS TO THE KUSKOKWIM DELTA COAST
OVERNIGHT...WHICH IS BEGINNING TO SPREAD INTO THE INLAND DELTA AND
BRISTOL BAY AS IT WEAKENS. EVEN WITH THE WARM AIR ADVECTION
ASSOCIATED WITH THE FRONT MOST AREAS HAVE REMAINED SNOW OVER THE
SOUTHWEST OVERNIGHT...WITH RAIN MIXING IN THE TO THE SOUTH OVER
THE AKPEN AND EASTERN ALEUTIANS. BEHIND THIS FRONT WIDESPREAD GALE
FORCE WINDS AND SNOW SHOWERS ARE BEGINNING TO SPREAD THROUGHOUT
THE BERING SEA AND INTO THE EASTERN ALEUTIANS. AHEAD OF THE FRONT
RIDGING CONTINUES TO KEEP QUIET WEATHER OVER MOST OF THE SOUTH
MAINLAND AND GULF OF ALASKA WITH LIGHT WINDS AND PATCHY LOW
CLOUDS/FOG. SO FAR MUCH OF THE LOW CLOUDS HAS OCCURRED OVER THE
COPPER RIVER BASIN...BUT THIS IS BEGINNING TO DEVELOP AND SPREAD
AROUND SOUTHCENTRAL WHERE IT IS EXPECTED TO PERSIST INTO MID
MORNING.

&&

.MODEL DISCUSSION...

THE MODELS REMAIN IN VERY GOOD SYNOPTIC AGREEMENT WITH BOTH THE
DISSIPATION OF THE FRONT OVER THE SOUTHWEST COAST TODAY...BUT THEN
BEGIN TO HAVE RELATIVELY MINOR ISSUES WITH THE PLACEMENT AND
INTENSITY OF THE SECONDARY LOW NEAR KODIAK ISLAND THIS EVENING.
THE EC WAS GENERALLY PREFERRED FOR THIS LOW TRACK WHICH IS A
SLIGHTLY WEAKER AND FURTHER SOUTH SOLUTION...BUT THIS IS
RELATIVELY CLOSE TO THE CURRENT FORECAST AND SHOULDN'T HAVE A
SIGNIFICANT IMPACT ON FORECAST CONFIDENCE. OTHERWISE THE MODELS
CONTINUE TO HAVE ISSUES WITH PRECIP TYPE FROM THE FRONT OVER THE
WEST COAST...THOUGH THEY HAVE COME INTO BETTER AGREEMENT SINCE
YESTERDAY AS THE NAM HAS COME MORE IN LINE WITH A WARMER SOLUTION.

&&

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

THE UPPER LEVEL RIDGE HAS MOVED OVER SOUTHCENTRAL ALASKA THIS
MORNING CREATING SUBSIDENCE THAT HAS LEAD TO AREAS OF FOG NEAR
COOK INLET AND IN THE COPPER RIVER BASIN. THIS FOG IS FAIRLY THIN
AROUND COOK INLET BUT THE INITIAL HEATING AS THE SUN COMES UP
COULD CAUSE THE FOG TO RAPIDLY INCREASE JUST AFTER SUNRISE (A
"SUNRISE SURPRISE"). THE FOG IN THE COPPER RIVER BASIN APPEARS TO
BE THICKER AND MORE WIDESPREAD THAN ANYWHERE ELSE IN THE REGION.
THIS FOG COULD BE DIFFICULT TO FULLY BURN OFF DURING THE DAYTIME
HOURS. A FRONT MOVING INTO THE WESTERN GULF OF ALASKA IS BRINGING
PRECIPITATION TO KODIAK ISLAND. THIS WILL BE MOSTLY ALL RAIN AT
SEA LEVEL BUT TURNING TO SNOW AT HIGHER ELEVATIONS. THIS FRONT
WILL STALL AS IT PUSHES INTO THE RIDGE CAUSING KODIAK TO REMAIN IN
THE RAIN AND SNOW INTO FRIDAY. SOME HIGH CLOUDS MAY MAKE IT OVER
THE RIDGE AND MOVE OVER THE COOK INLET AND SUSITNA VALLEY AREAS
LATER TODAY BUT THERE SHOULD STILL BE A GOOD AMOUNT OF SUN ABLE TO
MAKE IT THROUGH THESE THIN HIGH CLOUDS SHOULD THIS HAPPEN.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A STRONG AND MOIST WARM FRONT OVER THE SOUTHWEST COAST WILL
CONTINUE TO PUSH INLAND OVER THE SOUTHWEST MAINLAND THIS
MORNING...BRINGING STRONG SOUTHEAST WINDS AND PERIODS OF HEAVY
SNOW TO PARTS OF THE INTERIOR PORTIONS OF THE BRISTOL BAY AREA AND
PARTS OF THE LOWER KUSKOKWIM VALLEY. AREAS OF BLOWING SNOW WILL
CONTINUE TO BE OBSERVED OVER PARTS OF THE KUSKOKWIM DELTA AND THE
INTERIOR BRISTOL BAY AREA TODAY...AS GUSTY WINDS AND SNOW ACROSS
THE REGION CONTINUE TO CAUSE A REDUCTION IN VISIBILITIES. SOME
MIXING WITH RAIN MAY OCCUR FROM THE COAST OF BRISTOL BAY TO THE
SOUTHERN PORTION OF THE DELTA AS THE FRONT MOVES INLAND TODAY.
HOWEVER...AS COLDER AIR WRAPS IN BEHIND THE FRONT THIS EVENING...
THE PRECIPITATION TYPE WILL GRADUALLY CHANGE TO ALL SNOW OVERNIGHT
WEDNESDAY AND INTO THURSDAY...BEFORE TAPERING OFF BY FRIDAY
MORNING.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A POWERFUL GALE-FORCE WARM FRONT WILL PUSH INLAND OVER THE
SOUTHWEST MAINLAND THIS MORNING...WITH AN EQUALLY STRONG COLD
FRONT RAPIDLY ENTERING THE EASTERN BERING DIRECTLY BEHIND THE
ABOVE MENTIONED WARM FRONT. GUSTY WESTERLY WINDS WILL CONTINUE TO
SPREAD EASTWARD COVERING MUCH OF THE BERING AND ALEUTIANS THIS
MORNING...WITH STRONG COLD AIR ADVECTION AND INSTABILITY SNOW
SHOWERS MOVING ACROSS THE AREA. ANOTHER STRONG LOW WILL MOVE INTO
THE WESTERN BERING SEA THIS EVENING THROUGH THURSDAY...BRINGING A
MIX OF RAIN AND SNOW ALONG WITH STRONG GALE-FORCE TO NEAR
STORM-FORCE WINDS TO THE WESTERN AND CENTRAL ALEUTIANS. BY FRIDAY
THIS SYSTEM WILL STALL OVER THE CENTRAL AND EASTERN
ALEUTIANS/BERING...AND POSSIBLY SETTING UP A DEFORMATION BAND
OVER THE PRIBILOF ISLANDS.

&&

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

...FROM PREVIOUS DISCUSSION...

THE 500MB 5-WAVE GEOPOTENTIAL HEIGHTS ARE SHOWING THE SAME
WEATHER PATTERN THAT WE HAVE BEEN EXPERIENCING FOR THE LAST
MONTH. THEREFORE...LOOK FOR WARMER TEMPERATURES AND DRIER
CONDITIONS FOR THE SOUTHCENTRAL REGION WITH AN AMPLIFIED RIDGE
OVER THE SOUTHEAST PANHANDLE EXTENDING THROUGH THE SOUTHCENTRAL
INTERIOR. WHILE THE BERING SEA...SOUTHWEST AND THE ALEUTIANS WILL
BE DOMINATED BY AN UPPER LEVEL TROUGH THROUGH THE WEEKEND. THIS
SYNOPTIC FEATURE WILL BRING A SHOWERY WEATHER REGIME FOR THE MOST
PART AS WE HEAD INTO THE WEEKEND. THE MODELS IN GENERAL AT THE
SURFACE ARE GENERATING A BROAD AREA OF LOW PRESSURE DEVELOPING
JUST SOUTH OF THE EASTERN ALEUTIANS BY THE WEEKEND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY...152 155 161.
MARINE...GALES...130 132 138 150 155 160 165 170-179 185.
         HEAVY FREEZING SPRAY...178 185.

&&

SYNOPSIS AND MODEL DISCUSSION...DEK
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TP
LONG TERM...JR