Heavy Freezing Spray Warning 37, NWS Anchorage, AK

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

.ANALYSIS AND UPPER LEVELS...PATTERN REMAINS SLIGHTLY MORE DYNAMIC
OVER THE WESTERN HALF OF THE STATE THAN IT HAS BEEN THE PAST
SEVERAL WEEKS. A 75 KT JET FINGER IS RUNNING FROM SOUTHEAST TO
NORTHWEST ACROSS SOUTHWEST AK. THIS IS THE LAST VESTIGE OF UPPER
LEVEL SUPPORT FOR THE FRONT OVER THAT AREA. THE FRONT WILL NOW
DRIFT SLOWLY EAST AS IT STARTS TO WEAKEN AND FRAGMENT. SNOW WILL
CONTINUE FOR AREAS FROM ANIAK DOWN THROUGH KOLIGANEK AND LAKE
ILIAMNA THROUGH THURSDAY MORNING...WITH THE HEAVIEST AMOUNT IN THE
KILBUCK AND KUSKOKWIM MOUNTAINS. ON THE BACKSIDE OF THE
FRONT...ACROSS THE PRIBILOF ISLANDS AND ALASKA PENINSULA...850 MB
TEMPERATURES ARE PLUMMETING DOWN TOWARDS -15C. THIS IS MAKING FOR
WIDESPREAD SNOW SHOWERS AND GUSTY WINDS...ESPECIALLY THROUGH THE
FAVORED NORTHWEST CHANNELED TERRAIN.

ACROSS THE EAST...RIDGING REMAINS IN CONTROL. THIS LED TO SOME
SMALL POCKETS OF DENSE FOG THIS MORNING...ESPECIALLY ALONG THE
COOK INLET AND THE KNIK ARM. LOW STRATUS CONTINUES TO PLAGUE THE
COPPER RIVER BASIN. AS OFFSHORE FLOW INCREASES SLOWLY TODAY AND
THE FEBRUARY SUN WORKS ON THAT LAYER...THE THINKING IS STILL THAT
IT WILL BURN OFF BY THIS EVENING. THE OFFSHORE/DOWN-INLET FLOW
SHOULD MAKE FOR LESS FOG AND STRATUS TONIGHT AS DRY AIR GETS
ENTRAINED INTO THE BOUNDARY LAYER. BUT A FEW POCKETS WILL STILL BE
POSSIBLE ALONG OPEN WATER.

&&

.MODEL DISCUSSION...MODELS ARE IN GOOD AGREEMENT WITH OVERALL
PATTERN. THEY ARE NOT HOWEVER IN LOCK-STEP WITH THE EXACT
PLACEMENT OF FEATURES. IN THE EAST...HI-RES MODELS WERE FAVORED
WITH LOCAL OUTFLOW WINDS BEING THE PREDOMINANT CONCERN. ALSO...MODELS
HAVE TRENDED A BIT FURTHER SOUTH ON KODIAK ISLAND WITH THE TRIPLE
POINT LOW THIS AFTERNOON. THE EC WAS THE MOST AGGRESSIVE IN PULLING
IT "AWAY" IN THE GULF ON THURSDAY...BUT THEY HAVE COME INTO BETTER
CONSENSUS WITH THE LOW MORE OR LESS "STALLING" IN THE WESTERN
GULF. OUT WEST...A GFS/EC BLEND WAS USED IN HANDLING THE LOW THAT
WILL CLIP THE WESTERN ALEUTIANS THURSDAY WITH NEAR STORM- FORCE
WINDS. OVERALL...FORECAST CONFIDENCE IS MODERATE IN THE SHORT-
TERM. MODELS SHOW MORE UNCERTAINTY AS WE HEAD INTO THE
WEEKEND...SEE THE EXTENDED DISCUSSION FOR FURTHER DETAILS.

&&

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

SOME MINOR INSTABILITY ASSOCIATED WITH THE INVERTED TROUGH ACROSS
THE NORTHERN GULF HAS BEEN PRODUCING A BAND OF ISOLATED SHOWERS
WHICH WILL CONTINUE TO STREAM INTO PRINCE WILLIAM SOUND THROUGH
THIS EVENING. THE SURFACE LOW ASSOCIATED WITH THE FRONTAL SYSTEM
STRETCHING FROM SOUTHWEST ALASKA ACROSS KODIAK ISLAND IS CURRENTLY
CENTERED ALONG THE SOUTHERN TIP OF KODIAK ISLAND AND WILL CONTINUE
SLOWLY EAST TONIGHT THEN SOUTH ON THURSDAY. THE LOCATION OF THE
LOW AND STALLED FRONT WILL KEEP PRECIPITATION GOING STEADILY
ESPECIALLY ACROSS THE NORTHERN HALF OF KODIAK ISLAND WITH STRONG
WEST TO NORTHWEST WIND ALONG THE BACK SIDE OF THE LOW PRIMARILY
IMPACTING THE SOUTHERN HALF OF THE ISLAND. THE LOW WILL WEAKEN AS
IT CONTINUES TO DRIFT SLOWLY SOUTH THURSDAY NIGHT THEN WILL
DISSIPATE FRIDAY AS IT IS PULLED BACK TO THE WEST AS A NEW LOW
TRACKS IN FROM THE WEST JUST SOUTH OF THE EASTERN ALEUTIANS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A FRONT THAT HAS MOVED IN OVER THE AREA IS NOW STALLING OUT OVER
SOUTHWEST ALASKA BRINGING AN AREA OF SNOW FROM THE LOWER KUSKOKWIM
VALLEY THROUGH BRISTOL BAY. WITH CONSISTENT SNOW LINGERING IN THE
AREA FROM DILLINGHAM NORTH OVERNIGHT...SNOW ACCUMULATION LOOKS TO
BE HIGH ENOUGH FOR ADVISORY LEVELS. THERE IS ALSO THE POTENTIAL
THAT SOME OF THE STRONGER WINDS ALONG THE ALEUTIAN RANGE WILL MAKE
IT FURTHER INLAND CAUSING BLOWING SNOW. EARLY THURSDAY MORNING THE
SNOW WILL LIGHTEN...HOWEVER IT WILL LINGER THROUGHOUT MUCH OF THE
EARLY PART OF THE DAY. CONDITIONS WILL THEN BRIEFLY CLEAR UP
BEFORE ANOTHER LOW MOVES IN FROM THE SOUTH ON FRIDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE CURRENT PATTERN ACROSS THE BERING AND ALEUTIANS IS WESTERLY
FLOW AND SNOW SHOWERS. THIS WILL BEGIN TO CHANGE AS A NEW LOW
WEST OF THE WESTERN ALEUTIANS CONTINUES ITS TRACK NORTH AND SWINGS
ITS FRONT ACROSS THE BERING AND ALEUTIANS. IT WILL MOVE ACROSS
THE WESTERN ALEUTIANS LATER THIS EVENING THEN TO THE CENTRAL
ALEUTIANS THURSDAY MORNING AND FINALLY STALL OVER THE EASTERN
ALEUTIANS THURSDAY EVENING. MORE SNOW SHOWERS WILL FOLLOW THE
FRONT IN RENEWED WESTERLY FLOW.

&&

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

THE MAIN CHALLENGE IN THE LONG TERM FORECAST SURROUNDS THE UPPER
LOW...MOVING SOUTH OF THE ALASKA PENINSULA FRIDAY NIGHT. THIS
SYSTEM IS PROJECTED TO INITIALLY MOVE A WEAK FRONT ACROSS THE
WESTERN GULF AND KENAI PENINSULA DURING THE EARLY MORNING HOURS ON
SATURDAY. SURFACE RIDGING ACROSS SOUTHCENTRAL COMBINED WITH
DOWNSLOPING DUE TO STRONG LOW LEVEL EASTERLY WINDS...INHIBITS RAIN
POTENTIAL ACROSS SOUTHCENTRAL WITH THIS FIRST SYSTEM. A SECOND
FRONT DEVELOPS QUICKLY BEHIND THE FIRST AND PUSHES INTO THE
SOUTHERN GULF LATE SATURDAY MORNING. AT THE SAME TIME...THE UPPER
LEVEL JET STREAM BEGINS TO SHIFT INTO A FAVORABLE PATTERN TO BRING
A SATURATED PACIFIC AIR MASS ACROSS THE KENAI AND SOUTHCENTRAL.
THE FRONT IN THE SOUTHERN GULF PUSHES TO THE NORTH COAST IN THE
EVENING BRINGING GUSTY EASTERLY WINDS AND PRECIPITATION TO THE
COASTAL AREAS AND PRINCE WILLIAM SOUND. SEVERAL STRONG UPPER LEVEL
WAVES WILL MOVE NORTH SPREADING PRECIPITATION NORTH ACROSS
SOUTHCENTRAL INTO SUNDAY. THE COLDER AIR MASS ALONG THE COAST AND
JUST INLAND IS EXPECTED TO MODERATE QUICKLY TO A WARMER MARITIME
ENVIRONMENT WHICH WILL CHANGE SNOW OVER TO RAIN OR A MIX OF SNOW
AND RAIN DURING THIS EVENT.

TO THE WEST...NORTHERLY WINDS AND SHOWERY CONDITIONS PREVAIL
ACROSS THE BERING THROUGH THE WEEKEND. THE MAIN IMPACTS INITIALLY
WILL BE ACROSS THE EASTERN BERING WITH GALE WINDS AND MIXED
PRECIPITATION AS A LOW SOUTH OF THE ALASKA PENINSULA TRACKS INTO
BRISTOL BAY. A SECOND SYSTEM PUSHES A FRONT INTO THE WESTERN
ALEUTIANS LATE SUNDAY AFTERNOON SPREADING GUSTY EAST WINDS AND
PRECIPITATION INTO THE CENTRAL ALEUTIANS/SOUTHERN BERING BY EARLY
MONDAY.

AN ACTIVE WEATHER PATTERN CONTINUES THROUGH MID WEEK AS THE
ALEUTIAN LOW TRACKS EASTWARD AND ANOTHER DEVELOPING EASTERN
PACIFIC LOW TRACKS TOWARD THE GULF ON TUESDAY.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY...161.
MARINE...STORM...150
 		GALE...130 131 132 138 155 160 170 172 173 174 175 176 177 178
               179 185
		HEAVY FREEZING SPRAY...160 178 185

&&

SYNOPSIS AND MODEL DISCUSSION...MO
SOUTHCENTRAL ALASKA...JR
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DK
LONG TERM...KH