Heavy Freezing Spray Warning 4, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
501 PM AKST SAT JAN 23 2016

.ANALYSIS AND UPPER LEVELS...

A BROAD UPPER TROUGH ENCOMPASSES MUCH OF THE BERING AND NORTH PACIFIC.
THREE UPPER LEVEL LOWS ARE EMBEDDED WITHIN THIS TROUGH AND ARE CENTERED
NEAR SHEMYA... JUST SOUTH OF SAND POINT...AND JUST EAST OF THE PRIBILOF
ISLANDS. THE UPPER JET REMAINS WELL TO THE SOUTH OF ALASKA...ALONG
WITH THE MAIN MOISTURE SUPPLY. AS A RESULT ALL OF THESE UPPER LEVEL
LOWS REMAIN RELATIVELY WEAK AND ARE SLOWLY DIMINISHING IN STRENGTH.
MEANWHILE...A BROAD RIDGE STRETCHES ACROSS MAINLAND ALASKA...THE GULF
OF ALASKA AND WEST CANADA. A FRONT ASSOCIATED WITH THE LOW SOUTH OF
SAND POINT HAS BEEN SUPPORTING STEADY SHOWERS ACROSS KODIAK ISLAND AND
SOUTHERN PORTIONS OF BRISTOL BAY. MEANWHILE THE UPPER LOW JUST TO THE
EAST OF THE PRIBILOFS HAS BEEN BRINGING STEADY SHOWERS TO THE KUSKOKWIM
DELTA AND OCCASIONAL SHOWERS TO THE PRIBILOFS.

&&

.MODEL DISCUSSION...

TODAY MODELS ARE INDICATING LOWER CONFIDENCE THAN PREVIOUS DAYS IN THE
SHORT TERM. WHILE THE GFS AND NAM WERE INDICATING THE RAPID DEVELOPMENT
OF A LOW IN THE GULF OF ALASKA THAT WOULD PROGRESS QUICKLY TOWARDS
THE NORTH GULF COAST BY EARLY NEXT WEEK...THE ECMWF DID NOT INDICATE
THE DEVELOPMENT OF SUCH A LOW. CLOSE INSPECTION OF THE ENSEMBLE MEANS
OF NAEFS, GEFS AND ECMWF ALL INDICATE NO DEVELOPMENT OF SUCH A LOW.
AS A RESULT THE ECMWF MODEL WAS FAVORED FOR THE MODEL PACKAGE TODAY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
TWO SYSTEMS WILL IMPACT SOUTHCENTRAL ALASKA OVER THE NEXT 48 HOURS.
THE FIRST IS AN OCCLUDED FRONT MOVING THROUGH KODIAK ISLAND AND INTO
THE KENAI PENINSULA THIS AFTERNOON. A SHORTWAVE MOVING AHEAD OF THIS
FRONT HAS BEEN PRODUCING WIDESPREAD SHOWERS OVER THE REGION WITH SOME
MIXED PRECIPITATION OVER THE ANCHORAGE AREA THIS AFTERNOON. MOST OF
THE PRECIPITATION WILL CONTINUE OVER UPSLOPE AREAS OF THE ALASKA RANGE
AND THE NORTHERN GULF COAST. ALONG UPPER COOK INLET...DOWNSLOPING
WILL KEEP MOSTLY SCATTERED SHOWERS IN THE FORECAST.

AS THIS FIRST FRONT MOVES THROUGH SOUTHCENTRAL...FLOW ALOFT WILL TURN
SOUTHERLY...BRINGING A PUSH OF WARM MOIST AIR UP FROM THE SOUTH AND
INTO THE AREA. THIS WILL HELP PUSH HIGH TEMPERATURES THROUGH MONDAY
ABOVE FREEZING FOR MOST OF THE AREA WITH THE EXCEPTION OF THE COPPER
RIVER BASIN.

THE NEXT SYSTEM TO IMPACT THE REGION WILL BE A RAPIDLY DEVELOPING LOW
CURRENTLY AROUND 40N 165W THAT WILL MOVE TO A POSITION SOUTHWEST OF
KODIAK ISLAND BY MONDAY MORNING. THE FRONT ASSOCIATED WITH THIS SYSTEM
IS EXPECTED TO BE SOMEWHAT STRONGER THAN THE SYSTEM CURRENTLY MOVING
THROUGH THE AREA WITH A DEEPER TAP OF MOISTURE ASSOCIATED WITH IT.
THE FRONT WILL BEGIN TO IMPACT KODIAK SUNDAY EVENING BEFORE MOVING
ALONG THE NORTHERN GULF COAST BY MONDAY AFTERNOON. THIS FRONT WILL
PRODUCE OVERALL MODERATE PRECIPITATION TOTALS ALONG THE GULF COAST
AND THE SOUTHERN ALASKA RANGE WITH ACCUMULATING SNOW MAINLY ALONG
THE HIGHER ELEVATIONS. THE MAIN CHALLENGE WITH THIS SYSTEM WILL BE
PRECIPITATION TYPE ALONG COOK INLET. TEMPERATURES WILL BE RISING
ABOVE FREEZING UP TO ABOUT 925MB...BUT STAYING IN THE -2 TO -3 C
RANGE AT 850MB. WITH THIS IN MIND...MOSTLY LIKELY THE PRECIPITATION
TYPE WILL STAY MOSTLY RAIN IN THE SOUTHERN PARTS OF COOK INLET WITH
A GRADUAL TRANSITION TO A RAIN/SNOW MIX IN THE ANCHORAGE AREA AND
ALL SNOW FROM THE KNIK ARM REGION NORTHWARD.

&&

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

THE PATTERN SHIFT IS UNDERWAY AS THE FIRST WEAK UPPER LOW IS LIFTING
NORTHWARD OUT OF THE LOWER KUSKOKWIM VALLEY AND THE DELTA. RIGHT ON
ITS HEELS IS ANOTHER LOW TRACKING INTO THE ALASKA PENINSULA. THIS LOW
WILL MOVE INTO SOUTHWEST TONIGHT AND TOMORROW...BRINGING IN WARMER
AIR AND CHANGING PRECIPITATION TO PREDOMINANTLY RAIN ACROSS THE BRISTOL
BAY REGION...WITH A MIX ELSEWHERE. A STRONGER LOW WILL MOVE INTO THE
REGION MONDAY AND MONDAY NIGHT...SPREADING MORE WARM AIR AND STRONGER
SOUTHEAST WINDS INTO THE AREA.

&&

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

A RELATIVELY QUIET PATTERN FOR THE BERING WILL PERSIST AS A
COMPLEX BUT VERY ILL DEFINED UPPER LEVEL LOW REMAINS OVER THE
BERING...WITH A STATIONARY FRONT SOUTH OF THE ALEUTIAN CHAIN. THIS
WILL KEEP A SHOWERY AND LARGELY EASTERLY FLOW REGIME IN PLACE...WITH
THE EXCEPTION OF THE EASTERN ALEUTIANS WHERE TWO LOWS WILL MOVE NORTH
INTO SOUTHWEST ALASKA TONIGHT AND AGAIN MONDAY...BRINGING RAIN AND
GALE FORCE WINDS TO THAT AREA.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
NOT MANY CHANGES TO THE EXTENDED FORECAST TODAY AS FAR AS THE
LARGE SCALE PATTERN GOES. DAY THREE BEGINS WITH ONE UPPER LOW
WITHING THE BROAD SCALE BERING SEA TROUGH NEAR THE ALASKA
PENINSULA AND ATTENDANT FRONT PUSHING ASHORE THE NORTH GULF COAST.
A SECOND MORE POTENT SHORTWAVE IS AMPLIFYING UNDER A 200 KT EAST
ASIAN JET...STILL WELL SOUTH OF THE ALEUTIANS. THIS SYSTEM WILL
ACT TO SHIFT THE WHOLE LONGWAVE EASTWARD A LITTLE BIT AS IT MOVES
INTO THE GULF OF ALASKA ON LATE TUESDAY NIGHT. THE FRONT WILL
IMPACT THE NORTH GULF COAST...HOWEVER...MUCH LIKE MANY SYSTEMS
OVER THE RECENT TIMES IT IS WEAKENING RAPIDLY AS IT APPROACHES
WITH THE BRUNT OF PRECIPITATION STAYING CONFINED TO THE COAST. THE
AIR MASS IT BRINGS UP FROM THE SOUTH IS SLIGHTLY WARMER THAN WHAT
IS CURRENTLY IN PLACE...BUT IT IS NOT GOING TO BRING A HUGE WARM
UPFROM CURRENT TEMPERATURES. LOOKING OUT TOWARD THE END OF THE
WEEK...THE PATTERN LOOKS MOSTLY THE SAME WITH A TROUGH ANCHORED
OVER THE BERING/ALEUTIANS BUT WITH A LITTLE MORE RIDGING BEGINNING
TO BUILD OVER THE NORTHEASTERN PACIFIC. AS FAR AS SENSIBLE WEATHER
GOES...EXPECT TEMPERATURES SLIGHTLY ABOVE NORMAL IN MOST
LOCATIONS. ONE SOLID FRONT WILL IMPACT THE NORTH GULF COAST ON
WEDNESDAY...FOLLOWED BY A MORE SHOWERY/OCCASIONAL REGIME.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 119 120 130 131 132 136 137 138 150 351 352.

&&

SYNOPSIS AND MODEL DISCUSSION...EN
SOUTHCENTRAL ALASKA...RF
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA
LONG TERM...ML