Freezing Rain Advisory 21, NWS Anchorage, AK

823 
WWAK41 PAFC 101308
WSWAER

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE ANCHORAGE AK
408 AM AKST WED DEC 10 2014

AKZ145-101415-
/O.CAN.PAFC.ZR.Y.0021.000000T0000Z-141210T1400Z/
SUSITNA VALLEY-
INCLUDING THE CITIES OF...TALKEETNA...WILLOW...CANTWELL
408 AM AKST WED DEC 10 2014

...FREEZING RAIN ADVISORY IS CANCELLED...

THE NATIONAL WEATHER SERVICE IN ANCHORAGE HAS CANCELLED THE
FREEZING RAIN ADVISORY. 

$$

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
457 PM AKST TUE DEC 9 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW CENTERED OVER THE ALASKA PENINSULA
AND ANOTHER ONE OVER THE SOUTHEASTERN GULF OF ALASKA...WITH WEAK
CYCLONIC FLOW IN BETWEEN. THERE IS A RIDGE OF HIGH PRESSURE OVER
THE BERING SEA AND ALEUTIANS AND WEAK HIGH PRESSURE OVER THE
CENTRAL AND NORTHERN ALASKA MAINLAND.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN GOOD AGREEMENT THROUGH FORECAST HOUR
84 (FRIDAY AFTERNOON). THERE ARE NATURALLY SOME DIFFERENCES IN
SMALL SCALE FEATURES. A DIFFERENCE THAT AFFECTS THE FORECAST IS
HOW THE MODELS HANDLE THE UPPER LEVEL VORTICITY MAXIMUMS
ASSOCIATED WITH THE PANHANDLE LOW. THIS CREATES SOME
TIMING/LOCATION DIFFERENCES FOR PRECIPITATION ACROSS SOUTH CENTRAL
AND SOUTHWEST ALASKA. DUE TO GOOD MODEL AGREEMENT THE FORECAST
CONFIDENCE IS HIGHER THAN NORMAL.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...OUR
AIRMASS REMAINS QUITE MOIST THIS AFTERNOON AND WE HAVE SEVERAL
WEAK UPPER LEVEL IMPULSES PUSHING THROUGH THE AREA. THIS IS
LEADING TO LIGHT PRECIPITATION FALLING FROM THE GULF COAST THROUGH
THE ANCHORAGE BOWL AND DOWN TO THE KENAI PENINSULA. THE BIGGEST
PROBLEM IS WHAT TYPE OF PRECIPITATION IT WILL BE AS IT CONTACTS
THE SURFACE. MOST SURFACE OBSERVATIONS AND THE 00Z ANCHORAGE
SOUNDING SUPPORT RAIN. HOWEVER...SOME SPOTS IN EAST ANCHORAGE ARE
BELOW FREEZING ALREADY AND THUS...SOME OF THIS RAIN IS FREEZING ON
ROADWAYS.

AS ONE WAVE IS WINDING DOWN MOVING TO THE WEST OVER THE COOK
INLET...ANOTHER WAVE WILL MOVE INTO THE AREA FROM THE NORTHERN
GULF. OUR WARM DOWNSLOPE FLOW OVER THE CHUGACH AND KENAI MOUNTAINS
HAS ALL BUT DIED OFF...SO THE CHANCES FOR COOLING A FEW EXTRA
DEGREES ARE BETTER TONIGHT THAN THE PAST FEW NIGHTS. WITH A WARM
NOSE TRAPPED AROUND 1500 FEET...THIS WILL MEAN THAT PRECIPITATION
HAS A GOOD CHANCE TO FALL AS LIQUID WITH THE WAVE FROM THE GULF.
MANY KEY POPULATION CENTERS WILL HOVER RIGHT AROUND THE FREEZING
MARK OVERNIGHT...SO EVERYONE SHOULD PREPARE FOR SLICK ROADS AND
SIDEWALKS. THIS IMPULSE DOES NOT LOOK TO PRODUCE MUCH MORE THAN A
FEW HUNDREDTHS OF AN INCH OF PRECIPITATION...BUT EVEN A LITTLE
BIT COULD MAKE COMMUTING RATHER DIFFICULT. ON WEDNESDAY MOST AREAS
WILL SEE THE PRECIPITATION COME TO AN END BY MID TO LATE MORNING.
ANOTHER WEAK WAVE WILL WORK ITS WAY UP FROM KODIAK THROUGH THE
KENAI PENINSULA. IT WILL FALL APART AS IT DOES SO...BUT HAS ENOUGH
LIFT TO KEEP SOME RAIN AND SNOW SHOWERS IN THE FORECAST THROUGH
THE DAY.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A WEAK NORTH PACIFIC LOW POSITIONED NEAR THE CHIRIKOF ISLANDS
WILL BECOME NEARLY STATIONARY BEFORE DISSIPATING BY WEDNESDAY.
THIS WILL BRING WEAK SHORTWAVES THROUGH THE SOUTHWEST REGION WITH
MIXED WINTRY PRECIPITATION THROUGH WEDNESDAY. THE TEMPERATURES
WILL REMAIN STEADY WITH THE WARM AIR ADVECTION FROM THE SOUTH
BEFORE GRADUALLY COOLING WITH THE PREDOMINATE NORTHEASTERLY WIND
BY WEDNESDAY. THE MAIN CONCERN WILL BE THE INCREASING CHANCE FOR
LIGHT FREEZING RAIN NORTH AND WEST OF KING SALMON FROM MIDNIGHT
TONIGHT THROUGH LATE WEDNESDAY MORNING. THIS IS DUE TO THE
PERSISTENT LAYER OF WARM AIR ALOFT COMBINED WITH SUB-FREEZING
SURFACE TEMPERATURES IN THESE AREAS. WITH A MORE SUBSTANTIAL AREA
OF PRECIP EXPECTED TO MOVE INTO BRISTOL BAY TONIGHT...A FREEZING
RAIN ADVISORY HAS BEEN ISSUED FOR AREAS NORTH AND WEST OF KING
SALMON INCLUDING DILLINGHAM. ASIDE FROM THE PRECIPITATION TYPE
CHALLENGES...MODELS WERE IN GOOD SYNOPTIC AGREEMENT AND FORECAST
CONFIDENCE IS GENERAL ABOVE AVERAGE.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE EASTERN SIBERIAN HIGH CONTINUES TO REMAIN STATIONARY RESULTING
IN NORTHERLY WINDS THROUGHOUT THE BERING SEA/ALEUTIANS THROUGH
WEDNESDAY. THIS WILL CONTINUE TO BRING COOLER AIR INTO THE NORTHERN
BERING SEA WITH SHOWERY PRECIPITATION THROUGHOUT THE REGION. THE
AREA OF CONCERN WILL BE THE GAP WINDS SETTING UP WITH THE COLD AIR
ADVECTION COINCIDING WITH THE NORTH TO NORTHWESTERLY FLOW THROUGH
THE ALEUTIANS. FORECAST CONFIDENCE REMAINS HIGH HEADING INTO THE
MIDDLE OF THE WEEK.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
SHOWER ACTIVITY WILL BE ON A GENERAL DOWNWARD TREND BY THE END OF
THE WORK WEEK AS THE BROAD LOW CENTERED OVER THE ALASKA PENINSULA
GRADUALLY WEAKENS AND AN UPPER LEVEL RIDGE OVER THE NORTH PACIFIC
SKIRTS THE ALEUTIAN CHAIN. HOWEVER...THIS TREND WILL BE SHORT
LIVED AS ONE LOW APPROACHES THE GULF THIS WEEKEND AND ANOTHER
ENTERS THE WESTERN BERING. THIS WILL ALLOW THE BROAD UPPER TROUGH
TO BECOME RE-ESTABLISHED ACROSS THE BERING AND GULF BY THE
BEGINNING OF NEXT WEEK WITH SOUTHERLY FLOW OVER THE MAINLAND. AS A
RESULT...PRECIPITATION WILL CONTINUE TO BE FOCUSED ALONG THE GULF
COAST INTO NEXT WEEK WITH A MORE SHOWERY REGIME FARTHER INLAND AND
ACROSS THE BERING.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...FREEZING RAIN ADVISORY 161.
MARINE...GALE WARNING 177.
         HEAVY FREEZING SPRAY WARNING 180 181.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...MO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PD
LONG TERM...CB

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
902 PM AKST TUE DEC 9 2014

AKZ101-111-101815-
ANCHORAGE-MATANUSKA VALLEY-
INCLUDING THE CITIES OF...ANCHORAGE...EAGLE RIVER...INDIAN...
EKLUTNA...PALMER...WASILLA...SUTTON...CHICKALOON
902 PM AKST TUE DEC 9 2014

...FREEZING TEMPERATURES AND LIGHT FREEZING RAIN PRODUCING SLICK
ROAD CONDITIONS...

SURFACE TEMPERATURES HAVE DROPPED BELOW FREEZING FROM THE
ANCHORAGE BOWL NORTHWARD TO THE MATANUSKA VALLEY. THIS IS CAUSING
LIQUID TO REFREEZE ON AREA ROADWAYS. IN ADDITION...AREAS OF
FREEZING DRIZZLE OR LIGHT FREEZING RAIN ARE CONTRIBUTING TO SLICK
ROADS. PRECIPITATION IS EXPECTED TO END DURING THE OVERNIGHT
HOURS.

MOTORISTS ARE URGED TO USE EXTRA CAUTION WHEN TRAVELING ON AREA
ROADWAYS.