Small Craft Advisory 1023, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST THU DEC 19 2013

.ANALYSIS AND UPPER LEVELS...THE JET STREAM IS AHEAD OF OF AN UPPER
LEVEL TROUGH IN THE BERING SEA AND RIDES OVER THE TOP OF THE UPPER
LEVEL RIDGE SOUTH OF THE GULF. THIS PUT THE JET RIGHT OVER KODIAK
ISLAND AND ALONG THE NORTH GULF COAST. THE JET CAN BE SEEN ON THE IR
SATELLITE. THIS WILL SHIFT EASTWARD OVERNIGHT AS THE RIDGE RETREATS
TO THE SOUTHEAST.
AT THE SURFACE THE LOW THAT PRODUCED THE SNOW AND BLOWING SNOW IN
SOUTHCENTRAL ALASKA HAS WEAKENED AND MOVED INTO THE EASTERN GULF OF
ALASKA. THE MAIN LOW IS STILL IN THE CENTRAL ALEUTIANS.

.MODEL DISCUSSION...ALL MODELS INITIALIZED WELL FROM THE 12Z RUNS.
THE BIGGEST PROBLEM THE MODELS ARE HAVING IS WITH THE LOW IN THE
CENTRAL ALEUTIANS AND THE WAY IT WILL ELONGATE WITH MULTIPLE CENTERS
IN THE EASTERN BERING SEA. THE POSITIVE IS THAT THE TRACK FROM ALL
MODELS IS PRETTY MUCH THE SAME BUT THE SPEED AT WHICH THE FIRST LOW
MOVES AND THE STRENGTH ARE SUBJECTS OF DEBATE. IN ADDITION THE
SOUTHERN MOST LOW WILL BE WEAKER WHICH MAY BE CONTRIBUTING TO THE
LARGER DISCREPANCY BETWEEN MODELS WITH ITS SPEED AND TRACK. IN
GENERAL IT SHOULD MOVE OVER THE ALASKA PENINSULA AND TOWARD THE
SOUTHWEST GULF WHERE IT MERGES WITH ANOTHER LOW MOVING OUT OF THE
PACIFIC. THESE DIFFERENCE WILL HAVE SOME MINOR IMPACT ON THE
FORECASTS BUT NOT AS MUCH AS THE OTHER AREA OF UNCERTAINTY WHICH HAS
TO DO WITH THE TEMPERATURES ALOFT OVER SOUTH CENTRAL ALASKA THE REST
OF THE WEEK. THERE IS ENOUGH WARM AIR ALOFT TO BRING FREEZING RAIN
INTO SOUTHWEST ALASKA AND SOME OF THAT WARMTH WILL MOVE OVER SOUTH
CENTRAL ALASKA AS WELL. MODELS DIFFER AS TO HOW WARM IT WILL GET BUT
HAVE BEEN GENERALLY MOVING TOWARD A LITTLE COLDER SOLUTION THE PAST
FEW DAYS. THE NAM AND ECMWF NOW LOOK TO KEEP JUST ABOUT ALL
PRECIPITATION IN SOUTH CENTRAL ALASKA AS SNOW...WITH THE EXCEPTION OF
THE SOUTHERN KENAI PENINSULA WHERE IT WILL TURN TO RAIN. THE GFS IS
THE WARMEST MODELS AND FOR THE LAST FEW DAYS HAS BEEN PRODUCING
TEMPERATURES HIGHER THAN WHAT ACTUALLY HAS OCCURRED. EVEN WITH GFS
TEMPERATURES THE AMOUNT OF TIME THAT ANY FREEZING RAIN MIGHT OCCUR
FROM ANCHORAGE NORTHWARD WOULD BE FAIRLY SHORT IN DURATION. THEREFORE
WHEN EVERYTHING IS TAKEN INTO ACCOUNT THE CHANCE OF FREEZING RAIN IN
SOUTH CENTRAL ALASKA LOOKS UNLIKELY...THOUGH IT IS NOT ENTIRELY OUT
OF THE QUESTION. SOUTHWEST ALASKA IS ANOTHER STORY WHICH WILL BE
COVER IN THE NEXT SECTION.

.SHORT TERM FORECAST...
SOUTHCENTRAL...SOME CLEARING TODAY WILL RAPIDLY GIVE WAY TO CLOUDS BY
THIS EVENING AS THE NEXT DISTURBANCE MOVES INTO THE AREA. THIS WILL
BRING A LITTLE MORE SNOW TO THE REGION...WITH THE EXCEPTION OF THE
SOUTHERN KENAI PENINSULA WHICH WILL TURN TO RAIN BY LATE TOMORROW
MORNING. THERE IS A CHANCE FOR SOME FREEZING RAIN IN SOUTH CENTRAL
ALASKA WITH THIS DISTURBANCE....BUT AS DISCUSSED IN THE ABOVE
SECTION...IT  LOOKS MORE LIKELY TO BE SNOW. TEMPERATURES WILL BE
WARMING AND BE GENERALLY MILD INTO THE WEEKEND. THE EXCEPTION WILL BE
THE COPPER RIVER BASIN WHICH WILL REMAIN BELOW ZERO...BUT WILL WARM
INTO THE TEENS OR POSSIBLY A LITTLE HIGHER THIS WEEKEND.

SOUTHWEST...TEMPERATURES ALOFT WILL CONTINUE TO WARM AIR THE CORE OF
THE WARM AIR MOVES INTO SOUTHWEST ALASKA TOMORROW. TEMPERATURES AT
THE SURFACE WILL BE BELOW FREEZING TOMORROW MORNING WITH ABOVE
FREEZING AIR ALOFT WITH PRECIPITATION. THIS WILL FALL AS FREEZING
RAIN OVER THE KUSKOKWIM VALLEY AND DELTA. THE BRISTOL BAY REGION WEST
OF KING SALMON WILL ALSO BE CONDUCIVE FOR FREEZING RAIN TOMORROW.THE
AREA CLOSER TO THE ALEUTIAN RANGE WILL LIKELY WARM UP ABOVE FREEZING
CAUSING PRECIPITATION TO BE STRAIGHT RAIN INSTEAD OF FREEZING RAIN.
THE PRIBILOF ISLANDS WILL SEE RAIN TURN TO SNOW FRIDAY MORNING AS THE
LOW MOVES EAST OF THEM AND KICKS IN STRONG NORTHERLY WINDS. THERE
WILL BE SOME REDUCED VISIBILITY DUE TO THE SNOW AND BLOWING SNOW
TOMORROW BUT IT DOES NOT LOOK TO BE BAD ENOUGH TO WARRANT ANY
WARNINGS OR ADVISORIES.

.LONG TERM FORECAST...

A SLOW MOVING TROUGH WILL TRACK EASTWARD OVER SOUTHERN ALASKA...WITH
A NORTH PACIFIC LOW MOVING INTO THE GULF. THERE IS SOME UNCERTAINTY
WITH HOW THESE TWO SYSTEMS PHASE...BUT THERE IS THE POSSIBILITY OF
SOME MORE SNOW ACROSS MUCH OF SOUTHCENTRAL INCLUDING ANCHORAGE LATE
SATURDAY INTO SUNDAY...THOUGH IT WILL PROBABLY NOT BE VERY IMPRESSIVE
AMOUNTS. SOUTHERN ALASKA WILL DRY OUT BRIEFLY ON MONDAY INTO TUESDAY
BEFORE ANOTHER TROUGH BEGINS SPREADING MOISTURE INTO SOUTHWEST AND
SOUTHCENTRAL BY MIDWEEK...BRINGING MORE CHANCES FOR SNOW INTO THE
INTERIOR AND RAIN/SNOW ALONG THE COAST.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...FREEZING RAIN ADVISORY 152 155 161
MARINE...GALE 170 173-179 185.
         HEAVY FREEZING SPRAY 180 181 185.
FIRE WEATHER...NONE.

DEC 13

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1100 AM AKST THU DEC 19 2013

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1051 AM     SNOW             6 SSE ANCHORAGE         61.14N 149.80W
12/19/2013  M3.5 INCH                           AK   TRAINED SPOTTER

            THIS IS A STORM TOTAL.

1051 AM     SNOW             6 W ANCHORAGE           61.22N 150.05W
12/19/2013  M6.3 INCH        PKZ140             AK   OFFICIAL NWS OBS

            THIS IS A STORM TOTAL

1051 AM     SNOW             HOMER                   59.64N 151.52W
12/19/2013  E8.0 INCH                           AK   LAW ENFORCEMENT

            LAW ENFORCEMENT ESTIMATES 4 TO 8 INCHES OF SNOW FELL LAST
            NIGHT AND EARLY THIS MORNING.

1051 AM     SNOW             TALKEETNA               62.34N 150.09W
12/19/2013  M0.5 INCH                           AK   OTHER FEDERAL

1051 AM     SNOW             1 SW ANCHORAGE          61.20N 149.90W
12/19/2013  M3.5 INCH                           AK   BROADCAST MEDIA

            THIS IS A STORM TOTAL.

1051 AM     SNOW             2 SE EAGLE RIVER        61.30N 149.53W
12/19/2013  M1.1 INCH                           AK   NWS EMPLOYEE

&&

MCLAY

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
131 PM AKST THU DEC 19 2013

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0127 PM     SNOW             1 NW FLAT TOP MOUNTAIN  61.10N 149.69W
12/19/2013  M5.0 INCH                           AK   TRAINED SPOTTER

&&

MCLAY