Small Craft Advisory 282, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
138 PM AKDT SUN APR 6 2014

.ANALYSIS AND UPPER LEVELS...
A LONGWAVE TROUGH REMAINS ANCHORED OVER THE WEST COAST OF ALASKA
AND EXTENDS WELL SOUTH INTO THE PACIFIC NEARLY ALL THE WAY TO
HAWAII. AN ANCHORING UPPER LOW IS NEARLY STATIONARY SOUTH OF THE
ALASKA PENINSULA WITH MULTIPLE SIGNIFICANT SHORTWAVES RIDING
NORTHWARD INTO THE GULF ON A STRONG 140 KT JET. ONE OF THESE
SHORTWAVES HAS BROUGHT RAIN AND SNOW TO THE NORTH GULF COAST
TODAY...AND IS CURRENTLY ABOUT TO MOVE INTO PRINCE WILLIAM SOUND.
ANOTHER WAVE FURTHER NORTH HELPED DROP SEVERAL INCHES OF WET SNOW
OVER THE SUSITNA VALLEY THIS MORNING. OVER SOUTHWEST ALASKA...A
SLOW-MOVING UPPER TROUGH HAS PUSHED THROUGH THE DELTA REGION WHERE
SKIES HAVE NOW LARGELY CLEARED. HOWEVER LOCATIONS AHEAD OF THIS
FEATURE (BRISTOL BAY AND THE KUSKO VALLEY) REMAIN ON THE UNSTABLE
SIDE OF THIS TROUGH AND CONTINUE TO SEE WIDESPREAD LIGHT RAIN AND
SNOW SHOWER ACTIVITY. WAY OUT WEST...COLD AIR ADVECTION AND SNOW
SHOWERS PREVAIL ACROSS THE EASTERN BERING...WHILE A FRONT FURTHER
WEST IS IN THE PROCESS OF STALLING OVER THE CENTRAL ALEUTIANS.

&&

.MODEL DISCUSSION...
AS HAS BEEN THE CASE FOR A FEW DAYS THE MODELS REMAIN IN GOOD
SYNOPTIC AGREEMENT BUT HAVE SOME DIFFERENT DETAILS OVER THE NEXT
24-48 HOURS. THERE IS SOME QUESTION ABOUT HOW FAR NORTHWEST A
SHORTWAVE APPROACHING THE KENAI PENINSULA FROM THE GULF ON MONDAY
MORNING WILL MAKE IT BEFORE THE UPPER TROUGH PUSHES IT BACK TO THE
EAST. THE GFS CONTINUES TO BE THE MOST DRAMATIC (FARTHEST
NORTHWEST) WITH THIS FEATURE. WILL OPT TO STICK WITH THE
CONSISTENCY OF THE ECMWF AT THIS POINT...WITH THE USEFUL SUPPORT
OF THE HI-RES NAM...IN KEEPING THE SHORTWAVE A BIT FURTHER TO
THE EAST. HOWEVER...SHOULD THE GFS SOLUTION VERIFY THIS WOULD
LIKELY DELAY THE ONSET OF PRECIPITATION ACROSS ANCHORAGE AND THE
MAT-SU BY 3-6 HOURS AND PUSH THE START TIME BACK TO LATER IN THE
AFTERNOON ON MONDAY.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
WITH A GENERALLY LIGHT PRESSURE GRADIENT AROUND THE REGION MOST
AREAS WILL REMAIN VULNERABLE TO SHOWERS UNTIL THE APPROACHING
UPPER TROUGH PROVIDES MORE WIDESPREAD LIFT TOMORROW.
HOWEVER...THE BULK OF PRECIPITATION WILL BE CONFINED TO THE NORTH
GULF COAST DURING THIS PERIOD. FOR TOMORROW...CONFIDENCE IS
INCREASING THAT THE BULK OF THE ENERGY IN THE BASE OF THE UPPER
TROUGH WILL PASS OVER THE SOUTHERN KENAI PENINSULA...WHILE THE
MOST SIGNIFICANT COLD AIR ADVECTION WILL TAKE PLACE OVER THE
SUSITNA VALLEY. IF THESE TWO FORCING MECHANISMS WERE GOING TO
FOCUS ON THE SAME LOCATIONS THE POTENTIAL FOR SIGNIFICANT SNOW
WOULD BE MUCH HIGHER...BUT WITH THINGS SPREAD OUT LIKE THIS IT
SEEMS MOST LIKELY THAT A WIDESPREAD AREA WILL SEE OVERALL LIGHTER
SNOWFALL AMOUNTS...ON THE ORDER OF A FEW INCHES AT MOST LOCATIONS.
THE POSSIBLE EXCEPTION TO THIS LOOKS LIKE IT MAY BE UP NEAR
HATCHER PASS AND IN THE REST OF THE SOUTHERN TALKEETNA MOUNTAINS
AS AN ADDITIONAL SHORTWAVE TROUGH AND A RESULTING PROLONGED
SNOWFALL EVENT MAY LEAD TO SOME HIGHER SNOW AMOUNTS.

SOUTHWEST ALASKA...
THE TROUGH MENTIONED EARLIER WILL PASS FAIRLY BENIGNLY THROUGH THE
AREA TONIGHT AND TOMORROW...WITH THE MOST NOTICEABLE IMPACT BEING
A GRADUAL IMPROVEMENT OF CONDITIONS FROM WEST TO EAST. LOCATIONS
ALONG THE ALEUTIAN RANGE CURRENTLY SEEING A MIX OF RAIN AND SNOW
WILL LIKELY CHANGE BACK TO SNOW TONIGHT AND WILL HAVE THE BEST
CHANCE FOR SOME MINOR SNOW ACCUMULATIONS. CLEARER AND COLDER
CONDITIONS WILL PREVAIL THROUGH MIDWEEK AS NORTHWEST FLOW
CONTINUES.

BERING SEA/ALEUTIANS...
COLD ADVECTION SNOW SHOWERS OVER THE EASTERN BERING AND ALEUTIANS
WILL GRADUALLY SUBSIDE THROUGH MONDAY MORNING AS HIGH PRESSURE
MOVES INTO THE AREA. THE FIRST WEATHER FRONT THAT IS CURRENTLY
NEAR ADAK WILL STALL TONIGHT AND WEAKEN RAPIDLY AS A SECOND AND
STRONGER FRONT PUSHES INTO THE WESTERN ALEUTIANS BY MIDDAY
TOMORROW. THIS FRONT WILL MAKE MORE PROGRESS TO THE EAST...AND
REACH THE EASTERN ALEUTIANS WITH RAIN AND GALE-FORCE WINDS BY
TUESDAY MORNING.

&&

.LONG TERM FORECAST...
CLEARING SKIES WILL HELP TEMPERATURES REBOUND ACROSS THE MAINLAND
BY THE MIDDLE OF THE WEEK. EXTENDED MODELS CONTINUE TO INDICATE
CLOUDS AND UNSETTLED WEATHER FROM THE BERING SEA SPREADING INTO
THE SOUTHERN MAINLAND BY LATE IN THE WEEK...WITH THE POTENTIAL FOR
A MORE ACTIVE AND WINDY PATTERN POSSIBLE BY NEXT WEEKEND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 130 131. 173 175 177 178
         HEAVY FREEZING SPRAY 180
FIRE WEATHER...NONE.

&&

AMD APR 14