Small Craft Advisory 984, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
527 AM AKST WED DEC 10 2014

.ANALYSIS AND UPPER LEVELS...
THE MAIN FEATURE ON WATER VAPOR IMAGERY THIS MORNING IS A LARGE
BROAD COMPLEX LOW PRESSURE SITTING ALOFT OVER THE ALASKA
PENINSULA. THIS ABOMINATION IS THE PRODUCT OF THE JET STREAM
SENDING WAVE AFTER WAVE FROM THE MID-LATITUDES INTO THE GULF TO
SLOWLY WEAKEN AND DIE OVER THE PREVIOUS COUPLE WEEKS. IT IS A
WHOLLY DISORGANIZED BEAST WITH MANY DIFFERENT EMBEDDED
CIRCULATIONS MEANDERING AROUND THE LARGE SCALE CIRCULATION. THE
JET REMAINS WELL TO THE SOUTH WITH AN ACTUAL STRONG SHORTWAVE
IMPACTING THE PANHANDLE THIS MORNING. ANOTHER ONE OF THESE WAVES
AFFECTED THE COPPER RIVER BASIN OVERNIGHT AS WELL AS THE SUSITNA
VALLEY...BRINGING BOTH ACCUMULATING SNOW AS WELL AS SOME POCKETS
OF FREEZING RAIN. AT THE SURFACE THE ONLY DISCERNIBLE FEATURE IS
THE REMNANT OF THE LAST SYSTEM TO REINFORCE THIS CIRCULATION. ON
THE RADAR ANY VISIBLE PRECIPITATION IS SCATTERED AROUND WITH NO
WIDESPREAD ECHO SHOWING UP. RADIOSONDE OBSERVATIONS FROM YESTERDAY
AFTERNOON INDICATE THE LINGERING PRESENCE OF A WARM LAYER OFF THE
SURFACE WITH SUB-FREEZING TEMPERATURES AT THE SURFACE. ANY OF
THESE INTERMITTENT SHOWERS HAVE THE OPPORTUNITY TO FALL AS
FREEZING RAIN...BUT INTENSITY SHOULD BE LIGHT ENOUGH TO NOT BE
IMPACTFUL.

&&

.MODEL DISCUSSION...
SYNOPTICALLY GUIDANCE REMAINS IN GOOD AGREEMENT AND CONTINUES THAT
WAY FOR THE FORESEEABLE FUTURE IN THIS STAGNANT BLOCKED PATTERN.
WITH NO LARGE FEATURES TO KEY IN ON THE ONLY DIFFERENCES IN THE
GUIDANCE CONTINUES TO BE WHERE SHOWERS WILL BE AS THE CURRENT LOW
DISSIPATES. THE CONSENSUS IS THE CURRENT SURFACE LOW WILL DRIFT
INTO THE GULF TO DISSIPATE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE LOW OVER THE ALASKA PENINSULA IS TRYING TO BRING A WEAK WAVE
OVER THE SOUTHCENTRAL TODAY. IT SHOULD BE ENOUGH TO KICK OFF SOME
SHOWERS IN THE AREA AND THERE IS ENOUGH WARM AIR REMAINING ALOFT
FOR THE THREAT OF FREEZING RAIN TO CONTINUE. HOWEVER...THE
PRECIPITATION SHOULD BE LIGHT AND THE WARMER AIR ALOFT WILL BE
GETTING REPLACED BY COLDER AIR FROM THE NORTH BRINGING IN A CHANCE
THAT THE SHOWERS COULD BE SNOW. OVERALL CONFIDENCE IN A FREEZING
RAIN EVENT IS LOW. AS THE LOW WEAKENS PRECIPITATION SHOULD
DIMINISH AND THE SHOWER ACTIVITY WILL STAY SOUTH FOR THE MAJORITY
OF THE SOUTHCENTRAL. THIS WILL MAKE WAY FOR FOG TO DEVELOP IN MANY
LOCATIONS TODAY AND TONIGHT THROUGHOUT THE SOUTHCENTRAL.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
WITH A WEAK OVERALL SYNOPTIC PATTERN...THE FORECAST CHALLENGE IN
THE EARLY TERM FOCUSES ON PINPOINTING PRECIPITATION OVER THE
SOUTHWEST MAINLAND AND DETERMINING PRECIPITATION TYPE. AREAS OF
FREEZING RAIN ARE EXPECTED IN PRIMARILY IN THE KING SALMON AREA
THIS MORNING...AS DUAL-POL RADAR IS INDICATING RAIN SHOWERS ARE
MOVING IN FROM THE SOUTH WITH SURFACE TEMPERATURES JUST BELOW
FREEZING. THERE IS A SLIGHT CHANCE THAT THIS FREEZING RAIN COULD
ALSO STRETCH TOWARDS DILLINGHAM...HOWEVER WITH MOST OF THE RAIN
REMAINING TO THE SOUTHEAST THIS SHOULD BE RELATIVELY BRIEF AND
LIGHT IF IT DOES OCCUR. OVER NORTHERN BRISTOL BAY...TEMPERATURES
SHOULD REMAIN COLD ENOUGH FOR ACCUMULATING SNOW TO OCCUR THIS
MORNING...THOUGH A FEW BRIEF PERIODS OF RAIN MAY ALSO BE POSSIBLE.
THE FREEZING RAIN POTENTIAL SHOULD END BY LATE THIS MORNING AS
TEMPERATURES IN MOST AREAS RISE ABOVE FREEZING. THIS SYSTEM WILL
THEN DISSIPATE BY LATE TONIGHT AS WEAK RIDGING MOVES IN...KEEPING
PRECIPITATION CHANCES LIMITED TO ISOLATED SNOW SHOWERS BY
THURSDAY MORNING.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE WEATHER IN THE REGION WILL CONTINUE TO DOMINATED BY
NORTHWESTERLY FLOW AND SHOWERS THROUGH THURSDAY. A WEAK NORTH
PACIFIC LOW WILL APPROACH THE CENTRAL ALEUTIANS ON
THURSDAY...HOWEVER THIS SYSTEM WILL STAY FAR ENOUGH SOUTH THAT IT
WILL HAVE MINIMAL IMPACT TO THE OVERALL FORECAST.

&&

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

A STUBBORN AND PERSISTENT BLOCKING HIGH SITUATED OVER THE ARCTIC
CONTINUES TO PREVENT ANY SIGNIFICANT CHANGE IN THE UPPER LEVEL
PATTERN. WITH THE HIGH PRESSURE SITUATED OVER THE ARCTIC...THE JET
STREAM WILL CONTINUE TO MEANDER SOUTH OF THE ALEUTIAN ISLANDS IN
THE NORTH PACIFIC. THIS WILL CONTINUE THE UNSEASONABLY WARM
TEMPERATURES ACROSS SOUTHCENTRAL ALASKA AS A SERIES OF LOW
PRESSURE SYSTEMS FROM THE NORTH PACIFIC MOVE INTO THE GULF OF
ALASKA. THIS WILL ALLOW BOTH MOISTURE AND WARMER TEMPERATURES TO
ADVECT FROM THE NORTH PACIFIC TOWARD SOUTHCENTRAL AND SOUTHEASTERN
ALASKA. COLDER AIR SHOULD CONTINUE TO ADVECT SOUTHWARD OVER THE
BERING SEA AND ALEUTIAN ISLANDS THROUGH THIS WEEKEND. OVER THE
WEEKEND...AN AREA OF LOW PRESSURE WILL PUSH EASTWARD OFF THE
KAMCHATKA PENINSULA AND DRIVE A FRONT ACROSS THE BERING SEA...WITH
A TRIPLE POINT LOW DEVELOPING NEAR THE PRIBILOF ISLANDS LATE
SATURDAY. ALL-IN-ALL...THE BERING SEA AND SOUTHWEST ALASKA WILL
CONTINUE TO SEE PERIODS OF RAIN/SNOW SHOWERS.

&&

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

&&

SYNOPSIS AND MODEL DISCUSSION...MTL
SOUTHCENTRAL ALASKA...DK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK
LONG TERM...MMC