Small Craft Advisory 322, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1254 PM AKDT THU APR 17 2014

.ANALYSIS AND UPPER LEVELS...A LONG-WAVE TROUGH ENCOMPASSES ALL OF
ALASKA AND THE NORTH PACIFIC WITH A NEAR ZONAL SUBTROPICAL JET
CENTERED ALONG 40N. THERE IS ONE NOTABLE SHORTWAVE AND BUCKLE IN
THE JET BETWEEN 160W AND 170W WITH A DEEPENING SURFACE LOW. THIS
SYSTEM WILL BE THE PRIMARY FOCUS THIS WEEKEND OVER THE GULF.
MEANWHILE EMBEDDED WITHIN THE LONG-WAVE TROUGH IS A LARGE CLOSED
LOW CENTERED OVER THE SOUTHERN BERING/EASTERN ALEUTIANS. NUMEROUS
SHORT-WAVES CONTINUE TO ROTATE AROUND THIS LOW PRODUCING MAINLY
SHOWERS ACROSS THE REGION. ON THE DOWNSTREAM SIDE OF THE UPPER
TROUGH A COUPLE OF SHORT-WAVES/SURFACE LOWS OVER THE GULF ARE
LIFTING NORTHWARD. SUNNY SKIES DOMINATE MUCH OF THE SOUTHERN
MAINLAND THIS MORNING...ESPECIALLY INLAND AREAS. THAT WILL
CHANGE TONIGHT AS THE GULF SYSTEMS PROGRESS INLAND.

&&

.MODEL DISCUSSION...MODELS ALL INITIALIZED REASONABLY WELL WITH
MAJOR FEATURES AND SOLUTIONS GENERALLY SHOW THE SAME IDEA WITH
HANDLING OF INTENSIFYING SYSTEM OVER THE NORTH CENTRAL PACIFIC
AND DEVELOPMENT OF ANOTHER DEEP LOW OVER THE NORTHWEST
PACIFIC/ALEUTIANS THIS WEEKEND. AS THE NORTH PACIFIC LOW CURVES
NORTHEASTWARD TOWARD THE GULF EXPECT TRIPLE POINT DEVELOPMENT
CLOSER TO THE SUBTROPICAL JET. ALL OF THE GLOBAL MODELS SHOW THIS
ALTHOUGH THEY DIFFER ON EXACT POSITION OF THE TWO LOWS. SOLUTIONS
BEGIN TO DIVERGE FURTHER AS THESE LOWS CONSOLIDATE BACK INTO A
SINGLE LOW. THESE DIFFERENCES WILL MAINLY AFFECT KODIAK ISLAND
AND THE GULF MARINE AREAS. FOR NOW PREFER THE VERY CONSISTENT
ECMWF.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...A SERIES OF WEAK UPPER LEVEL WAVES WILL
LIFT NORTHWARD ACROSS SOUTHCENTRAL ALASKA TONIGHT THROUGH FRIDAY.
AS HAS BEEN THE CASE IN RECENT DAYS THE BULK OF PRECIP WILL FALL
ALONG THE COAST...HOWEVER DO EXPECT MOST AREAS TO SEE A SHOWER OR
TWO AS THESE WAVES PASS OVERHEAD. AS THESE WAVES EXIT TO THE NORTH
AND THE PACIFIC LOW APPROACHES THE GULF A SURFACE RIDGE WILL
BRIEFLY BUILD ALONG THE NORTH GULF COAST AND KICK UP WINDS ALONG
TURNAGAIN ARM (INTO PORTIONS OF ANCHORAGE) AND THE KNIK RIVER
VALLEY (INTO PALMER). THIS RIDGE WILL BE SHUNTED QUICKLY NORTHWARD
FRIDAY NIGHT AS THE LOW CONTINUES NORTHWARD. FLOW WILL SHIFT TO
OFFSHORE AHEAD OF THE LOW WHILE A SHORT-WAVE RIDGE BUILDS OVER
SOUTHCENTRAL. THIS WILL PRODUCE A CRYSTAL CLEAR DAY FOR MOST OF
SOUTHCENTRAL ON SATURDAY. CLOUDS WILL LIKELY BE ON THE INCREASE
SUNDAY WITH A CHANCE OF RAIN ALONG THE COAST AS WAVES ROTATING
AROUND THE LOW APPROACH SOUTHCENTRAL.

SOUTHWEST ALASKA...A SERIES OF SHORT-WAVES ROTATING AROUND THE
BERING/ALEUTIAN LOW WILL ROTATE THROUGH SOUTHCENTRAL TONIGHT
THROUGH FRIDAY NIGHT. PRECIP WON'T BE WIDESPREAD...BUT LIKE
SOUTHCENTRAL EXPECT MOST AREAS TO SEE A LITTLE SOMETHING.
MARGINALLY COLDER AIR WILL MOVE IN FROM THE SOUTHWEST WITH THE
STRONGEST OF THE UPPER WAVES LATE TONIGHT AND FRIDAY MORNING. THIS
MAY TURN PRECIPITATION TO SNOW OR A MIX OF RAIN AND SNOW...BUT
DON'T EXPECT ANY ACCUMULATION. THE BERING SYSTEM WILL COMPLETELY
FALL APART THIS WEEKEND AS THE LOW MOVING INTO THE GULF BECOMES
DOMINANT. GENERALLY EXPECT DRY CONDITIONS...ALTHOUGH SOME CLOUDS
AND PRECIP MAY BACK THERE WAY FROM THE WESTERN GULF INTO BRISTOL
BAY.

BERING SEA/ALEUTIANS...THE BERING/ALEUTIAN LOW WILL WOBBLE ITS WAY
EASTWARD TOWARD THE SOUTHERN ALASKA PENINSULA TONIGHT AND FRIDAY
AND WILL THEN BE TORN APART AS HALF OF THE ENERGY IS PUSHED
NORTHWARD BY THE SYSTEM MOVING INTO THE GULF AND THE OTHER HALF
IS PUSHED SOUTHWARD AS A RIDGE BUILDS INTO THE WESTERN BERING
AHEAD OF A RAPIDLY INTENSIFYING LOW OVER THE NORTHWEST PACIFIC.
THIS RIDGE WILL QUICKLY SHIFT EASTWARD...PROVING BENIGN CONDITIONS
FOR THE WESTERN TO EASTERN BERING THROUGH THE WEEKEND. THE
NORTHWEST PACIFIC LOW WILL BOTTOM OUT AS IT NEARS THE
ALEUTIANS...SO EXPECT FULL IMPACT OF THIS STORM TO AFFECT THE
ALEUTIANS ON SUNDAY.

&&

.LONG TERM FORECAST...THE SYSTEM MOVING TO THE WESTERN ALEUTIANS
ON SUNDAY WILL BE THE PRIMARY FEATURE OF CONCERN IN THE DAY 4
THROUGH 7 PERIOD AS IT SLOWLY WEAKENS AND SPREADS OUT ACROSS THE
BERING SEA POSSIBLY AS FAR AS THE SOUTHWEST COAST. THE GULF LOW
WILL SINK SOUTHWARD WHILE RIDGING SETS UP OVER MUCH OF MAINLAND
ALASKA. THUS EXPECT A QUIET WEEK OVER SOUTHCENTRAL AND INTERIOR
SOUTHWEST ALASKA. LOW LEVEL THICKNESS LOOK VERY SPRING-LIKE...SO
EVEN WITH SOME SUNSHINE EXPECT HIGH TEMPERATURES TO BE NEAR NORMAL
IN THE 40S ALONG THE COAST AND 50S INLAND. WITH GOOD AGREEMENT IN
THE LARGER SCALE PATTERN AMONG THE GLOBAL MODELS...FORECAST
CONFIDENCE IS ABOVE AVERAGE.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.
&&

SEB APR 14