Small Craft Advisory 302, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1238 PM AKDT THU APR 10 2014

.ANALYSIS AND UPPER LEVELS...A HIGH AMPLITUDE RIDGE CENTERED OVER
SOUTHWEST ALASKA THIS MORNING IS MOVING RATHER QUICKLY EASTWARD
INTO SOUTHCENTRAL ALASKA. THIS WILL BRING AN END TO LOW LEVEL
COLD ADVECTION OVER SOUTHCENTRAL. THERE HAVE BEEN SOME STRONG
GUSTY GAP WINDS THIS MORNING...PARTICULARLY IN THE THOMPSON
PASS/VALDEZ AREA. THESE WILL QUICKLY DIE OFF THIS AFTERNOON WITH
THE END OF THE COLD ADVECTION AND A SLACKENING PRESSURE GRADIENT.
WITH PLENTY OF SUNSHINE ACROSS THE SOUTHERN MAINLAND EXPECT
TEMPERATURES TO QUICKLY MODERATE THIS AFTERNOON AFTER A CHILLY
START THIS MORNING.

UPSTREAM OF THE RIDGE A VERY LARGE CLOSED LOW IS NEARLY STATIONARY
OVER THE WESTERN ALEUTIANS. A DIGGING SHORT-WAVE OVER THE NORTH-
CENTRAL PACIFIC HAS PRODUCED SIGNIFICANT AMPLIFICATION OF THE
PATTERN. EARLY SIGNS OF CYCLOGENESIS ARE EVIDENT IN SATELLITE
IMAGERY (AROUND 40N 148W) WITH DEEP MOISTURE BEGINNING TO STREAM
NORTHWARD TOWARD THE EASTERN ALEUTIANS AND ALASKA PENINSULA. THIS
DEVELOPING SYSTEM IS THE FOCUS OF THE SHORT-TERM FORECAST.

&&

.MODEL DISCUSSION...ALL 12Z SOLUTIONS EXCEPT FOR THE NAM SHOW A
SIMILAR SOLUTION WITH THE DEVELOPING SURFACE LOW OVER THE NORTH
PACIFIC. THERE HAS BEEN A GRADUAL TREND TOWARD A MORE AMPLIFIED
TROUGH AND DEEPER SURFACE LOW OVER THE PAST COUPLE DAYS...SO WILL
TREND THE WIND FORECAST ACCORDINGLY. A LARGER SPREAD IN SOLUTIONS
ARISES WITH THE HANDLING OF WEAKER FEATURES...INCLUDING
DEVELOPMENT OF TRIPLE POINT LOWS IN THE KODIAK ISLAND/ALASKA
PENINSULA REGION AND PROGRESSION OF LOWS BEHIND THIS FIRST STORM
SYSTEM. FORTUNATELY...NONE OF THESE DIFFERENCES WILL HAVE TOO MUCH
IMPACT ON THE GENERAL FORECAST. THUS...FORECAST CONFIDENCE IS
ABOUT AVERAGE.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...AFTER A COUPLE CHILLY DAYS TEMPERATURES WILL
BEGIN TO MODERATE FRIDAY AS THE FIRST RIDGE EXITS TO THE EAST AND
A RIDGE BUILDING AHEAD OF THE DEVELOPING PACIFIC LOW BRINGS WARMER
AIR FROM THE SOUTH. CLOUDS AND PRECIPITATION WON'T BE FAR BEHIND.
THE RIDGE WILL INITIALLY KEEP THE WORST OF THE WEATHER CONFINED TO
KODIAK ISLAND AND THE WESTERN GULF FRIDAY NIGHT AND SATURDAY...BUT
AS THE RIDGE SHIFTS EASTWARD OVER THE WEEKEND MAINLAND ALASKA
WILL BECOME ENVELOPED IN THE UPPER TROUGH. THIS WILL PROVIDE MORE
ACTIVE WEATHER LATE THIS WEEKEND AND INTO NEXT WEEK.

WITH MODELS TRENDING TOWARD A STRONGER NORTH PACIFIC LOW ALSO
EXPECT A STRONGER FRONTAL SYSTEM MOVING INTO THE WESTERN GULF.
THERE ARE SOME MODEL DIFFERENCES WITH EXTENT OF TRIPLE POINT
DEVELOPMENT IN THE KODIAK ISLAND REGION. IF THE TRIPLE POINTS DO
DEVELOP INTO LOWS WINDS WILL BE EVEN STRONGER. THE OTHER AFFECT
OF TRIPLE POINT DEVELOPMENT WILL BE TO BEND LOW LEVEL FLOW MORE
TOWARD THE NORTH OUT AHEAD OF THE FRONT WHICH WILL HELP HOLD IN
COLDER AIR LONGER OVER SOUTHCENTRAL. IT WILL CERTAINLY BE COLD
ENOUGH FOR SNOW AS PRECIPITATION ARRIVES ALONG THE NORTH GULF
COAST SATURDAY NIGHT INTO SUNDAY MORNING. THE BIG CHALLENGE IS
DETERMINING HOW QUICK THE TRANSITION TO RAIN WILL BE. EVEN THOUGH
IT IS APRIL LOW LEVEL THICKNESSES SUPPORT A FAIRLY SLOW TRANSITION
ON SUNDAY. THERE ARE SOME KEY MODEL DIFFERENCES IN THE ORIENTATION
OF THE UPPER TROUGH AS IT LIFTS NORTHWARD ACROSS THE SOUTHERN
MAINLAND SUNDAY...WHICH MAKES IT A CHALLENGE TO DETERMINE HOW MUCH
PRECIPITATION WILL MAKE IT INTO INTERIOR SOUTHCENTRAL. UPPER LEVEL
FLOW WILL ACCELERATE...SO ANYTHING THAT DOES FALL WILL BE SHORT-
LIVED.

SOUTHWEST ALASKA...DUE ITS CLOSER PROXIMITY TO THE DEVELOPING
PACIFIC STORM SOUTHWEST ALASKA WILL EXPERIENCE THE BRUNT OF THE
IMPACTS WITH THE FRONTAL SYSTEM. STRONG LOW LEVEL SOUTHEAST FLOW
WILL PRODUCE SOME DOWNSLOPE DRYING IN THE LEE OF THE ALASKA AND
ALEUTIAN RANGES AND TO A LESSER EXTENT IN THE LEE OF THE AHKLUN
AND KILBUCK MOUNTAINS. DO EXPECT WIDESPREAD WINDS AND
PRECIPITATION IN THE UPSLOPE AREAS. THE AIR MASS WILL BE COLD
ENOUGH TO SUPPORT ALL SNOW AS PRECIP FIRST MOVES IN FRIDAY NIGHT
INTO SATURDAY...BUT EXPECT A QUICK WARM-UP FOR MOST AREAS ON
SATURDAY DUE TO WARM ADVECTION AND DOWNSLOPE WARMING. WITH UPPER
FLOW BECOMING MORE PROGRESSIVE LATER IN THE WEEKEND...EXPECT ONLY
A SHORT BREAK SUNDAY AFTERNOON/EVENING BEFORE THE NEXT SYSTEM
MOVES IN SUNDAY NIGHT/MONDAY.

BERING SEA/ALEUTIANS...BASED ON A STRONGER PACIFIC LOW WILL
INCREASE WIND FORECAST FOR THE EASTERN BERING/EASTERN
ALEUTIANS/ALASKA PENINSULA AREAS LATE TONIGHT THROUGH FRIDAY
NIGHT. THE STORM WILL MOVE AT A PRETTY GOOD CLIP SO THE STRONGEST
WINDS WON'T BE OF A RELATIVELY SHORT DURATION. AFTER THIS SYSTEM
MOVES THROUGH AND THE UPPER TROUGH LIFTS OVER MAINLAND ALASKA
ANOTHER UPPER LEVEL CLOSED LOW WILL MOVE IN FROM ASIA. THE FLOW
AROUND THIS LOW WILL BE FAST MAKING IT DIFFICULT TO TRACK THE MANY
FEATURES ROTATING AROUND THE LOW. BOTTOM LINE...ACTIVE WEATHER
WILL CONTINUE.

&&

.LONG TERM FORECAST...LARGE UPPER LEVEL LOW WILL REMAIN ANCHOREDOVER
THE BERING SEA NEXT WEEK. PREDICTABILITY OF INDIVIDUAL FEATURES
EMBEDDED WITHIN THE FLOW AROUND THE LOW OR WITHIN THE LARGER SCALE
TROUGH IS LOW. GENERALLY EXPECT UNSETTLED WEATHER TO PERSIST
ACROSS THE REGION. THERE ARE INDICATIONS OF AMPLIFICATION OF THE
TROUGH OVER THE NORTH PACIFIC THE MIDDLE OF NEXT WEEK WHICH COULD
SHIFT MOST OF THE ACTION FURTHER SOUTH AND PRODUCE QUIETER WEATHER
OVER THE MAINLAND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...155 160 165 170 171 180.
FIRE WEATHER...NONE.

&&

SEB APR 14