Small Craft Advisory 296, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
146 PM AKDT WED APR 9 2014

.ANALYSIS AND UPPER LEVELS...THE UPPER LEVEL WAVE TRAIN IS
PROGRESSING EASTWARD ACROSS THE REGION THIS MORNING. A TROUGH
OVER THE EASTERN MAINLAND IS EXITING TO CANADA WITH JUST A FEW
AREAS OF LIGHT SNOW REMAINING ACROSS THE COPPER RIVER BASIN AND
IN THE VICINITY OF A WEAK SURFACE LOW OVER THE NORTHERN GULF. A
RIDGE IS BUILDING FROM THE EASTERN BERING INTO THE SOUTHWEST
MAINLAND WITH CRYSTAL CLEAR SKIES BEING OBSERVED ACROSS SOUTHWEST
ALASKA AND THE WESTERN HALF OF SOUTHCENTRAL. PEOPLE IN THIS REGION
WOKE UP TO BELOW NORMAL TEMPERATURES RANGING FROM BELOW ZERO OVER
INTERIOR SOUTHWEST TO SINGLE DIGITS AND TEENS ELSEWHERE. THE
PLENTIFUL SUNSHINE IS HELPING TO MODERATE THESE TEMPERATURES
QUICKLY. OUT WEST A LARGE CLOSED LOW IS SHIFTING EASTWARD ALONG
THE ALEUTIANS. FEATURES ASSOCIATED WITH THIS LOW (UPPER LEVEL AND
SURFACE) ARE WEAK...SO IMPACT ON THE REGION IS MINIMAL.

&&

.MODEL DISCUSSION...MODELS CONTINUE TO PERFORM WELL IN THE SHORT-
TERM. SOLUTIONS BEGIN TO DIVERGE FRIDAY WITH DEVELOPMENT OF A
SURFACE LOW OVER THE NORTH CENTRAL PACIFIC AND TRACK NORTHWARD
TO THE BERING SEA. GFS/ECMWF SOLUTIONS ARE VERY SIMILAR AND THESE
MODELS DISPLAY THE BEST RUN-TO-RUN CONSISTENCY. FORECAST CONFIDENCE
IS ABOVE AVERAGE UNTIL ARRIVAL OF THIS SYSTEM.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...THE UPPER TROUGH OVER THE EASTERN MAINLAND
WILL EXIT TO THE EAST TONIGHT BRINGING AN END TO ANY REMAINING
SNOW OVER THE COPPER RIVER BASIN. MODELS ARE ALL KEYING IN ON A
WEAK SHORT-WAVE ROUNDING THE EASTERN BERING RIDGE AND DROPPING
DOWN ACROSS SOUTHCENTRAL. THIS WILL HELP AMPLIFY THE EXITING
TROUGH AND PRODUCE A PERIOD OF ENHANCED COLD ADVECTION ACROSS THE
REGION. THUS...EXPECT SOME LOCALLY GUSTY WINDS THROUGH GAPS IN THE
TERRAIN...MOST NOTABLY THOMPSON PASS INTO VALDEZ. THE COLD
ADVECTION AND WINDS WILL BE SHORT-LIVED AS THE UPPER RIDGE QUICKLY
BUILDS IN ON THURSDAY. TEMPERATURES WILL REMAIN BELOW NORMAL
TONIGHT AND FRIDAY BUT WILL THEN QUICKLY MODERATE THIS WEEKEND AS
THE FIRST RIDGE EXITS AND ANOTHER BUILDS NORTHWARD FROM THE
PACIFIC BRINGING MUCH WARMER AIR WITH IT. CLOUDS AND A CHANCE OF
PRECIPITATION WILL RETURN TO THE REGION FRIDAY NIGHT AND SATURDAY
AS A SERIES OF SYSTEMS MOVE UP THE WEST SIDE OF THE BUILDING
RIDGE.

SOUTHWEST ALASKA...EXPECT ONE MORE DRY AND COOL DAY BEFORE CLOUDS
AND PRECIPITATION BEGIN TO MOVE UP FROM THE SOUTH LATE FRIDAY AND
INTO SATURDAY. THE PREDOMINANT LOW LEVEL FLOW WILL BE OUT OF THE
SOUTHEAST...SO DO EXPECT DOWNSLOPING TO KEEP THINGS DRY IN THE LEE
OF THE ALASKA AND ALEUTIAN RANGES. THE AIR MASS WILL INITIALLY BE
COLD ENOUGH TO SUPPORT SNOW BUT WILL WARM QUICKLY OVER THE WEEKEND
CAUSING A TRANSITION TO RAIN. THE INCREASING AMOUNT OF SUNLIGHT
ALSO FAVORS WARMER SURFACE TEMPERATURES MAKING IT HARD FOR SNOW TO
ACCUMULATE.

BERING SEA/ALEUTIANS...THE UPPER LOW AND ASSOCIATED WEAK WAVES
WILL CONTINUE TO PRODUCE LARGELY DISORGANIZED AREAS OF RAIN AND
WIND ACROSS THE WESTERN BERING AND ALEUTIANS. A MORE SUBSTANTIAL
SURFACE LOW WILL DEVELOP OVER THE NORTH PACIFIC THURSDAY NIGHT AND
MOVE INTO THE CENTRAL BERING FRIDAY NIGHT. THIS WILL SHIFT THE
FOCUS EASTWARD TO THE EASTERN BERING...EASTERN ALEUTIANS AND ALASKA
PENINSULA. ACTIVE WEATHER WILL CONTINUE THROUGH THE WEEKEND AND
INTO NEXT WEEK AS YET ANOTHER UPPER LOW DROPS OUT OF ASIA TO
REPLACE THE CURRENT ONE WHICH EXITS NORTHWARD LATER THIS WEEKEND.

&&

.LONG TERM FORECAST...A SERIES OF SHORT-WAVES MOVING THROUGH THE
LONG-WAVE TROUGH WILL PUSH THE UPPER RIDGE EASTWARD EARLY NEXT
WEEK ALLOWING SYSTEMS TO PUSH INTO MAINLAND ALASKA. CONDITIONS
DON'T LOOK FAVORABLE FOR DEVELOPMENT OF ANY MAJOR STORM
SYSTEMS... SO GENERALLY EXPECT RUN OF THE MILL WIND AND
PRECIPITATION EVENTS TO AFFECT THE REGION. THERE MAY BE SOME DRIER
CLEARER PERIODS IN BETWEEN FEATURES...BUT IT IS WAY TO CHAOTIC OF
A FLOW PATTERN TO BE ABLE TO IDENTIFY WHEN AND WHERE INDIVIDUAL
FEATURES WILL BE.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...HEAVY FREEZING SPRAY WARNING 160.
FIRE WEATHER...NONE.
&&

SEB APR 14