Small Craft Advisory 514, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
130 PM AKDT SAT JUN 29 2013

.ANALYSIS AND UPPER LEVELS...
A PATTERN-CHANGING STORM SYSTEM IS IN THE PROCESS OF CROSSING INTO
THE FAR WESTERN BERING SEA THIS AFTERNOON. AS THIS SYSTEM MOVES INTO
THE AREA THE OVERALL HIGH PRESSURE THAT HAS CONTROLLED THE WEATHER
OVER MOST OF THE MAINLAND FOR THE PAST SEVERAL WEEKS IS BEING FORCED
EASTWARD INTO CANADA. HEAVY SHOWERS WITH A FEW EMBEDDED THUNDERSTORMS
FORMED THIS MORNING OVER THE EASTERN COPPER RIVER BASIN AND DOWN
TOWARD CORDOVA...BUT THIS LINE OF CONVECTION IS DIMINISHING RAPIDLY
AS THE UPPER LEVEL HIGH OVER THE INTERIOR IS CONTINUING TO BE PUSHED
EASTWARD. WIDESPREAD LOW-LEVEL MOISTURE AROUND COOK INLET AND PRINCE
WILLIAM SOUND THIS MORNING IS HAVING A HARD TIME BURNING OFF TODAY
DUE TO CONTINUING SOUTHWESTERLY SURFACE FLOW COUPLED WITH THE
RELATIVELY WEAK NATURE OF THE SUBSIDENCE AHEAD OF AN APPROACHING
SHORTWAVE RIDGE. OUT WEST...A MODERATE STRENGTH FRONT IS MAKING
LANDFALL ACROSS THE KUSKOKWIM DELTA THIS AFTERNOON WITH GALE-FORCE
WINDS AND LIGHT TO MODERATE RAINFALL. BEHIND THIS FRONT...DEEP-LAYER
SOUTHWEST FLOW WILL BE USHERING A MUCH MOISTER AIRMASS TOWARD THE
MAJORITY OF THE STATE OVER THE WEEKEND.

.MODEL DISCUSSION...
THE MODELS ARE IN VERY GOOD AGREEMENT...ESPECIALLY CONSIDERING THE
ONGOING PATTERN CHANGE. THERE IS A BIT OF DISAGREEMENT ABOUT HOW
SIGNIFICANT A POSSIBLE WEAK LOW FORMING ALONG THE FRONT NEAR KODIAK
ISLAND MON AFTERNOON. THE NAM HAS BEEN THE MOST AGGRESSIVE...WITH THE
CANADIAN GEM ALSO HINTING AT A WEAK CIRCULATION. THE ECMWF AND GFS
HAVE BEEN MORE CONSISTENT IN DOWNPLAYING THIS FEATURE...AND IS
GENERALLY THE PREFERRED SOLUTION TODAY. THE REASON THIS FEATURE IS
IMPORTANT IS BECAUSE IF A LOW FORMS IT WILL CHANGE THE ORIENTATION OF
THE FRONT SUCH THAT INLAND AREAS OF SOUTHCENTRAL LIKE ANCHORAGE WOULD
GET MUCH LESS RAINFALL DUE TO DOWNSLOPING. AT THIS TIME...THINK
ANCHORAGE AND MAT-SU WILL GET RAIN DURING THE DAY MONDAY BEFORE WEAK
DOWNSLOPING DOES EVENTUALLY DEVELOP DURING THE EVENING.

.SHORT TERM FORECAST...
EXPECT LOW AND MID-LEVEL CLOUDS WILL CONTINUE TO BREAK UP ALONG
COASTAL AREAS AS WELL AS COOK INLET THROUGH THIS EVENING. THIS IS DUE
TO WEAK HIGH PRESSURE AND ASSOCIATED DOWNWARD MOTION BUILDING IN
AHEAD OF THE BERING STORM. PERIODS OF SUN TOMORROW MORNING WILL GIVE
WAY TO INCREASING HIGH CLOUDS DURING THE AFTERNOON WITH RAIN REACHING
KODIAK ISLAND BY LATE TOMORROW AFTERNOON. OVER THE COPPER RIVER
BASIN...A FEW SUNNY BREAKS THIS AFTERNOON WILL ALLOW DIURNAL SHOWERS
TO DEVELOP ONCE AGAIN...WITH A FEW LIGHTNING STRIKES POSSIBLE THROUGH
THE EVENING HOURS AS THE LAST VESTIGES OF THE THERMAL TROUGH RETREAT
EASTWARD TONIGHT.

SOUTHWEST MAINLAND...STEADY RAIN AND STRONG WINDS HAVE MOVED ONTO THE
DELTA COAST...AND WILL BE PUSHING INLAND AS WELL AS INTO THE BRISTOL
BAY ZONE BY EARLY THIS EVENING. THE FRONT WILL BE WEAKENING AND
SLOWING DOWN AS IT MOVES TO THE EAST...BUT WILL REMAIN INTACT ENOUGH
TO BRING VIRTUALLY ALL LOCATIONS THE MOST SIGNIFICANT RAINFALL IN THE
LAST SEVERAL WEEKS. BEHIND THE FRONT...MOIST SOUTHWEST FLOW WILL
CONTINUE THROUGH EARLY NEXT WEEK...WITH MUCH COOLER TEMPERATURES AND
ONGOING SCATTERED RAIN SHOWERS.

BERING SEA AND ALEUTIANS...AFOREMENTIONED BERING LOW WILL MOVE SLOWLY
TO THE NORTHERN BERING BY MONDAY AFTERNOON BEFORE STALLING AND
RE-CURVING SLIGHTLY WESTWARD INTO THE LONGWAVE TROUGH. THIS WILL KEEP
COOL TEMPERATURES AND SHOWERS ACROSS MOST OF THE REGION THROUGH THE
MIDDLE OF NEXT WEEK. THE UNSETTLED WEATHER WILL CONTINUE TO HELP MIX
UP THE STABLE ENVIRONMENT OF THE LAST FEW WEEKS THAT HAS LED TO
ONGOING PROBLEMS WITH MARINE FOG AND STRATUS.

.LONG TERM FORECAST...
LONG-RANGE MODELS ARE COMING INTO GOOD AGREEMENT THAT THE LONGWAVE
TROUGH WILL SET UP SHOP OVER THE EASTERN BERING SEA THROUGH AT LEAST
THE END OF NEXT WEEK. AFTER A SIGNIFICANT COOL DOWN EARLY IN THE WEEK
TEMPERATURES WILL REBOUND CLOSER TO NORMAL FOR MOST OF THE MAINLAND
BY THE MIDDLE OF THE WEEK...BUT REMAIN MUCH COOLER AND CLOUDIER THAN
THE LAST FEW WEEKS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 130 160 165 170 172 175 176 180
FIRE WEATHER...FIRE WEATHER WATCH 141

DIXON JUN 13