Small Craft Advisory 491, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKDT THU JUN 20 2013

.ANALYSIS AND UPPER LEVELS...THE UPPER LEVEL PATTERN HAS BECOME A
LITTLE MORE COMPLEX TODAY AS THE RIDGE HAS RECEDED INTO WESTERN
CANADA AND AN UPPER LEVEL LOW IS DIGGING JUST EAST OF THE KAMCHATKA
PENINSULA. IN BETWEEN THESE FEATURES THERE IS A HIGH AMPLITUDE RIDGE
AND THEN A WEAKENING UPPER LEVEL LOW OVER THE SOUTHWEST ALASKA COAST.
A STRONG JET STREAM IS RUNNING JUST SOUTH OF THE KAMCHATKA LOW AND IS
PERFECTLY POSITIONED TO FURTHER INTENSIFY AN EXTRA TROPICAL SURFACE
LOW THAT IS APPROACHING THE ALEUTIAN ISLANDS. THIS LOW WILL REACH THE
LOWER 960S MB RANGE AND WOULD BE CONSIDERED A STRONG LOW EVEN IN THE
WINTER.
A WEAKENING FRONT IS OVER SOUTHWEST ALASKA AND THE ALASKA PENINSULA
WHICH HAS ALSO TURNED THE FLOW SOUTHEAST OVER MOST OF THE MAINLAND
FORECAST AREA. THE SURFACE RIDGE IN THE GULF WILL REMAIN FOR THE NEXT
FEW DAYS AS WELL.

.MODEL DISCUSSION...THE MODELS ARE SETTLING DOWN AND SEEM TO HAVE
COME TOGETHER NICELY ON THE TRACK OF THE EXTRA TROPICAL LOW IN THE
ALEUTIANS. ONE TREND THEY ALL HAVE SHOWN OVER THE PAST DAY IS THAT
THE LOW WILL BE STRONGER AND FARTHER NORTH THAN THEY HAD BEEN
DEPICTING. THIS CHANGE MAKE A LOT OF SENSE DUE TO THE LOWS ORIGIN AND
THE EXTRA CHALLENGES THE MODELS ENCOUNTER WITH THESE SYSTEMS. THIS
WILL IMPACT THE FORECASTS IN THAT IT WILL SHIFT THE PRECIPITATION IN
THE ALEUTIANS AND BERING SEA FARTHER NORTH...BRINGING IN STORM FORCE
WINDS INTO THE WESTERN ALEUTIAN MARINE ZONES WHICH IS NOT VERY COMMON
IN JUNE.

.SHORT TERM FORECAST...CONVECTION STRONG ENOUGH TO PRODUCE
THUNDERSTORMS WILL BE LIMITED TO THE ALASKA RANGE IN THE NORTHERN
COPPER RIVER BASIN THE NEXT FEW DAYS. THERE ARE SOME SHOWERS THAT
WILL LINGER MAINLY OVER THE MOUNTAINS IN SOUTHWEST ALASKA UNTIL THE
WEATHER FRONT ASSOCIATED WITH THE ALEUTIAN STORM MOVES TO THE
SOUTHWEST ALASKA COAST FRIDAY NIGHT AN INCREASES THE WINDS AS WELL AS
THE CHANCES OF RAIN.
WIDESPREAD FOG WILL PERSIST IN THE GULF OF ALASKA REGION AS THE
SOUTHEAST GRADIENT KEEP CONDITIONS FAVORABLE FOR LOW CLOUDS AND FOG.

.LONG TERM FORECAST...THE EXTRA TROPICAL LOW WILL BE SHUNTED SOUTH OF
THE GULF OF ALASKA BY THE HIGH PRESSURE OVER THE STATE THIS WEEKEND.
THE FRONT ASSOCIATED WITH THIS LOW WILL RAPIDLY WEAKEN WHEN IT PUSHES
INTO THE HIGH PRESSURE AS IT MOVES EASTWARD. THIS WILL BRING SOME
PRECIPITATION TO THE GULF COAST AND REGION THIS WEEKEND BUT WILL
LIKELY ONLY INCREASE CLOUD COVER IN THE REST OF SOUTHWEST AND SOUTH
CENTRAL ALASKA. THE UPPER LEVEL HIGH PRESSURE WILL BUILD BACK OVER
THE STATE EARLY NEXT WEEK BRINGING WARMER AND DRIER CONDITIONS THAN
THE WEEKEND...BUT NOWHERE AS WARM AS EARLIER THIS WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 155 160 165 170 172 175 179 180 185.
         STORM 176.
FIRE WEATHER...NONE.

JUN 13