Small Craft Advisory 258, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT THU MAR 21 2013

WINDS ALONG THE NORTH GULF COAST AND SOUTHERN MAINLAND AREAS BECOMING
LIGHTER AS TROF MOVES OFF ACROSS THE SOUTHEAST COAST. AN UPPER RIDGE
AXIS MOVING EAST TO BRISTOL BAY HAS SEVERAL BANDS OF MOISTURE SLIDING
OVER THE TOP. FIRST BAND IS CIRRUS ENHANCING ALONG THE ALASKA RANGE AS
IT MOVES EAST. THE 2ND IS MOSTLY MID AND HIGH CLOUDS ABOVE 8-9K WHICH
GRADUALLY LOWERS TO MVFR/IFR LEVELS OUT TOWARD THE COAST. SNOW
GRADUALLY EDGING EASTWARD SHOULD REACH THE ALASKA RANGE LATER THURSDAY
EVENING.

MODEL DIFFERENCES ARE MINOR WITH THE GFS PREFERRED FOR THE WESTERN
DOMAIN, AND THE NAM FOR THE EASTERN FORECAST AREA. THE NAM IS A LITTLE
SLOW WITH THE SNOW THAT IS CURRENTLY FALLING ALONG THE COAST BUT IS
SLIGHTLY FASTER BRING IT EAST OF THE MOUNTAINS BY 06Z.

COLD UPPER LOW ACROSS NORTHERN ALASKA PROVIDING WESTERLY FLOW ACROSS
THE BERING INTO THE MAINLAND. FRONTAL SYSTEM RIDING IN THIS FLOW HAS
PRODUCED MORNING SNOW FROM THE PRIBILOFS TO NUNIVAK ISLAND AND IS
GRADUALLY SPREADING INLAND. MOISTURE WITH THIS SYSTEM SEEMS TO BE AS
SIGNIFICANT AS THE MODELS SUGGEST WITH THE MODERATE TO HEAVY RATES
OCCURRING AT ST PAUL TODAY.

SURFACE LOW TRACKS NORTHEAST ALONG THE KUSKOKWIM RIVER VALLEY TO JUST
NORTH OF MCGRATH BY MIDDAY FRI. THE GRADIENT BETWEEN THIS LOW AND THE
HIGHER PRESSURE ALONG THE EASTERN GULF COAST MAKES THE ONSET OF
PRECIPITATION FOR THE AREA FROM KENAI TO PALMER VERY DIFFICULT DUE TO
CHINOOK TYPE CONDITIONS. I'LL FOLLOW THE PREVIOUS SHIFTS NOTION THAT
OVERRUNNING WILL PREVAIL. ONCE IT BEGINS EARLY FRIDAY PERIODS OF SNOW
WILL CONTINUE ALONG THE NORTH GULF COAST AND PRINCE WILLIAM SOUND, AS
WELL AS INLAND AREAS EAST OF THE CHUGACH RANGE, THROUGH THE WEEKEND.
SNOW MAY MIX OR CHANGE OVER TO RAIN ALONG THE COAST SUNDAY AS MILDER
CONDITIONS SPREAD NORTHWARD.

INTERESTING PATTERN SETS UP EARLY NEXT WEEK AS A STRONG ARCTIC FRONT
DEVELOPS ALONG THE WESTERN ALASKA RANGE SUNDAY NIGHT. A 983 MB STORM
MOVES INTO THE GULF BY EARLY MONDAY. THIS WILL GIVE POSSIBLE STORM
FORCE WINDS FOR KAMISHAK BAY AND THE KODIAK MARINE ZONES AND GALES FOR
COOK INLET. A FULL GALE WOULD ALSO BE POSSIBLE FOR THE NORTH GULF COAST
SUNDAY NIGHT AND MONDAY.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING 130 176 185 411 412.
         HEAVY FREEZING SPRAY WARNING 130 412.
FIRE WEATHER...NONE.

D PERCY MAR 13