Small Craft Advisory 304, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
400 AM AKDT TUE APR 7 2009

.ANALYSIS AND UPPER LEVELS...
AT THE SURFACE...A WEAK TRIPLE POINT LOW OVER THE EASTERN GULF OF
ALASKA IS DRIFTING NORTHWARD. THE LOW OVER THE NORTHERN BERING IS
WEAKENING WHILE MOVING EASTWARD. THE FRONT ASSOCIATED WITH THIS LOW
IS DISSIPATING OVER INTERIOR ALASKA. A LOW SOUTH OF THE CENTRAL
ALEUTIANS IS MOVING INTO THE NORTHEAST PACIFIC WHILE WEAKENING.
TRANSITORY HIGH PRESSURE BEHIND THIS LOW IS CURRENTLY BUILDING INTO
THE WESTERN ALEUTIANS.

IN THE UPPER LEVELS...A RIDGE IS LOCATED OVER MAINLAND ALASKA. A
LONGWAVE TROUGH IS CENTERED OVER THE BERING SEA...WITH A STRONG UPPER
LOW IN THE NORTHERN BERING. THE TROUGH AND ASSOCIATED UPPER LOW WILL
DRIFT EAST TODAY...WITH THE UPPER LOW EXPECTED TO BE OVER SAINT
LAWRENCE ISLAND TONIGHT.

.MODEL DISCUSSION...
MODELS ARE IN GENERAL AGREEMENT THROUGH LATE WEDNESDAY. DIFFERENCES
PERTAINING TO HOW LONG THE LOW WILL REMAIN IN THE GULF EXIST...WITH
THE GFS HANGING ON A BIT LONGER THAN OTHER MODELS. MAIN DISCREPANCIES
ARISE CONCERNING THE EVOLUTION OF THE NORTH PACIFIC LOW APPROACHING
THE ALEUTIANS ON WEDNESDAY. MODELS ARE TRENDING TOWARDS A TRACK
FARTHER NORTH AND WEST WITH THIS LOW...RESULTING IN A WETTER FORECAST
FOR SOUTHCENTRAL TOWARD THE END OF THE WEEK. THE GFS/NAM WERE
PREFERRED FOR CONSTRUCTING THE MORNING FORECASTS.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...THE WEAK LOW IN THE NORTHERN GULF WILL KEEP
PRECIPITATION AROUND COASTAL AREAS OF SOUTHCENTRAL TODAY. REMNANT
MOISTURE FROM THE WEATHER FRONT ASSOCIATED WITH THE BERING LOW WILL
RESULT IN SCATTERED SHOWERS ACROSS THE REMAINDER OF SOUTHCENTRAL
THROUGH TONIGHT. A SHORTWAVE TROUGH WILL SWING THROUGH SOUTHCENTRAL
WEDNESDAY...KEEPING THE CHANCE OF PRECIPITATION IN THE FORECAST.
ANTICIPATE PRECIP TYPE TO BE MAINLY SNOW...WITH RAIN MIXING IN ALONG
COASTAL AREAS.

.SOUTHWEST...SCATTERED SHOWERS WILL CONTINUE OVER THE NEXT SEVERAL
DAYS AS MOISTURE ASSOCIATED WITH THE NORTHERN BERING LOW WRAPS INTO
THE REGION. PRECIPITATION WILL BE MOST WIDESPREAD ALONG THE KUSKOKWIM
VALLEY TODAY...POTENTIALLY MIXING WITH RAIN THIS AFTERNOON. RAIN MAY
ALSO MIX WITH SNOW ALONG PORTIONS OF BRISTOL BAY AND THE AKPEN.
CONDITIONS WILL BE DETERIORATING ALONG THE AKPEN LATE WEDNESDAY AS A
FRONT ASSOCIATED WITH A NORTH PACIFIC LOW PUSHES INTO THE AREA.

.BERING SEA AND ALEUTIANS...TODAY WILL BE RELATIVELY QUIET OVER THE
ALEUTIANS AS HIGH PRESSURE MOVES OVER THE REGION. CONDITIONS WILL BE
DEGRADING ACROSS THE ISLANDS WEDNESDAY AS A NORTH PACIFIC LOW
APPROACHES FROM THE SOUTHWEST. WIDESPREAD RAIN AND SNOW CAN BE
EXPECTED WITH THIS SYSTEM...ALONG WITH WINDS TO STORM FORCE. ACROSS
THE PRIBILOFS...SCATTERED SNOW SHOWERS WILL PERSIST THROUGH WEDNESDAY
AS THE LOW IN THE NORTHERN BERING DISSIPATES.

.LONG TERM FORECAST...
MAIN FOCUS WILL BE ON THE NORTH PACIFIC LOW MOVING ALONG THE ALEUTIAN
CHAIN AND CURVING NORTH INTO THE GULF OF ALASKA ON FRIDAY. REGARDING
THE LARGE SCALE PATTERN...THE TROUGH CURRENTLY OVER THE BERING SEA
LOOKS TO SHIFT EASTWARD OVER THE AK MAINLAND AS WE HEAD INTO THE
WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE...170 172 185
         STORM...175 176
FIRE WEATHER...NONE

NRH APR 09