Small Craft Advisory 360, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT TUE APR 23 2013

.MODEL DISCUSSION...
NUMERICAL GUIDANCE IS IN GOOD AGREEMENT TODAY. THIS IS NOT A
SURPRISE AS THE DEVELOPING PATTERN OF A "REX BLOCK" OVER THE BERING
SEA IS A STABLE AND PREDICTABLE PATTERN. FORECAST CONFIDENCE IS
HIGHER THAN NORMAL TODAY.

.ANALYSIS AND UPPER LEVELS...
THERE IS A LARGE UPPER LOW SOUTH OF THE EASTERN ALEUTIANS AND
ANOTHER NORTH OF ALASKA. THERE IS AN UPPER LEVEL HIGH OVER THE
CENTRAL AND EASTERN BERING SEA AND ANOTHER IN THE NORTHEAST PACIFIC
NUDGING INTO THE PANHANDLE OF ALASKA. SOUTHERN ALASKA IS IN THE
"COL" BETWEEN THESE FOUR SYSTEMS. THERE IS A SHORT-WAVE TROUGH
CURRENTLY IN THE COL PROVIDING PRECIPITATION TO MOST OF SOUTH
CENTRAL ALASKA AND THE FAR EASTERN PORTION OF SOUTHWEST ALASKA.

.SHORT TERM FORECAST...
FOR SOUTH CENTRAL AND SOUTHWEST ALASKA...THE SOUTHERN ALASKA TROUGH
WILL WORK ITS WAY INTO THE NORTHERN STREAM AND MOVE INTO THE
PANHANDLE WED MORNING. AS THIS HAPPENS THE NORTHEAST PACIFIC HIGH
WILL RETREAT SOUTHWARD ALLOWING NORTHWESTERLY FLOW TO DEVELOP OVER
THE AREA BY WEDNESDAY AFTERNOON. THIS WILL ALSO BE ENCOURAGED BY THE
BERING HIGH BECOMING A "REX BLOCK" (WHICH IS A HIGH NORTH OF A
LOW...SPECIFICALLY THE LOW SOUTH OF THE ALEUTIANS) ON THURSDAY THE
FLOW ALOFT WILL BECOME ALMOST STRAIGHT NORTHERLY AND WILL REMAIN
THAT WAY THROUGH FRIDAY.

FOR THE BERING SEA AND ALEUTIANS...A REX BLOCK WILL DEVELOP OVER THE
BERING SEA TONIGHT AS MENTIONED ABOVE. THIS IS A VERY STABLE AND
PREDICTABLE PATTERN AND WILL REMAIN IN PLACE THROUGH FRIDAY.

.LONG TERM FORECAST...
THE BLOCKING RIDGE WILL SLOWLY RETROGRADE (MOVE WEST) THROUGH THE
EXTENDED PERIOD...ENTERING EXTREME EASTERN RUSSIA BY LATE IN THE
WEEKEND. THIS WILL KEEP NORTHERLY/NORTHWESTERLY FLOW ALOFT OVER THE
AREA. BY TUESDAY THE LOW WILL HAVE MOVED FAR ENOUGH WEST THAT AN
UPPER LOW MAY CARVE OUT OVER SOUTHERN ALASKA AND THE NORTHERN GULF.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING 176.
FIRE WEATHER...NONE.

LUDWIG APR 13