Small Craft Advisory 164, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM AST THU FEB 15 2007

.DISCUSSION...
FAIRLY WEAK FLOW ALOFT OVER ALASKA AND THE BERING SEA THIS MORNING.
THERE IS A BROAD TROUGH THAT STRETCHES FROM KAMCHATKA TO ABOUT
YAKUTAT. A RIDGE OVER THE ARCTIC OCEAN NORTH OF EASTERN SIBERIA
AND ALASKA EXTENDS A WEAK ARM SOUTHEASTWARD ACROSS ALASKA INTO THE
YUKON. THE JET STREAM AND ASSOCIATED STORM TRACK LEAVES ASIA NEAR
JAPAN AND DIPS SOUTH OF 30 NORTH LATITUDE NEAR THE DATE LINE THEN
CURVES NORTHEASTWARD TO REACH NORTH AMERICA CENTERED AT ABOUT
VANCOUVER ISLAND. THREE WEAK UPPER LOWS ARE AFFECTING THE AREA...ONE
OVER THE WESTERN BERING SEA...ONE SOUTH OF COLD BAY...AND ONE OVER
SOUTH CENTRAL AND SOUTHWEST ALASKA. ALL OF THESE ARE MOVING VERY
SLOWLY AND PRODUCING MINIMAL WEATHER (BY ALASKAN STANDARDS).

THINGS WILL START TO GET MORE INTERESTING BEGINNING FRIDAY. AN
ENERGETIC SHORT WAVE JUST EAST OF JAPAN WILL SPIN UP A DEEP LOW THAT
WILL CROSS THE CENTRAL AND WESTERN ALEUTIANS THEN INTO THE BERING
SEA EARLY SATURDAY. THIS LOW IS STRONG ENOUGH THAT IT WILL BECOME A
STEERING LOW...STEERING THE JET STREAM NORTHWARD TOWARDS ALASKA. BY
LATE SATURDAY A SYSTEM WILL BEGIN AFFECTING SOUTHWEST ALASKA...AND
THEN SOUTH CENTRAL ON SUNDAY.

BY EARLY NEXT WEEK A FULL FLEDGED PATTERN CHANGE WILL BE WELL UNDER
WAY. THE MEAN LOW POSITION WILL MOVE INTO THE NORTHERN GULF MONDAY
AND TUESDAY...AND A DEEP UPPER LOW WILL CARVE OUT OVER THE STATE.
FLOW BY MID WEEK WILL BE HIGHLY AMPLIFIED...WITH A DEEP LOW OVER
EASTERN AND CENTRAL ALASKA AND A SHARP RIDGE OVER THE EASTERN
BERING SEA...WITH ANOTHER DEEP LOW JUST WEST OF THE ALEUTIANS. THE
NUMERICAL MODELS ARE STRUGGLING WITH THE POSITIONS OF THESE
FEATURES...BUT THE ENSEMBLE MEAN HOLDS THE TROUGH OVER THE STATE
LONGER THAN THE OPERATIONAL MODELS...AND THIS SEEMS REASONABLE.

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

LUDWIG FEB 07