Small Craft Advisory 52, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST WED JAN 16 2013

.ANALYSIS AND UPPER LEVELS...THE STRONG LOW SOUTHWEST OF ATTU IS VERY
SLOWLY BUT STEADILY WEAKENING AND HAS HALTED MOST OF ITS
NORTHEASTWARD PROGRESS AS IT PUSHES INTO AN UPPER LEVEL RIDGE OVER
THE NORTHEAST BERING SEA. THE LOW SHOULD CONTINUE TO WEAKEN AND MOVE
ON A WESTERLY COURSE BACK TOWARD THE KAMCHATKA PENINSULA THROUGH
FRIDAY.
AN UPPER LEVEL TROUGH OVER SOUTHWEST AND SOUTH CENTRAL ALASKA AS WELL
AS AN ELONGATED FRONTAL BAND STRETCHING FROM THE WESTERN GULF THOUGH
SOUTH CENTRAL ALASKA IS PROVIDING PLENTY OF MOISTURE AND LIFT OVER
SOUTH CENTRAL ALASKA TODAY.

.MODEL DISCUSSION...MODELS ARE DOING WELL IN THE SHORT TERM AND HOLD
ON TO A REASONABLE OVERALL SOLUTION THROUGH THE WEEKEND. THERE ARE
SOME SIGNIFICANT DIFFERENCES ON HOW TO HANDLE A LOW THAT WILL DEVELOP
ALONG A FRONTAL BAND SOUTH OF THE EASTERN ALEUTIANS THURSDAY AND MORE
TO THE NORTH. THE NAM AND ECMWF MODELS BOTH DEVELOP MULTIPLE LOWS
ALONG THIS FRONT...ALTHOUGH IN DIFFERENT LOCATIONS. THE GFS
CONSOLIDATES THE ENERGY INTO ONE STRONGER LOW IN A CENTRAL LOCATION
ALONG THE FRONT...BUT THIS SEEMS TO BE THE LEAST LIKELY SOLUTION.
THE ALASKA PENINSULA THROUGH THE CENTRAL ALEUTIANS AND NORTHWARD TO
THE PRIBILOF ISLANDS WILL BE THE AREAS MOST AFFECTED BY THE DIFFERING
SOLUTIONS.

.SHORT TERM FORECAST...WHILE THE PRINCE WILLIAM SOUND THROUGH THE
COPPER RIVER BASIN IS GETTING GOOD SNOW AMOUNTS AS EXPECTED THE AREAS
IN THE COOK INLET REGION THROUGH SUSITNA VALLEY ARE GETTING A LITTLE
MORE THAN ANTICIPATED FROM YESTERDAY. IT LOOKS LIKE WEAK COLD
ADVECTION FROM THE WEST HAS EXPANDED THE AREA OF OPTIMAL LIFT IN THE
REGION TO INCLUDE THE KENAI PENINSULA AND NORTHWARD. THIS SHOULD
TAPER OFF FROM THE INTO SCATTERED SNOW SHOWERS THIS AFTERNOON THROUGH
OVERNIGHT. A QUESTION FOR THE ANCHORAGE THROUGH MAT-SU AREA IS HOW
LONG THIS SNOW WILL LINGER. THERE IS A POSSIBILITY THAT THE DYNAMICS
WILL KEEP FAVORABLE LIFT OVER ANCHORAGE THROUGH THE MAT-SU VALLEY FOR
MOST OF THE EVENING AND LIGHT SNOW COULD LINGER IN THE AREA FOR MOST
OF THE NIGHT. THE BULK OF THE SNOW SHOULD OCCUR BY EARLY EVENING BUT
THERE IS A CHANCE OF IT LINGERING FOR A WHILE LONGER IN THIS PATTERN.

A SIGNIFICANT AMOUNT OF COLD AIR HAS MOVED INTO SOUTHWEST ALASKA
TODAY UNDER THE UPPER LEVEL TROUGH AND WEAK SURFACE RIDGE. THE RIDGE
IS ALLOWING FOR PARTIAL CLEARING IN SOUTHWEST ALASKA. THIS COLD AIR
WILL SLOWLY FILTER INTO SOUTH CENTRAL ALASKA OVER THE NEXT DAY OR
TWO.

THE FRONT EXTENDING FROM THE LARGE LOW SOUTHWEST OF ATTU IS SLOWLY
WEAKENING BUT WILL CONTINUE TO CREATE STRONG WINDS IN THE CENTRAL AND
WESTERN ALEUTIANS INTO THURSDAY.

.LONG TERM FORECAST...THE COMPLEX UPPER LOW OVER THE BERING
SEA/ALEUTIAN CHAIN COUPLED WITH A RIDGE IN THE GULF SHOULD DIRECT
STORMS TOWARDS THE SOUTHERN MAINLAND PART OF THE STATE. THE RESULTING
SOUTHERLY FLOW FROM THE PACIFIC SHOULD LEAD TO SLIGHTLY WARMER THAN
AVERAGE TEMPERATURES AND AN OVERALL ACTIVE PATTERN INTO NEXT WEEK.

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

JAN 13