Small Craft Advisory 285, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKDT SAT MAR 30 2013

.ANALYSIS AND UPPER LEVELS...THE UPPER LEVELS ARE IN THE PROCESS OF
TRANSITIONING INTO A BLOCKING PATTERN OVER THE WESTERN HALF OF THE
STATE AS THE UPPER LEVEL RIDGE IN THE EASTERN BERING SEA CONTINUES TO
AMPLIFY AND PUSH EASTWARD THE UPPER LEVEL TROUGH OVER THE MIDDLE OF
THE STATE. THE STRONG UPPER LEVEL LOW IS NEAR THE KAMCHATKA PENINSULA
AND IT WILL STAY IN THAT REGION THROUGH THE WEEKEND.
AT THE SURFACE THERE IS A STRONG RIDGE OVER THE EASTERN BERING SEA
WHICH IS BLOCKING THE EASTWARD PROGRESSION OF A FRONT IN THE CENTRAL
BERING. EAST OF THIS RIDGE THE FEATURES ARE RATHER WEAK WITH A LOW
SOUTH OF KODIAK THAT WILL DISSIPATE BY SUNDAY MORNING AND A SMALL
CIRCULATION IN COOK INLET.

.MODEL DISCUSSION...MODELS ARE HANDLING THE PATTERN SHIFT WELL
OVERALL. THERE IS GOOD AGREEMENT IN THE OVERALL PATTERN WITH A FEW
LOCAL ISSUES STANDING OUT. THE FIRST IS WITH THE MOVEMENT OF A WEAK
LOW THAT WILL DEVELOP IN THE SOUTHERN GULF OF ALASKA TOMORROW. THIS
LOW WILL MOVE NORTHWARD TO THE COAST BUT SOLUTIONS VARY AS TO HOW FAR
EAST IT WILL GO. THE GFS AND NAM BOTH MOVE IT ON SHORE NEAR ICY BAY
WITH THE UKMET FARTHER WEST AND ECMWF FARTHER EAST. THE HIGHER
RESOLUTIONS OF THE GFS/NAM LIKELY ARE HELPING THOSE MODELS RESOLVE
THE IMPACT OF THE COLDER AIR FROM OUTFLOW WINDS AND HOW THEY WILL
IMPACT THE LOWS COURSE. THEREFORE THE NAM AND GFS ARE PREFERRED
MODELS FOR THE GULF REGION ON SUNDAY.
IN THE BERING SEA THERE WILL BE A LOW DEVELOPING ALONG THE FRONT
TONIGHT WHICH WILL THEN MOVE NORTHWARD THROUGH MONDAY. THIS
DEVELOPING LOW IS CAUSING MORE ISSUES FOR THE MODELS THAT THE ONE IN
THE GULF. THE BEST TRACK FOR THIS LOW APPEARS TO COME FROM THE ECMWF
WITH THE NAM LAGGING TOO FAR BEHIND WITH THE SPEED OF ITS MOVEMENT.
THE MODELS ARE ALL IN VERY GOOD AGREEMENT WITH THE STRONG LOW THAT
WILL MOVE SOUTH OF THE ALEUTIANS MONDAY THROUGH TUESDAY.

.SHORT TERM FORECAST...THE WEAK LOW IN COOK INLET AND A SHORT WAVE IN
THE NORTHERN GULF OF ALASKA ARE BRINGING SOME RAIN AND SNOW SHOWERS
TO SOUTH CENTRAL ALASKA THIS AFTERNOON. SHOWERS SHOULD DIMINISH
OVERNIGHT AS THESE FEATURES FURTHER WEAKEN AS HIGH PRESSURE BECOMES
MORE PRONOUNCED OVER THE MAINLAND PART OF THE STATE TOMORROW.
THE NORTH GULF COAST WILL BE A BIT OF AN EXCEPTION AS SOUTHERLY FLOW
ALOFT WILL PERSIST FROM PRINCE WILLIAM EASTWARD. THIS WILL KEEP RAIN
AND SNOW SHOWERS ALONG THE COAST THROUGH THE WEEKEND.
A WEAK LOW IN EASTERN BRISTOL BAY IS KEEPING SOME RAIN AND SNOW
SHOWERS AROUND THAT AREA AS WELL. TEMPERATURES ALOFT IN THAT AREA ARE
COOL AND THAT IS ALSO HELPING CREATE SOME CONVECTIVE LIFT AND
ENHANCING THE SHOWERS. THIS LOW WILL DIMINISH OVERNIGHT AND REMAINING
SHOWERS SHOULD BE TAPERING OFF THROUGH SUNDAY.
A COLD FRONT IN THE CENTRAL BERING SEA WILL SLOWLY MOVE EASTWARD
THROUGH SUNDAY NIGHT. PRECIPITATION AHEAD OF THIS FRONT WILL BE A
RAIN AND SNOW MIXTURE AND THERE IS ENOUGH WARM AIR AHEAD OF THIS
FRONT TO MAKE ANY BLOWING SNOW IN THE ALEUTIANS OF PRIBILOF ISLANDS
UNLIKELY.

.LONG TERM FORECAST...THE KAMCHATKA UPPER LEVEL LOW WILL RETROGRADE
OVER SIBERIA AND CAUSE STRONG RIDGING OVER THE BERING SEA AHEAD OF
THE POTENT ALEUTIAN LOW EARLY NEXT WEEK. MOST OF THE ACTIVE WEATHER
WILL REMAIN OVER AND SOUTH OF THE ALEUTIANS WHILE DRY AND CLEAR
CONDITIONS WILL REMAIN OVER MOST OF THE MAINLAND. THE BIG QUESTION
WILL BE HOW MUCH COLD AIR SETTLES INTO THE EASTERN INTERIOR/COPPER
RIVER BASIN AFFECTING THE STRENGTH OF THE ENSUING OUTFLOW WINDS ALONG
THE GULF COAST.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 172 175 179 185.
FIRE WEATHER...NONE.

MAR 13

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1220 PM AKDT SAT MAR 30 2013

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1100 AM     SNOW             UPPER HILLSIDE          61.10N 149.72W
03/26/2013  M23.5 INCHES                        AK   NWS SPOTTER

            STORM TOTAL ACCUMULATION THROUGH WEEKEND.
            DELAYED REPORT

1100 AM     SNOW             GLEN ALPS               61.10N 149.69W
03/26/2013  M 28.0 INCHES                       AK   NWS SPOTTER

            STORM TOTAL ACCUMULATION THROUGH WEEKEND.
            DELAYED REPORT

&&

CB