Small Craft Advisory 294, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
428 PM AKDT FRI APR 3 2015

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL PATTERN HAS THE UPPER LEVEL LOW IN THE SOUTHEAST
GULF MOVING SLOWLY SOUTHEASTWARD AS AN UPPER LEVEL RIDGE BUILDS
OVER SOUTHWEST MAINLAND ALASKA. THE JET STREAM AT 250 MB IS RIDING
OVER THE TOP OF THIS RIDGE WITH A GOOD JET STREAK OVER THE WESTERN
GULF OF ALASKA THIS AFTERNOON. THIS WILL MOVE EASTWARD OVERNIGHT
AND KEEP GUSTY OUTFLOW WINDS ALONG THE NORTH GULF COAST THROUGH
SATURDAY MORNING. AT THE SURFACE THERE IS A STRONG HIGH PRESSURE
OVER MAINLAND ALASKA WITH A WEAK TROUGH ALONG THE NORTH GULF COAST.
THIS TROUGH IS ALSO SIGNIFICANT IN KEEPING THESE STRONG OUTFLOW
WINDS ALONG THE NORTH GULF COAST. FARTHER WEST A STRONG LOW IN THE
CENTRAL BERING SEA IS PUSHING A FRONT INTO SOUTHWEST ALASKA TONIGHT.
THIS LOW IS THE FIRST IN A NUMBER OF LOWS THAT WILL MOVE THROUGH
THE BERING SEA THROUGH THE MIDDLE OF NEXT WEEK.

&&

.MODEL DISCUSSION...
MODELS ARE ALL IN GOOD AGREEMENT DEALING WITH THE PATTERN CHANGE
THAT WILL BE OCCURRING OVER THE STATE THIS WEEKEND. THE OVERALL
PATTERN WILL BECOME MORE PROGRESSIVE NEXT WEEK WITH FEATURES MOVING
QUICKLY ACROSS THE BERING SEA TO MAINLAND ALASKA.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (TONIGHT THROUGH SUN NIGHT)...
MOSTLY CLEAR SKIES ARE EXPECTED TO CONTINUE THROUGH SATURDAY AFTERNOON
BEFORE AN AREA OF LOW PRESSURE MOVES FROM BRISTOL BAY INTO THE WESTERN
GULF OF ALASKA. IN THE MEAN TIME...AN UPPER LEVEL TROUGH WELL DEPICTED
ON WATER VAPOR IMAGERY WILL SLIDE EASTWARD TOWARD THE COPPER RIVER
BASIN THIS EVENING. MODELS HAVE PROGGED DECENT OMEGA AHEAD OF THE
UPPER TROUGH...WITH LIGHT SNOW LIKELY BY LATE THIS EVENING EAST OF
THE RICHARDSON HIGHWAY IN THE COPPER RIVER BASIN. THIS LIGHT SNOW
IS EXPECTED TO CONTINUE INTO SATURDAY AFTERNOON BUT ACCUMULATION
WILL BE LIGHT.

MODELS HAVE HAD A HARD TIME RESOLVING THE LOW AS IT PUSHES FROM
BRISTOL BAY INTO THE WESTERN GULF LATE SATURDAY. IN THE PAST 24
HOURS MODELS HAVE SWITCHED FROM MOSTLY CLEAR SKIES TO NOW A DECENT
SHOT OF PRECIPITATION. IT APPEARS THAT A SHORTWAVE TROUGH WILL
PUSH ACROSS SOUTHCENTRAL ALASKA LATE SATURDAY NIGHT INTO EASTER
SUNDAY MORNING WHICH WILL LIKELY BE MORE THAN ENOUGH TO SPARK SNOW
SHOWERS ACROSS THE ANCHORAGE AND MATANUSKA VALLEY BEFORE PUSHING
INTO THE COPPER RIVER VALLEY. SNOW WILL BE LIGHT AND BRIEF AS THE
TROUGH QUICKLY SLIDES EAST BUT THE ANCHORAGE HILLSIDE AND PARTS
OF THE MATANUSKA VALLEY COULD SEE AN INCH OR TWO OF SNOWFALL...WITH
THE ANCHORAGE BOWL LIKELY SEEING JUST A LIGHT DUSTING.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE FRONTAL SYSTEM SWINGING ACROSS THE BERING SEA WILL REACH THE
WEST COAST OF SOUTHWEST ALASKA AROUND MIDNIGHT WITH SNOW SPREADING
INLAND THROUGH SATURDAY MORNING. BREEZY CONDITIONS ALONG THE COAST
HAVE THE POTENTIAL TO CREATE SOME AREAS OF BLOWING SNOW BUT WITH
LACK OF SNOW CURRENTLY ON THE GROUND AND TEMPERATURES WARMING AS
THE EVENT CONTINUES THINK VISIBILITIES WILL STAY WELL ABOVE ADVISORY
LEVELS. QPF AMOUNTS CURRENTLY LOOK HIGHEST FOR THE KUSKOKWIM DELTA
WITH THE POTENTIAL FOR 3 TO 5 INCHES BETWEEN LATE TONIGHT AND
SATURDAY MORNING.

BY THE TIME THE FRONT MAKES IT INLAND IT WILL BE WEAKENING WITH
AN INCH OR TWO POSSIBLE OUT OF IT AND THE SNOW SHOWERS WHICH FOLLOW.
SNOW SHOWERS WILL TAPER OFF SATURDAY NIGHT FOR A BRIEF BREAK BEFORE
THE NEXT FRONTAL SYSTEM ARRIVES SUNDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE LOW CURRENTLY IN THE BERING WILL LIFT NORTH TONIGHT AS THE
ASSOCIATED FRONTAL SYSTEM SLIDES EAST. THE NEXT INBOUND SYSTEM
WILL REACH THE WESTERN ALEUTIANS SATURDAY AFTERNOON AND THEN
RAPIDLY DEEPEN AS IT CROSSES INTO THE BERING SATURDAY NIGHT AND
SUNDAY. WITH STRONG JET SUPPORT AND A SHARP UPPER TROUGH SWINGING
IN FROM THE WEST BRINGING IN SOME RATHER COLD AIR ALOFT...THINK
THE STRENGTHENING TREND IN THE MODELS IS RIGHT ON AND FAIRLY BROAD
AREA OF STORMS TO THE SOUTH OF THE LOW IS A GOOD POTENTIAL.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
AS THE UPPER LEVELS SETTLE INTO A PROGRESSIVE PATTERN...TWO
SYSTEMS WILL MOVE STEADILY ACROSS OUR FORECAST AREA SUN NIGHT
THROUGH FRIDAY. THE FIRST WILL BE A BERING LOW AND ASSOCIATED
FRONT THAT AFFECTS WESTERN AK SUN NIGHT INTO TUE...AND
SOUTHCENTRAL PRIMARILY SUN INTO MON...BUT LINGERS ALONG THE GULF
COAST INTO THU. THE SECOND SYSTEM WILL BE A FRONT THAT SWEEPS
ACROSS THE ALEUTIANS MON NIGHT THROUGH WED...WESTERN AK WED AND
THU...AND WHICH THEN SPAWNS A TRIPLE POINT LOW ON THU THAT MOVES
NEAR THE KENAI ON FRI. THERE IS INCREASING CONFIDENCE WITH THE
FIRST SYSTEM AS THE EC AND GFS ARE IN GOOD AGREEMENT. THE FORECAST
UTILIZES SOME EC THROUGH WED...AND THEN DEFERS TO WPC THROUGH FRI
AS THE SPEED OF SYSTEMS MOVING THROUGH NEAR ZONAL FLOW IS BEST
HANDLED BY AN ENSEMBLE APPROACH.

THE FIRST SYSTEM WILL BRING RAIN AND SNOW TO THE ALEUTIANS AND SW
AK INTO TUE AND RAIN ALONG THE GULF COAST WITH A MIX INLAND EARLY
NEXT WEEK. THE SECOND SYSTEM IS FORECAST TO BE COLDER...WITH A
BETTER CHANCE OF SNOW MOVING INTO SW AK WED INTO THU. FOR SOUTHCENTRAL
RAIN IS EXPECTED ALONG THE GULF COAST. THESE SCENARIOS HAVE A TENDENCY
TO WARM WITH SUBSEQUENT MODEL RUNS...BUT FOR NOW...SOME SNOW FOR
INTERIOR AREAS OF SOUTHCENTRAL REMAINS A POSSIBILITY LATE NEXT WEEK.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING 170 173 174 175 176 177 178 179 180 181 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...MC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
LONG TERM...DS