Small Craft Advisory 179, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
425 PM AKST TUE FEB 23 2016

.ANALYSIS AND UPPER LEVELS...

AN ACTIVE WEATHER PATTERN CONTINUES AROUND A LARGE CONSOLIDATED
ANCHOR LOW CENTERED 400 MILES SOUTH OF THE ALASKA PENINSULA. THE
MOST ACTIVE AND IMPACTFUL QUADRANT OF THIS COMPLEX LOW IS THE
NORTHEASTERN QUADRANT WITH A TRAIN OF WEATHER DISTURBANCES MOVING
FROM THE EASTERN PACIFIC NORTH TOWARD THE GULF AND SOUTHERN
ALASKA.

WEATHER RADAR HAS SHOWN SCATTERED SHOWER ACTIVITY TRANSITIONING TO
WIDESPREAD RAIN AS IT MOVES TO THE NORTHERN AND WESTERN GULF
COAST AS THE NEXT STRONG DISTURBANCE MOVES THROUGH. WITH THE
700-MB JET STREAKS DISPLACED A LITTLE TO THE NORTH OF THE 500-MB
AND 850-MB JET STREAKS AND WITH AN ONGOING LOW-STABILITY ENVIRONMENT
OVER THE GULF...WE ARE SEEING A LITTLE BIT OF SPILLOVER PRECIPITATION
ONTO THE WESTERN SLOPES OF THE KENAI AND CHUGACH MOUNTAIN RANGES.
HOWEVER...WITH FAIRLY DECENT DOWN-INLET FLOW PROVIDING A CONTINUAL
SOURCE OF DRY AIR IN THE LOWER LEVELS...MOST OF THE PRECIPITATION
IS NOT REACHING THE GROUND.

WITH THE APPROACHING FRONT TOWARD THE NORTH GULF COAST...EAST
WINDS CONTINUE TO INCREASE TO STORM-FORCE STRENGTH FOR THE
NORTHERN GULF AND INNER WATERS FROM LOWER COOK INLET THROUGH THE
BARREN ISLANDS TO SHELIKOF STRAIT. THESE WINDS WILL DIMINISH FIRST
TOWARD THE INNER WATERS THIS EVENING AND THEN WEDNESDAY MORNING
ALONG THE NORTH GULF COAST AS THE FRONT MOVES INLAND.

&&

.MODEL DISCUSSION...

MODELS ARE IN GENERALLY GOOD AGREEMENT WITH THE BROAD-SCALE
PATTERN. THE DIFFERENCES ARISE WITH THE TIMING AND EXACT STORM
TRACKS OF THE TRAIN OF SYSTEMS MOVING FROM THE EASTERN PACIFIC
NORTH TO THE GULF COAST...AS WELL AS THE STRENGTH OF THE WINDS AS
THEY APPROACH THE GULF COAST FAVORED BARRIER-JET AREAS.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

A STRONG STORM FORCE FRONT IS PUSHING INTO THE NORTHERN GULF COAST
AS EVIDENCED BY THE MIDDLETON RADAR AND BUOYS ACROSS THE GULF.
THIS IS SPREADING HEAVY PRECIPITATION ACROSS COASTAL LOCATIONS
WITH SOME LOCAL LIGHT PRECIP ACROSS THE WESTERN KENAI...AND A FEW
FLURRIES ACROSS ANCHORAGE. THE FRONT WILL MOVE TO THE COAST THEN
STALL TONIGHT BEFORE SLOWLY WEAKENING THROUGH WEDNESDAY EVENING.
A SERIES OF WEAKER LOWS ALONG THE BASE OF THE MAIN TROUGH WILL
SWING NORTH INTO SOUTHCENTRAL WEDNESDAY EVENING AND
THURSDAY...BRINGING SLIGHT CHANCES OF PRECIP TO INLAND
LOCATIONS...ALTHOUGH ANY INLAND PRECIPITATION WILL BE LIGHT.
STRONG EASTERLY WINDS WILL ACCELERATE DOWN TURNAGAIN ARM AND
THROUGH PORTAGE VALLEY AND PASSAGE CANAL THROUGH TOMORROW BEFORE
DIMINISHING AS THE FRONT WEAKENS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...

THE FRONT IS MOVING INTO SOUTHWEST MAINLAND ALASKA THIS AFTERNOON
AND BRINING GUSTY WINDS AND WARMER TEMPERATURES WITH IT. THERE
WILL BE A BIT OF DOWNSLOPE WEST OF THE ALASKA AND ALEUTIAN RANGES
SO PRECIPITATION WILL BE LIMITED. THERE IS A BETTER CHANCE OF
PRECIPITATION WEST OF KING SALMON IN THE BRISTOL BAY ZONE AS THE
DOWNSLOPE WILL BE LESS. AREAS CLOSER TO BETHEL WILL LIKELY REMAIN
COLD ENOUGH TO REMAIN SNOW FOR UNTIL WEDNESDAY AFTERNOON. HOWEVER
THERE ARE LOW QPF VALUES THAT FAR WEST SO SNOWFALL...WHILE LIKELY
TO OCCUR...WILL BE OF LIMITED AMOUNTS.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

THE FAR EASTERN BERING SEA WILL BE WARMING UP SOME WITH THE FRONT
MOVING INTO THE REGION. THIS FRONT WILL STALL TOMORROW AS IT
MOVES WESTWARD. THIS WILL BRING A CHANCE FOR SOME BLOWING SNOW TO
THE PRIBILOF ISLANDS AS THERE SHOULD BE NORTHWEST FLOW KEEPING
THEM COLD ENOUGH FOR SNOW. THE HIGHEST AMOUNTS OF SNOW WILL LIKELY
REMAIN EAST OF THAT AREA SO THE VISIBILITIES SHOULD NOT BE REDUCED
OVERLY LOW IN ANY BLOWING SNOW THAT OCCURS THERE.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
FORECAST THINKING THROUGH EARLY NEXT WEEK REMAINS LARGELY
UNCHANGED AS RIDGING OVER WESTERN CANADA AND THE NORTH PACIFIC
LONGWAVE TROUGH HELP TO STEER A SERIES OF LOWS TOWARDS THE ALASKA
PENINSULA. THIS WILL KEEP BROAD ONSHORE FLOW AND ASSOCIATED
PRECIPITATION FOCUSED ALONG THE GULF COAST THROUGH MUCH OF THE
NEXT WEEK WHILE INLAND AREAS IN THE LEE OF THE COASTAL RANGES STAY
RELATIVELY DRY AS A RESULT OF PERSISTENT DOWNSLOPE FLOW. THE BEST
CHANCES FOR SHOWERS OVER THE COOK INLET AND MAT-SU REGIONS WILL
COME AS INDIVIDUAL DISTURBANCES PUSH INLAND LATE THIS WEEK AND
AGAIN TOWARDS THE BEGINNING OF NEXT WEEK. MEANWHILE...THE BERING
WILL REMAIN IN A FAIRLY BENIGN SHOWERY REGIME ON THE NORTHERN
PERIPHERY OF THE LONGWAVE TROUGH AS ALL OF THE UPPER LEVEL JET
ENERGY REMAINS WELL SOUTH OF THE ALEUTIAN CHAIN. THE LOWS
APPROACHING THE AKPEN WILL BRING THE OCCASIONAL POTENTIAL FOR
STRONGER WINDS AND HEAVIER PRECIPITATION TO PORTIONS OF THE
SOUTHEAST BERING.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM WARNING 119 120 125 130 131.
 GALE WARNING 129 132 136 137 138 139 140 150 155 160 165 170 171
172 173 174 179 180 185.
 HEAVY FRZ SPRAY 185.

&&

SYNOPSIS AND MODEL DISCUSSION...CC
SOUTHCENTRAL ALASKA...JA
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...EZ
LONG TERM...CB