Gale Warning 861, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
444 PM AKST WED DEC 30 2015

.ANALYSIS AND UPPER LEVELS...
UPPER LEVEL ANALYSIS TODAY SHOWS A STRONG BLOCKING RIDGE OVER
WESTERN CANADA AND EASTERN ALASKA WITH A DEEP UPPER LOW OVER THE
CENTRAL BERING AND NORTHERN PACIFIC. A 110KT JET STREAK IS
CURRENTLY MOVING OUT OF THE TROUGH INTO THE RIDGE...CAUSING THE
PATTERN TO SHIFT SLIGHTLY EASTWARD. THIS MERIDIONAL FLOW IS
EXPECTED TO CONTINUE OVER THE NEXT FEW DAYS AS THE STRONG RIDGE
REMAINS IN PLACE.

AT THE SURFACE A 955 MB LOW LIES JUST NORTHWEST OF THE KUSKOKWIM
DELTA. THIS LOW MOVED IN VERY QUICKLY FROM THE NORTH PACIFIC
OVERNIGHT AS IT WAS SUPPORTED BY THE STRONG JET ALOFT. AS IT MOVED
NORTHWARD IT RAPIDLY STRENGTHENED ALTHOUGH AT THIS POINT IT HAS
REACHED ITS MAX STRENGTH AND WILL BEGIN TO WEAKENED AS THE UPPER
LEVEL SUPPORT MOVES INTO THE RIDGE. THIS LOW IS EXPECTED TO MOVE
INTO THE BERING STRAIT AND WILL BECOME LESS OF AN ISSUE FOR THE
SOUTHERN PORTION OF THE STATE LATER TODAY. THE ACCOMPANYING FRONT
WAS ALSO IMPRESSIVELY STRONG...WITH RAPID CHANGES AHEAD AND BEHIND
THE FRONT. THESE PRESSURE CHANGES...COMBINED WITH A SIGNIFICANT
LOW LEVEL JET AND CHANNELED TERRAIN...BROUGHT VERY STRONG AND
GUSTY WINDS TO MOST OF THE ANCHORAGE FORECAST AREA...INCLUDING
BOTH SOUTHCENTRAL AND SOUTHWEST ALASKA. THE FRONT HAS PASSED
THROUGH MOST OF THE AREA THIS MORNING AND WINDS ARE SWITCHING TO A
MORE SOUTHERLY FLOW AND RAPIDLY WEAKENING.

SATELLITE INDICATES THAT ALTHOUGH THIS MAIN SYSTEM HAS PASSED
THERE ARE SEVERAL DEVELOPING TROUGHS IN THE NORTH PACIFIC ALONG
THE SAME PATH. AT THIS TIME THEY ARE EXPECTED TO REMAIN ALONG THE
SAME TRAJECTORY...ALTHOUGH NOT AS STRONG AS THE SYSTEM THAT PASSED
THROUGH TODAY. REGARDLESS...AS LONG AS THE UPPER LEVEL JET
MAINTAINS SOUTHERLY FLOW OVER THE MAINLAND THE WEATHER PATTERN
WILL CONTINUE TO BE QUITE ACTIVE FOR MOST PARTS OF THE FORECAST
AREA.

&&

.MODEL DISCUSSION...
IN GENERAL THE MODEL CONSISTENCY ON HANDLING THE SYSTEM CURRENTLY
IN THE BERING SEA HAS BEEN GOOD OVER THE PAST FEW DAYS. THE GFS
HAS BEEN MOST CONSISTENT OVERALL AND HAS HANDLED THE TIMING AND
STRENGTH OF THE ASSOCIATED FRONT VERY WELL AND WAS CHOSEN FOR
TODAYS FORECAST. THE MODELS CONTINUE TO BE IN PRETTY GOOD
AGREEMENT ON A SECOND TROUGH MOVING NORTHWARD WEDNESDAY
AFTERNOON...HOWEVER A DEVELOPING SYSTEM IN THE BASE OF THE
LONGWAVE TROUGH IN THE NORTH PACIFIC SEEMS TO BE CAUSING SOME
GRIEF. THIS SYSTEM...CURRENTLY ANALYZED NEAR 978 MB...WILL
CONTINUE TO STRENGTHEN AS IT MOVES EASTWARD BEFORE TURNING TOWARDS
THE NORTH ON THURSDAY MORNING. THERE IS SOME DISPARITY BETWEEN THE
MODELS ON THIS SYSTEM IN BOTH STRENGTH AND LOCATION...WITH THE
NAM BEING FURTHEST EAST AND WEAKEST PRESSURE. GIVEN THE FACT THAT
IT DIFFERS SO GREATLY...GFS CONTINUES TO BE THE MODEL OF CHOICE
FOR THE SHORT TERM. HOWEVER WITH THE DISPARITY IN SOLUTIONS...CONFIDENCE
ON THAT LOW...EXPECTED TO BEGIN AFFECTING ALASKA ON FRIDAY...IS
MODERATE AT BEST.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE MAIN ISSUE CONTINUES TO BE THE STRONG GRADIENTS AND STRONG
WARM MOIST ADVECTION INTO THE SOUTHERN MAINLAND AROUND THE STORM
THAT PASSED ACROSS THE ALASKA PENINSULA LAST NIGHT. A 100 PLUS
KNOT DUE SOUTH JET IS FOCUSED ON THE KENAI PENINSULA. THE FRONT
ASSOCIATED WITH THE STRONG BRISTOL BAY STORM HAS PUSHED ACROSS THE
SOUTHERN COAST AND INLAND WITH A CONTINUED WARM MOIST SOUTHERLY
FLOW BEHIND THE FRONT. THE NEXT STORM TO IMPACT THE GULF OF ALASKA
AND SOUTHERN MAINLAND IS A RAPIDLY MOVING LOW THAT IS NOW OVER
700 MILES SOUTH OF KODIAK ISLAND. AS THIS LOW DISSIPATES TO A
TROUGH AS IT CROSSES KODIAK ISLAND THIS EVENING ANOTHER SHOT OF
STRONG WINDS IS EXPECTED ALONG THE NORTH GULF COAST AND ACROSS
SOUTH CENTRAL ALASKA TONIGHT. HOWEVER THIS SHOT OF WIND WILL NOT
BE NEARLY AS STRONG AS THE HIGH WINDS THAT BLEW THROUGH THE REGION
LAST NIGHT AND THIS MORNING.

COLDER AIR IS WRAPPING IN AROUND THE LOW BEHIND THE FRONT THAT
SHOULD RESULT IN ENOUGH COOLING TO HAVE A MIX OF SNOW INTO THE
RAIN SHOWERS BEHIND THE FRONT...THOUGH TEMPERATURES WILL REMAIN
WARM ENOUGH TO INHIBIT ANY SNOW ACCUMULATIONS AT THE LOWER
ELEVATIONS. THE ONLY AREA THAT SHOULD SEE COLD ENOUGH AIR TO THE
SURFACE TO SUPPORT SOME SNOW ACCUMULATION WILL BE THE NORTHERN
SUSITNA VALLEY AND NORTHERN COPPER RIVER BASIN.

&&

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

THE POWERFUL LOW WHICH PASSED THROUGH THE REGION TODAY WILL
QUICKLY MOVE OFF TO THE NORTH...WITH DIMINISHING WINDS AS THE
PRESSURE GRADIENT WEAKENS. ANOTHER MUCH WEAKER NORTH PACIFIC LOW
WILL MOVE INTO THE BRISTOL BAY REGION TONIGHT THEN THE LOWER
KUSKOKWIM VALLEY TOWARD THE MORNING HOURS...BRINGING RAIN AND
SNOW AND BREEZY EASTERLY WINDS. BRIEF DRYING WILL DEVELOP THURSDAY
EVENING BEFORE ANOTHER FRONT MOVES IN FRIDAY AFTERNOON AND
EVENING...WITH INCREASING NORTHEAST WINDS AND MORE PRECIPITATION
CHANCES.

&&

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

BROAD LOW PRESSURE WILL ENCOMPASS THE REGION THROUGH FRIDAY...WITH
RAIN AND SNOW SHOWERS ROTATING THROUGH THE AREA...ESPECIALLY
ACROSS THE WESTERN BERING AND ALEUTIANS WHERE COLDER AIR WILL HELP
DESTABILIZE THE ATMOSPHERE. A NORTH PACIFIC LOW AND ASSOCIATED
OCCLUDED FRONT WILL MOVE INTO THE EASTERN BERING ON
FRIDAY...BRINGING STRONGER EASTERLY WINDS AND RAIN AND SNOW.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
AN ACTIVE WEATHER PATTERN CONTINUES THROUGH THE EXTENDED FORECAST
AS A BROAD UPPER TROUGH OVER THE BERING SLIDES FURTHER EAST
THROUGH THE MIDDLE OF NEXT WEEK. MODELS ARE IN GOOD GENERAL
AGREEMENT THAT THE UPPER RIDGE HOLDS OVER THE ALCAN BORDER WHICH
KEEPS THE LONGWAVE TROUGH CENTERED OVER THE BERING. THE LONG RANGE
FORECAST STARTING ON SATURDAY NIGHT BEGINS WITH A STORM SYSTEM
PUSHING A WARM FRONT INLAND ALONG THE SOUTHWEST BRINGING SCATTERED
RAIN AND SNOW SHOWERS INLAND ALONG WITH GUSTY CONDITIONS ALONG
THE BOUNDARY. A WEAKER WAVE FOLLOWS ON SUNDAY AND MOVES ACROSS THE
ALASKA PENINSULA AND WESTERN GULF...THIS WILL BRING ANOTHER ROUND
OF PRECIPITATION. THERE IS A BIT OF UNCERTAINTY ON THE NEXT STORM
SYSTEM THAT TRACKS SOUTH OF THE ALEUTIANS LATE SUNDAY INTO MONDAY.
THIS STORM SHOULD TAKE A NORTHWARD TURN...HOWEVER A DEVELOPING
WAVE LOOKS TO CLOSE OFF A NEW LOW CENTER IN THE EASTERN PACIFIC WHICH
WOULD SLOW THE TRACK OF THE FIRST SYSTEM AS RIDGING OVER THE ALCAN BUILDS
BACK OVER THE SOUTHEAST.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...SNOW ADVISORY 141. HIGH SURF ADVISORY(EVENING) 155.
MARINE...GALE 119 130 131 132 138 150 178 180 181.

&&

SYNOPSIS AND MODEL DISCUSSION...LF
SOUTHCENTRAL ALASKA...SA
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA
LONG TERM...KH