Gale Warning 364, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
140 PM AKDT SUN APR 14 2013

.ANALYSIS AND UPPER LEVELS...
THE DOMINANT FEATURE ACROSS THE ALASKAN DOMAIN THIS MORNING IS A HIGH
AMPLITUDE RIDGE OF HIGH PRESSURE ORIENTED SOUTHEAST-TO-NORTHWEST THAT
STRETCHES FROM THE NORTH PACIFIC ACROSS THE ALASKA PENINSULA AND INTO
THE NORTHERN BERING SEA. A MID-LEVEL SHORTWAVE MOVED THROUGH THE
SOUTHERN MAINLAND OVERNIGHT...BRINGING MID-LEVEL CLOUDINESS TO MOST
AREAS...AND IS NOW MOVING EAST INTO THE PANHANDLE WITH CLEARING SKIES
BEHIND THE FEATURE. A COLD CORE UPPER LOW NEAR THE NORTON PENINSULA
IS ACCELERATING SOUTHWARD ENROUTE TO SOUTHCENTRAL ALASKA. THIS LOW IS
GENERATING AREAS OF LIGHT SNOW ACROSS PARTS OF THE INTERIOR INCLUDING
THE LOWER KUSKOKWIM VALLEY. FURTHER TO THE SOUTH...A COMPLEX BUT WEAK
LOW SOUTH OF THE ALEUTIAN CHAIN IS MAKING SLOW PROGRESS
NORTHWARD...WITH INCREASING CLOUDS ALREADY OCCURRING ACROSS MUCH OF
THE EASTERN BERING SEA AND ALEUTIAN ISLANDS.

.MODEL DISCUSSION...
ALL MODELS INITIALIZED THE CURRENT MAJOR FEATURES WELL. THE MOST
SIGNIFICANT DISCREPANCY RELEVANT TO THE FORECAST IS THE ULTIMATE FATE
OF THE AFOREMENTIONED UPPER LOW CURRENTLY IN THE INTERIOR OF THE
STATE. ALL MODELS CONTINUE A SOUTHEASTWARD MOVEMENT THROUGH MONDAY
AFTERNOON...BRINGING THE CENTER OF THE LOW TO THE COPPER RIVER BASIN.
STARTING MONDAY NIGHT...THE ECMWF MOVES THE LOW DOWN INTO THE
GULF...WHILE THE GFS/NAM/GEMGLB/UKMET INSTEAD RETROGRADE THE LOW INTO
THE WESTERN INTERIOR. THE CONSENSUS SOLUTION WOULD KEEP MORE CLOUDS
ACROSS THE REGION WITH AN INCREASED CHANCE OF DIURNAL SHOWERS OVER
THE MOUNTAINS...WHILE THE ECMWF SOLUTION WOULD LIKELY BRING A BIT
SUNNIER AND DRIER WEATHER. THE FURTHER SOUTH POSITION OF THE ECMWF
WOULD ALSO KEEP A WEAK LOW THAT MOVES UP INTO THE GULF A BIT FURTHER
TO THE SOUTH THAN THE OTHER MODELS...WHICH WILL DETERMINE HOW FAR
WESTWARD RAIN/SNOW WILL SPREAD ALONG THE NORTH GULF COAST ON TUESDAY
NIGHT. THE CURRENT THINKING IS THAT THE AFOREMENTIONED 00Z ECMWF
SOLUTION IS UNREALISTICALLY TOO FAR SOUTH...BUT THAT THE OTHER MODELS
MAY BE A BIT TOO FAR TO THE NORTH...WITH A COMPROMISE SOLUTION MOST
LIKELY.

TAKING A QUICK LOOK AT THE 12Z ECMWF...THE UPPER LOW HAS INDEED MOVED
FURTHER NORTH...BUT NOT AS FAR AS THE OTHER MODELS. THIS RAISES
CONFIDENCE IN THE MIDDLE-GROUND SOLUTION.

.SHORT TERM FORECAST...
SOUTHCENTRAL...SUNNY SKIES HAVE RETURNED AGAIN TO THE REGION BEHIND
THE DEPARTING SHORTWAVE. WIDESPREAD LOW CLOUDINESS WITH LIGHT SNOW
WILL HAVE A VERY HARD TIME CROSSING THE ALASKA RANGE TODAY...WITH
ONLY MID AND HIGH LEVEL CLOUDS ABLE TO CROSS THE RANGE OVERNIGHT.
AHEAD OF THIS...AM EXPECTING SOME DIURNAL CONVECTIVE CLOUDS TO FORM
ALONG THE TALKEETNA AND CHUGACH RANGES LATE THIS AFTERNOON AND AGAIN
TOMORROW AS THE UPPER LOW RACES APPROACHES FROM THE NORTH. NOT
EXPECTING MUCH IN THE WAY OF PRECIP AT ANY LOCATIONS...BUT WILL HAVE
THE EFFECT OF INTRODUCING ADDITIONAL MID-LEVEL MOISTURE TO THE REGION
AND LIKELY RESULT IN MORE CLOUD-COVER THAN IN RECENT DAYS. OFFSHORE
GAP WINDS WILL DIMINISH THIS AFTERNOON AS THE PRESSURE GRADIENT
RELAXES BEHIND THE DEPARTING SHORTWAVE. BY MONDAY NIGHT...THE REGION
WILL START TO FEEL THE DISTANT EFFECTS OF APPROACHING LOW PRESSURE IN
THE GULF...WHICH WILL RESULT IN WIDESPREAD (BUT GENERALLY LIGHT)
NORTHEAST WINDS DOWN COOK INLET AND ALONG THE GULF COAST. ON
TUESDAY...LOW PRESSURE CROSSES THE GULF AND MOVES INLAND NEAR
YAKUTAT. ASSOCIATED PRECIP SHIELD WILL GENERALLY ALONG AND EAST OF A
LINE FROM KODIAK CITY TO CORDOVA...WITH THE BRUNT OF THE STORM GOING
INTO THE PANHANDLE.

SOUTHWEST MAINLAND...LIGHT ONSHORE WINDS AND HIGH PRESSURE AT THE
SURFACE ARE COMBINING WITH WEAK LIFT ASSOCIATED WITH THE UPPER LOW TO
THE NORTH TO PRODUCE AREAS OF LOW CLOUDS AND SOME LIGHT SNOW FROM THE
KUSKOKWIM DELTA TO THE KUSKOKWIM VALLEY THIS AFTERNOON AND EARLY
EVENING. LIGHT ONSHORE FLOW WILL BECOME MORE NORTHEASTERLY AND
OFFSHORE OVERNIGHT AS LOW PRESSURE ADVANCES FROM THE SOUTH. THIS
SHOULD SLOWLY DRY OUT THE LOWER LEVELS AND LIKELY BREAK UP THE
WIDESPREAD STRATUS/LOW CLOUDS FOR MUCH OF THE AREA DURING THE DAY
MONDAY. THE ONE EXCEPTION MAY BE ALONG THE WESTERN SLOPES OF THE
ALASKA AND ALEUTIAN RANGES WHERE LOW CLOUDS MAY GET TRAPPED AND
PULLED SOUTH INTO EASTERN SECTIONS OF THE BRISTOL BAY ZONE TOMORROW.
OVERALL...DECREASING CLOUDS AND INCREASING NORTHEAST WINDS WILL
PREVAIL THROUGH MIDWEEK FOR MOST OF THE AREA.

BERING SEA AND ALEUTIANS...WEATHER ACROSS THE AREA WILL BE PRIMARILY
AFFECTED BY THE COMPLEX LOW IN THE NORTH PACIFIC OVER THE NEXT
SEVERAL DAYS. EXPECT EASTERLY WINDS AND A RAIN/SNOW MIX TO CONTINUE
TO ADVANCE INTO THE SOUTHERN HALF OF THE REGION THIS EVENING. WITH
THE SYSTEM REMAINING DISORGANIZED AM NOT EXPECTING PRECIP AMOUNTS TO
BE TOO IMPRESSIVE...AND WILL BE FAIRLY EPISODIC IN NATURE THROUGH
WEDNESDAY AS A SERIES OF WEAK FRONTS MOVES NORTHWARD. PRECIP WILL
START AS SNOW FROM DUTCH HARBOR TO THE AKPEN...BUT SHOULD TRANSITION
TO A RAIN/SNOW MIX ON MONDAY.

.LONG TERM FORECAST...
A COLD CORE UPPER LOW PERSISTING ACROSS THE REGION WILL KEEP
TEMPERATURES BELOW NORMAL THIS WEEK. THE STORM TRACK WILL STAY FAR
ENOUGH SOUTH TO KEEP THE MAINLAND LARGELY DRY...WITH THE EXCEPTION OF
A FEW DIURNAL INSTABILITY SHOWERS DEVELOPING OVER THE MOUNTAIN RANGES
THROUGH MIDWEEK. THE ALEUTIANS WILL SEE THE MOST UNSETTLED WEATHER
ACROSS THE DOMAIN AS THE COMPLEX LOW REMAINS NEARLY STATIONARY OVER
THE NORTH PACIFIC.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 155 170 172 175 179 411 412 413 414
         HEAVY FREEZING SPRAY 140
FIRE WEATHER...NONE

DIXON APR 13