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000
FXAK68 PAFC 271359
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
459 AM AKST FRI FEB 27 2015

.ANALYSIS AND UPPER LEVELS...THE PATTERN REMAINS RELATIVELY QUIET
FOR MOST OF THE MAINLAND. A POTENT RIDGE AT THE MID-LEVELS
IS CAUSING A NEARLY 1040 MB HIGH STAMPED RIGHT OVER SOUTH
CENTRAL. THUS FAR...IT APPEARS THE AIRMASS WITH THIS HIGH IS
ACTUALLY DRY ENOUGH TO INHIBIT FOG/LOW STRATUS DEVELOPMENT LIKE WE
SAW THURSDAY MORNING. THAT SAID...IT IS STILL EARLY AND IT COULD
CERTAINLY STILL REAR ITS HEAD AROUND SUNRISE. A VERY WEAK SURFACE
LOW IS TRACKING TOWARDS THE EASTERN ALEUTIANS AND ALASKA PENINSULA
THIS MORNING. IT IS BRINGING SOME GUSTY SOUTHEASTERLY WINDS AND
LIGHT RAIN TO THE EASTERN ALEUTIANS AND SHOULD EVENTUALLY SPREAD
SOME PRECIPITATION INTO KODIAK LATER TODAY. THE MOST IMPORTANT
VARIABLE THIS DECAYING SYSTEM WILL BRING TO THE FIGHT IS TO SPREAD
SOME MOISTURE FROM THE NORTH PACIFIC OVER SOUTH CENTRAL. LOOKING
AT THE JET STREAM...THERE IS STILL 80-90 KT MOVING FROM SOUTH TO
NORTH OVER THE WEAKENING SURFACE FRONT TOWARDS THE CENTRAL
ALEUTIANS. THE BIGGER STORY IS SOME VERY COLD CLOUD TOPS STREAMING
TOWARDS THE WESTERN ALEUTIANS ON A 130 KT ZONAL JET. THIS FEATURE
IS GOING TO DRIVE TOWARDS THE WEST COAST TODAY AND SATURDAY AND
WILL KEEP THE PATTERN MOVING RATHER QUICKLY.

&&

.MODEL DISCUSSION...MODELS REMAIN IN VERY GOOD AGREEMENT THROUGH
JUST ABOUT ALL OF THE SHORT TERM. THUS...FORECAST CONFIDENCE IS
HIGH THROUGH MOST OF THE WEEKEND. ONCE AGAIN THIS MORNING THERE
ARE SOME LOCALIZED SPOTS SEEING BOUTS OF LOW STRATUS AND FOG. IT
HAS REMAINED CONFINED FOR NOW TO SOUTHWEST ALASKA...TO INCLUDE
ILIAMNA AND DILLINGHAM. BUT IT IS CERTAINLY NOT OUT OF THE
QUESTION WITH THE RIDGE OVERHEAD TO SEE SOME STRATUS/FOG
DEVELOPMENT...ESPECIALLY NEAR ANY OPEN WATER SOURCE. SO FAR HI-RES
MODELS ARE HANDLING THE FOG...OR LACK THEREOF...WELL THIS MORNING.
GOING INTO THE WEEKEND...THERE HAS BEEN A KEEN EYE ON HOW THE
MODELS ARE TREATING THE QUICK HITTING SYSTEM LATE SATURDAY. AFTER
A LITTLE SHUFFLING THE PAST FEW DAYS...IT SEEMS THEY ARE ALL
LOCKING ON TO A CONSISTENT MESSAGE. THE MOISTURE COMING UP FROM
THE NORTH PACIFIC WILL GET SWEPT UP BY A QUICK MOVING MID-LEVEL
TROUGH. THIS SHOULD MAKE FOR WIDESPREAD SNOWFALL FOR SOUTH CENTRAL
LATE SATURDAY INTO SUNDAY. HOWEVER...IT DOES NOT LOOK TO BRING
MUCH IN THE WAY OF ACCUMULATION AS THE BULK OF THE ENERGY WILL
REMAIN NORTH OF THE ALASKA RANGE. THE GEM GLOBAL WAS THE FIRST TO
SHOW THIS AND HAS CONTINUED TO BE CONSISTENT. THE GFS WAS LATE TO
THE PARTY...BUT NOW CONCURS WITH THE OTHER MEMBERS.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
LOCALIZED GAP WINDS ALONG THE NORTH GULF COAST WILL QUICKLY
DIMINISH DURING THE MORNING HOURS AS THE UPPER LEVEL RIDGE SHIFTS
EASTWARD AND BRINGS AN END TO THE DEEP LAYER OF OFFSHORE FLOW.
CONDITIONS APPEARED FAVORABLE FOR FOG FORMATION IN NORTHERN COOK
INLET OVERNIGHT WITH STEEP SURFACE INVERSIONS SETTING UP UNDER
MOSTLY CLEAR SKIES. MAY STILL SEE SOME PATCHY FOG...BUT NO LONGER
THINK ANY WIDESPREAD FOG WILL FORM.

ATTENTION WILL TURN TO A WEAK SURFACE LOW AND UNORGANIZED UPPER
WAVE MOVING UP THE WEST SIDE OF THE RIDGE TOWARD THE ALASKA
PENINSULA AND KODIAK ISLAND. THE UPPER LEVEL WAVE WILL QUICKLY
OUTPACE THE SURFACE LOW AND PRODUCE LITTLE MORE THAN CLOUDS AS IT
CROSSES SOUTHCENTRAL FRIDAY NIGHT. THIS WAVE WILL FLATTEN OUT THE
EXITING RIDGE CAUSING STEERING FLOW TO BECOME MORE WESTERLY. THIS
WILL CAUSE THE SURFACE LOW TO TRACK EAST-NORTHEAST ACROSS KODIAK
ISLAND INTO THE NORTHERN GULF ON SATURDAY...KEEPING MOST OF THE
PRECIP CONFINED TO THAT GENERAL AREA.

MEANWHILE...THE MAIN WEATHER PRODUCER FOR THE REMAINDER OF
SOUTHCENTRAL WILL BE A TROUGH CURRENTLY OVER THE WESTERN BERING
SEA WHICH WILL PICK UP SPEED AS IT LIFTS NORTHEASTWARD AND
DEAMPLIFIES. AS HAS BEEN ADVERTISED THE BULK OF ENERGY WILL HEAD
NORTH OF THE ALASKA RANGE. HOWEVER...THERE WILL CERTAINLY BE
ENOUGH LIFT AHEAD OF THE TROUGH TO PRODUCE A SHORT-DURATION OF
PRECIP ACROSS MUCH OF SOUTHCENTRAL SATURDAY AFTERNOON THROUGH
SATURDAY EVENING. ROBUST UPSLOPE FLOW ALONG THE WEST SIDE OF THE
TALKEETNA AND CHUGACH MOUNTAINS ALONG WITH A LITTLE BIT OF COLD
AIR ADVECTION WILL HELP ENHANCE THE SNOWFALL IN THESE AREAS.
HOWEVER...WITH SUCH RAPID MOVEMENT OF THE UPPER TROUGH THE SNOW
WILL NOT LAST VERY LONG AND AMOUNTS WILL GENERALLY BE QUITE LIGHT.

GAP WINDS WILL QUICKLY DEVELOP ALONG THE NORTH GULF COAST AS THE
UPPER TROUGH EXITS SATURDAY NIGHT. OTHERWISE EXPECT SKIES TO CLEAR
AND TEMPERATURES TO DROP AS COLDER AIR QUICKLY SETTLES OVER THE
REGION.

&&

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

A RIDGE OF HIGH PRESSURE ALOFT WILL GIVE WAY TO A NORTH PACIFIC
LOW LATE THIS AFTERNOON INTO SATURDAY. CLOUDS AND MOISTURE WILL
STREAM IN FROM THE SOUTH...WITH RAIN AND SNOW DEVELOPING ACROSS
BRISTOL BAY BEFORE RAPIDLY SPREADING NORTHWARD. ALL SNOW IS
EXPECTED ACROSS THE KUSKOKWIM DELTA AND LOWER KUSKOKWIM
VALLEY...WITH RAIN ALONG THE ALASKA PENINSULA. COOLER AIR AND
CLEARING SKIES WILL RETURN TO THE REGION BEHIND THE WEATHER
SYSTEM BY SATURDAY NIGHT.

&&

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

A SLOW MOVING WEATHER FRONT WILL MOVE SLOWLY OVER THE CENTRAL
BERING AND ALEUTIANS THROUGH THIS AFTERNOON BEFORE WEAKENING AND
MOVING EAST TOWARD THE SOUTHWEST MAINLAND AND AKPEN SATURDAY.
COLDER AIR WILL FILTER INTO THE CENTRAL BERING SEA ALONG WITH
NORTH TO NORTHWEST WINDS. RAIN AND SNOW SHOWERS WILL MOVE INTO
THE PRIBILOF ISLANDS AND EASTERN ALEUTIANS AS THE FRONT MOVES
EAST...AND A WEAK NORTH PACIFIC LOW MOVES NEAR AND ALONG THE
ALASKA PENINSULA MOVING TOWARD THE NORTHWEST GULF. A NEAR STORM
FORCE LOW WILL MOVE INTO THE FAR WESTERN ALEUTIANS LATE TONIGHT.
ENOUGH COLD AIR WILL BE IN PLACE FOR PRECIPITATION TO BEGIN AS
SNOW...WITH GALE FORCE WINDS SUGGESTIVE OF BLOWING SNOW POTENTIAL
EVEN THOUGH SNOW MAY BE A BIT ON THE WET SIDE. THIS SNOW WILL BE
SHORT-LIVED AS WARMER AIR MOVING ACROSS THE REGION QUICKLY CHANGES
THE SNOW TO RAIN SAT MORNING. UP TO 1 OR 2 INCHES OF SNOW CAN BE
EXPECTED AT SHEMYA BEFORE THE CHANGEOVER TO RAIN.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
DRY CONDITIONS WILL PERSIST ACROSS THE EASTERN ALEUTIANS AND
MAINLAND AK ON SUN BENEATH A RIDGE OF HIGH PRESSURE. FORECAST
CONFIDENCE IS THEN HIGH THAT A FRONT MOVING ACROSS THE BERING WILL
PHASE WITH A NORTH PACIFIC LOW ON MON...AND THEN CONTINUE INTO
MAINLAND AK MON NIGHT INTO TUE. THIS WILL BRING RAIN AND SNOW TO
MUCH OF THE ALEUTIANS SUN THROUGH TUE...TO SOUTHWEST AK MON
THROUGH WED...AND TO SOUTH CENTRAL LATE MON THROUGH THU. THE NEXT
FRONT WILL CROSS THE BERING AND ALEUTIANS WED AND THU WITH ANOTHER
ROUND OF WIND AND RAIN...MIXED INITIALLY WITH SNOW.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 177 178
         HEAVY FREEZING SPRAY 180
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...MO
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CC
LONG TERM...DS