552
FXAK68 PAFC 170316
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
616 PM AKST SAT NOV 16 2024
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (THROUGH TUESDAY)
A DEEP LONG-WAVE TROUGH WITH MULTIPLE CENTERS STRETCHES FROM THE
BEAUFORT SEA THROUGH THE SOUTHWESTERN MAINLAND AND DOWN INTO THE
GULF OF ALASKA. THE MAIN UPPER LOW CENTER AFFECTING OUR WEATHER IS
CENTERED OVER NORTON SOUND, WITH A WEAKER CENTER MOVING EASTWARD
IN THE GULF OF ALASKA. LIGHT RADAR RETURNS ARE LINGERING FROM THE
WESTERN KENAI PENINSULA THROUGH THE MATANUSKA VALLEY. LIGHT SNOW
IS LINGERING MOSTLY ALONG THE FRONT RANGE OF THE CHUGACH AND KENAI
MOUNTAINS. DRIER AND COLDER AIR IS FILTERING THROUGH THE ALASKA
RANGE, WITH TED STEVENS INTERNATIONAL AIRPORT'S DEWPOINT FALLING
FROM 27F TO 9F THOUGH THE DAY SATURDAY, MARKING THE END OF THE
SNOW. GAP WINDS ARE BEGINNING TO RAMP UP ALONG THE NORTH GULF
COAST THROUGH KAMISHAK BAY AND KODIAK ISLAND.
LIGHT SNOW WILL SLOWLY TAPER OFF THROUGH SUNDAY MORNING FOR THE
FRONT RANGE OF THE CHUGACH. STRONG GAP WINDS AND A MUCH COLDER
ARCTIC AIR MASS WILL BE THE IMPACTFUL FACETS OF THE FORECAST. AS
COLD ADVECTION POURS THROUGH THE ALASKA RANGE, KAMISHAK BAY AND
SHELIKOF STRAIT/KODIAK ISLAND WILL SEE THE BRUNT OF GUSTY GAP
WINDS, WITH WINDS NEAR HURRICANE-FORCE AT TIMES THROUGH SUNDAY
NIGHT.
ON SUNDAY NIGHT, CLOUDS OVER MUCH OF SOUTHCENTRAL ALASKA SHOULD
ERODE ENOUGH TO GET SUBSTANTIAL RADIATIONAL COOLING, WHICH WILL
GIVE US THE COLDEST LOW TEMPERATURES OF THE WINTER SO FAR WITH
MUCH OF THE AREA FROM THE KENAI PENINSULA THROUGH THE MATANUSKA
VALLEY SEEING LOW TEMPERATURES IN THE SINGLE DIGITS. PLACES SUCH
AS WILLOW COULD SEE LOW TEMPERATURES WELL BELOW ZERO INTO THE
NEGATIVE TEENS AND THE COPPER RIVER BASIN COULD SEE LOW
TEMPERATURES IN THE NEGATIVE TWENTIES.
MONDAY INTO TUESDAY, A DISTURBANCE DROPS SOUTHWARD IN RESPONSE TO
A BUILDING RIDGE OVER THE BERING SEA. IN RESPONSE, THE MID-UPPER
LEVELS WILL BECOME MORE FAVORABLE FOR GAP WINDS FORCED BY COLD AIR
IN THE COPPER RIVER BASIN. THE MATANUSKA VALLEY WINDS WILL
INCREASE, BUT THOMPSON PASS/VALDEZ WILL SEE STRONGER GUSTS
APPROACHING 50 MPH OR MORE. AT THIS POINT THERE DOESN'T APPEAR TO
BE STRONG ENOUGH WINDS ALOFT TO GET TO HIGH WINDS CRITERIA BUT IT
WILL BE WORTH WATCHING.
THERE IS VERY HIGH CONFIDENCE IN THIS FORECAST THROUGH EARLY NEXT
WEEK IN DRY AND COLD IN ALL AREAS, WITH GUSTY COASTAL WINDS.
MTL
.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (DAYS 1 THROUGH 3)...
MULTIPLE SHORTWAVES AHEAD OF AN UPPER-LEVEL LOW PRESSURE SYSTEM
OVER THE CHUKCHI SEA WILL MOVE OVER THE EASTERN BERING, ALEUTIANS,
ALASKA PENINSULA, AND THE COASTLINE OF SOUTHWEST THROUGH TOMORROW
EVENING. MOISTURE AND COLD AIR ALOFT FROM THESE WAVES WILL RESULT
IN PERIODS OF CONVECTIVE SNOW SHOWERS. THERE ARE TWO MORE FOCUSED
WAVES THAT WILL BE FELT MAINLY OVER THE ALEUTIANS. THE FIRST WAVE
WILL COVER AREAS FROM DUTCH HARBOR TO NELSON LAGOON, STARTING
THIS EVENING AND CONTINUING INTO TOMORROW MORNING. THE SECOND WAVE
WILL TAKE PLACE TOMORROW MORNING AND LAST INTO THE AFTERNOON,
STRETCHING FROM PILOT POINT WEST TO NELSON LAGOON. IN ADDITION,
THE NORTHERN PERIPHERY OF A LOW IN THE NORTH PACIFIC WILL MOVE
OVER THE WESTERN ALEUTIANS STARTING TONIGHT AND CONTINUE THROUGH
THE DAY ON SUNDAY, PROVIDING RAIN SHOWERS FOR LOCATIONS WEST OF
ADAK.
AS THIS ARCTIC LOW MOVES SOUTH AND AWAY FROM SOUTHWEST, A STRONG
PUSH OF COLD AND DRY AIR TAKES ITS PLACE OVER THE AREA. STRONG
NORTHWESTERLY FLOW WILL RESULT IN BITTER COLD TEMPERATURES OVER
SOUTHWEST FOR THE START OF THE UPCOMING WORKWEEK. MANY AREAS EAST
OF BETHEL WILL STRUGGLE TO GET ABOVE ZERO AFTER SUNDAY NIGHT,
ESPECIALLY NEAR THE KUSKOKWIM RIVER VALLEY. DAYTIME HIGHS WILL
LIKELY BE IN THE NEGATIVE SINGLE DIGITS MONDAY, WITH LOWS CLOSER
TO -10. INCREASING NORTHWESTERLY WINDS OVER PLACES SUCH AS
SLEETMUTE, IGIUGIG, AND KOLIGANEK MONDAY AFTERNOON WILL AID IN
LOWERING TEMPERATURES EVEN FURTHER THAT EVENING. CURRENTLY,
TUESDAY MORNING LOWS COULD DROP BELOW -10, WITH WIND CHILLS
DROPPING INTO THE -20S AND EVEN THE -30S IN SOME OF THE INTERIOR
VALLEYS.
FOR THE ALEUTIANS, A STRONG RIDGE OF HIGH PRESSURE WILL BUILD IN
STARTING SUNDAY NIGHT. THE RIDGE WILL SLOWLY SHIFT EASTWARD
THROUGH THE REMAINDER OF THE FORECAST PERIOD BEFORE COVERING MOST
OF THE BERING BY TUESDAY. AS WARM AIR FEEDS IN ALOFT WITH THE
RIDGE, THE POTENTIAL FOR PATCHY FOG OVER THE BERING, ALEUTIANS,
AND PRIBILOFS WILL ALSO INCREASE AS EACH DAY PASSES.
-BS
.LONG TERM FORECAST (DAYS 4 THROUGH 7: WEDNESDAY THROUGH
SATURDAY)...
BY WEDNESDAY, HIGH AMPLITUDE RIDGING PUSHING IN FROM THE BERING
SEA/ALEUTIANS WILL COVER THE MAJORITY OF THE STATE, BRINGING
NORTHERLY FLOW TO MOST OF SOUTHERN MAINLAND ALASKA. WARMER AIR
FROM THE PACIFIC IS ASSOCIATED WITH THIS FEATURE, SO WE ARE
EXPECTING THE COLD TEMPERATURES FROM THE FIRST HALF OF THE WEEK TO
GIVE WAY TO MORE MODERATE TEMPS, ESPECIALLY FOR THE SOUTHWEST.
A NORTH PACIFIC LOW LOOKS TO ENTER THE BERING SEA THURSDAY NIGHT,
TIGHTENING THE PRESSURE GRADIENT AND BRINGING MODERATELY STRONG
SOUTHERLY WINDS TO THE WESTERN ALEUTIANS AND CENTRAL BERING SEA.
THIS SYSTEM WILL BE PUSHED TO THE NORTHEAST AS IT MOVES THROUGH
THE TOP EDGE OF THE AMPLIFIED RIDGE. THE LOW CENTER SHOULD STAY IN
NORTHERN ALASKA, BUT THERE IS SOME MODEL DISAGREEMENT HERE ABOUT
HOW MUCH IT WILL FLATTEN OUT THE RIDGE. THIS WILL BE SOMETHING TO
KEEP AN EYE ON GOING FORWARD AS IT COULD POTENTIALLY IMPACT
SOUTHCENTRAL.
LIGHT WINDS AND LITTLE PRECIPITATION ARE EXPECTED THROUGHOUT THE
LONG TERM OUTLOOK FOR MOST OF SOUTHCENTRAL AND SOUTHWEST ALASKA.
.AVIATION...
PANC...THE BIG QUESTION FOR THE AIRPORT IS WHETHER OR NOT THERE IS
ANOTHER BATCH OF LIGHT SNOW THAT DEVELOPS THIS EVENING OR WHETHER
THE SNOW IS DONE FOR GOOD WITH THIS SYSTEM. CONFIDENCE OF MUCH
ADDITIONAL SNOWFALL AT THE TERMINAL HAS BEEN GOING DOWN THROUGH
THE DAY AS IT LOOKS MORE LIKELY THAT THE AIRPORT IS JUST FAR
ENOUGH WEST TO REMAIN MOSTLY DRY. EVEN IF THERE IS SOME SNOW THIS
EVENING, EXPECT ANY ADDITIONAL ACCUMULATION TO BE LESS THAN AN
INCH.
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