218
FXAK68 PAFC 210043
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
343 PM AKST WED NOV 20 2024
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH
3/TONIGHT THROUGH FRIDAY AFTERNOON)...
A HIGH AMPLITUDE RIDGE CENTERED OVER THE EASTERN ALEUTIANS
CONTINUES TO EXTEND ITS AXIS NORTHEASTWARD OVER SOUTHCENTRAL
ALASKA. THE RIDGE/PATTERN WILL CONTINUE TO HOLD IN PLACE THROUGH
FRIDAY, ALLOWING FOR DRY CONDITIONS TO PERSIST OVER THE ENTIRETY
OF THE FORECAST AREA. THE MAIN POINTS OF EMPHASIS FOR THIS
FORECAST WILL BE THE GAP WINDS AND TEMPERATURES. COOLER OFFSHORE
FLOW, IN ADDITION TO A TIGHT THERMAL AND PRESSURE GRADIENT, ARE
RESULTING IN GUSTY COASTAL GAP WINDS, INCLUDING RESURRECTION BAY,
PASSAGE CANAL, THOMPSON PASS, AND VALDEZ DOWN THROUGH THE ARM AND
NARROWS. GAP WINDS ARE ESPECIALLY STRONG NEAR WHITTIER TODAY
WHERE GUSTS GOT CLOSE TO 60 KT AT TIMES. THIS GAP WIND PATTERN IS
EXPECTED TO CONTINUE THROUGH THE END OF THE WORKWEEK BEFORE WANING
OFF ON SATURDAY.
THOUGH THE RIDGE WILL KEEP CONDITIONS DRY THROUGH THE FORECAST
PERIOD, A SIGNIFICANT WARM UP WILL BEGIN TO TAKE PLACE STARTING
TONIGHT AND CONTINUE THROUGH THURSDAY. AS THE RIDGE AXIS ROTATES
AWAY FROM SOUTHCENTRAL TOWARDS THE GULF, WARMER LOW LEVEL AIR
FROM SOUTHWEST ALASKA WILL FILL IN OVER SOUTHCENTRAL. WHILE LOW-
LYING AREAS THAT ARE EXPERIENCING LITTLE TO NO WINDS WILL ONLY
EXPERIENCE A GRADUAL WARM UP, TEMPERATURES AT HIGHER ELEVATIONS
IN THE MOUNTAINS (AROUND 2500-8000 FEET SPECIFICALLY) WILL QUICKLY
RISE ABOVE FREEZING AND POTENTIALLY GET UP IN THE 40S. THE
STRONGEST WARMING WILL TAKE PLACE OVER THE KENAI MOUNTAINS AND
WESTERN CHUGACH MOUNTAINS. AS THE NORTHERLY FLOW CONTINUES TO
SHIFT SOUTHWARD TOWARDS THE COAST, TEMPERATURES WILL CONTINUE TO
RISE, ALLOWING COASTAL LOCATIONS NEAR SEA LEVEL TO GET INTO THE
40S AS WELL. THIS WARMING TREND WILL BE RELATIVELY SHORT-LIVED,
AS THE WARMEST DAY WILL LIKELY BE THURSDAY DUE TO COLDER AIR
FILLING BACK IN OVER SOUTHCENTRAL THURSDAY NIGHT INTO FRIDAY.
ANOTHER SURGE OF WARM AIR COULD FILL IN OVER THE AREA AS THE NEXT
RIDGE AXIS CROSSES OVER TOWARDS THE GULF, THOUGH CURRENT GUIDANCE
IS UNCERTAIN ON THE TIMING AND HOW WARM THE AIR MASS WILL BE AT
THIS TIME.
-BS/SEB
.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (DAYS 1 THROUGH 3: TODAY THROUGH SATURDAY
MORNING)...
A LARGE RIDGE OF HIGH PRESSURE REMAINS ANCHORED OVER THE EASTERN
BERING SEA, PROMOTING BOTH CLEAR SKIES FOR PORTIONS OF THE
SOUTHEASTERN BERING AND BRISTOL BAY, AND LOW STRATUS MIXED WITH
AREAS OF FOG OVER THE CENTRAL BERING AND THE KUSKOKWIM DELTA
COASTLINE. THESE INFLUENCES FROM THE RIDGE ARE EXPECTED TO
CONTINUE INTO THE WEEKEND, AS WELL AS WARMER DAYTIME
TEMPERATURES AND COLD NIGHTS DUE TO RADIATIONAL COOLING TAKING
AFFECT WITH CLEARER CONDITIONS. UNCERTAINTY REMAINS WITH REGARDS
TO THE SPATIAL COVERAGE OF THE FOG, AND IT'S PERSISTENCE OVER
AREAS SUCH AS BETHEL AND THE KUSKOKWIM DELTA.
IN THE WESTERN ALEUTIANS ON THE PERIPHERY OF THE RIDGE, THE
EASTERN EXTENT OF A TROUGH IS RIDING UP THE EDGE OF THE RIDGE,
GETTING STRETCHED OVER THE WESTERN BERING INTO THE BERING STRAIT.
THIS WESTERN AREA OF THE BERING WILL SEE THE ONLY ACTIVE WEATHER,
WITH PERSISTENT RAINY WEATHER OVER SHEMYA AND NEARBY ISLANDS. AN
EMBEDDED LOW PRESSURE SYSTEM IN THE RIDGE WILL SPIN UP INTO THE
WESTERN BERING BY FRIDAY MORNING. THIS WILL PROMOTE A MORE
CONCERTED EFFORT BY THE TROUGH AND RIDGE MOVEMENT TO SPREAD RAIN
AND GUSTY SOUTHERLY WINDS EASTWARD INTO THE CENTRAL ALEUTIANS,
REACHING ADAK BY VERY EARLY FRIDAY MORNING. THE STRENGTH OF THE
LOW IS STILL UNCERTAIN, HOWEVER CONFIDENCE REMAINS STRONG THAT
IT'S TRAJECTORY WILL BE NORTHWARD WHICH MAY LIMIT IT'S INFLUENCE
OVER THE CENTRAL BERING. THERE IS POTENTIAL THAT THE LOW WILL
CONTINUE TO STEADILY ADVANCE IT'S FRONT EASTWARD, REACHING THE
PRIBILOFS AND CENTRAL ALEUTIANS BY SATURDAY, HOWEVER CONFIDENCE IS
LOW ON THIS AS MODELS TEND TO STRUGGLE WITH THE LONGEVITY OF
RIDGES.
-CL
LONG TERM FORECAST (DAYS 4 THROUGH 7: SUNDAY THROUGH WEDNESDAY)
THE ALASKA WEATHER MAP WILL BECOME A BIT MORE ELASTIC AND ACTIVE
AS A STRONG SHORTWAVE RIPPLES ACROSS THE TOP OF THE INTERIOR
ALASKA UPPER LEVEL RIDGE THROUGH TUESDAY. THE BERING SHORTWAVE
EXTENDING FROM AN ANADYR LOW MOVES OVER THE RIDGE INTO CANADA FOR
TUESDAY. THE RIDGE RESETS OVER THE WESTERN MAINLAND THROUGH
WEDNESDAY. AREAS OF MODERATE RAIN AND SOME GUSTY WINDS SPREAD OVER
THE WESTERN AND CENTRAL ALEUTIANS ON SUNDAY BEFORE THE SYSTEM
MOVES OVER THE BERING. THIS SYSTEM WILL TURN EASTWARD, BRIEFLY
FLATTENING THE RIDGE. MOST OF THE SOUTHERN INTERIOR IS EXPECTED TO
HAVE LIGHT WINDS, OVERALL DRY CONDITIONS AND SOMEWHAT MODERATE
TEMPERATURES IN THE ZONAL FLOW OVER THE LOWER HALF OF THE STATE,
ALTHOUGH COOLEST OVERALL TEMPERATURES SHOULD LINGER OVER THE
EASTERN INTERIOR THROUGH TUESDAY. PRECIPITATION, IF ANY, WILL BE
LIGHT AND INTERMITTENT THROUGH THE WEEKEND WITH A VERY SMALL AND
BRIEF RISK OF FREEZING PRECIPITATION OVER INTERIOR LOCATIONS.
AVIATION
PANC...VFR CONDITIONS WILL PERSIST THROUGH THE TAF PERIOD.
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