395
FXAK68 PAFC 221209
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
309 AM AKST FRI NOV 22 2024
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH
3/FRIDAY THROUGH SUNDAY NIGHT)...
THE BLOCKING RIDGE CENTERED OVER THE ALASKA PENINSULA WILL REMAIN
THE DOMINANT WEATHER PATTERN ACROSS SOUTHCENTRAL THROUGH THE
WEEKEND. PERSISTENT ANTICYCLONIC FLOW AND ASSOCIATED SINKING
MOTION EXTENDS ACROSS ALL OF THE SOUTHERN MAINLAND AND INTO THE
GULF OF ALASKA, LEADING TO VERY DRY CONDITIONS. WARM AIR ALOFT
STILL REMAINS OVER MUCH OF SOUTHCENTRAL, HOWEVER THE WARMEST CORE
OF AIR WILL BEGIN TO SHIFT SOUTHWARD THROUGH SATURDAY AS THE
RIDGE AXIS MOVES TOWARDS THE GULF. THE STEEP TEMPERATURE INVERSION
IN PLACE, ALONG WITH A TIGHTENED PRESSURE GRADIENT OVER THE KENAI
AND CHUGACH MOUNTAINS, IS STILL PRODUCING GUSTY GAP WINDS ALONG
THE GULF COAST, ESPECIALLY IN WHITTIER AND SEWARD WHERE WIND GUSTS
COULD STILL GET UP TO 40-50 MPH THROUGH SATURDAY AFTERNOON.
AS THE RIDGE AXIS SLIPS SOUTH OF THE REGION SATURDAY, THE
INVERSION WILL WEAKEN AND WARMER TEMPERATURES ALOFT OVER THE
MOUNTAINS WILL BEGIN TO TREND DOWNWARD, FALLING TO NEAR OR JUST
ABOVE FREEZING SUNDAY AFTERNOON. ADDITIONALLY, INLAND VALLEYS
COULD SEE A SLIGHT WARM UP FROM BITTER COLD TEMPERATURES, THOUGH
STAYING BELOW FREEZING. HOW COLD OVERNIGHT LOW TEMPERATURES FALL
SATURDAY AND SUNDAY MORNING ACROSS INTERIOR SOUTHCENTRAL WILL BE
HIGHLY DEPENDENT ON THE AMOUNT OF CLOUD COVER SLIPPING OVER THE
RIDGE FROM THE NORTH AS THE RIDGE MOVES SOUTH.
GAP WINDS ARE THEN EXPECTED TO WEAKEN QUICKLY FOR SUNDAY AS THE
PRESSURE GRADIENT WEAKENS AND THE FLOW ALOFT BOTH WEAKEN AND
SHIFT TO THE SOUTHWEST. THIS SHIFT WILL ALLOW FOR TEMPERATURES TO
MODERATE AND USHER IN ADDITIONAL CLOUD COVER SUNDAY NIGHT INTO
MONDAY AHEAD OF A FRONT SYSTEM THAT LOOKS TO BRING A ROUND OF
LIGHT SNOW TO MUCH OF SOUTHCENTRAL TO START THE NEXT WEEK.
-TM/BS
.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING SEA/ALEUTIANS
(DAYS 1 THROUGH 3: TODAY THROUGH MONDAY MORNING)...
THE CORE OF THE LARGE BLOCKING RIDGE WILL CONTINUE TO SLIDE SOUTH
INTO THE NORTH PACIFIC TODAY THROUGH SUNDAY. QUIET WEATHER WILL
CONTINUE TO BE EXPECTED ACROSS MAINLAND SOUTHWEST ALASKA TODAY
THROUGH THE FIRST PART OF SUNDAY AS WELL. THE PATTERN WILL BEGIN
TO CHANGE ON SATURDAY AS UPPER-LEVEL FLOW TURNS MORE SOUTHWESTERLY
AND COLDER OFF THE BERING SEA. A SURFACE LOW PRESSURE OVER THE
WESTERN AND CENTRAL ALEUTIANS CURRENTLY PRODUCING RAIN AND GUSTY
GUSTY WINDS FROM SHEMYA TO ATKA WILL ALSO HELP DRIVE THE PATTERN
SHIFT.
A SOUTHWARD DIGGING TROUGH ACROSS THE WESTERN BERING WILL HELP TO
PULL PACIFIC MOISTURE NORTHWARD SATURDAY EVENING AND DELIVER A
ROUND OF STEADY RAIN TO THE PRIBILOF ISLANDS THROUGH SUNDAY
MORNING. SHOWERY PRECIPITATION MAKES IT TO THE KUSKOKWIM DELTA
COAST SATURDAY AFTERNOON AND TURNS MORE STEADY FOR SUNDAY.
PRECIPITATION, AT THIS TIME, IS EXPECTED TO BE MOSTLY IN THE FORM
OF RAIN. HOWEVER, THERE IS A CHANCE FOR SOME BRIEF FREEZING RAIN
OR FREEZING DRIZZLE AROUND THE BETHEL AREA SATURDAY AFTERNOON AND
EVENING AS THE INVERSION MIGHT BE SLOW TO WEAKEN AND MIX OUT. ANY
FRONT-END FREEZING RAIN OR DRIZZLE IS EXPECTED TO BE VERY LITTLE.
BY MID-SATURDAY EVENING, PRECIPITATION SHOULD MOSTLY BE IN THE
FORM OF RAIN WITH TEMPERATURES HOVERING A LITTLE ABOVE FREEZING.
THE FRONTAL SYSTEM OF THE ELONGATING LOW PRESSURE, NOW NEAR ST.
LAWRENCE ISLAND, BEGINS TO SAG SOUTHWARD AS IT PUSHES FURTHER
INLAND TO MAINLAND SOUTHWEST SUNDAY AFTERNOON AND EVENING. STEADY
PRECIPITATION IS LIKELY FROM THE EASTERN ALEUTIANS TO THE
KUSKOKWIM DELTA SUNDAY AFTERNOON INTO THE DAY ON MONDAY.
CONFIDENCE IN THE PROGRESSION OF THE FRONT AND MOISTURE SURGE ARE
RELATIVELY HIGH THROUGH SUNDAY MORNING WITH REGARDS TO THE
KUSKOKWIM DELTA. HOWEVER, CONFIDENCE DWINDLES TOWARDS SUNDAY
AFTERNOON INTO MONDAY WITH THE PROGRESSION AND TIMING OF THE FRONT
FURTHER INLAND WITH REGARDS TO PRECIPITATION ONSET TIME FOR
BRISTOL BAY AND THE LOWER KUSKOKWIM VALLEY. STAY TUNED FOR THE
LATEST FORECAST UPDATES ON THIS AS THE DRY PERIOD ACROSS SOUTHWEST
ALASKA LOOKS TO COME TO AN END THIS WEEKEND INTO EARLY NEXT WEEK.
LONG TERM FORECAST (DAYS 4 THROUGH 7: MONDAY THROUGH THURSDAY)
ON THE UPPER LEVEL ALASKAN WEATHER MAP, A MODERATELY STRONG
SHORTWAVE MUSCLES ITS WAY ACROSS THE NORTHERN TWO-THIRDS OF THE
STATE, FLATTENING AND SHIFTING THE RIDGE TO THE EAST MORE THAN IN
PREVIOUS FORECAST RUNS. THIS EFFECTIVELY ANCHORS COLDER AIR
FURTHER SOUTH OVER THE MAINLAND THROUGH THE FORECAST PERIOD, AND
MATCHES MODEL CHANGES IN THE ENSEMBLE MEANS. A WELL DEVELOPED
SURFACE FRONT PUSHES INTO THE WESTERN ALASKA COASTS, WITH
PRIMARILY SNOW OVER NORTHERN AND INTERIOR AREAS CHANGING TO A
RAIN-SNOW MIX, WITH CHANCES OF LOCAL FREEZING PRECIPITATION OVER
PARTS OF SOUTHWEST ALASKA AND THE ALASKA PENINSULA ON MONDAY, AND
SOUTHERN INTERIOR AND SOUTHCENTRAL PORTIONS THROUGH WEDNESDAY. THE
FRONT DECAYS OVER THE CENTRAL INTERIOR BY WEDNESDAY.
A DEVELOPING NORTH PACIFIC LOW BRINGS ITS ACTIVE WEATHER TO THE
CENTRAL ALEUTIANS LATE MONDAY, SPREADING INTO THE AKPEN AND
WESTERN ALEUTIANS BY THURSDAY. LOCALLY HEAVY RAIN AND WINDS
INCREASING TO GALE FORCE EXTEND INTO THE SOUTHERN BERING TUESDAY
AND WEDNESDAY, DIMINISHING THURSDAY. IN THE DISTANT WEST, A
SIBERIAN HIGH IS WORKING ITS WAY INTO ALASKAN WATERS JUST AFTER
THE END OF THE FORECAST PERIOD.
.AVIATION...
PANC...VFR CONDITIONS AND LIGHT WINDS WILL PERSIST.
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