014
FXAK68 PAFC 171246
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
446 AM AKDT THU SEP 17 2026
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3:
TODAY THROUGH SATURDAY EVENING)...
KEY MESSAGES:
- UNSETTLED WEATHER WITH SCATTERED SHOWERS ALONG THE COAST AND
ACROSS THE HIGHER TERRAIN TODAY. WETTER CONDITIONS RETURN FROM
FRIDAY INTO THE WEEKEND AS TWO STORMS MOVE NORTH ACROSS THE GULF
AND INTO SOUTHCENTRAL.
- TRENDING COLDER, WITH OVERNIGHT LOWS DIPPING INTO THE LOW 40S TO
LOW 30S BY FRIDAY NIGHT/SATURDAY MORNING.
DISCUSSION:
SATELLITE IMAGERY THIS MORNING SHOWS WIDESPREAD CLOUD COVER
LINGERING ACROSS INTERIOR SOUTHCENTRAL WITH GENERALLY MOSTLY
CLEAR SKIES ALONG THE IMMEDIATE COAST AND GULF OF ALASKA. A WEAK
SHORTWAVE TROUGH AND LINGERING OCCLUDED FRONT OVER THE ALASKA
RANGE IS PRODUCING A FEW SCATTERED SHOWERS ACROSS THE COPPER RIVER
BASIN. A SOUTHEASTERLY FLOW BEHIND THE TROUGH IS ALSO PRODUCING A
FEW SHOWERS AROUND CORDOVA, MAINLY ALONG AND OVER THE COASTAL
MOUNTAINS DUE TO THE UPSLOPE FLOW.
THE WEAK, TRANSIENT RIDGE IN PLACE OVER THE GULF OF ALASKA TODAY
WILL KEEP WEATHER CONDITIONS FAIRLY BENIGN THROUGH THIS AFTERNOON.
AFTER THAT TIME, THERE IS GOOD MODEL CONSENSUS THAT A SHORTWAVE
TROUGH MOVING NORTHEAST FROM THE ALASKA PENINSULA TOWARD KODIAK
ISLAND WILL SHIFT THE NEAR SURFACE FLOW AND WIND FLOW ALOFT MORE
SOUTHERLY THEN SOUTHEASTERLY. THERE IS HIGH CONFIDENCE (>90%) THAT
THIS SHIFT IN THE WIND FIELD WILL DRIVE MOISTURE FROM THE GULF
TOWARD PRINCE WILLIAM SOUND AND THE EASTERN KENAI PENINSULA,
RESULTING IN WIDESPREAD RAIN SHOWERS FOR THESE AREAS BY THIS
EVENING. AS THE SHORTWAVE GAINS STRENGTH, A DEVELOPING SURFACE LOW
MOVES NORTH FROM THE EASTERN GULF INTO THE EASTERN PRINCE WILLIAM
SOUND/CAPE SUCKLING FOR FRIDAY. THIS SOLUTION, COMBINES WITH A
BROAD SOUTHEASTERLY WIND FLOW ALOFT ADVECTING MOISTURE WESTWARD
TOWARD A LARGER UPPER-LEVEL LOW, RESULTS IN A HIGH LIKELIHOOD
(70-80%) OF RAIN SHOWERS SPREAD ACROSS MOST OF THE SOUTHCENTRAL
MAINLAND LATE TOMORROW INTO FRIDAY. ALTHOUGH THIS FIRST SHORTWAVE
AND SURFACE LOW QUICKLY LIFT NORTH INTO THE INTERIOR SATURDAY,
THE IS A HIGH LIKELIHOOD (70-80%) THAT SHOWERS LINGER ACROSS MUCH
OF SOUTHCENTRAL, WITH THE HEAVIEST PRECIPITATION ALONG THE
COASTAL MOUNTAINS AND HIGHER ELEVATIONS, AS THE UPPER- LEVEL LOW
OVER SOUTHWEST ALASKA SLIDES EAST BEFORE SLOWLY WEAKENING.
LOOKING AHEAD: A MUCH STORMIER WEEKEND IS IN STORE AS A STRONG
SHORTWAVE AND A BROAD LOW MOVE UP FROM THE GULF AND TOWARDS
SOUTHCENTRAL FOR THE LATTER HALF OF THE WEEKEND. MODELS ARE
CONVERGING ON A CENTRAL PRESSURE OF 975 TO 985 MB FOR THIS LOW,
WITH WINDS TO GALE FORCE. RAIN AMOUNT AND INTENSITY WILL ALSO BE
SOMETHING TO WATCH, AS THE NORTH GULF COAST (INCLUDING PRINCE
WILLIAM SOUND AND EASTERN KENAI PENINSULA) COULD SEE A LONG
DURATION OF MODERATE RAIN.
-TM/KC
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS
(DAYS 1 THROUGH 3: TODAY THROUGH SUNDAY MORNING)...
KEY MESSAGES:
* A WEAK LOW MOVES THROUGH THE BERING SEA BRINGING WEAKER WINDS
AND PRECIPITATION TO SOUTHWEST ALASKA TODAY. THIS LOW LINGERS
ACROSS THE SOUTHWESTERN MAINLAND THROUGH THE FIRST HALF OF
SATURDAY.
* A LOW MOVING OFF OF KAMCHATKA AND THROUGH THE WESTERN BERING
HAS THE POTENTIAL TO PRODUCE A FEW ISOLATED MARINE
THUNDERSTORMS THIS AFTERNOON THROUGH FRIDAY AFTERNOON.
* A MORE POTENT ARCTIC FRONT BRINGS NORTHERLY WINDS THROUGH THE
ALEUTIANS AND ALASKA PENINSULA (AKPEN) THE SECOND HALF OF
SATURDAY AND INTO SUNDAY. THERE IS ALSO POTENTIAL FOR SOME
RAIN/SNOW MIX LATE SATURDAY NIGHT INTO EARLY SUNDAY MORNING
ACROSS PORTIONS OF THE KUSKOKWIM DELTA COAST.
DISCUSSION:
A WEAK LOW PRESSURE SYSTEM IS CURRENTLY JUST WEST OF ST. MATTHEW
ISLAND THIS MORNING. SOUTHWEST FLOW AHEAD OF THIS SYSTEM IS
ALLOWING FOR SHOWERS TO MOVE INTO SOUTHWEST ALASKA FROM THE
EASTERN BERING SEA. THE SHOWERY REGIME WILL CONTINUE TO RULE THE
ROOST ACROSS THE SOUTHWESTERN MAINLAND THROUGH SATURDAY AFTERNOON
AS UPPER-LEVEL DISTURBANCES ASSOCIATED WITH THE LOW REMAIN OVER
THE AREA.
BACK TO THE WEST, CONFIDENCE IS HIGH THAT A SEPARATE LOW PRESSURE
SYSTEM WILL MOVE OFF OF KAMCHATKA AND MOVE THROUGH THE WESTERN
AND SOUTHERN BERING SEA TODAY AND FRIDAY BEFORE EXITING TO THE
NORTH PACIFIC FRIDAY EVENING. AS THIS LOW MOVES THROUGH THE
WESTERN AND SOUTH-CENTRAL BERING THIS AFTERNOON THROUGH FRIDAY
AFTERNOON, A FEW MARINE LIGHTNING STRIKES MAY OCCUR (20 TO 40%
CHANCE) ACROSS THE AREA. THE MAIN DRIVING FACTOR FOR THIS
POTENTIAL MARINE CONVECTIVE EPISODE IS THAT THIS LOW WILL BRING IN
STEEPER LAPSE RATES ACROSS THE AREA WITH COLDER AIR COMING IN
ALOFT.
A STRONGER PUSH OF NORTHERLY FLOW ALONG WITH A STRONGER RE-
ENFORCING SHOT OF COLD AIR ALOFT BEGINS TO DIG SOUTH THROUGH THE
BERING SEA FRIDAY NIGHT THROUGH SUNDAY MORNING. LATE SATURDAY
NIGHT INTO SUNDAY MORNING, THE KUSKOKWIM DELTA COULD CONTEND WITH
RAIN/SNOW MIX. TUNUNAK, TOKSOOK BAY, AND NUNIVAK ISLAND HAVE THE
BEST CHANCE AT SEEING SOME RAIN/SNOW MIX DURING THIS TIME. THE
OTHER STORY WITH THIS STRONGER PUSH OF NORTHERLY FLOW AND COLD AIR
ADVECTION WILL BE THE RESULTANT GUSTY GAPS WINDS THROUGH THE
EASTERN ALEUTIANS AND THE AKPEN SATURDAY AND SUNDAY. THE ARRIVAL
OF THIS ARCTIC AIRMASS WILL ALSO USHER IN COOLER TEMPERATURES
ACROSS MAINLAND SOUTHWEST FOR THE WEEKEND. STAY TUNED FOR FORECAST
UPDATES AS THE FALL-LIKE PATTERN BEGINS TO TRANSITION TO MORE OF
A WINTER-LIKE PATTERN FOR THE WEEKEND.
LONG TERM FORECAST (DAYS 4 TO 7, SUNDAY THROUGH WEDNESDAY)
BY SUNDAY MORNING, HEAVY RAINFALL WILL BE ONGOING FOR THE
NORTHERN GULF COAST AND SMALL-CRAFT TO GALE FORCE WINDS WILL BE
PRESENT THROUGHOUT THE GULF AROUND AN OCCLUDING LOW. FURTHER AWAY
FROM THE LOW, LIGHTER SHOWERS ARE LIKELY ACROSS THE WESTERN
SUSITNA VALLEY AND PORTIONS OF THE AKPEN, WITH MORE ISOLATED
SHOWERS ACROSS THE REST OF SOUTHCENTRAL AND SOUTHWEST. WITH STRONG
COLD AIR ADVECTION BEHIND THE LOW, SNOW LEVELS WILL HAVE DROPPED
TO AROUND 2000 FEET ACROSS SOUTHWEST ALASKA AND THE AKPEN AND
AROUND 4000-4500 FEET ACROSS SOUTHCENTRAL BY SUNDAY MORNING. AT
HIGHER ELEVATIONS, ESPECIALLY ACROSS SOUTHWEST ALASKA,
PRECIPITATION SUNDAY AND ONWARDS LIKELY FALLS AS SNOW. IN THE
EASTERN BERING THROUGH THE ALEUTIANS AND AKPEN, NORTHWESTERLY
WINDS UP TO SMALL-CRAFT FORCE ARE LIKELY ONGOING SUNDAY MORNING
DUE TO COLD AIR ADVECTION ON THE WEST SIDE OF THE LOW.
WHILE THE UPPER LEVEL LOW REMAINS OVER THE GULF, THE SURFACE LOW
LOOKS TO MOVE INTO THE COAST BY SUNDAY AFTERNOON AND RAPIDLY
WEAKEN ONCE ONSHORE. WINDS SIGNIFICANTLY DECREASE SUNDAY NIGHT
AROUND THE GULF AS THE PRESSURE GRADIENT WEAKENS. EVEN AS THE LOW
WEAKENS, NORTHWESTERLY GAP WINDS WILL PERSIST THROUGH THE AKPEN
AND EASTERN ALEUTIANS. THOUGH IT APPEARS THE STRONGEST WINDS WILL
BE SATURDAY INTO SUNDAY, CONSTANT COLD AIR ADVECTION WILL ALLOW
NORTHWEST WINDS TO PERSIST AT OR NEAR SMALL- CRAFT FORCE THROUGH
MONDAY EVENING. WITH THE WEAKENING LOW, SHOWERS SHOULD TAPER OFF
FOR SOUTHWEST ALASKA BY MONDAY AFTERNOON. DUE TO WINDS UPSLOPING
IN THE AKPEN, SHOWERS LIKELY PERSIST THERE THROUGH TUESDAY. GIVEN
CONTINUOUS COLD AIR ADVECTION, SNOW LEVELS DROP FURTHER ON MONDAY
TO AROUND 1000 FEET ACROSS SOUTHWEST, 1500-2000 FEET IN THE
AKPEN. PLACES ABOVE ELEVATIONS MENTIONED WILL LIKELY RECEIVE SOME
SNOWFALL, ESPECIALLY IF PRECIPITATION PERSISTS INTO MONDAY. SINCE
SOUTHCENTRAL IS CLOSER TO THE LOW, PRECIPITATION WILL PERSIST
THERE LONGER. THE HEAVIEST PRECIPITATION WILL BE SUNDAY INTO
MONDAY MORNING ALONG THE NORTHERN GULF COAST WITH LIGHTER
PRECIPITATION INLAND AS THE LOW MOVES ONSHORE. THIS MEANS RAIN
BELOW 4000 FEET AND SNOW ABOVE 4000-5000 FEET. WITH THE LOW
WEAKENING, PRECIPITATION SHOULD SLOWLY TAPER OFF AT LOWER
ELEVATIONS BY MONDAY AFTERNOON WHILE PERSISTING AT HIGHER
ELEVATIONS THROUGH TUESDAY MORNING. COLD AIR ADVECTION BEGINS TO
DROP SNOW LEVELS MONDAY TO AROUND 2500-3500 FEET. FOR PLACES ABOVE
2500-3500 FEET, ANY PRECIPITATION THAT LINGERS MONDAY AND ONWARDS
LIKELY FALLS AS SNOW. ADDITIONALLY, BELOW AVERAGE TEMPERATURES
WILL ALLOW FOR MANY PLACES ACROSS SOUTHWEST AND SOUTHCENTRAL TO
DROP BELOW FREEZING FOR THIS FIRST TIME THIS FALL.
TROUGHING LOOKS TO PERSIST ACROSS MAINLAND ALASKA THROUGH TUESDAY
AS THE UPPER LOW REMAINS STATIONARY OVER THE GULF. REMNANTS OF
THE SURFACE LOW SHOULD MOVE AWAY FROM SOUTHCENTRAL BY TUESDAY
AFTERNOON, TAPERING OFF ANY LINGERING PRECIPITATION ALONG THE
COAST. MEAN ENSEMBLES SHOW ANOTHER POTENTIAL LOW ENTERING THE
WESTERN BERING AND WESTERN ALEUTIANS TUESDAY INTO WEDNESDAY, WHICH
MAY BRING MORE RAIN AND WIND THERE. THERE ALSO IS SOME POTENTIAL
FOR POST-TROPICAL ACTIVITY TO MAKE ITS WAY TO THE WESTERN
ALEUTIANS BETWEEN TUESDAY-WEDNESDAY. CONFIDENCE WITH EITHER
SOLUTION IS CURRENTLY LOW, AND DETAILS WILL BECOME MORE CLEAR IN
THE COMING DAYS. OTHERWISE CONDITIONS LOOK TO BE RELATIVELY
BENIGN ACROSS MOST SOUTHERN ALASKA TUESDAY INTO WEDNESDAY.
- PA
AVIATION
PANC...WINDS REMAIN SOUTHERLY WITH OCCASIONAL GUSTS UP TO 15 OR
20 KTS LIKELY THROUGH THIS EVENING. VFR CONDITIONS WILL PREVAIL
THROUGH THE PERIOD, THOUGH CEILINGS COULD LOWER TO AROUND 4,000 FT
TONIGHT AS LIGHT RAIN SHOWERS DEVELOP AROUND THE AREA. A STEADIER
RAIN MOVES OVER THE TERMINAL BY EARLY FRIDAY MORNING WITH
INCREASING CHANCES (50-60%) OF MVFR CEILINGS AND VISIBILITY.
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