690
FXAK68 PAFC 190703
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1103 PM AKDT FRI SEP 18 2026
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3:
TODAY THROUGH MONDAY EVENING)...
AS OF THIS AFTERNOON, A RELATIVELY COMPACT, BUT STRONG LOW
PRESSURE SYSTEM IS SPINNING ACROSS THE NORTH-CENTRAL GULF. OUT
AHEAD OF IT, PERIODS OF MODERATE RAINFALL ALONGSIDE A FAIRLY
NARROW BARRIER JET WITH EASTERLY WINDS GUSTING UP TO STORM FORCE
IS IMPACTING THE IMMEDIATE NORTHERN GULF COAST FOR PLACES LIKE
KAYAK ISLAND, JUST SOUTH OF CORDOVA, AND SOUTHERN PRINCE WILLIAM
SOUND LOCATIONS. CONDITIONS ARE ON TRACK TO IMPROVE QUICKLY
OVERNIGHT AS THE LOW DRIVES INLAND AND THE JET COLLAPSES. STEADIER
RAIN WILL ALSO FALL FROM PRINCE WILLIAM SOUND NORTHWARD ACROSS
MUCH OF THE COPPER RIVER BASIN. MOISTURE ALSO LOOKS TO GET PULLED
WESTWARD TOWARD THE TROUGH MOVING OVER THE COOK INLET NORTHWARD
INTO THE SUSITNA VALLEY. THIS WILL LIKELY RESULT IN ANOTHER ROUND
OF RAIN FROM KENAI TO TALKEETNA THROUGH EARLY SATURDAY MORNING
BEFORE THE PRECIPITATION BECOMES MORE SCATTERED AND SHOWERY. IT
MAY ALSO BE COLD ENOUGH OVERNIGHT FRIDAY INTO SATURDAY MORNING FOR
THE PRECIPITATION TO FALL AS SNOW, OR A RAIN/SNOW MIX FROM EUREKA
WEST TOWARD SHEEP MOUNTAIN. NOW MAY BE THE TIME TO START THINKING
ABOUT WINTERIZING, ESPECIALLY AS TEMPERATURES BEGIN TO TREND
COOLER HEADING INTO NEXT WEEK.
ELSEWHERE, THE FLOW ALOFT IS CHARACTERIZED BY BROAD TROUGHING
WITH A COUPLE OF KEY FEATURES. WITH A NEGATIVELY TILTED TROUGH
AXIS LIFTING NORTHWARD FROM THE NORTHERN GULF AND INLAND OVER
SOUTHCENTRAL, UPSTREAM OF THIS FEATURE IS A MORE ROBUST SHORTWAVE
ROUNDING THE BASE OF THE MAIN TROUGH AXIS LOCATED SOUTH OF THE
EASTERN HALF OF THE ALEUTIAN CHAIN AND THE ALASKA PENINSULA. THE
LATTER WILL BE THE MAIN DRIVER OF DEEPENING A LARGE LOW PRESSURE
SYSTEM ENTERING THE GULF SATURDAY AFTERNOON. WITH THE OVERALL
TROUGH AXIS TAKING A NEGATIVE TILT AND AN ARCTIC TROUGH PROGGED TO
WORK SOUTHWARD FROM THE BERING STRAIT, THIS WILL CAUSE THE
SURFACE LOW TO BEGIN RETROGRADING NORTHWESTWARD ACROSS THE PRINCE
WILLIAM SOUND AS IT NEARS THE GULF COAST SUNDAY AFTERNOON. MODELS
SUGGEST THAT THE ATMOSPHERE LOOKS CONDUCIVE FOR MARINE LIGHTNING
(70-80% CHANCE) DURING THIS LOW'S JOURNEY ACROSS THE GULF
(SATURDAY AFTERNOON THROUGH SUNDAY AFTERNOON), MAINLY DUE TO THE
UPPER LOW COMPONENT OF THE SURFACE LOW STEEPENING LAPSE RATES, AND
THAT THE GULF WILL BE UNDER THE INFLUENCE OF BEING BELOW THE LEFT
EXIT REGION OF A 300 MB JET STREAK, WHICH WILL FURTHER ENHANCE
INSTABILITY. ASIDE FROM THAT, WIDESPREAD WESTERLY TO SOUTHWESTERLY
SMALL CRAFTS AND GALES ARE ALSO TO BE EXPECTED IN THE WAKE OF
THIS SYSTEM ACROSS THE GULF AS THE COLD AIR ADVECTION ASSOCIATED
WITH THE ARCTIC TROUGH SPILLS SOUTHWARD STARTING SUNDAY AFTERNOON.
-AM/TM
.SHORT TERM FORECAST SOUTHWEST ALASKA AND BERING SEA/ALEUTIANS
(DAYS 1 THROUGH 3/ SATURDAY THROUGH MONDAY)...
AN ACTIVE PATTERN CONTINUES THROUGH THE WEEKEND AND INTO NEXT WEEK
ACROSS SOUTHWEST ALASKA, WITH WIDESPREAD RAIN SHOWERS AND
INCREASINGLY COOLER CONDITIONS. LOOKING AT CURRENT SATELLITE
IMAGERY, AN UPPER- LEVEL TROUGH HAS SPUN UP A 998 MB SURFACE LOW
JUST SOUTH OF THE CENTRAL ALEUTIANS, WHICH IS EXPECTED TO RAPIDLY
INTENSIFY AS IT TRACKS INTO THE GULF TOMORROW. STRONG NORTHERLY
FLOW DEVELOPS IN THE WAKE OF THIS SYSTEM, BRINGING A BROAD SWATH
OF SMALL CRAFT WINDS ACROSS THE CENTRAL BERING TONIGHT.
MEANWHILE, SHOWERY CONDITIONS CONTINUE ACROSS THE SOUTHWEST THIS
AFTERNOON AS A WEAK LOW PRESSURE SYSTEM STALLS OUT AND SLOWLY DISSIPATES
OVER THE REGION.
BY SATURDAY MORNING THE AFOREMENTIONED GULF LOW REACHES 980 MB
SOUTH OF KODIAK ISLAND, CAUSING THE CORE OF STRONG WINDS TO SHIFT
EASTWARD ACROSS THE CENTRAL/EASTERN ALEUTIANS AND EVENTUALLY THE
AKPEN BY THE EVENING. STRONG COLD AIR ADVECTION WILL ACCOMPANY
THIS NORTHERLY FLOW, REINFORCING STRONG GAP WINDS THROUGH COLD BAY
AND KING COVE, WITH GUSTS TO 60 MPH POSSIBLE SATURDAY. LIGHT
SHOWERS WILL ALSO CONTINUE ACROSS PORTIONS OF SOUTHWEST ALASKA AND
THE ALEUTIANS AS THE LINGERING UPPER TROUGH MOVES ACROSS THE
REGION.
THE NORTHERLY FLOW ACROSS THE BERING GRADUALLY TURNS MORE
NORTHWESTERLY SUNDAY AS A RIDGE BUILDS OVER THE WESTERN ALEUTIANS,
ALLOWING THE ARCTIC AIRMASS TO SPREAD ACROSS THE SOUTHWEST. THIS
WILL USHER IN MUCH COOLER AIR, PARTICULARLY ACROSS THE KUSKOKWIM
DELTA, WHERE LOWS SUNDAY MORNING HAVE A 25% CHANCE OF DROPPING
BELOW FREEZING. SNOW LEVELS WILL DIP BETWEEN 1,000 FT TO 1,500
FT, ALLOWING ANY PRECIPITATION ACROSS THE HIGHER TERRAIN TO
TRANSITION TO SNOW. THE LOWER ELEVATION WILL SEE A RAIN/SNOW MIX.
COLD AIR CONTINUES TO FILTER IN OVERNIGHT SUNDAY AND INTO MONDAY
MORNING, DROPPING SNOW LEVELS AS LOW AS 500 FT. TEMPERATURES WILL
DIP BELOW FREEZING ACROSS A MORE WIDESPREAD AREA ON MONDAY
MORNING. ANY SNOWFALL WILL BE LIGHT AND CONFINED TO THE HIGHER
TERRAIN, WITH ANY LINGERING SHOWERS GRADUALLY DIMINISHING THROUGH
THE DAY.
-CW
.LONG TERM FORECAST (DAYS 4 THROUGH 7: TUESDAY THROUGH
FRIDAY)...
THE LONGTERM PERIOD BEGINNING TUESDAY MORNING WILL START OUT WITH
A LONGWAVE TROUGH EXTENDING ACROSS MUCH OF MAINLAND ALASKA DOWN
INTO THE ALASKA GULF. A GALE FORCE LOW WILL LIKELY BE MATURING AND
REACHING MAXIMUM INTENSITY SOMEWHERE OVER THE CENTRAL TO EASTERN
GULF. CURRENT MODEL CONSENSUS SUGGESTS THIS SYSTEM WILL STALL OUT
OVER OPEN WATERS AS IT SLOWLY WEAKENS THROUGH THE MIDDLE OF NEXT
WEEK, RESULTING IN LIMITED IMPACTS TO SOUTHCENTRAL. OUT TO THE
WEST, A LONGWAVE RIDGE IS ANTICIPATED TO BE MOVING ACROSS MUCH OF
THE BERING SEA IN BETWEEN THE GULF LOW AND A SHORTWAVE TROUGH AND
ATTENDANT LOW EVOLVING NEAR THE KAMCHATKA PENINSULA ON TUESDAY.
MUCH OF THE REMAINDER OF THE LONG TERM BEYOND TUESDAY WILL HINGE
HEAVILY ON THE DEGREE OF INTERACTION BETWEEN THE TROUGH/LOW
MOVING OFF OF KAMCHATKA INTO THE WESTERN BERING AND THE REMNANTS
OF WHAT IS CURRENTLY TYPHOON DUJUAN OUT IN THE WEST PACIFIC.
DUJUAN WILL RECURVE NORTH AND EAST AFTER MAKING A CLOSE PASS WITH
JAPAN THIS WEEKEND, EVENTUALLY APPROACHING THE WESTERN PARTS OF
THE ALEUTIAN CHAIN AFTER TRANSITIONING TO AN EXTRATROPICAL LOW
AROUND TUESDAY TO WEDNESDAY NEXT WEEK. MODELS ARE STILL STRUGGLING
QUITE A BIT TO DETERMINE HOW THE REMNANTS OF DUJUAN WILL BEHAVE
AS THE CENTER GETS CLOSER TO THE SEPARATE LOW PRESSURE SYSTEM
PROGRESSING ACROSS THE BERING. SOME EARLIER DETERMINISTIC
SOLUTIONS AND CURRENT EPS/GEFS ENSEMBLE MEMBERS SUGGEST THAT A
STRONG PHASING INTERACTION COULD OCCUR BETWEEN THE TWO LOWS,
PERHAPS RESULTING IN A MUCH STRONGER LOW THAT DEEPENS RAPIDLY
SOMEWHERE ACROSS THE SOUTHERN BERING SEA AND ALEUTIANS/AKPEN AS
THE TWO SYSTEMS ESSENTIALLY MERGE. IF THIS COMES TO FRUITION
(ABOUT A 20-30% CHANCE), HIGH WINDS AND WAVES COULD BECOME A
SUBSTANTIAL HAZARD ACROSS A LARGE PORTION OF THE BERING SEA,
ALEUTIANS AND POSSIBLY SOUTHWEST TOWARDS THE MIDDLE TO LATTER PART
OF NEXT WEEK.
IN CONTRAST TO THE SCENARIO ABOVE, MUCH OF THE 12Z DETERMINISTIC
GUIDANCE COMING IN TODAY IS DEPICTING DUJUAN'S REMNANTS TAKING A
LITTLE MORE TIME TO MOVE NORTHEAST ACROSS THE NORTH PACIFIC,
EFFECTIVELY CAUSING IT TO MISS THE STRONGER INTERACTION WITH THE
OTHER LOW PROGRESSING ACROSS THE BERING SEA. THIS VERSION OF
EVENTS (MORE LIKELY SCENARIO, AROUND 70% CHANCE) WOULD KEEP
DUJUAN TRACKING OFF TO THE SOUTH OF THE ENTIRE ALEUTIAN CHAIN,
WITH AN OVERALL LOWER THREAT FOR STRONG WINDS AND LARGE WAVES
ACROSS THE BERING SEA NEAR THE SECONDARY LOW TO THE NORTH. EVEN
SO, THE LOW MOVING OFF OF KAMCHATKA COULD STILL PULL A SIGNIFICANT
AMOUNT OF MOISTURE NORTH FROM DUJUAN'S REMNANTS AS THEY PASS TO
THE SOUTH, ENOUGH TO SUPPORT A HEAVY RAIN THREAT ACROSS PARTS OF
THE PRIBILOFS, ALEUTIANS AND SOUTHWEST SOMETIME BETWEEN WEDNESDAY
AND FRIDAY AS THE SYSTEM TRACKS NORTHEAST TOWARDS THE WESTERN
COASTLINE. THE INFLUX OF WARM, MOIST AIR COULD ALSO HELP DEEPEN
THE KAMCHATKA SYSTEM TO A GALE FORCE LOW AS IT TRACKS ACROSS THE
BERING, SO THE WIND AND WAVE POTENTIAL ACROSS THE ALEUTIANS AND
SOUTHWEST WOULD CERTAINLY NOT BE ZERO IN THIS CASE. BOTTOM LINE,
ANTICIPATE A STRONG LOW TO AFFECT PARTS OF THE ALEUTIANS, BERING
AND SOUTHWEST NEXT WEEK, REGARDLESS OF EXACTLY HOW THE REMNANTS OF
DUJUAN PLAY A ROLE.
MEANWHILE, MUCH QUIETER CONDITIONS ARE EXPECTED FOR THE MOST PART
ACROSS SOUTHCENTRAL BY THE MIDDLE OF NEXT WEEK. A SEASONABLY COOL
AIR MASS WILL BE IN PLACE ACROSS THE REGION INITIALLY, BUT SOME
WARMING IS LIKELY TOWARDS WEDNESDAY AND THURSDAY AS THE BERING
RIDGE MOVES OVERHEAD. THERE COULD BE A THREAT FOR STRONG SOUTHERLY
GAP WINDS TO DEVELOP LATE IN THE WEEK ALONG WITH INCREASING RAIN
CHANCES, BUT THIS WILL BE HIGHLY DEPENDENT ON THE COMPLEX AND
UNCERTAIN INTERACTION BETWEEN MULTIPLE SYSTEMS OUT WEST AS
DESCRIBED ABOVE.
-AS
AVIATION
PANC...MVFR CEILINGS ARE EXPECTED TO DEVELOP THIS EVENING AS AN
AREA OF LOW PRESSURE MOVES INTO PRINCE WILLIAM SOUND. THERE IS A
CHANCE FOR MVFR VISIBILITIES AT TIMES IN THE RAIN, BUT VFR
VISIBILITY SHOULD BE PREVAILING THROUGH THE TAF PERIOD. A LIGHT
NORTH WIND WILL SHIFT TO THE SOUTHWEST THIS EVENING THEN TO A
GUSTY SOUTHEAST WIND OUT OF TURNAGAIN ARM AROUND MIDNIGHT AS THE
LOW TRACKS INLAND AND NORTH OF THE REGION. AS THE LOW WEAKENS AND
CONTINUES TO MOVE NORTH, THE GUSTY WINDS WILL DIMINISH AND RAIN
TAPER OFF. THE LIGHT AND VARIABLE WINDS OVERNIGHT AND INTO
SATURDAY, COMBINED WITH LINGERING LOW-LEVEL MOISTURE, COULD RESULT
IN PATCHY FOG NEAR OR OVER THE TERMINAL SATURDAY MORNING.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page