088
FXAK68 PAFC 041327
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
527 AM AKDT SUN MAY 4 2025
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3)
AN UPPER-LEVEL WAVE MOVING INLAND IS PROVIDING SUPPORT FOR
CONTINUED SHOWER ACTIVITY OVER THE COASTAL MOUNTAINS ALONG WITH A
FEW ISOLATED SHOWERS MOVING THROUGH THE SUSITNA VALLEY. THE
SOUTHEASTERLY GAP WINDS OF YESTERDAY HAVE FINALLY ABATED, DUE TO A
SLACKENING AND REORIENTING OF THE PRESSURE GRADIENT IN ADVANCE OF
THE NEXT WEATHER FEATURE SETTING ITS SIGHTS ON THE SOUTHERN
MAINLAND.
A VIGOROUS UPPER-LEVEL SHORT WAVE MOVING FROM THE NORTH PACIFIC
TOWARD THE WESTERN GULF IS AIDING IN THE DEVELOPMENT OF WHAT WILL
BE A STORM-FORCE LOW TO THE EAST OF THE NOW-DECAYING VERTICALLY
STACKED LOW SOUTH OF SAND POINT. THIS SURFACE LOW WILL RAPIDLY
DEEPEN THROUGH THE DAY AS IT DRIVES A FRONT FROM KODIAK ISLAND TO
THE NORTHERN GULF COAST.
BY SUNDAY AFTERNOON, THE FRONT DRIVES INTO THE SOUTHCENTRAL
COAST, FORCING HEAVY PRECIPITATION AND A STRONG BARRIER JET ALONG
THE COASTLINE. INLAND AREAS WILL BE SHELTERED FROM MOST
PRECIPITATION DUE TO DOWNSLOPING AND WILL SEE LOWER PRECIPITATION
CHANCES. ONCE AGAIN, HIGHER ELEVATIONS GENERALLY ABOVE 2500 FT
COULD SEE SNOWFALL, ESPECIALLY AT NIGHT. WINDS WILL BE GREATLY
ENHANCED AS WELL FROM THIS FRONT. INLAND, GAP WIND LOCATIONS SUCH
AS THE TURNAGAIN ARM AND TO A LESSER EXTENT, THE KNIK ARM, AGAIN
PICK UP SUNDAY AFTERNOON, BUT THE TURNAGAIN WIND WILL BE
REDIRECTED AWAY FROM THE ANCHORAGE BOWL AS THE FLOW WILL LIKELY BE
DOWN-INLET. STRONG WINDS ALOFT, HOWEVER, COULD ALSO RESULT IN
GUSTS NOT ONLY FOR GAP LOCATIONS BUT FOR THE ANCHORAGE AND EAGLE
RIVER HILLSIDES FROM THIS AFTERNOON THROUGH TONIGHT.
ALSO BY SUNDAY AFTERNOON, WINDS WILL HAVE INCREASED TO STORM
FORCE ALONG THE FRONT NEAR THE BARREN ISLANDS, WITH HIGH END GALE
FORCE WINDS OVER THE NORTHERN GULF AND INCREASING TO STORM-FORCE
SOUTH OF PRINCE WILLIAM SOUND. HURRICANE FORCE WIND GUSTS CANNOT
BE RULED OUT (64 KTS OR GREATER).
THE BARRIER JET QUICKLY COLLAPSES WITH THE FRONTAL PASSAGE DURING
MONDAY MORNING AS AN ONSLAUGHT OF HEAVY PRECIPITATION OVERWHELMS
THE IMMEDIATE SOUTHCENTRAL COASTAL AREAS. QPF AMOUNTS WILL LIKELY
BE IMPRESSIVE WITH THIS SYSTEM, WITH 2 TO 4"+ OF RAINFALL
POSSIBLE FOR MUCH OF THE COASTLINE AND AREAS THAT BENEFIT FROM
OROGRAPHIC LIFT, SUCH AS ALONG THE SOUTHERN FACING SLOPES OF THE
CHUGACH AND EASTERN FACING SLOPES OF THE KENAI MOUNTAINS.
CONDITIONS WILL MOST LIKELY SLOWLY IMPROVE DURING THE DAY AND
AFTERNOON HOURS OF TUESDAY, WITH THE SPRAWLING ATTENDANT AREA OF
LOW PRESSURE STILL SPINNING IN THE SOUTHERN GULF.
-AM/TM
.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 THROUGH 3: TODAY
THROUGH TUESDAY NIGHT)...
A LOW SOUTH OF THE ALASKA PENINSULA THIS MORNING PUSHES A FRONT UP
INTO BRISTOL BAY TODAY, WHERE RAIN SHOWERS WILL INCREASING FILL IN
OVER NORTHERN/INTERIOR BRISTOL BAY. WINDS INCREASE IN TANDEM, WITH
GUSTY WINDS THROUGH KAMISHAK GAP INCREASING TO GUST AS HIGH AS 45
MPH FOR PORTIONS OF BRISTOL BAY. DOWNSLOPING KEEPS AREAS CLOSER
TO THE ALASKA/ALEUTIAN RANGE DRIER, THOUGH PERIODS OF RAIN ARE
STILL EXPECTED. FURTHER NORTH, IN THE KUSKOKWIM VALLEY AND DELTA,
EXPECT DRIER AND SUNNIER CONDITIONS THROUGH EARLY THIS AFTERNOON
BEFORE SCATTERED RAIN SHOWERS DEVELOP AND CLOUD COVER INCREASES
THIS AFTERNOON/EVENING. HIGH TEMPERATURES REMAIN RELATIVELY
DEPRESSED IN THE MID 40S FOR BRISTOL BAY, WITH MOST AREAS ALONG
THE KUSKOKWIM RIVER REACHING AT LEAST 50 TODAY. THE LOW MOVES
SLOWLY NEAR KODIAK ISLAND THROUGH MONDAY, WHICH WILL KEEP THE BEST
PRECIPITATION CHANCES IN BRISTOL BAY THROUGH AT LEAST TONIGHT.
UNCERTAINTY INCREASES WITH PRECIPITATION FOR MONDAY, WHERE MODEL
GUIDANCE IS INDECISIVE OVER WHAT PORTIONS OF BRISTOL BAY RECEIVE
RAINFALL WITH EMBEDDED SHORTWAVES TRACKING THROUGH THE AREA WITHIN
THE BROADER LOW PRESSURE. BY MONDAY EVENING, MOISTURE WORKS FAR
ENOUGH NORTH FOR A WEAK FRONT TO BRING LIGHT RAIN TO PORTIONS OF
THE KUSKOKWIM VALLEY AND DELTA. FOR MONDAY NIGHT, THE LOW TRACKS
SOUTH OF KODIAK ISLAND AND INTO THE GULF OF ALASKA, AND UPPER-
LEVEL FORCING OVER SOUTHWEST ALASKA DIMINISHES, LEADING TO
DECREASING RAIN CHANCES. ON TUESDAY, HOWEVER, CLEARING SKIES ALLOW
TEMPERATURES TO WARM INTO THE MID 50S OVER BRISTOL BAY AND THE
LOWER KUSKOKWIM VALLEY, WHICH WILL PROMOTE INSTABILITY FOR RAIN
SHOWERS, AND COOLING TEMPERATURES ALOFT LEAD TO POTENTIAL FOR
ISOLATED THUNDERSTORMS. AN UPPER-LEVEL LOW DIVES SOUTH TOWARD
NUNIVAK ISLAND BY TUESDAY NIGHT, WHICH LEADS TO COOLING
TEMPERATURES FOR THE KUSKOKWIM DELTA REGION.
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 THROUGH 3: TODAY
THROUGH TUESDAY NIGHT)...
A GALE FORCE LOW SOUTH OF THE ALASKA PENINSULA INTENSIFIES TODAY
AS IT TRACKS TOWARD KODIAK ISLAND. ITS FRONT EXTENDS ACROSS THE
ALASKA PENINSULA AND THE EASTERN ALEUTIANS, PRODUCING PRIMARILY
RAIN. SNOW MAY MIX IN AT TIMES, ESPECIALLY FURTHER WEST ALONG THE
ALEUTIAN CHAIN, WHERE COLDER AIR IS PRESENT ALOFT. HOWEVER,
ACCUMULATION IS EXPECTED TO BE LITTLE TO NONE AS TEMPERATURES
REMAIN GENERALLY ABOVE FREEZING NEAR SEA LEVEL. COLD AIR WRAPPING
AROUND THE BACK SIDE OF THE LOW WILL ALSO HELP TO INTENSIFY WINDS
AND GALES SPREAD ACROSS THE EASTERN BERING/ALEUTIANS AND SOUTHERN
ALASKA PENINSULA THROUGH TONIGHT. AS THE LOW SHIFTS SLOWLY EAST,
PRECIPITATION BECOMES MORE SHOWERY AND MORE LIKELY TO BE SNOW OVER
TIME, THOUGH DRIER AIR MOVING ACROSS THE CENTRAL BERING SEA WILL
ALSO LEAD TO A DOWNTREND IN PRECIPITATION INTENSITY. HIGH PRESSURE
OVER THE WESTERN BERING SEA SINKS SOUTH AS A LOW NEAR KAMCHATKA
PUSHES A FRONT INTO THE WESTERN ALEUTIANS ON MONDAY. A BAND OF
RAIN AND SOUTHERLY WINDS BELOW GALE FORCE PUSH INTO THE WESTERN
BERING SEA MONDAY NIGHT AND REACH THE CENTRAL BERING/ALEUTIANS FOR
TUESDAY.
.LONG TERM FORECAST (DAYS 4 THROUGH 7/WEDNESDAY THROUGH
SATURDAY)...
WEDNESDAY, A WEAKENING LOW SITS IN THE SOUTHERN GULF WITH AN
OCCLUDED FRONT WRAPPED AROUND THE GULF COAST. WITH A HIGH
AMPLITUDE RIDGE BUILDING ACROSS NORTHWESTERN CANADA, THE UPPER
LEVEL LOW WILL LINGER OVER THE GULF THROUGH FRIDAY. SHORTWAVES
ROTATING AROUND THE LOW CENTER MAY LEAD TO DEVELOPMENT OF MULTIPLE
ADDITIONAL SURFACE LOWS, BUT ALL OF THEM WILL ULTIMATELY END UP
TRACKING TO THE POSITION OF THE UPPER CENTER. THE MOST IMPACTED
AREAS WILL BE ALONG THE GULF COAST AND KODIAK ISLAND, WITH
OCCASIONAL RAIN OR RAIN SHOWERS. NONE OF THE SURFACE LOWS LOOK
PARTICULARLY STRONG, SO WINDS FOR THE GULF COASTAL WATERS LOOK TO
REMAIN AT OR BELOW SMALL CRAFT ADVISORY LEVELS. FOR SOUTHCENTRAL
AND SOUTHWEST AK, THIS PATTERN WILL BRING A MIX OF SUN AND CLOUDS,
WITH SOME WEAK RIDGING AT TIMES BUT ALSO THE LIKELIHOOD OF UPPER
LEVEL SHORTWAVES ROTATING THROUGH WITH SOME CLOUDS AND SHOWERS.
MEANWHILE, A DEEP LOW WILL TRACK INTO THE FAR WESTERN BERING SEA
THURSDAY, WITH A LEADING FRONTAL SYSTEM PROGRESSING EASTWARD
ACROSS THE BERING AND ALEUTIANS. THE GFS AND CANADIAN MODELS
INDICATE THIS LOW EXITING INTO THE NORTH PACIFIC BY SATURDAY, BUT
THESE MIGHT BE OUTLIERS AS ENSEMBLES DEPICT THE SURFACE LOW
REMAINING IN THE CENTRAL BERING THROUGH THE WEEKEND. IN EITHER
CASE, EXPECT LOW IMPACT WEATHER FOR THE BERING AND ALEUTIANS NEXT
WEEKEND.
AVIATION
PANC...VFR CONDITIONS WILL PERSIST WITH ANY PRECIPITATION LIKELY
IN THE FORM OF A FEW SPRINKLES. ANY LINGERING SOUTHEASTERLY WINDS
EARLY THIS MORNING ARE EXPECTED TO BECOME LIGHT AND VARIABLE,
THEN NORTH-NORTHEASTERLY, AS A DEVELOPING AREA OF LOW PRESSURE
SOUTH OF THE ALASKA PENINSULA BEGINS TO BEND THE TURNAGAIN ARM
WIND DOWN COOK INLET. AS THE FRONTAL WAVE ASSOCIATED WITH THE
SURFACE LOW MOVES TOWARD THE NORTHERN GULF TODAY, SOUTHEASTERLY
TURNAGAIN ARM WINDS AND WINDS ALOFT WILL REDEVELOP. THIS WILL
LIKELY CREATE A PERIOD OF LLWS FOR THE TERMINAL BY AROUND NOON
TODAY.
WHILE WINDS NEAR THE TERMINAL WILL LIKELY MAINTAIN A NORTHERLY
COMPONENT, THERE IS STILL SOME UNCERTAINTY AS TO WHETHER ANY
DAYTIME HEATING AND WARMER TEMPERATURES IN THE INTERIOR WILL ALLOW
THE PRESSURE GRADIENT TO WEAKEN OR SHIFT FOR A PERIOD OF TIME
THIS AFTERNOON AND ALLOW THE SOUTHEASTERLY TURNAGAIN ARM WIND TO
MOVE OVER THE TERMINAL. CURRENTLY, THIS IS A LOW CONFIDENCE
SCENARIO, AND HAS BEEN KEPT OUT OF THE 12Z TAF. HOWEVER, IT DOES
BEAR WATCHING.
BY THIS EVENING, THE DOWN INLET PRESSURE GRADIENT WILL SOLIDLY
TAKE HOLD, WITH INCREASING NORTHERLY WINDS AND GUSTS FOR THE
TERMINAL. AGAIN, LLWS MAY REMAIN/DEVELOP FOR A PERIOD OF TIME
BEFORE THE GUSTY SOUTHEAST WINDS ALOFT ALSO SHIFT AND BECOME MORE
NORTHEASTERLY TONIGHT AND INTO THE OVERNIGHT HOURS.
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