335
FXAK68 PAFC 051326
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
526 AM AKDT SAT JUL 5 2025
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3/TODAY
THROUGH MONDAY NIGHT)...
IN THE UPPER LEVELS, A REX BLOCK IS IN PLACE ACROSS ALASKA, WITH
A RIDGE CENTERED OVER NORTHERN ALASKA AND A LOW CENTERED ALONG
AND SOUTH OF THE ALEUTIANS. THE WEATHER OVER SOUTHCENTRAL CONTINUES
TO BE DRIVEN BY FLOW AROUND THE PERIMETER OF THE RIDGE THOUGH
THAT WILL CHANGE AS WE HEAD THROUGH THE WEEKEND. OVERNIGHT, A
FEW CLOUDS AND ISOLATED SHOWERS MOVED OUT OF THE YUKON AND ACROSS
INLAND PORTIONS OF SOUTHCENTRAL. LOW CLOUDS HAVE SET UP SHOP
ALONG THE NORTH GULF COAST AND PRINCE WILLIAM SOUND IN A MORE
STABLE AIRMASS. IN BETWEEN, SKIES ARE MOSTLY CLEAR. MEANWHILE,
SHORT-WAVE TROUGHS ROUNDING THE FRONT SIDE OF THE UPPER LEVEL
LOW ARE DRIVING A SURFACE OCCLUDED FRONT NORTHWARD TOWARD KODIAK
ISLAND AND THE WESTERN GULF, LEADING TO RAIN AND STRENGTHENING
EASTERLY WINDS.
SHORT-WAVES ROUNDING THE RIDGE ACROSS THE YUKON WILL TRACK
WESTWARD ACROSS INTERIOR SOUTHCENTRAL TODAY, INITIATING AFTERNOON
SHOWERS AND THUNDERSTORMS. THERE HAS BEEN SOME NORTH-SOUTH SPREAD
IN THE MODELS WITH WHERE THE BULK OF CONVECTION SETS UP, LARGELY
DUE TO SUBTLE DIFFERENCES WITH HOW MUCH INFLUENCE THE TROUGH IN
THE GULF HAS ON THE FLOW. HOWEVER, 06Z MODEL GUIDANCE IS IN BETTER
AGREEMENT IN DEPICTING THE BULK OF CONVECTION OVER THE NORTHERN
COPPER RIVER BASIN, TALKEETNA MOUNTAINS, AND NORTHERN SUSITNA
VALLEY. THUS, IT LOOK LIKE ANOTHER DRY DAY FOR THE KENAI
PENINSULA, ANCHORAGE, AND SOUTHERN MAT-SU - THOUGH A STRAY
SHOWER CAN'T BE COMPLETELY RULED OUT ACROSS THE SOUTHERN MAT-SU
LATER TODAY. THE SHORT-WAVES WON'T COMPLETELY EXIT UNTIL LATE
TONIGHT, SO SHOWERS WILL LIKELY KEEP GOING THROUGH THE OVERNIGHT
HOURS FOR THE TALKEETNA MOUNTAINS AND NORTHERN SUSITNA VALLEY.
THE TROUGH TO THE SOUTH WILL STRUGGLE TO LIFT NORTHWARD TOWARD
SOUTHCENTRAL, KEEPING RAIN CONFINED TO KODIAK ISLAND AND THE GULF
TODAY. HOWEVER, A CLASSIC EAST-WEST SURFACE RIDGE WILL SET UP
ALONG THE GULF COAST BETWEEN THE FRONT IN THE GULF AND THERMAL
TROUGH INLAND. THIS WILL LEAD TO STRONG AND GUSTY SOUTHEASTERLY
GAP WINDS THIS AFTERNOON AND EVENING.
SUNDAY WILL BE A TRANSITION DAY AS THE RIDGE WEAKENS TO THE NORTH
AND THE UPPER LOW SHIFTS INTO THE GULF, WITH SHORT-WAVES ROTATING
NORTHWARD TOWARD SOUTHCENTRAL. INCREASED CLOUD COVER WILL LEAD TO
SOMEWHAT MORE STABLE CONDITIONS INLAND, WITH MUCH LESS CONVECTION
EXPECTED. STEADY RAIN WILL SETTLE IN ALONG THE NORTH GULF COAST
AND PRINCE WILLIAM SOUND. SHORT-WAVES WILL THEN ROTATE NORTHWARD
INTO SOUTHCENTRAL SUNDAY NIGHT THROUGH MONDAY, THOUGH MODEL
GUIDANCE VARIES ON THE EXACT TRACK OF SHORT-WAVES. RAIN IS LIKELY
AHEAD OF THE SHORT-WAVES, ESPECIALLY FROM PRINCE WILLIAM SOUND TO
THE COPPER RIVER BASIN. THE BIG QUESTION IS HOW FAR WEST RAIN
WILL MAKE IT, AS THE UPPER LOW IN THE GULF WILL CONTINUE EASTWARD
TOWARD SOUTHEAST ALASKA, CAUSING FLOW OVER SOUTHCENTRAL TO SHIFT
TOWARD NORTHERLY AND CHANGE THE DIRECTION OF FLOW (AND MOVEMENT OF
SHORT-WAVES). STAY TUNED, AS THERE IS POTENTIAL FOR WIDESPREAD
WETTING RAINS TO START THE WORK WEEK.
FORECAST CONFIDENCE CONTINUES TO FALL MONDAY NIGHT INTO TUESDAY
AS AN ARCTIC TROUGH DIGS SOUTHWARD ACROSS MAINLAND ALASKA. MODEL
GUIDANCE CONTINUES TO STRUGGLE WITH THE ULTIMATE TRACK AND
AMPLITUDE OF THE ARCTIC TROUGH, WITH INDIVIDUAL SHORT-WAVES
LEADING TO WILDLY DIFFERENT SOLUTIONS AMONG THE GUIDANCE. THE
LIKELY BET IS THAT UNSETTLED WEATHER WILL PERSIST AS WE CONTINUE
THROUGH THE WORK WEEK.
-SEB
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (DAYS
1 THROUGH 3: TODAY THROUGH TUESDAY)...
UPPER LEVEL HIGH PRESSURE REMAINS CENTERED OVER THE NORTHERN
ALASKA COASTLINE WITH THE BEAUFORT SEA. A WEAKENING LOW PRESSURE
SYSTEM IS CENTERED IN THE EASTERN BERING, NORTHWEST OF UNIMAK
ISLAND, WITH A FRONT THAT EXTENDS SOUTHEAST INTO THE NORTH
PACIFIC. THIS FRONT WILL CONTINUE TO BRING GUSTY WIND AND
PRECIPITATION ACROSS THE ALASKA PENINSULA AND INTO BRISTOL BAY AS
IT WEAKENS THROUGH THIS AFTERNOON. THESE TWO LARGER SYNOPTIC
FEATURES (HIGH AND LOW PRESSURE CENTERS) WILL DIRECT NEARLY ZONAL
FLOW ACROSS THE ALASKAN INTERIOR THROUGH SUNDAY. MODELS ARE HONING
IN ON AN UPPER LEVEL VORTICITY MAXIMUM, MOVING THROUGH SUNDAY
MORNING, THAT WILL BRING AN INCREASED CHANCE OF MODERATE RAIN
SHOWERS AND THUNDERSTORM DEVELOPMENT WESTWARD ACROSS THE KUSKOKWIM
RIVER VALLEY AND DIVING SOUTHWEST ACROSS THE KUSKOKWIM DELTA,
BEFORE DIMINISHING SUNDAY AFTERNOON OVER KUSKOKWIM BAY. MODEL
RUNS HAVE PROGRESSIVELY BROUGHT THE TRACK OF THIS SYSTEM
SOUTHWARD, FROM OVER NUNIVAK ISLAND TO OVER KUSKOKWIM BAY. THE GFS
AND ECMWF WERE PREVIOUSLY HOLDING ONTO A MORE NORTHERN TRACK AND
ARE VERY INCREMENTALLY COMING INTO BETTER ALIGNMENT WITH THE MORE
SOUTHERN TRACK OF THE NAM/GEM.
DRIER CONDITIONS ARE EXPECTED ON MONDAY AND TUESDAY FOR THE
ALASKA PENINSULA AND BRISTOL BAY WITH THE LINGERING POTENTIAL FOR
AFTERNOON SHOWERS ACROSS MORE INTERIOR REGIONS OF THE STATE.
LONG TERM FORECAST (DAYS 4 THROUGH 7: TUESDAY THROUGH FRIDAY)
THE LONG-TERM PERIOD BEGINS WITH UPPER-LEVEL LOWS ACROSS THE
SOUTHEAST GULF OF ALASKA/SOUTHEAST MAINLAND ALASKA AND OVER THE
CENTRAL ALEUTIANS. BETWEEN THESE LOWS IS A WEAK RIDGE ACROSS THE
SOUTHCENTRAL AND SOUTHWESTERN MAINLANDS. EXPECT DRIER CONDITIONS
TOWARDS THE SOUTHERN MAINLAND COAST ON TUESDAY WITH SHOWERS IN THE
AFTERNOON FOR THE INTERIOR AND ALONG THE INTERIOR TERRAIN.
LIGHT RAIN MOVES ACROSS THE ALEUTIAN CHAIN FROM THE WESTERN
ALEUTIANS TUESDAY TO THE SOUTHERN ALASKA PENINSULA (AKPEN) THROUGH
WEDNESDAY EVENING IN ASSOCIATION WITH AN EASTWARD TRACK NORTH
PACIFIC LOW. SHOWERS CONTINUE ACROSS THE SOUTHWESTERN INTERIOR AND
THE NORTHERN SUSITNA VALLEY TUESDAY AND WEDNESDAY AS AN ARCTIC
TROUGH DIGS SOUTHWARD. ONE TREND FROM YESTERDAY'S LONG-TERM
FORECAST IS THAT THIS ARCTIC TROUGH DOES NOT LOOK TO DIG AS FAR
SOUTH, BUT ONLY AS FAR SOUTH AS THE TROUGH AXIS REACHING NORTON
SOUND. THEREFORE, DO NOT EXPECT TEMPERATURES TO BE WAY LOWER THAN
NORMAL BUT MORE SLIGHTLY BELOW NORMAL FOR SOUTHWEST ALASKA.
MEANWHILE, THE NORTH PACIFIC LOW THAT TRACKED FROM THE WESTERN
ALEUTIANS TO THE SOUTHERN AKPEN LOOKS TO HAVE ITS ENERGY MOVE TO
THE GULF BY THURSDAY. THERE ARE STILL SOME QUESTIONS ABOUT THE
EXACT TRACK OF THE LOW AND ITS TIMING. HOWEVER, THERE IS
REASONABLE CONFIDENCE TO SAY THAT THE SOUTHCENTRAL COAST,
INCLUDING KODIAK ISLAND, WILL BE THE WETTER LOCATIONS THURSDAY AND
FRIDAY WHEN COMPARED TO THE INTERIOR LOCATIONS. BACK TO THE WEST,
A KAMCHATKA SYSTEM LOOKS TO MOVE CLOSE THE WESTERN ALEUTIANS BY
FRIDAY BRINGING ANOTHER CHANCE FOR RAIN AND GUSTY WINDS BY THEN.
.AVIATION...
PANC...VFR CONDITIONS WILL PERSIST. THERE IS HIGH CONFIDENCE IN
STRONG GUSTY SOUTHEASTERLY WINDS DEVELOPING THIS AFTERNOON, WITH
TIGHTENING PRESSURE GRADIENTS AHEAD OF A FRONT LIFTING NORTHWARD
ACROSS THE GULF. FORECAST PRESSURE OVER THE SUSITNA VALLEY WILL
BE WEAKLY LOWER THAN ANCHORAGE. AS A RESULT, THE CORE OF STRONGEST
TURNAGAIN WINDS SHOULD STAY SOUTH OF THE TERMINAL. STILL, WITH
CONTINUED SUNSHINE AND A WELL MIXED BOUNDARY LAYER, WINDS WILL BE
QUITE GUSTY. THE ONLY UNCERTAINTY IS HOW HIGH THE WIND GUSTS WILL
GET. BASED ON FORECAST SOUNDINGS, 30 KTS SEEMS MOST LIKELY, THOUGH
THERE COULD BE SOME ISOLATED STRONGER GUSTS OF AROUND 35 KTS.
WINDS WILL SLOWLY DIMINISH AFTER 06Z AS A SURFACE LOW DEVELOPS
OVER THE NORTHWESTERN GULF AND THE TURNAGAIN JET BENDS SOUTHWARD.
-SEB
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