541  
FXAK68 PAFC 230027  
AFDAFC  
 
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE ANCHORAGE AK  
427 PM AKDT FRI JUN 22 2018  
   
ANALYSIS AND UPPER LEVELS
 
 
AN UPPER LEVEL LOW OVER THE BERING SEA AND A WEAKER TROUGH OVER  
THE GULF OF ALASKA CONTINUE TO BRING CLOUDY AND COOL WEATHER TO  
MUCH OF THE STATE TODAY. AS THE UPPER LEVEL TROUGH SLOWLY MOVES  
THROUGH THE SOUTHCENTRAL REGION, THE RADAR REFLECTS A SLOWLY  
SHIFTING PRECIP BOUNDARY ALONG THE KENAI PENINSULA. OVER THE  
WESTERN MAINLAND, RADAR IS SHOWING A SERIES OF SHOWERS TRAINING  
OVER BETHEL THAT IS ASSOCIATED WITH A TROUGH FROM THE LOW IN THE  
BERING SEA. THESE SHOWERS ARE HEAVIER IN NATURE AND ARE REDUCING  
VISIBILITIES BUT HAVEN'T HAD MUCH OTHER IMPACT. MEANWHILE, A  
SHORTWAVE RIDGE IN THE FAR WESTERN ALEUTIANS IS LEADING TO BROAD  
AREAS OF FOG ACROSS THE WESTERN BERING SEA.  
 

 
   
MODEL DISCUSSION
 
 
MODELS ARE IN GOOD AGREEMENT ON THE LARGER FEATURES IN THE NEXT 48  
HOURS. DUE TO THE OVERALL LEVEL OF INSTABILITY, ACTUAL LOCATIONS  
OF SHOWERS ARE DIFFICULT TO RESOLVE BETWEEN THE DIFFERENT MODEL  
RUNS. MOVING INTO THE SUNDAY/MONDAY TIMEFRAME, UPPER LEVELS ARE IN  
PRETTY GOOD AGREEMENT ABOUT AN EASTERLY WAVE MOVING INTO THE  
COPPER RIVER BASIN, BUT HOW THIS PLAYS OUT LATER ON AT THE SURFACE  
HAS SOME DIFFERENCES BETWEEN THE MODEL RUNS. IF THE NAM PLAYS OUT,  
THIS EASTERLY WAVE WILL REMAIN FURTHER TO THE EAST, WITH FEWER  
IMPACTS OVER THE SOUTHCENTRAL AREA.  
 

 
   
AVIATION
 
 
PANC...SOME MVFR CONDITIONS ARE EXPECTED THIS AFTERNOON, BUT  
THESE LINGERING LOWER CLOUDS SHOULD BREAK UP BY EVENING. VFR  
CONDITIONS AND LIGHT WINDS ARE THEN EXPECTED THROUGH SATURDAY  
EVENING.  
 

 
   
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)
 
 
WEAK CYCLONIC FLOW ALOFT COMBINED WITH WEAK INSTABILITY WILL ALLOW  
A FEW LIGHT SHOWERS TO LINGER ACROSS SOUTHCENTRAL THROUGH THIS  
EVENING, THOUGH DO EXPECT A DRYING TREND. AFTER THIS, INSTEAD OF A  
WEAK UPPER LEVEL RIDGE BUILDING IN, IT NOW LOOKS LIKE SOUTHCENTRAL  
WILL REMAIN UNDER THE INFLUENCE OF CYCLONIC FLOW, WITH ALL  
COMPUTER MODELS NOW INDICATING A DISTINCT SHORT-WAVE TROUGH  
MOVING FROM THE EASTERN GULF TONIGHT TO THE COPPER RIVER BASIN ON  
SATURDAY. BASED ON THIS, HAVE TRENDED WETTER ACROSS THE COPPER  
RIVER BASIN. WEAK FLOW AND INSTABILITY ELSEWHERE SHOULD KEEP THE  
REMAINDER OF THE AREA MOSTLY DRY, WITH JUST A FEW SHOWERS FOCUSED  
ALONG THE MOUNTAINS. THE SHORT-WAVE WILL ALSO REINFORCE CLOUD  
COVER ACROSS THE REGION, BUT DO THINK AREAS FARTHEST AWAY SHOULD  
SEE AT LEAST SOME BREAKS OF SUN DURING THE DAY SATURDAY. THIS  
INCLUDES THE KENAI PENINSULA ON UP TO ANCHORAGE AND PERHAPS EVEN  
PORTIONS OF THE MAT-SU.  
 
THE UPPER LEVEL WILL FLATTEN OUT AND LINGER OVER INTERIOR  
SOUTHCENTRAL SATURDAY NIGHT THROUGH SUNDAY. STORM MOTION WILL  
ADVECT SHOWERS WESTWARD FROM THE COPPER RIVER BASIN TO THE MAT-SU.  
A FEW SHOWERS MAY MAKE IT AS FAR SOUTH AS ANCHORAGE AND THE KENAI  
PENINSULA. SUNDAY DEFINITELY LOOKS LIKE THE CLOUDIER DAY OF THE  
WEEKEND. A SECOND UPPER WAVE WILL APPROACH THE COPPER BASIN FROM  
THE EAST ON SUNDAY. LOW LEVEL WARMING JUST AHEAD OF IT LOOKS LIKE  
ENOUGH TO DESTABILIZE THE ATMOSPHERE AND PRODUCE A FEW  
THUNDERSTORMS.  
 
THE FLOW BECOMES MORE CHAOTIC ON MONDAY AND IT'S HARD TO HONE IN  
ON ANY SPECIFIC FEATURE TO FOCUS SHOWERS. FOR NOW, HAVE USED A  
VERY BROAD BRUSH APPROACH TO THE PRECIPITATION FORECAST.  
 

 
   
SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 THROUGH 3)
 
 
A FAIRLY STAGNANT PATTERN IS SETTING UP ACROSS THE MAINLAND. THE  
BANDS OF SHOWERS ACROSS THE KUSKOKWIM DELTA AND GREATER BRISTOL  
BAY WILL WANE THIS EVENING. AT THE SAME TIME ANY SHOWER ACTIVITY  
WILL STAY CONFINED TO THE MOUNTAINS, POSSIBLY SOME DRIFTING OFF  
TOWARD NAKNEK OVERNIGHT. THE NEXT TWO AFTERNOONS WILL LOOK MUCH  
THE SAME. OVERALL, DECREASING CLOUD COVER WITH BREAKS OF SUN IN  
THE AFTERNOON WILL LEAD TO LATE AFTERNOON SHOWER ACTIVITY, MAINLY  
ALONG HIGHER TERRAIN. THE NEXT FRONT WILL APPROACH FROM THE  
BERING SEA EARLY NEXT WEEK, BUT WILL BE WEAKENING AS IT DOES.  
EXPECT TEMPERATURES SLIGHTLY ABOVE NORMAL, AND LIGHT WINDS FOR THE  
PERIOD.  
 

 
   
SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 THROUGH 3)
 
 
A WEAK FRONT WITH RAIN SHOWERS WILL FALL APART OVER THE CENTRAL  
BERING SEA THIS AFTERNOON AND EVENING. THE NEXT FRONT, SUB-GALE-  
FORCE, WILL PIVOT FROM WEST TO EAST ACROSS THE CHAIN BEGINNING  
LATE TONIGHT. RAIN WILL SPREAD ACROSS MOST OF THE AREA THROUGH THE  
WEEKEND, SHIFTING TO THE ALASKA PENINSULA EARLY NEXT WEEK.  
 

 
   
LONG TERM FORECAST (DAYS 3 THROUGH 7)
 
 
THE LONG TERM FORECAST BEGINS MONDAY NIGHT WITH THE SUNDAY NIGHT  
WITH THE MAIN FEATURE THE LOW IN THE EASTERN BERING SEA NEAR THE  
PRIBILOF ISLANDS. THE DETERMINISTIC MODELS, ENSEMBLE RUNS, AND WPC  
ARE IN AGREEMENT WITH THIS LOW POSITION AND INTENSITY THROUGH THE  
WEEK. THE MODELS, ENSEMBLE AND WPC REMAIN IN GOOD AGREEMENT WITH  
THE RESOLUTION OF THE RIDGE IN THE GULF OF ALASKA BEING SQUEEZED  
AND PUSHED TO THE EAST AS A FRONTAL LOW FROM THE BERING SEA LOW  
PUSHES INTO THE GULF LATE WEDNESDAY. AS WE MOVE OUT INTO THE  
LATTER PART OF NEXT WEEK THE MAIN LOW MOVES OVER THE MAINLAND AS A  
RIDGE BUILDS IN BEHIND IT OVER THE BERING SEA.  
 
THIS ALL TRANSLATES TO A CONTINUATION OF THE COOL, CLOUDY, AND  
WET PATTERN OVER THE SOUTHERN MAINLAND. AS THE FRONTAL LOW PUSHES  
INTO THE GULF WEDNESDAY, MORE RAIN AND CLOUDS CAN BE EXPECTED  
ALONG THE GULF COAST TO KODIAK ISLAND.  
 

 
 
   
AFC WATCHES/WARNINGS/ADVISORIES
 
 
PUBLIC...NONE.  
MARINE...NONE.  
 

 
 

 
 
SYNOPSIS AND MODEL DISCUSSION...LF  
SOUTHCENTRAL ALASKA...SB  
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ML  
LONG TERM...SA  
 
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