944  
FXAK68 PAFC 161208  
AFDAFC  
 
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE ANCHORAGE AK  
408 AM AKDT THU AUG 16 2018  
   
ANALYSIS AND UPPER LEVELS
 
 
THE LONGWAVE PATTERN FEATURES A DEEP TROUGH COVERING MOST OF  
MAINLAND ALASKA AND THE ALEUTIANS. THERE IS A DOME OF HIGH  
PRESSURE THAT HAS BEGUN TO MOVE OUT OF NE RUSSIA AND INTO THE  
CENTRAL BERING. THERE ARE NUMEROUS WEAK SHORTWAVES ACROSS  
SOUTHCENTRAL, THE INTERIOR OF ALASKA AND OVER SOUTHWEST ALASKA.  
THE MOST ORGANIZED DISTURBANCES ARE NEAR THE AKPEN AND SOUTH OF  
THE CENTRAL ALEUTIANS. THE WEST PACIFIC TO THE NORTH PACIFIC  
CORRIDOR HAS BECOME VERY DYNAMIC. THE RADARS ON KENAI AND  
MIDDLETON ISLAND CONTINUE TO PING INTO WEAK RETURNS/LIGHT  
PRECIPITATION.  
   
MODEL DISCUSSION
 
 
MODELS HAVE COME INTO BETTER AGREEMENT WITH THE SERIES OF STORMS  
IN THE WEST AND NORTH PACIFIC. THE GFS/NAM ARE IN GOOD AGREEMENT  
AT BOTH THE SURFACE AND AT 500 MB. THE MODEL CONSENSUS IS MORE  
CLOUDY/WET WEATHER FOR SOUTHCENTRAL ALASKA, KODIAK AND THE AKPEN  
FOR TODAY. FRIDAY IS STILL ON TRACK TO BE THE DRIEST DAY OF THE  
WEEK FOR THE ANCHORAGE METRO AREA WITH THE POSSIBILITY OF THE DRY  
CONDITIONS LINGERING INTO SATURDAY.  
 

 
   
AVIATION
 
 
PANC...VFR CONDITIONS EXPECTED. THE PATTERN IS GOING TO REMAIN  
UNSETTLED, EXPECT CLOUDS AND POCKETS OF PRECIPITATION FOR PANC FOR  
THE FORECAST PERIOD. THE KENAI RADAR/PAHG HAS DETECTED A BAND OF  
PRECIPITATION OVER THE NORTHERN COOK INLET.  
 

 
   
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)
 
 
WIDESPREAD SHOWERS CURRENTLY AROUND THE COOK INLET REGION SHOULD  
WANE THIS MORNING AS THE UPPER LOW SHIFTS NORTHEASTWARD. HOWEVER,  
WEAK STABILITY, ABUNDANT MOISTURE, AND LINGERING CYCLONIC FLOW  
WILL KEEP AT LEAST A CHANCE OF SHOWERS THROUGH THE MORNING AND  
EARLY AFTERNOON. THE BEST CHANCE FOR SHOWERS THIS MORNING WILL  
REMAIN AROUND THE NORTH GULF COAST, MORE UNDER THE INFLUENCE OF  
THE UPPER LOW. THE SAME CONDITIONS WILL STICK AROUND THROUGH THE  
AFTERNOON AND EVENING HOURS, BUT FORCING IN NON-EXISTENT, WHICH  
WILL LEAD TO DIURNAL INSTABILITY. THE RESULTANT SHOWER ACTIVITY  
WILL MAINLY BE FOCUSED NEAR THE MOUNTAINS, BUT A STRAY SHOWER  
CAN'T BE COUNTED OUT IN MOST AREAS. FRIDAY WILL BE DRIER,  
INCLUDING A REDUCTION IN CLOUD COVER AND SUNSHINE MAKING A CAMEO.  
THE NEXT REAL WEATHER MAKER WILL BE A FRONT APPROACHING FROM THE  
SOUTHERN GULF OVER THE WEEKEND. TEMPERATURES WILL BE RIGHT AROUND  
CLIMATOLOGICAL NORMAL AND WINDS RELATIVELY LIGHT FOR THE FORECAST  
PERIOD.  
 

 
   
SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 THROUGH 3)
 
 
LOW PRESSURE SOUTHWEST OF CAPE NEWENHAM WILL CONTINUE TO SLOWLY  
DRIFT SOUTH THROUGH THE EASTERN BERING TODAY. THE WEAK ONSHORE  
FLOW WITH THIS SYSTEM WILL KEEP COASTAL REGIONS OF SOUTHWEST  
ALASKA AND THE ALASKA PENINSULA COOL AND SHOWERY WITH A FEW BREAKS  
OF SUNSHINE FOR INTERIOR LOCATIONS. WEAK RIDGING WILL BUILD OVER  
SW AK FOR FRIDAY AS THE LOW MOVES INTO THE NORTH PACIFIC AND  
BECOMES ABSORBED BY A SECOND SYSTEM MOVING NORTH. AREAS OF FOG ARE  
POSSIBLE FRIDAY MORNING UNDER THIS RIDGE WITH LIGHT WINDS AND  
LINGERING LOW-LEVEL MOISTURE. CLOUDS AND PRECIPITATION WILL BEGIN  
TO OVERSPREAD THE ALASKA PENINSULA FRIDAY AS A FRONT ASSOCIATED  
WITH A DEVELOPING AREA OF LOW PRESSURE PUSHES OVER THE REGION.  
EAST TO SOUTHEAST WINDS WILL ALSO INCREASE AHEAD OF THE LOW, WITH  
GALES DEVELOPING ALONG THE AKPEN COAST AND IN BRISTOL BAY BY  
FRIDAY EVENING. SOUTHEASTERLY GAP WINDS WILL ALSO INCREASE FRIDAY  
AND LINGER THROUGH SATURDAY EVENING. RAIN WILL PUSH INTO SW AK BY  
SATURDAY WITH SOME INITIAL LEE-SIDE DRYING (DOWNSLOPING) DUE TO  
THE SOUTHEASTERLY WINDS. WINDS AND RAIN DIMINISH FOR SUNDAY AS  
THE FRONT WEAKENS.  
 

 
   
SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 THROUGH 3)
 
 
A COMPACT, VERTICALLY-STACKED LOW WILL CONTINUE TO PRODUCE GUSTY  
NORTHERLY WINDS AND SHOWERS ACROSS THE EASTERN BERING AS IT DRIFTS  
SOUTH TOWARD COLD BAY. BY FRIDAY MORNING, THIS LOW WILL BECOME  
ABSORBED BY A SECOND DEVELOPING NORTH PACIFIC LOW. THIS SYSTEM  
WILL PUSH A FRONT TOWARDS THE AKPEN BRINGING GALE-FORCE SUSTAINED  
WINDS WITH STORM-FORCE GUSTS ALONG THE EASTERN ALEUTIANS THROUGH  
SATURDAY EVENING. THIS SYSTEM WILL ALSO HAVE A DEEP SUB- TROPICAL  
MOISTURE FETCH ASSOCIATED WITH IT ALLOWING FOR ANOTHER ROUND OF  
MODERATE TO HEAVY RAIN ACROSS THE EASTERN ALEUTIANS, ALASKA  
PENINSULA, AND EASTERN BERING THROUGH SATURDAY AS THE FRONT LIFTS  
NORTH AND WEAKENS BY SUNDAY.  
 
FARTHER WEST, HIGH PRESSURE WILL DOMINATE THE WEATHER PATTERN OVER  
THE CENTRAL BERING AND ALEUTIANS THROUGH THE WEEKEND. STABLE AIR  
UNDERNEATH THIS RIDGE WILL PRODUCE AREAS OF LOW STRATUS AND FOG  
ACROSS THE CENTRAL BERING AND PRIBILOFS. A WARM FRONT ASSOCIATED  
WITH A DEVELOPING KAMCHATKA LOW WITH MOVE ACROSS THE WESTERN  
ALEUTIANS FRIDAY EVENING AND INTO THE WESTERN BERING SATURDAY,  
BRINGING RAIN AND GUSTY WINDS. CONDITIONS WILL REMAIN UNSETTLED  
OVER THE WESTERN LOCALES THROUGH SUNDAY AS THE TRAILING COLD  
FRONT MOVES THROUGH.  
 

 
   
LONG TERM FORECAST (DAYS 3 THROUGH 7)
 
 
THE LONG TERM BEGINNING FRIDAY NIGHT STARTS WITH A NORTH PACIFIC  
LOW SANDWICHED BETWEEN TWO RIDGES. THE FIRST RIDGE WILL BE OVER  
THE EASTERN GULF WHILE THE OTHER IS OVER THE CENTRAL BERING. THERE  
IS SOME DISCREPANCY BETWEEN THE MODELS ON THE EXACT POSITION OF  
THE LOW AND SUBSEQUENTLY ITS FRONT, BUT THE GENERAL CONSENSUS IS  
THAT THE FRONT WILL BRING RAIN TO THE ALASKA PENINSULA AND KODIAK  
ISLAND FRIDAY NIGHT. THROUGH THE WEEKEND THE SYSTEM WILL SLOWLY  
TRACK NORTH SPREADING RAIN TO THE SOUTHERN MAINLAND WITH THE  
HEAVIEST AMOUNTS ALONG THE NORTH GULF COAST AND ALASKA PENINSULA.  
 
MEANWHILE OUT WEST, ANOTHER SYSTEM WILL PUSH INTO THE BERING OVER  
THE WEEKEND AS THE CENTRAL BERING RIDGE BREAKS DOWN. EARLY NEXT  
WEEK THE UPPER LEVEL LOW CENTERS OF THE TWO MAIN LOWS LOOK TO  
MERGE INTO A BROAD AREA OF LOW PRESSURE OVER THE BERING WITH  
RIDGING OFF TO THE EAST. THIS SETUP WOULD KEEP A RAINY PATTERN  
FOR THE REGION INTO MID NEXT WEEK.  
 

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

 
 

 
 
SYNOPSIS AND MODEL DISCUSSION...PJS  
SOUTHCENTRAL ALASKA...ML  
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TM  
LONG TERM...DK  
 
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