470  
FXAK68 PAFC 231303  
AFDAFC  
 
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE ANCHORAGE AK  
503 AM AKDT SUN APR 23 2017  
   
ANALYSIS AND UPPER LEVELS
 
 
A BROAD AREA OF CYCLONIC FLOW REIGNS OVER MUCH OF THE ALEUTIANS  
WITH THE PARENT LOW WEST OF ADAK. IMPULSE AFTER IMPULSE BRINGS  
PACIFIC MOISTURE INTO THE DOMAIN...WITH BATCHES OF DISTURBED  
WEATHER FROM THE KENAI PENINSULA TO THE WESTERN ALEUTIANS.  
 

 
   
MODEL DISCUSSION
 
THE MODELS ARE IN GOOD AGREEMENT THROUGH THE  
SHORT TERM. THIS FORECAST PACKAGE INCORPORATED A BLEND OF THE NAM  
TO BETTER REFLECT SOME OF THE LOCAL WINDS AND LOCALIZED QPF.  
BEYOND 72 HRS THE MODELS DIVERGE OVER THE HANDLING OF THE SYSTEM  
IN THE GULF OF ALASKA... WITH THE GFS BEGINNING THE MOST BULLISH,  
STEERING IT INTO SE AK. MEANWHILE...THE LATEST RUNS OF THE NAM AND  
ECMWF ARE PROGGING IT TO REMAIN IN THE GULF OF AK AND BEING  
BLOCKED BY THE RIDGE. FOR THE CLOSED LOW OVER THE WESTERN  
ALEUTIANS...THE GEM/NAM/ECMWF AND GFS ARE TIGHTLY CLUSTERED WITH  
THE POSITION OF THE H5 LOW.  
 

 
   
AVIATION
 
 
PANC...VFR CONDITIONS ARE EXPECTED FOR THE PERIOD. THE TURNAGAIN  
ARM WIND WILL BEND NORTH RESULTING IN SOUTHEASTERLY GUSTS AT PANC  
BEGINNING AT 00Z.  
 

 
   
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)
 
 
HIGH PRESSURE OVER SOUTHCENTRAL ALASKA WILL SLIDE EAST AND NORTH  
OF THE AREA BY TONIGHT. A WEAK WEATHER FRONT THAT IS BRINGING SOME  
SHOWERS TO THE KENAI PENINSULA WILL SLOWLY DRIFT NORTH ON MONDAY.  
THIS FRONT WILL MOVE ONTO THE GULF COAST DURING THE AFTERNOON AND  
EVENING HOURS. MOST OF THE RAIN WILL FALL ALONG THE COAST AND  
COASTAL MOUNTAINS, WITH ONLY CHANCE/SLIGHT CHANCE POPS FOR INLAND  
AREAS.  
 

 
   
SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2...SUN AND MON)
 
 
THE PATTERN WILL NOT CHANGE MUCH OVER THE NEXT FEW DAYS. A BROAD  
LOW WILL BECOME ENTRENCHED OVER THE BERING LEAVING SW AK IN  
WARM/MOIST SOUTHEAST FLOW. THE BULK OF THE ENERGY ASSOCIATED WITH  
THE WARM FRONT IS LIFTING THROUGH THIS MORNING. THIS IS RESULTING  
IN SOME STEADY PRECIPITATION ACROSS PORTIONS OF BRISTOL BAY AND  
THE YK- DELTA, ESPECIALLY ALONG FAVORED UPSLOPE AREAS LIKE THE  
KILBUCK MOUNTAINS. THE RAIN SHOULD BECOME MORE SHOWERY AS WE MOVE  
THROUGH THE DAY AS INSTABILITY INCREASES WITH SOME COLDER AIR  
ALOFT MOVING IN. THIS INSTABILITY COULD ALSO HELP TO MIX DOWN SOME  
GUSTY WINDS THIS AFTERNOON, ESPECIALLY THROUGH SOUTHEAST TO  
NORTHWEST ORIENTED GAPS. THINGS WILL REMAIN SHOWERY AND  
TEMPERATURES WILL CONTINUE TO HOLD ABOVE SEASONAL NORMALS TO START  
THE WORK WEEK.  
 

 
   
SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2
 
SUN AND  
MON)...  
A VERY BROAD LOW WILL LEAVE THE ENTIRE REGION UNDER CYCLONIC FLOW  
FOR THE NEXT FEW DAYS AS IT ESTABLISHES RESIDENCE OVER THE CENTRAL  
ALEUTIANS. IT WILL PINWHEEL MOISTURE AROUND FROM THE NORTH  
PACIFIC AND GULF OF AK AND FERRY IT FROM EAST TO WEST ACROSS THE  
BERING. THE FIRST CONTIGUOUS BATCH OF MOISTURE IS ASSOCIATED WITH  
THE WARM FRONT OVER SW AK THAT IS ALSO BEING STRETCHED THROUGH THE  
PRIBILOFS AS IT SLOWLY DECAYS. IT WILL ALSO MAKE FOR TYPICAL  
WIDESPREAD MARINE STRATUS AND SOME PATCHY FOG AS THE WARMER AIR  
MOVES OVER THE COLDER BERING SEA. ON THE EXTREME WESTERN FLANK OF  
THE CIRCULATION, SOME RAIN/SNOW SHOWERS WILL TRY TO DEVELOP ALONG  
WITH SOME GUSTIER WINDS. BUT EVEN THESE WILL ONLY AFFECT THE  
WESTERNMOST ALEUTIANS.  
 

 
   
LONG TERM FORECAST (DAYS 3 THROUGH 7)
 
 
AS HAS BEEN ADVERTISED, THE DAYS OF ENDLESS SUNSHINE ARE COMING TO  
A CLOSE. THE START OF THE WORK WEEK WILL HAVE AN OVERALL INCREASE  
IN CLOUDS ACROSS THE MAINLAND. SHOWERS WILL INCREASE FROM COASTAL  
LOCATIONS AND SOME INLAND AREAS, BUT THE MAJORITY OF THE ANCHORAGE  
METRO SHOULD BE RAIN SHADOWED. A LARGE BUT WEAKENING LOW PRESSURE  
SYSTEM CURRENTLY MOVING INTO THE CENTRAL ALEUTIANS WILL SLOWLY  
MAKE ITS WAY TO SOUTHWEST ALASKA. WINDS SHOULD REMAIN RELATIVELY  
LIGHT THROUGHOUT THE STATE AS THE OVERALL PRESSURE GRADIENT WILL  
BE MINIMAL.  
 

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

 
 

 
 
SYNOPSIS AND MODEL DISCUSSION...PJS  
SOUTHCENTRAL ALASKA...BL  
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MSO  
LONG TERM...SS  
 
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