992  
FXAK68 PAFC 121321  
AFDAFC  
 
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE ANCHORAGE AK  
521 AM AKDT SUN JUL 12 2020  
   
ANALYSIS AND UPPER LEVELS
 
 
AN UPPER LEVEL LOW OVER SOUTHWEST ALASKA CONTINUES TO GENERATE  
SHOWERS OVER THE GREATER BRISTOL BAY AREA THIS MORNING. ANOTHER  
SWATH OF SHOWERS OVER SOUTHERN COOK INLET AND PRINCE WILLIAM SOUND IS  
MOVING TO THE NORTHEAST. FARTHER WEST, A PAIR OF SURFACE LOWS ARE  
SLOWLY TRACKING EASTWARD SOUTH OF THE ALEUTIAN CHAIN. A LAYER OF  
MARINE STRATUS REMAINS IN PLACE ACROSS MUCH OF THE BERING AS WELL  
AS THE GULF OF ALASKA THIS MORNING.  
 

 
   
MODEL DISCUSSION
 
 
MODEL SOLUTIONS REMAIN IN FAIRLY GOOD AGREEMENT. THERE IS GOOD  
CONSENSUS THAT THE UPPER LEVEL LOW CURRENTLY OVER SOUTHWEST  
ALASKA DEEPENS AND MOVES OVER THE GULF OF ALASKA. AT THE SURFACE,  
THERE IS LESS CONSISTENCY REGARDING WHERE THIS LOW TRACKS BEYOND  
TUESDAY. THE NAM WAS THE PREFERRED MODEL FOR THE PLACEMENT OF THIS  
LOW IN THE GULF. FARTHER WEST, MODEL SOLUTIONS AGREE ON AN  
INBOUND LOW OVER THE WESTERN ALEUTIANS MIDWEEK, THOUGH THERE IS  
LESS CONSISTENCY WITH THE TRACK AND STRENGTH OF THIS LOW AS IT  
PROGRESSES EASTWARD. IN THE MEANTIME, HIGHER RESOLUTION MODELS  
WERE PREFERRED, PARTICULARLY GIVEN THE CONVECTIVE ENVIRONMENT.  
 

 
   
AVIATION...PANC
 
GUSTY SOUTHEASTERLY WINDS MAY LULL EARLY THIS  
MORNING BEFORE RAMPING BACK UP BY LATE MORNING. LOW LEVEL WIND  
SHEAR WILL BE THE MAIN CONCERN DURING THE DAY SUNDAY BEFORE WINDS  
DIMINISH BY SUNDAY EVENING. CEILINGS SHOULD REMAIN ABOVE VFR BUT  
MAY DROP TO MVFR WITH PASSING SHOWERS.  
 

 
 
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2: TODAY AND  
MONDAY)...  
 
THE UPPER LEVEL LOW OVER SOUTHWEST ALASKA WILL MOVE SOUTHWARD  
THROUGH THE DAY TODAY. THIS WILL CAUSE THE BROAD FLOW OVER  
SOUTHCENTRAL TO TURN SOUTHWESTERLY. THE SOUTHWEST ONSHORE FLOW IS  
BEGINNING TO TRANSPORT A MUCH MORE STABLE MARINE AIR MASS INTO  
SOUTHCENTRAL, ALONG WITH ADDITIONAL PACIFIC MOISTURE. THUS, THE  
WEATHER PATTERN TODAY WILL FEATURE SCATTERED SHOWER ACTIVITY FOR  
MUCH OF SOUTHCENTRAL FROM THE SOUTHERN SUSITNA VALLEY SOUTH AND  
EAST. NORTH OF THERE, THE UNSTABLE AIR MASS ALONG WITH AN AIRFLOW  
THAT TURNS MORE OUT OF THE EAST LATER IN THE DAY WILL SUPPORT A  
CHANCE OF ISOLATED THUNDERSTORMS ALONG THE ALASKA RANGE AND  
TALKEETNA MOUNTAINS. THE OVERALL COVERAGE OF THUNDERSTORMS WILL  
BE MUCH LESS TODAY THAN PREVIOUS DAYS.  
 
ANOTHER CHANGING ASPECT TO THE FORECAST WILL BE THE GUSTY GAP  
WINDS THROUGH TURNAGAIN ARM, KNIK RIVER VALLEY, AND THE COPPER  
RIVER BASIN. AS THE LOW LEVEL FLOW TURNS SOUTHEASTERLY TODAY, THE  
WINDS WILL BE FORCED THROUGH THOSE GAPS. MEANWHILE THE LOW OVER  
SOUTHWEST ALASKA WILL HELP TO FURTHER PULL THOSE WINDS WESTWARD.  
TODAY SHOULD BE A BIT COOLER THAN YESTERDAY FOR MOST OF  
SOUTHCENTRAL, PRIMARILY DUE TO SIGNIFICANT CLOUD COVER AND  
SCATTERED RAIN SHOWER ACTIVITY.  
 
THEN ON MONDAY, THE UPPER LOW DRIVING THE WEATHER ACROSS  
SOUTHCENTRAL WILL SHIFT EASTWARD NEAR KODIAK ISLAND IN THE  
MORNING. THIS WILL AID IN THE DEVELOPMENT OF A NORTH PACIFIC LOW  
OVER THE GULF THROUGH THE DAY. STRENGTHENING EASTERLY WINDFLOW  
AHEAD OF THE LOW WILL GET UP TO GALE FORCE ACROSS THE OFFSHORE  
WATERS SOUTH OF MIDDLETON ISLAND. MEANWHILE, THE LIFT TO THE EAST  
OF THE UPPER LOW WHICH HAS BEEN OVER SOUTHCENTRAL THE PAST SEVERAL  
DAYS WILL SHIFT WITH THE LOW OVER THE GULF. THUS, MOST INLAND  
AREAS WILL FINALLY GET A BREAK FROM ALL PRECIPITATION ON MONDAY AS  
RIDGING AND SUNSHINE RETURN, ALONG WITH SOMEWHAT WARMER  
TEMPERATURES. CLOUD COVER AND RAIN WILL PERSIST ALONG THE COAST  
DUE TO THE GULF LOW, BUT SINCE THE LOW IS EXPECTED TO TRACK  
EASTWARD, THE STRONGEST WINDS WILL REMAIN WELL OFFSHORE OF THE  
COAST. EVEN SOME COASTAL LOCATIONS MAY SEE SOME SUNSHINE AT THE  
END OF THE DAY. THE LOW WILL ALSO BEGIN TURNING THE WINDS TO THE  
OFFSHORE NORTHERLY DIRECTION ON MONDAY, WHICH IN ADDITION TO  
BEGINNING A DRIER WEATHER PATTERN, WILL END THE GAP WINDS AS WELL.  
 

 
   
SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 THROUGH 3)
 
 
THE UPPER LEVEL LOW THAT TRACKED SOUTH INTO THE REGION YESTERDAY  
CAN BE OBSERVED SPINNING IN PLACE OVER SOUTHWEST AK. THIS IS AS  
EXPECTED. THIS MEANS MORE THUNDERSTORM ACTIVITY TODAY, THOUGH NOT  
QUITE AS INTENSE AS YESTERDAY. WIDELY SCATTERED THUNDERSTORMS ARE  
IN THE FORECAST. THIS WILL BE THE LAST DAY OF WIDESPREAD  
CONVECTION. WEATHER BEGINS TO CLEAR OUT TOMORROW WITH QUIET  
WEATHER FOR THE FIRST PART OF THIS WEEK.  
 

 
   
SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 THROUGH 3)
 
 
LITTLE CHANGE TO THE WEATHER AGAIN TODAY. HIGH PRESSURE CONTINUES  
TO DOMINATE MUCH OF THE BERING WITH STRATUS AND FOG TRAPPED  
BENEATH IT. LOW PRESSURE CONTINUES TO MARCH SLOWLY EAST JUST SOUTH  
OF THE ALEUTIANS, WITH ITS STRETCHED OUT FRONT RIDING RIGHT OVER  
THE ISLANDS THEMSELVES. THIS WILL CONTINUE CLOUD COVER AND RAIN  
SHOWERS FOR THEM. MORE OF THE SAME FOR THE NEXT FEW DAYS WITH HIGH  
CONFIDENCE IN THE FORECAST.  
 

 
   
MARINE (DAYS 3 THROUGH 5: TUESDAY THROUGH THURSDAY)
 
 
HIGH PRESSURE LINGERS ACROSS THE BERING WITH EASTERLY WINDS AND  
WAVES ACROSS THE LOWER HALF AND SOUTHERLY WINDS AND WAVES OVER THE  
UPPER HALF THROUGH THU. HIGH UNCERTAINTY COMES WITH THE INITIAL  
POSITION AND TRACK OF A NORTH PACIFIC LOW, BRINGING PROBLEMS WITH  
MOVEMENTS AND WIND DIRECTIONS WITH THE LOW THROUGH THU. CONFIDENCE  
IS GOOD FOR LESS THAN SMALL CRAFT WINDS AND WAVES SOUTH OF THE  
ALEUTIANS THROUGH THU.  
 
OVER THE GULF, A LOW CENTER WILL TRACK ACROSS THE GULF, HOWEVER  
CERTAINTY IS LOW FOR FRONTAL POSITIONS THROUGH THU. EAST TO  
SOUTHEAST WINDS AND WAVES EXPECTED ACROSS THE NORTHERN GULF LESS  
THAN SMALL CRAFT SPEEDS, SHIFTING TO NORTHERLY WINDS AND WAVES  
AROUND KODIAK ISLAND AND THE WESTERN GULF BY THU.  
 

 
   
LONG TERM FORECAST (DAYS 3 THROUGH 7: MONDAY THROUGH THURSDAY)
 
 
BY TUESDAY, THE UPPER LEVEL LOW THAT IS NEAR SOUTHWEST ALASKA  
TODAY WILL HAVE MOVED OVER KODIAK ISLAND AND BE IN THE CENTRAL  
GULF OF ALASKA. THIS WILL START THE PERIOD WITH HIGH PRESSURE OVER  
SOUTHWEST ALASKA AND A FRONT ALONG THE NORTH GULF COAST. THE HIGH  
PRESSURE IS NOT TERRIBLY STRONG BUT SHOULD SPREAD OVER  
SOUTHCENTRAL ALASKA FOR THE MIDDLE OF NEXT WEEK. SOUTHWEST ALASKA  
WILL BE SUSCEPTIBLE FOR LOW STRATUS TO ADVECT INTO THE REGION OFF  
THE BERING SEA, THOUGH RAINFALL SHOULD MAINLY BE AFTERNOON AND EVENING  
SHOWERS OVER HIGHER TERRAIN.  
 
AFTERNOON AND EVENING SHOWERS ARE ALSO LIKELY OVER INTERIOR PARTS  
OF SOUTHCENTRAL ALASKA THROUGHOUT THE PERIOD.  
 

 
 
   
AFC WATCHES/WARNINGS/ADVISORIES
 
 
PUBLIC...NONE.  
MARINE...GALES...351.  
FIRE WEATHER...NONE.  
 

 
 

 
 
SYNOPSIS AND MODEL DISCUSSION...KO  
SOUTHCENTRAL ALASKA...JW  
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...BJB  
MARINE/LONG TERM...MK/EZ  
 
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