572  
FXAK68 PAFC 141252  
AFDAFC  
 
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE ANCHORAGE AK  
452 AM AKDT WED APR 14 2021  
   
ANALYSIS AND UPPER LEVELS
 
 
THE UPPER LEVELS FEATURE A RIDGE NEAR THE WESTERN ALEUTIANS WITH A  
LONG WAVE TROUGH FROM THE BERING EXTENDING INTO THE GULF WITH A  
RIDGE TO THE EAST IN THE YUKON. THREE DISTINCT FEATURES WILL  
AFFECT THE WEATHER OVER THE NEXT FEW DAYS OVER THE AREA. FIRST IS  
A STRONG LOW PRESSURE SYSTEM EAST OF KODIAK ISLAND MOVING TOWARDS  
THE KENAI PENINSULA TODAY ITS ACCOMPANYING FRONT IS PRODUCING  
RAIN AND SNOW FROM CORDOVA INTO PRINCE WILLIAM SOUND AND THE KENAI  
PENINSULA EXTENDING SOUTHWEST OVER BRISTOL BAY. TEMPERATURES ARE  
IN THE 30S ACROSS MUCH OF SOUTHCENTRAL WITH RAIN IN MOST VALLEYS  
AND SNOW IN THE MOUNTAINS. THE SECOND DISTINCT FEATURE IS A LOW  
SOUTHEAST OF THE AKPEN THIS FEATURE WILL NOT AFFECT SOUTHCENTRAL  
UNTIL LATER IN THE WEEK. A THIRD LOW IS NORTH OF NUNIVAK ISLAND  
THIS FEATURE IS PRODUCING LIGHT SNOW SHOWERS ACROSS THE BERING.  
OTHERWISE NORTHERLY FLOW FROM THE PRIBILOFS AND EASTERN ALEUTIANS  
WILL PRODUCE SNOW SHOWERS WITH CURRENT TEMPERATURES IN THE LOW TO  
MID 30S ACROSS THE AREA. A RIDGE BUILDING INTO THE WESTERN  
ALEUTIANS IS BRINGING WARMER AND QUIETER WEATHER TO THAT REGION  
TODAY. FINALLY PATCHY FOG AND LOW CLOUDS DOMINATE THE KUSKOKWIM  
DELTA REGION WITH TEMPERATURES IN THE 20S.  
 

 
   
MODEL DISCUSSION
 
 
MODELS CONTINUE TO HAVE GOOD AGREEMENT WITH MAJOR FEATURES WITH  
HIGH CONFIDENCE IN THE FORECAST THROUGH FRIDAY. THEY CONTINUE TO  
HANDLE THE LOW OVER THE GULF WELL WITH GOOD AGREEMENT WITH  
PRECIPITATION AND WINDS. A SECOND LOW WILL MOVE INTO THE SOUTHERN  
GULF BY THURSDAY WITH GOOD AGREEMENT WITH WINDS AND PRECIPITATION  
FOR KODIAK ISLAND AND COASTAL AREAS OF SOUTHCENTRAL. ALL MODELS  
ARE FORECASTING A RIDGE TO DEVELOP ACROSS THE MAINLAND OF ALASKA  
AS A BLOCKING PATTERN SETS UP THIS WEEK ACROSS CANADA. MEANWHILE  
MODELS ARE IN GOOD AGREEMENT WITH A FRONT MOVING ACROSS THE  
WESTERN ALEUTIANS AND BERING WEDNESDAY AND THURSDAY.  
 

 
   
AVIATION
 
 
PANC...TURNAGAIN WINDS WILL DEVELOP THIS AFTERNOON AND CONTINUE  
OVERNIGHT AND MAY BE A BIT GUSTY AT TIMES UP TO 35 KNOTS. SOME  
LIGHT RAIN IS POSSIBLE THIS MORNING BUT BETTER CHANCES LATER TODAY  
IN THE EVENING HOURS, HOWEVER VFR CONDITIONS ARE EXPECTED TO  
CONTINUE THROUGH THE TAF PERIOD.  
 

 
 
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3/TODAY  
THROUGH FRIDAY NIGHT)...  
A LARGE VERTICALLY STACKED LOW OVER THE WESTERN GULF IS TRACKING  
QUICKLY NORTHWARD TOWARD THE SOUTHERN KENAI PENINSULA, LED BY A  
STRONG SHORT-WAVE AND JET STREAK DRIVING RIGHT INTO THE HEART OF  
SOUTHCENTRAL ALASKA. THE FORECAST FOR THIS STORM IS MOSTLY ON  
TRACK, WITH JUST SOME MINOR UPDATES THIS MORNING. THE BIGGEST  
IMPACTS WILL BE ALONG THE COAST, WITH WIDESPREAD HEAVY  
PRECIPITATION AND STRONG WINDS. THIS WILL LARGELY BE A RAIN EVENT  
FOR THE ROAD SYSTEM AND COMMUNITIES OF PRINCE WILLIAM SOUND, WITH  
HEAVY WET SNOW IN THE MOUNTAINS. PRECIPITATION-TYPE FOR INLAND  
AREAS THIS MORNING IS A LITTLE MORE COMPLEX, WITH MANY AREAS ON  
THE THRESHOLD BETWEEN RAIN AND SNOW. IN ANY CASE, DRY LOW LEVEL  
AIR IS DELAYING ONSET OF PRECIPITATION INLAND AND IT WON'T LAST  
VERY LONG AS DOWNSLOPE FLOW OFF THE COASTAL MOUNTAINS WILL KICK  
IN BY LATE THIS MORNING.  
 
THE LOW DOES LOOK A LITTLE WEAKER THAN PREVIOUS FORECASTS  
INDICATED AS IT REACHES THE KENAI PENINSULA MIDDAY. THEREFORE,  
HAVE LOWERED FORECAST WINDS WITH THE LATEST PACKAGE. EVEN SO,  
WINDS WILL STILL BE STRONG AND GUSTY IN MANY AREAS. SPECIFICALLY,  
STRONG GAP WINDS WILL DEVELOP AS THE LOW HEADS INLAND. THIS  
INCLUDES THE USUAL CULPRITS OF TURNAGAIN ARM, KNIK RIVER VALLEY,  
AND THE COPPER RIVER. GUSTY SOUTHEAST WINDS WILL DEVELOP IN ALL  
OF THESE LOCATIONS BY MIDDAY, THEN STRENGTHEN THIS AFTERNOON AND  
EVENING AS PRESSURE RISES BEHIND THE LOW CENTER TRACKING INLAND.  
THE TRACK OF THE LOW IS FAVORABLE FOR WIDESPREAD GUSTY WINDS  
ACROSS ANCHORAGE, THE MATANUSKA VALLEY, AND THE COPPER RIVER  
BASIN. WINDS WITH THIS STORM WILL FINALLY BEGIN TO DIE DOWN  
OVERNIGHT TONIGHT.  
 
PRECIPITATION WILL ACCOMPANY THE LOW ACROSS THE KENAI PENINSULA  
THIS AFTERNOON AND UP TO THE SUSITNA VALLEY THIS EVENING.  
DESPITE THE STRONG SOUTHEAST FLOW ACROSS THE KENAI AND CHUGACH  
MOUNTAINS, WILL LIKELY SEE AREAS OF LIGHT RAIN (OR SPRINKLES)  
IN THE ANCHORAGE AREA LATE THIS AFTERNOON AND EVENING DO TO THE  
CLOSE PROXIMITY TO THE LOW CENTER. THE HEAVIEST PRECIPITATION  
WILL REMAIN ALONG THE COAST, WITH A TRAILING SHORT-WAVE TROUGH  
APPROACHING AND UPSLOPE FLOW REMAINING STRONG. THE BEST CHANCE  
FOR SNOW WILL BE OVER THE NORTHERN SUSITNA VALLEY/BROAD PASS,  
WHERE THERE COULD BE SEVERAL INCHES OF WET SNOW TONIGHT.  
 
PRECIPITATION AND WINDS WILL ALL COME TO AN END ACROSS INTERIOR  
SOUTHCENTRAL ON THURSDAY. HOWEVER, ANOTHER SHORT-WAVE TROUGH  
LIFTING NORTHWARD ACROSS THE GULF WILL CONTINUE TO PRODUCE PERIODS  
OF RAIN (AND MOUNTAIN SNOW) ALONG THE COAST. THE TROUGH WILL  
ROTATE WESTWARD ACROSS SOUTHCENTRAL THURSDAY AFTERNOON AND EVENING  
BEFORE WEAKENING. THUS, THERE COULD BE SOME LIGHT RAIN SPILLING  
OVER THE COASTAL MOUNTAINS INTO THE MAT VALLEY, ANCHORAGE, AND  
WESTERN KENAI.  
 
AN UPPER LEVEL RIDGE WILL BUILD IN FROM THE SOUTHEAST THURSDAY  
NIGHT THROUGH FRIDAY NIGHT, LEADING TO DRY CONDITIONS AND  
DECREASING CLOUDS. THE COMBINATION OF SUBSIDENCE WARMING UNDER  
THE RIDGE AND INCREASING SUNSHINE WILL LEAD TO WARMING  
TEMPERATURES. EXPECT FRIDAY AND BEYOND WE'LL START TO SEE MORE  
50 DEGREE TEMPERATURES, ESPECIALLY FOR THE TYPICALLY WARMER  
INLAND LOCATIONS.  
 

 
   
SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 THROUGH 3)
 
 
AS SEEN ON SATELLITE AND OBSERVATIONS, FOG WILL CONTINUE THROUGH  
THE MORNING HOURS ACROSS THE KUSKOKWIM DELTA.  
 
A SURFACE LOW APPROACHING KODIAK ISLAND IS EXPECTED TO BRING SOME  
INCREASED WINDS TO BRISTOL BAY AND WATERS SOUTH OF THE ALASKA  
PENINSULA, ALONG WITH THE LOWER KUSKOKWIM VALLEY ON WEDNESDAY. A  
RAIN/SNOW MIX IS ANTICIPATED ACROSS THE MIDDLE KUSKOKWIM VALLEY  
BEGINNING WEDNESDAY AFTERNOON AND CONTINUING THROUGH THURSDAY  
MORNING.  
 
EXPECT CONDITIONS TO CALM THURSDAY NIGHT THROUGH FRIDAY AS A  
RIDGE OF HIGH PRESSURE APPROACHES THE REGION. TEMPERATURES WILL  
WARM AS PRECIPITATION WANES THROUGH THIS TIMEFRAME.  
 

 
   
SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAY 1 THROUGH 3)
 
 
EXPECT NORTHERLY WINDS ACROSS THE CENTRAL AND EASTERN ALEUTIANS AS  
A RIDGE OF HIGH PRESSURE BUILDS OVER THE BERING SEA THROUGH  
THURSDAY. GUSTY CONDITIONS WILL PERSIST THROUGH GAPS AND PASSES  
WITH OCCASIONAL RAIN AND SNOW SHOWERS.  
 
WEDNESDAY AFTERNOON, ENERGY RIDING ATOP THE RIDGE WILL BRING  
CHANCES FOR RAIN TO THE CENTRAL ALEUTIANS. OTHER THAN THIS, EXPECT  
WARM AND DRY CONDITIONS TO PERSIST FOR MUCH OF THE BERING AND THE  
ALEUTIANS UNTIL LATE THURSDAY/EARLY FRIDAY.  
 
BEGINNING LATE THURSDAY/EARLY FRIDAY, A GALE TO STORM FORCE FRONT  
WILL ENTER THE WESTERN ALEUTIANS AND BERING. AS IT APPROACHES THE  
CENTRAL ALEUTIANS LATE FRIDAY, AN INCREASE IN WINDS, WAVES AND  
PRECIPITATION WILL ACCOMPANY THIS FEATURE. PRECIPITATION LOOKS TO  
START OFF AS RAIN FOR THE WESTERN BERING BEFORE THE POTENTIAL FOR  
A WINTRY MIX WORKS ITS WAY INTO THE CENTRAL BERING.  
 

 
   
MARINE (DAYS 3 THROUGH 5: FRIDAY THROUGH SUNDAY)
 
 
BERING SEA/ALEUTIANS:  
 
HIGH PRESSURE EXPANDING ACROSS THE EASTERN BERING BY FRIDAY WILL  
PRIMARILY LEAD TO NO SIGNIFICANT WEATHER AND GENERALLY LIGHT WINDS  
THROUGH EARLY SUNDAY. A WEAKENING LOW DRIFTING SOUTH OF THE  
WESTERN ALEUTIANS WILL BRING DIMINISHING SOUTHEAST GALES TO THE  
FAR WESTERN BERING/ALEUTIANS THROUGH EARLY SATURDAY. THE HIGH WILL  
SHIFT TOWARDS THE WESTERN BERING SUNDAY AS A LOW MOVES SOUTH OF  
THE GULF AND ALASKA PENINSULA, ALLOWING NORTHEAST WINDS TO  
INCREASE TO AS HIGH AS GALE FORCE ACROSS THE SOUTHERN BERING BY  
SUNDAY EVENING. FORECAST CONFIDENCE IS HIGH OVERALL.  
 
GULF OF ALASKA:  
 
HIGH PRESSURE OVER THE GULF OF ALASKA WILL LEAD TO BENIGN WEATHER  
CONDITIONS WITH LIGHT WINDS AND SEAS 5-10 FEET OR LESS THROUGH  
SATURDAY. A BROAD LOW WILL APPROACH THE FAR SOUTHERN GULF AS IT  
DRIFTS TOWARDS THE ALASKA PENINSULA ON SUNDAY. THIS WILL LEAD TO  
INCREASING NORTHEAST WINDS UP TO GALE FORCE ACROSS THE SOUTHEAST  
GULF AND THROUGH SHELIKOF STRAIT THROUGH SUNDAY EVENING. SOME  
DIFFERENCES PERSIST WITH THIS LOW, BUT OVERALL FORECAST CONFIDENCE  
IS GOOD.  
 

 
   
LONG TERM FORECAST (DAYS 3 THROUGH 7: SATURDAY THROUGH TUESDAY)
 
 
THE LONG TERM PATTERN CONTINUES TO FEATURE AN UNUSUAL DEGREE OF  
BLOCKING AT THE SYNOPTIC LEVEL THROUGH EARLY NEXT WEEK.  
ANOMALOUSLY HIGH 500 MB HEIGHTS WILL SPAN ACROSS NEARLY THE ENTIRE  
STATE AND ACROSS THE BERING THROUGH AT LEAST SUNDAY NORTH OF A  
DEEP, CLOSED LOW OVER THE NORTH PACIFIC. THESE FEATURES TOGETHER  
WILL SUPPORT A PRONOUNCED REX BLOCKING FORMATION. THIS WILL FAVOR  
MILD, DRY AND INACTIVE CONDITIONS FOR NEARLY THE ENTIRE REGION,  
WITH THE POLAR JET RECESSED WELL INTO THE ARCTIC AND THE PACIFIC  
JET SIMILARLY REMAINING WELL SOUTH OF ALASKA, OR NEAR SUBTROPICAL  
LATITUDES. OPERATIONAL MODELS AND THE ENSEMBLE MEANS STRONGLY  
SUGGEST THIS MILD AND DRY PATTERN WILL CONTINUE THROUGH MONDAY AND  
TUESDAY NEXT WEEK. HOWEVER, THE STRONGEST BLOCKING MAY BEGIN TO  
SHIFT UPSTREAM BY THIS POINT AS AN OMEGA RIDGE BUILDS INTO THE  
WESTERN BERING/KAMCHATKA, AND AS THE LARGE NORTH PACIFIC LOW  
RETROGRADES NORTHWEST CLOSER TO THE ALEUTIAN CHAIN. DEPENDING ON  
THE TRACK OF THE LOW CENTER, THIS COULD LEAD TO INCREASING  
PRECIPITATION POTENTIAL NEAR THE AKPEN AND KODIAK ISLAND AREAS BY  
AS EARLY AS MONDAY. THE PRONOUNCED RIDGE AXIS EXTENDING ALL THE  
WAY FROM THE US WEST COAST TO THE AK INTERIOR SHOULD CONTINUE TO  
FAVOR DRIER CONDITIONS AND AVERAGE TO ABOVE AVERAGE TEMPERATURES  
FOR THE REST OF THE MAINLAND THROUGH THE END OF THE PERIOD. THIS  
SHOULD SOLIDIFY A CLEAR TRANSITION TO MORE TYPICAL SPRING WARMING  
FOR THE FORESEEABLE FUTURE. THE DEEP SNOW COVER WILL BE A LIMITING  
FACTOR FOR GETTING TEMPERATURES SIGNIFICANTLY ABOVE AVERAGE, BUT  
INCREASED MELTING AND RUNOFF IS HIGHLY LIKELY TO CONTINUE THROUGH  
EARLY NEXT WEEK.  
 

 
 
   
AFC WATCHES/WARNINGS/ADVISORIES
 
 
PUBLIC...NONE.  
MARINE...GALE: 120,125,128,129,130,131,138,139,140,351,352  
STORM: 119  
FIRE WEATHER...NONE.  
 

 
 

 
 
SYNOPSIS AND MODEL DISCUSSION...RC  
SOUTHCENTRAL ALASKA...SB  
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CRK  
MARINE/LONG TERM...AS  
 
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