452  
FXAK68 PAFC 070058  
AFDAFC  
 
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE ANCHORAGE AK  
458 PM AKDT MON APR 6 2020  
   
ANALYSIS AND UPPER LEVELS
 
 
A STRONG, VERTICALLY-STACKED LOW OVER THE INTERIOR CONTINUES TO  
DOMINATE WEATHER OVER MUCH OF THE MAINLAND. THIS LOW HAS BEEN  
RESPONSIBLE FOR THE WINDS ACROSS MUCH OF SOUTHCENTRAL THE PAST 36  
HOURS. A STRONG UPPER LEVEL JET (300 MB 30,000') HAS OFFERED  
SUPPORT FLOWING QUICKLY FROM WEST TO EAST AT 150 KTS. A "PARTING"  
SHORTWAVE PASSED ACROSS THE SUSITNA VALLEY DOWN THROUGH THE KENAI  
PENINSULA THIS MORNING. THIS FEATURE BROUGHT THE LAST, BEST SURGE  
OF WINDS. OVERALL, THE WINDS SHOULD CONTINUE TO DIMINISH ACROSS  
THE AREA. THINGS ARE RELATIVELY QUIET ACROSS THE BERING WITH JUST  
ONE SMALLER SHORTWAVE PASSING BY THE PRIBILOF ISLANDS. THIS SYSTEM  
HAS SOME COLD AIR BEHIND IT (850 MB -18C), SO WITH STEEP LAPSE  
RATES, IT WILL BRING SOME HEAVY SNOW SHOWERS TO THE PRIBILOF  
ISLANDS AND THE EASTERN BERING. ANOTHER FINGER OF THE 300 MB JET  
IS PUSHING DOWN THE BACKSIDE OF THIS SYSTEM AT ABOUT 85 KTS.  
 
FINALLY, THE MAIN PLAYER ASSOCIATED WITH A DEVELOPING STORM SYSTEM  
CAN BE SEEN ON SATELLITE. ALL OF THE MOISTURE OVER THE N PACIFIC  
IS SLOWLY DRIFTING NE TOWARDS THE GULF OF AK. THE SHORTWAVE OVER  
THE BERING (AND ITS TRAILING COLD AIR ADVECTION) WILL WORK IN  
TANDEM WITH THIS MOISTURE TO PRODUCE A STRONG SYSTEM JUST EAST OF  
KODIAK ISLAND ON TUESDAY.  
 

 
   
MODEL DISCUSSION
 
 
MODELS HAVE STRUGGLED GREATLY WITH THE UPCOMING STORM IN THE GULF  
OF AK. YESTERDAY, ALL MODELS TRENDED IT FURTHER TO THE EAST AND  
LEFT IT TO REALLY ONLY IMPACT WINDS AND WAVES ACROSS THE GULF.  
NOW, ALL MODELS HAVE TRENDED SIGNIFICANTLY FURTHER TO THE WEST  
WITH THE LOW. THE NET EFFECT WILL BE THE POTENTIAL FOR HEAVY SNOW  
AND STRONG WINDS FOR KODIAK ISLAND. THIS FORECAST PACKAGE HAS  
TRENDED TOWARDS THAT SOLUTION AND VASTLY INCREASED QPF, WINDS, AND  
WAVES. HOWEVER, WE DID NOT GO 100% TO ANY ONE SOLUTION AS THE  
MODELS CONTINUE TO SHOW SIGNS OF VARIABILITY. ALL THAT SAID, THERE  
IS POTENTIAL TO BRING IN MORE SIGNIFICANT WEATHER TO KODIAK AND  
THE GULF COAST IF THE EVENING MODEL RUNS PROVIDE BETTER CLARITY.  
 

 
   
AVIATION
 
 
PANC...VFR CONDITIONS WILL PERSIST. SW WINDS WILL PERSIST THROUGH  
THE DAYLIGHT HOURS BEFORE THEY TAPER OFF LATER THIS EVENING.  
 

 
 
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3/TONIGHT  
THROUGH THURSDAY)...  
 
A FEW SCATTERED SNOW SHOWERS ALONG WITH GUSTY WESTERLY WINDS WILL  
PERSIST THROUGH THE EVENING HOURS BEFORE DIMINISHING OVERNIGHT AS  
THE UPPER-LEVEL TROUGH SLIDES EAST. THE LIGHTER WINDS AND  
DIMINISHED CLOUD COVER WILL ALLOW OVERNIGHT LOW TEMPERATURES TO  
DROP INTO THE TEENS ACROSS MUCH OF SOUTHCENTRAL, WITH SOME AREAS  
OF SINGLE DIGITS WITHIN SHELTERED VALLEYS AND THE COPPER RIVER  
BASIN. COOL AND DRY CONDITIONS CONTINUE ACROSS THE SOUTHCENTRAL  
MAINLAND TOMORROW AS A RIDGE BUILDS OUT AHEAD OF AN UPPER-LEVEL  
SHORTWAVE SLIDING SOUTHEAST ACROSS THE AKPEN. THIS SYSTEM WILL  
INDUCE THE DEVELOPMENT OF A POTENT NORTH PACIFIC LOW THAT WILL  
STRENGTH AS IT MOVES EAST OF KODIAK TUESDAY, WITH GALES INCREASING  
TO STORM-FORCE WINDS ALONG THE NORTH GULF COAST BY LATE TUESDAY  
NIGHT INTO WEDNESDAY MORNING.  
 
WHILE THERE IS STILL A BIT OF UNCERTAINTY WITH THE EXACT TRACK OF  
THIS LOW, THERE HAS BEEN BETTER MODEL CONSENSUS KEEPING THE  
CENTER OF CIRCULATION CLOSER TO THE EAST COAST OF KODIAK ISLAND.  
THIS WOULD YIELD STRONGER WINDS AND HEAVIER PRECIPITATION FOR THE  
ISLAND BEGINNING TUESDAY MORNING, CONTINUING THROUGH THE EARLY  
MORNING HOURS ON WEDNESDAY. IT ALSO LOOKS LIKE TEMPERATURES WILL  
REMAIN COLD ENOUGH ALOFT AND JUST COLD ENOUGH NEAR THE SURFACE FOR  
THIS TO BE MAINLY A SNOW EVENT, ALBEIT A HEAVY, WET SNOW. RAIN  
MAY MIX IN AT TIMES ALONG THE IMMEDIATE COAST, BUT ACCUMULATING  
SNOW IS EXPECTED, WITH 5 TO 10 INCHES POSSIBLE. A WINTER STORM  
WATCH IS CURRENTLY OUT FOR THIS EVENT.  
 
BY LATE TUESDAY, SNOW AND GUSTY NORTHERLY WINDS WILL ALSO DEVELOP  
OVER CORDOVA, AHEAD OF THE STORM-FORCE FRONT. THE SNOW AND BLOWING  
SNOW IS THEN EXPECTED TO SPREAD OVER THOMPSON PASS AND PARTS OF  
THE SOUTHERN COPPER RIVER BASIN OVERNIGHT TUESDAY AND LINGER INTO  
WEDNESDAY AFTERNOON. WITH A STORM TRACK FROM EAST OF KODIAK TO  
YAKUTAT, AREAS OF SOUTHCENTRAL NORTH AND EAST OF THE KENAI AND  
CHUGACH MOUNTAINS SHOULD REMAIN COOL AND DRY, ONLY HAVING TO  
CONTENT WITH AN INCREASE IN CLOUD COVER. AS THE STORM EXITS ON THE  
REGION ON WEDNESDAY, OFFSHORE GAP WINDS WILL ONCE AGAIN  
STRENGTHEN ALONG THE NORTH GULF COAST AND PRINCE WILLIAM SOUND.  
 

 
 
.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 THROUGH 3: TONIGHT  
THROUGH THURSDAY)...  
 
THE EASTERN PERIPHERY OF A LOW CENTERED EAST OF THE PRIBILOFS WILL  
BE MOVING INTO THE KUSKOKWIM DELTA AND THE WESTERN CAPES TONIGHT.  
THIS WILL CAUSE SNOW SHOWERS TO DEVELOP, BUT ACCUMULATIONS SHOULD  
BE LIMITED TO A FEW INCHES AT MOST. DURING THE DAY TUESDAY, THE  
SHOWERS WILL SHIFT SOUTHWARD, WITH THE SNOW SHOWER ACTIVITY  
SHIFTING TO AROUND THE COASTAL BRISTOL BAY AREA. CLOUDS WILL  
PERSIST OVER THE AREA THROUGH THURSDAY. ANOTHER FRONT WILL SKIRT  
THE KUSKOKWIM DELTA ON THURSDAY, BRINGING ANOTHER ROUND OF SNOW  
SHOWERS TO THE AREA. TEMPERATURES THROUGH THURSDAY WILL REMAIN  
WELL BELOW NORMAL, WITH HIGHS IN THE UPPER 20S AND 30S, WHILE LOWS  
ARE IN THE SINGLE DIGITS AND TEENS.  
 

 
 
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 THROUGH 3: TONIGHT  
THROUGH THURSDAY)...  
 
A SMALL LOW CENTERED JUST EAST OF THE PRIBILOFS IS PRODUCING A  
SMALL AREA OF GALE FORCE WINDS IN THE WATERS AROUND AND EAST OF  
THE ISLANDS THIS AFTERNOON. THE MODELS HAVE FINALLY COME INTO  
BETTER AGREEMENT THAT THE LOW WILL SHIFT SOUTHWARD. THE CENTER OF  
THE LOW WILL BE NEAR THE PORT HEIDEN AREA ON TUESDAY MORNING.  
THUS, SMALL CRAFT TO MINIMAL GALE FORCE NORTHERLY WINDS WILL  
CONTINUE ON THE BERING SIDE OF THE ALASKA PENINSULA THROUGH  
TUESDAY. A SECOND LOW WILL MOVE ACROSS THE NORTHERN BERING ON  
TUESDAY, BUT IT WILL BE WEAK, AND WILL DISSIPATE ON WEDNESDAY.  
 
A FRONT AND ASSOCIATED LOW WILL MOVE INTO THE WESTERN ALEUTIANS  
TUESDAY AFTERNOON AND EVENING. IT WILL GRADUALLY SHEAR APART AS IT  
MOVES INTO THE CENTRAL BERING, BUT A PORTION OF THE FRONT WILL  
PERSIST INTO THE NORTHERN BERING ON WEDNESDAY. THE ASSOCIATED LOW  
WILL TRACK NEAR THE WESTERN AND CENTRAL ALEUTIANS WEDNESDAY NIGHT.  
 

 
   
MARINE (DAYS 3 THROUGH 5)
 
(THURSDAY THROUGH SATURDAY)  
 
BERING SEA/ALEUTIANS  
 
A 998 MB LOW JUST SOUTH OF THE RAT ISLANDS THURSDAY AFTERNOON  
WILL SEND AN ASSOCIATED NEAR GALE FORCE FRONT INTO THE WEST  
CENTRAL ALEUTIANS. THIS FRONT WILL REACH THE ALASKA PENINSULA BY  
FRIDAY AFTERNOON AND LOOKS TO REMAIN JUST UNDER GALE FORCE. THE  
ASSOCIATED LOW MOVES INTO THE NORTHWEST BERING AS ANOTHER LOW AND  
ASSOCIATED FRONT APPROACHES THE WESTERN ALEUTIANS FROM THE NORTH  
PACIFIC.  
 
GULF OF ALASKA  
 
A STRONG AREA OF HIGH PRESSURE CENTERED OVER THE COPPER RIVER BASIN  
WILL KEEP THE GULF DRY WITH LIGHT WINDS FOR THURSDAY AND FRIDAY,  
BEFORE A NEAR GALE FORCE FRONT APPROACHES THE SOUTHERN GULF ON  
SATURDAY.  
 

 
   
LONG TERM FORECAST (DAYS 3 THROUGH 7)
 
 
MODEL GUIDANCE REMAINS IN GOOD AGREEMENT ON THE UPPER LEVEL  
PATTERN FRIDAY INTO SATURDAY AS AN UPPER LEVEL RIDGE DOMINATES  
MOST OF THE MAINLAND OF ALASKA. THIS WILL CONTINUE THE THEME OF A  
WARMING TREND IN TEMPERATURES WITH EACH DAY BEING WARMER THAN THE  
PREVIOUS. OVERALL, A WARMER AND DRY PATTERN FOR THE MAINLAND.  
BEYOND SATURDAY, SOME DIFFERENCES ARE BEGINNING TO EMERGE THAT  
WERENT QUITE EVIDENT IN THE MODELS YESTERDAY. MODEL GUIDANCE IS  
NOW HINTING AT A STORM SYSTEM OVER THE NORTH PACIFIC SOUTH OF THE  
CENTRAL ALEUTIANS BEING DRAWN NORTHWARD THAT MAY UNDERCUT THE  
RIDGE AND BRING A POSSIBLE PERIOD OF UNSETTLED WEATHER OUT THERE  
FOR THE SECOND HALF OF NEXT WEEKEND. MODEL GUIDANCE THEN REALLY  
SPREADS OUT BEYOND SUNDAY NIGHT OF NEXT WEEKEND WITH THE GFS  
SHOWING A MORE AMPLIFIED RIDGE WHILE THE OTHER MODEL SHOWS A  
FLATTER WEAKER RIDGE MOVING IN BEHIND THE AFOREMENTIONED STORM  
SYSTEM. AN UPPER LEVEL TROUGH IS EXPECTED TO BE PRESENT OVER  
EASTERN RUSSIA AND INTO THE NORTH PACIFIC SUNDAY NIGHT THROUGH  
MONDAY SHOWING A POTENTIAL STORM SYSTEM MOVING NORTHWARD. THIS MAY  
BRING A PERIOD OF UNSETTLED WEATHER AND INCREASE IN WINDS TO THE  
ALEUTIAN CHAIN AND THE BERING DURING THIS TIME. HOWEVER, THE EXACT  
TRACK AND STRENGTH OF THIS FEATURE IS STILL YET TO BE DETERMINED  
WITH DIMINISHING FORECAST CONFIDENCE BEYOND SUNDAY.  

 
   
AFC WATCHES/WARNINGS/ADVISORIES
 
 
PUBLIC...WINTER STORM WATCH 171.  
MARINE...GALE 131 132 138 179.  
STORM 119 120.  
HEAVY FREEZING SPRAY 180-185.  
FIRE WEATHER...NONE.  
 

 

 
 
SYNOPSIS AND MODEL DISCUSSION...MSO  
SOUTHCENTRAL ALASKA...TM  
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JW  
MARINE/LONG TERM...PD/MV  
 
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