683  
FXAK68 PAFC 260141  
AFDAFC  
 
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE ANCHORAGE AK  
541 PM AKDT MON MAR 25 2019  
   
ANALYSIS AND UPPER LEVELS
 
 
THE UPPER-LEVEL WIND PATTERN IS SHOWING ANOTHER HIGH-AMPLITUDE  
WAVE OVER ALASKA. A SKINNY RIDGE HAS FORMED OVER THE REGION. THIS  
SETUP IS ALLOWING HIGH CLOUDS OVER PORTIONS OF SOUTHCENTRAL AND IS  
STEERING STRONG BERING SEA LOWS FROM SOUTH TO NORTH TOWARD THE  
ARCTIC. THE NET EFFECT HAS BEEN AND IS ABOVE- NORMAL TEMPERATURES  
FOR THE MAINLAND AND CONTINUED UNSETTLED WEATHER FOR SOUTHWEST AND  
THE ALEUTIAN CHAIN.  
 
STORM TO HURRICANE FORCE WINDS OVER THE SOUTHERN BERING BEGAN THE  
MORNING, BUT AS THE LOW MOVED NORTH BY NEARLY 10-DEGREES LATITUDE  
IN 12 HOURS, WINDS HAVE BEEN SUBSIDING AND A HIGH WIND WARNING  
WAS ALLOWED TO EXPIRE EARLY THIS MORNING OVER THE CENTRAL  
ALEUTIANS. GUSTY WINDS CONTINUED THERE, AND WERE ALSO NOTABLE ON  
THE WRAP- AROUND NORTH FLOW MOVING THROUGH THE WESTERN CHAIN.  
 
RAIN AND SNOW CONTINUED FOR THE KUSKOKWIM DELTA, ESPECIALLY IN THE  
NORTH, WHERE HOOPER BAY AND COASTAL POINTS SOUTH TO KIPNUK TRUDGED  
THROUGH THE MORNING UNDER IFR CONDITIONS. INLAND AREAS WERE MILDER  
AND WETTER. GUSTY CONDITIONS WERE AN ADDED BONUS.  
 
CONCERN FOR MINOR RISES IN COASTAL AREAS OF THE NORTHERN KUSKOKWIM  
BAY HAVE THE ATTENTION OF FORECAST TEAM. THERE ARE TOO MANY  
UNKNOWNS WITH SHOREFAST ICE, FEW TIDE GAUGES, AND MINIMAL  
REPORTS.  
 

 
   
MODEL DISCUSSION
 
 
PRESSURE AND MOISTURE FIELDS INITIALIZED WELL IN ALL THE MAIN  
MODELS THIS MORNING. THERE WERE NO SIGNIFICANT DIFFERENCES OUTSIDE  
OF NORMAL MODEL BIASES, THOUGH THE ECMWF DID SEE TO BE SLIGHTLY  
SLOWER WITH THE SOUTHERLY SURGE OF WARMTH INTO SOUTHWEST ALASKA  
EARLY THIS WEEK.  
 
GFS IS A WETTER SOLUTION IN THE MID-RANGE, WHILE THE NAM IS DRIER  
SOLUTION IN THIS TIMEFRAME. FORECASTER CHOICE LEANED TOWARD A GFS  
PREFERENCE TO KEEP SOME PRECIPITATION IN THE OUTCOME INTO THE  
WEEK.  
 
THE FORECAST CHALLENGES FOR THE WEEK WILL BE CONSIDERING SKY  
COVER VERSUS TEMPERATURE VERSUS INCREASING LENGTH OF DAYLIGHT  
HOURS, ALL WITH RESPECT TO FOG FORMATION OVER THE MAINLAND.  
 
FOR SOUTHWEST, ESPECIALLY INLAND AREAS, A CHALLENGE WILL BE TO  
DETERMINE HOW MUCH THE DEVELOPING GULF OF ALASKA RIDGE EATS AWAY  
AT PRECIPITATION CHANCES WHILE BERING SEA TROUGHS ATTEMPT TO PLOW  
THROUGH THE STABILITY.  
 

 
   
AVIATION
 
 
PANC... VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. THE ONLY  
UNKNOWN AT THIS TIME IS ANY POTENTIAL FOR VICINITY FOG DUE TO  
RECENT SNOWMELT AND POTENTIAL FOR BREAKS IN CLOUD COVER. TURNAGAIN  
ARM WINDS ARE NOT EXPECTED TO PLAY A ROLE IN THE FORECAST GOING  
FORWARD.  
 

 
   
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)
 
 
A HIGH AMPLITUDE UPPER RIDGE IS BUILDING OVER SOUTHCENTRAL, AND  
THIS WILL PROMOTE DRY WEATHER ACROSS THE MAINLAND. THE POSITION OF  
THE UPPER RIDGE WITH SOUTHCENTRAL ALONG THE WESTERN SIDE WILL KEEP  
QUITE A BIT OF HIGH CLOUDS OVER THE AREA, SO THIS WILL LIMIT FOG  
AND KEEP LOW TEMPERATURES ABOVE AVERAGE. THAT SAID, SOME FOG WILL  
BE POSSIBLE OVERNIGHT ESPECIALLY ALONG AND NEAR COOK INLET AND  
KNIK ARM. OFFSHORE WINDS WILL BECOME A LITTLE GUSTY THROUGH  
FAVORED GAPS THIS EVENING AS A SHORTWAVE TROUGH ROUNDS THE TOP OF  
THE RIDGE, BUT THESE WINDS WILL NOT BE STRONG AND THEY WILL END  
TOMORROW AFTERNOON.  
 

 
   
SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)
 
(TONIGHT  
THROUGH WEDNESDAY AFTERNOON)  
 
THE FRONTAL BOUNDARY ASSOCIATED WITH THE DEPARTING STORM FORCE LOW  
IN THE BERING CONTINUES TO MOVE EASTWARD ACROSS SOUTHWEST ALASKA.  
GUSTY SOUTHERLY WINDS WILL CONTINUE ALONG THE NORTHERN KUSKOKWIM  
DELTA COAST OVERNIGHT ALLOWING FOR THE POSSIBILITY OF ELEVATED  
WATER LEVELS AROUND THE HAZEN BAY AREA NORTHWARD.  
 
PRECIPITATION WILL GRADUALLY DIMINISH THIS EVENING FROM WEST TO  
EAST. AN UPPER LEVEL RIDGE POSITIONED OVER THE MAINLAND WEAKENS  
THIS FRONT SIGNIFICANTLY ALLOWING FOR GENERALLY DRIER CONDITIONS  
ACROSS SOUTHWEST FOR TUESDAY. A SURFACE RIDGE OVER THE EASTERN  
BERING WILL PROVIDE ONSHORE FLOW ALONG THE BRISTOL BAY COAST  
TUESDAY EVENING INTO WEDNESDAY MORNING. WITH WEAK ONSHORE FLOW AND  
AMPLE MOISTURE, AREAS OF FOG ARE LIKELY ALONG THE SOUTHWEST COAST  
WEDNESDAY MORNING, ESPECIALLY AROUND THE BRISTOL BAY AREA.  
 
MEANWHILE, A WEAK UPPER LEVEL SHORTWAVE THAT DEVELOPS OVER THE  
PRIBILOFS TUESDAY EVENING QUICKLY MOVES NORTHWARD OVER NUNIVAK  
ISLAND AND HOOPER BAY FOR WEDNESDAY MORNING. THIS FEATURE MAY  
PRODUCE A PERIOD OF GUSTY SOUTHERLY WINDS AND SNOW SHOWERS OVER  
THE NORTHERN KUSKOKWIM DELTA COAST WEDNESDAY MORNING BEFORE  
QUICKLY LIFTING NORTH.  
   
SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)
 
 
(TONIGHT THROUGH WEDNESDAY AFTERNOON)  
 
THE STORM FORCE LOW THAT HAS BROUGHT UNSETTLED CONDITIONS ACROSS  
THE BERING SEA OVER THE LAST FEW DAYS CONTINUES TO EXIT THE  
BERING TO THE NORTH THIS AFTERNOON. STORM FORCE WINDS OVER THE  
NORTHERN BERING WILL DIMINISH TO GALES TONIGHT. BEHIND THE LOW, A  
SHOWERY REGIME WILL MOVE OVER THE BERING WITH WIDESPREAD SOUTHWESTERLY  
FLOW PERSISTING THROUGH TUESDAY. ONE FEATURE TO NOTE IS A WEAK  
UPPER LEVEL SHORTWAVE THAT MOVES OVER THE PRIBILOFS TUESDAY NIGHT  
INTO EARLY WEDNESDAY MORNING. THIS WILL LIKELY BRING A FEW SNOW  
SHOWERS TO THE PRIBILOF ISLANDS, THOUGH NO ACCUMULATION IS  
EXPECTED. BY WEDNESDAY AFTERNOON, A WARM FRONT ASSOCIATED WITH A  
KAMCHATKA LOW MOVES OVER THE WESTERN ALEUTIANS, BRINING ANOTHER  
ROUND OF WARM SOUTHERLY FLOW TO THE SOUTHERN BERING.  
 

 
   
MARINE (DAYS 3 THROUGH 5)
 
 
GULF OF ALASKA...CONFIDENCE IS HIGH THAT THAT HIGH PRESSURE WILL  
BE ESTABLISHED OVER THE GULF THURSDAY THROUGH SATURDAY.  
 
BERING SEA...THE LOW TRACK IS EXPECTED TO REMAIN IN THE WESTERN  
BERING SEA THURSDAY THROUGH SATURDAY. THIS SHOULD KEEP PERSISTENT  
SOUTHERLY WINDS OVER THE MAJORITY OF THE BERING SEA WITH SOME GALES  
LIKELY AT TIMES.  
 

 
   
LONG TERM FORECAST (DAYS 3 THROUGH 7)
 
 
A DISSIPATING SHORT WAVE OVER SOUTHWEST MAINLAND ALASKA WILL BRING  
IN A CHANCE OF PRECIPITATION LATE THURSDAY INTO THURSDAY NIGHT AND  
THAT WILL BE THE LAST SHOT OF PRECIPITATION FOR SOUTHERN MAINLAND  
ALASKA FOR THE WEEK. BY FRIDAY THE OVERALL PATTERN WILL BECOME  
MUCH MORE SETTLED OVER THE REGION THAN IT HAS BEEN FOR AWHILE.  
THIS IS DUE TO THE UPPER LEVEL RIDGE BUILDING IN STRONG OVER THE  
MAINLAND PART OF ALASKA AND THEN PERSISTING INTO EARLY NEXT WEEK  
AT LEAST. THE LOW TRACK WILL BE OVER THE WESTERN BERING SEA  
THROUGH THE WEEKEND AND THEN SOME UNCERTAINTY INCREASES AS THE LOW  
TRACK BEGINS TO EDGE EASTWARD ACROSS THE BERING SEA.  
 
SOUTHCENTRAL AND SOUTHWEST MAINLAND ALASKA WILL THEREFORE BE UNDER  
A WARM CORE HIGH PRESSURE DOME THROUGH THE WEEKEND. WHILE THIS IS  
A COMMON PATTERN FOR THIS TIME OF YEAR IT WILL BRING IN ABOVE  
NORMAL TEMPERATURES FOR THE REGION. THE BIGGEST QUESTION WILL BE  
WHETHER FOG AND/OR LOW STRATUS DEVELOPS IN LOW LYING AREAS  
INCLUDING COOK INLET DURING THE PERIOD. SHOULD THE FOG OR STRATUS  
DEVELOP, IT WILL KEEP THE TEMPERATURE SPREAD LESS, BUT STILL  
ABOVE NORMAL. SHOULD CLEAR SKIES DOMINATE, THE LOWS WILL STILL BE  
ABOVE NORMAL DUE TO THE WARMTH ALOFT OF THE RIDGE. HOWEVER THE  
DAYTIME HIGHS WILL THEN BE WELL ABOVE NORMAL WITH SOME AREAS  
PUSHING INTO THE 50S.  
 

 
 
   
AFC WATCHES/WARNINGS/ADVISORIES
 
 
PUBLIC...NONE.  
MARINE...STORM 185 412. GALES 177-179 411 413 414.  
 

 
 

 
 
SYNOPSIS AND MODEL DISCUSSION...DS  
SOUTHCENTRAL ALASKA...JA  
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KO  
MARINE/LONG TERM...EZ  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab AK Page Main Text Page