312  
FXAK67 PAJK 191547 CCA  
AFDAJK  
 
SOUTHEAST ALASKA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE JUNEAU AK  
510 AM AKST WED FEB 19 2020  
   
SHORT TERM
 
THE EASTWARD MOVING COLD FRONT JUST OFF SHORE THE  
PANHANDLE COAST WEDNESDAY MORNING, IS TRACKING A TOUCH SLOWER  
THAN EARLIER FORECASTED. IT WILL MOVE IN DURING THE DAY AND WILL  
BE WEAKENING. SHOWERY ACTIVITY WRAPPING IN BEHIND THE FRONT,  
MAINLY TO IMPACT THE NORTHEAST GULF AND NORTHERN PANHANDLE, AND TO  
A LESSER EXTEND THE SOUTHERN PANHANDLE.  
 
A BETTER THAN EXPECTED WARM PUSH THROUGH LYNN CANAL, HAS HAINES  
AND SKAGWAY IN THE UPPER 30S THIS MORNING AND THIS PERMEATED ALL  
THE WAY TO THE BORDER ON THE HAINES HIGHWAY. WITH SUCH A WARM AIR  
MASS, THE WINTER STORM WARNING WAS CANCELLED. THE WHITE PASS AREA IS  
STILL BELOW FREEZING SO HAVE KEPT THAT ONE.  
 
MODELS A LITTLE BETTER WITH TIMING FOR THURSDAY SYSTEM, BUT STILL  
SOME TIMING AND STRENGTH DIFFERENCES. WE KEPT A SLIGHTLY SLOWER  
SPEED FACTOR BETWEEN THE SOLUTIONS, AND HAVE A PREFERENCE FOR THE  
GFS MOISTURE COMING ACROSS.  
 
THE AIR MASS MOVING ACROSS THE BEHIND THE THURSDAY SYSTEM LOOKS  
MUCH COOLER THAN THAT ONE BETWEEN THE WED AND THURSDAY EVENT. WE  
TRENDED AWAY FROM SEA LEVEL ACCUMULATIONS THURSDAY, A MIX IS  
POSSIBLE IT WAS JUST LOOKING THAT WE WERE NOT GOING TO HAVE THE  
COOLER SURFACE TEMPERATURES TO ACCUMULATE THE SNOW.  
 
WIND WISE THE LARGEST ISSUE IS THE GUSTY AND STRONG WINDS IN THE  
SKAGWAY AREA INTO THURSDAY, ALTHOUGH SOME LOCATIONS WILL SEE THE  
REALLY GUSTY WINDS RETURN THURSDAY AFTERNOON WITH THE NEXT FEATURE  
ARRIVING.  
 
   
LONG TERM
 
THE CHALLENGES OF WINTER-TIME SPLIT FLOW PERSIST IN  
THE MID- RANGE INTO EARLY NEXT WEEK, AS MOIST PACIFIC SYSTEMS  
RAIL ACROSS 50 N AND OCCASIONALLY FROM LATITUDES SOUTHWARD AND  
INTERACT WITH PERSISTENT AND COLDER BERING SEA SYSTEMS THAT  
PERIODICALLY REPLANT THEMSELVES IN THE GULF OF ALASKA. THIS  
INTRODUCES MANY COMPLICATIONS THAT FRANKLY MODELS (AND  
FORECASTERS) OFTEN STRUGGLE WITH. WITH TEMPERATURES MARGINALLY  
HOVERING IN THE METEOROLOGICALLY SCARY NEIGHBORHOOD OF THE  
MYTHICALLY WELL-MARKED RAIN/SNOW LINE, SMALL ERROR POTENTIAL CAN  
SPAN THE IMPACT SCALE FROM LITTLE TO GREAT.  
 
AFTER A VIGOROUS FRONT CLEARS THE PANHANDLE A MARITIME, A  
RELATIVELY COOL AIR MASS SPREADS ACROSS SOUTHEAST ALASKA,  
SUPPORTING SHOWERS. THESE SHOWERS WILL FALL AS MAINLY RAIN FOR  
THE SOUTH AND A MIX FOR THE NORTH. POORLY RESOLVED SHORT- WAVES  
COULD ENHANCE SOME ACCUMULATIONS DURING THIS TIME, ESPECIALLY AS  
THICKNESSES AND TEMPERATURES DROP INTO FRIDAY NIGHT.  
 
SATURDAY, IT INCREASINGLY LOOKS AS THOUGH THE SOUTHERN STREAM  
ENERGY BECOMES EVEN MORE ACTIVE AS A STORM LOOKS TO BARREL INTO  
THE BC COAST. THIS HELPS SPEED COOLING ACROSS SOUTHEAST AND  
PROBABLY INCREASES FRONTOGENESIS SOMEWHERE ACROSS EITHER THE  
EASTERN GULF OF ALASKA OR THE COASTAL PANHANDLE. MUCH OF THIS  
PRECIPITATION COULD FALL AS SNOW, GIVEN LOW THICKNESSES AND  
COOLING 850 MB TEMPERATURES. WHILE IT IS STILL AN EVOLVING STORY,  
WE LOWERED QPF DURING THE WEEKEND, AS UNCERTAINTY IS UNCOMFORTABLY  
HIGH. YET IT IS CERTAINLY PLAUSIBLE THAT A FEW COMMUNITIES COULD  
GET SIGNIFICANT SNOW FROM THIS SCENARIO. EVENTUALLY, EITHER  
SUNDAY OR SUNDAY NIGHT THE STEERING FLOW TURNS WESTERLY AND  
POTENTIALLY SETS UP ANOTHER OVERRUNNING EVENT LATE IN THE WEEKEND  
OR EARLY NEXT WEEK. BUT SHOULD THE SOUTHERN TRACK ROB THE NORTH OF  
MOISTURE, THIS SETUP MAY BE MUCH ADO ABOUT NOTHING.  
 
ENSEMBLES AND OPERATIONAL RUNS THEN HINT AT A MORE DEEPLY  
SUBTROPICAL SYSTEM PERHAPS BEGINNING AS SNOW AND ENDING AS RAIN  
FOR MUCH OF THE PANHANDLE MID NEXT WEEK. WHEN EXACTLY THIS  
HAPPENS, WE ARE STILL MERELY WAGERING. BUT AS WE HINTED EARLIER,  
THERE IS CONFIDENCE THAT SOUTHEAST ALASKA REGION-WIDE WILL  
EXPERIENCE A COOL-DOWN THIS WEEKEND INTO AT LEAST MONDAY BEFORE  
WARMING INTO MID NEXT WEEK. THIS PROBABLY MEANS MORE SNOW FOR  
SOME.  
 
WESTERLY WINDS FRIDAY WILL BE RELATIVELY HIGH IN THE GULF WITH  
WIDESPREAD 30 KT AND EVEN SOME GALE FORCE WINDS. BUT AS THE SYSTEM  
TO THE SOUTH NEARS THE BC COAST, WINDS LARGELY DIMINISH ACROSS THE  
PANHANDLE EVEN AS THE INNER CHANNELS FLIP NORTH SATURDAY. WINDS  
LOOK TO HAVE LITTLE IMPACT THIS WEEKEND UNTIL AN ANTICIPATED  
FRONT ARRIVES MID NEXT WEEK WITH STRONG SOUTHEASTERLIES.  
 

 
   
AJK WATCHES/WARNINGS/ADVISORIES
 
 
PUBLIC...WINTER STORM WARNING UNTIL 9 AM AKST THIS MORNING FOR  
AKZ018.  
STRONG WIND THROUGH LATE TONIGHT FOR AKZ018.  
STRONG WIND UNTIL 9 AM AKST THIS MORNING FOR AKZ028.  
MARINE...GALE WARNING FOR PKZ041-052.  
SMALL CRAFT ADVISORY FOR PKZ012-013-022-031>036-042-043-051-053.  
 

 
 

 
 
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VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU  
 
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