760  
FXAK67 PAJK 230123  
AFDAJK  
 
SOUTHEAST ALASKA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE JUNEAU AK  
523 PM AKDT MON OCT 22 2018  
   
UPDATE
 
COOLER TEMPERATURES NEAR WHITE PASS TODAY AND INTO  
TONIGHT PROMPTED THE UPDATED TO LOWER TEMPERATURES. WEB CAMS FROM  
RWIS (ROAD WEATHER INFORMATION SYSTEM) SITE NEAR THE PASS IS  
SHOWING SNOW FALLING AND IT SHOULD CONTINUE THROUGH THE EVENING  
WITH A FEW INCHES OF ACCUMULATION NEAR THE PASS. WARM AIR  
ADVECTION FROM THE SOUTH WILL SPREAD A WARM LAYER NORTH, HOWEVER  
NEAR THE SURFACE, A LIGHT NORTH WIND SHOULD CONTINUE INTO EARLY  
TUESDAY. THINK THE SNOW WILL MELT TO RAIN, AND WILL FALL THROUGH  
THE COOLER AIR AND MAY START FREEZING ON SURFACES NEAR THE PASS.  
AS A RESULT HAVE ISSUED A WINTER WEATHER ADVISORY FOR SNOW AND  
FREEZING RAIN OVERNIGHT. INTENSITY OF THE WARMING COULD WIPE OUT  
THE COLD LOWER AIR LAYER NEAR SURFACE EARLIER, SO THE WILL NEED  
TO MONITOR FOR THE CONTINUATION OF THIS WINTER WEATHER.  
 

 
   
PREV DISCUSSION......ISSUED AT
 
246 PM AKDT OCT 22 2018  
 
SHORT TERM...A VERY DYNAMIC SYSTEM CONTINUES TO DEVELOP OVER THE  
GULF THIS AFTERNOON, AND A VERY ACTIVE PATTERN IS EXPECTED TO  
CONTINUE THROUGH THIS SHORT TERM FORECAST PERIOD. AN EVEN STRONGER  
LOW IS THEN EXPECTED TO DEVELOP AND TAKE A SIMILAR TRACK TO OUR  
CURRENT SYSTEM BEGINNING THIS WEDNESDAY.  
 
ACCORDING TO CURRENT WV SATELLITE IMAGERY, A BROAD UPPER LEVEL  
TROUGH EXTENDS SOUTH THROUGH THE ALEUTIAN ISLANDS AND WESTERN  
GULF, EXTENDING EVEN DEEPER INTO THE PACIFIC. A STRONG UPPER  
LEVEL RIDGE OVER THE WESTERN CONUS PUSHES EVEN FURTHER NORTH INTO  
BRITISH COLUMBIA, ANSWERING THE DEEPENING RIDGE. THE TIGHTENING  
PRESSURE GRADIENT BETWEEN THESE TWO FEATURES HAS ALLOWED A  
RELATIVELY STRONG JET TO FORM, WHICH CONTINUES TO ADVECT LARGE  
AMOUNTS OF MOISTURE INTO THE ALASKAN PANHANDLE. MANY LOCATIONS  
AUTOMATED SURFACE OBSERVING SYSTEMS CONTINUE TO REPORT MODERATE  
RAINFALL THIS AFTERNOON, WITH HOURLY OBSERVATIONS BETWEEN A TENTH  
AND TWO TENTHS OF AN INCH. RAIN, HEAVY AT TIMES, WILL CONTINUE  
THROUGH TONIGHT FOR AREAS IN THE NORTHERN PANHANDLE AS THE STREAM  
OF MOISTURE PIVOTS NORTH WITH THE DEVELOPING SHORTWAVE. THIS  
SHORTWAVE CAN ALSO BE SEEN ON SATELLITE EMBEDDED WITHIN THE MAIN  
TROUGH AND BEGINNING TO LIFTING NORTH AND STRENGTHEN. IN ADDITION  
TO THE UPPER LEVEL JET MENTIONED PREVIOUSLY, IT ALSO LIES WITHIN  
THE LEFT EXIT REGION OF AN ADDITIONAL JET STREAK, PROVIDING  
DIVERGENCE ALOFT AND ALSO HELPING TO STRENGTHEN THIS FEATURE. AS  
THIS LOW FURTHER DEVELOPS TUESDAY, THE DYNAMICS WILL BECOME  
FAVORABLE FOR THUNDERSTORM DEVELOPMENT, ESPECIALLY OVER THE  
EASTERN GULF WATERS, BUT LIGHTNING STRIKES CANNOT BE DISCOUNTED ON  
LAND, ESPECIALLY FOR AREAS SUSCEPTIBLE TO TERRAIN ENHANCEMENT.  
BOTH GFS AND NAM FORECAST SOUNDINGS FOR KLAWOCK AND SITKA SHOW  
SFC-3KM LAPSE RATES GREATER THAN 7 DEGREES C/KM AND CAPE IN EXCESS  
OF 300 J/KG. THERE WILL BE DECENT INSTABILITY AS THE LOW FURTHER  
LIFTS NORTH TUESDAY EVENING.  
 
MODELS CONTINUE TO COME INTO BETTER AGREEMENT ON ANOTHER STRONG  
LOW IMPACTING SE ALASKA BEGINNING WEDNESDAY. THIS WILL TAKE A  
SOMEWHAT SIMILAR TRACK TO THE LOW IMPACTING US TOMORROW, BUT  
STRONGER JET DYNAMICS WILL MAKE THIS A STRONGER CONTENDER. THE  
BIGGEST CONCERNS WITH BOTH THE SYSTEM FOR TUESDAY AND THIS  
DEVELOPING SYSTEM FOR WEDNESDAY WILL BE THE WINDS. AT ISSUE FIRST  
WILL BE A HIGH WIND EVENT FOR THE SOUTHERN OUTER COAST TONIGHT.  
925MB STREAMLINES AND ISOTACHS INDICATING 65 KTS OF WIND ALONG THE  
COAST OF PRINCE OF WALES ISLAND WITH AS MUCH AS 55 KTS OF WIND  
OVER NORTHERN KUIU ISLAND - MORE THAN ENOUGH TO PRODUCE 60 MPH  
WIND GUSTS AT THE SURFACE. HIGH WIND WARNING FOR WESTERN PORTIONS  
OF ZONE 26 - TO INCLUDE KAKE AND POINT BAKER - ZONE 27, AND  
SOUTHERN BARANOF ISLAND. MAIN FOCUS ON BARANOF WILL BE THE EASTERN  
SHORE AND THE COMMUNITIES OF PORT ALEXANDER, PORT WALTER, AND PORT  
ARMSTRONG. DO NOT THINK HIGH WIND GUSTS WILL MAKE IT AS FAR NORTH  
AS SITKA, BUT THE LOW LEVEL JET SETUP IS VERY SIMILAR TO THE LAST  
STRONG WIND EVENT, WHEN SITKA HARBOR RECORDED A 70 MPH WIND GUST.  
AS THE FRONT ASSOCIATED WITH THESE HIGH WINDS TRACKS NORTH,  
YAKUTAT WILL SEE HIGH WINDS BEGINNING TOMORROW MORNING AND A HIGH  
WIND WARNING HAS BEEN ISSUED FOR THERE AS WELL. STREAMLINE FLOW  
HAS ENOUGH OF AN OFFSHORE COMPONENT THAT WIND GUSTS IN ZONE 22  
SHOULD REMAIN BELOW 60 MPH. STRONG WIND HEADLINES THERE, AS WELL  
AS VARIOUS OTHER PLACES ON THE INSIDE. MARINE WINDS TONIGHT AND  
TOMORROW OVER THE EASTERN GULF WILL BE AT THE HIGH END OF GALE,  
POSSIBLY HIGHER. HIGH CONFIDENCE IS A STORM FORCE BARRIER JET  
BETWEEN ICY BAY AND CAPE SUCKLING TOMORROW MORNING. THERE WILL BE  
A BRIEF BREAK IN THE WIND ACTION TUESDAY NIGHT AND WEDNESDAY IN  
THAT THERE WILL BE NO WIND WARNINGS, BUT ANOTHER STORM FORCE LOW  
IS FORECAST TO ENTER THE GULF FROM THE SOUTH WEDNESDAY AFTERNOON,  
TAKING A SIMILAR TRACK AS THE LOW RESPONSIBLE FOR HIGH WINDS  
TONIGHT & TOMORROW. HIGH HINDS POSSIBLE ONCE AGAIN FOR ZONES 23,  
26, AND 27 WEDNESDAY AFTERNOON AND OVERNIGHT. IF MODELS REMAIN  
CONSISTENT, ANOTHER HIGH WIND WATCH MAY BE ISSUED ONCE THE CURRENT  
STORM IS OUT OF THE PICTURE. WE'RE NOT IN KANSAS ANY MORE.  
 
LONG TERM.../ THURSDAY TO MONDAY AS OF 10 PM SUNDAY / THE ACTIVE  
WEATHER PATTERN WILL PERSIST FROM THE MIDDLE OF THE WEEK THROUGH  
THE WEEKEND AS A PARADE OF LOWS AND WEATHER FRONTS CONTINUE TO  
MOVE THROUGH THE GULF ON A SIMILAR TRACK. OVERALL THE LONG RANGE  
PATTERN HAS NOT CHANGED THROUGH THIS TIMEFRAME.  
 
SHOWERS ACROSS THE GULF AND PANHANDLE FOR FRIDAY INTO SATURDAY.  
THE NEXT SYSTEM APPROACHING OUT OF THE NORTH PACIFIC MOVES TO THE  
SOUTHERN GULF BY SATURDAY MORNING. MODELS HAVE CONTINUED  
CONSISTENCY ISSUES OF POSITION ON THIS AND WILL STRENGTHENING SOME  
THOUGH SUNDAY. FORECAST CONFIDENCE IS AVERAGE IN THE LATE TIME  
FRAMES.  
 
TEMPERATURES FROM THURSDAY TO SATURDAY WERE WERE COOLED SLIGHTLY  
BEHIND THE BIG THURSDAY FRONT AND SNOW LEVELS AS A RESULT LOWERED  
SLIGHTLY TOO, ALTHOUGH ONLY THE HIGHER ELEVATION SHOULD EXPECT TO  
SEE ANY SNOW.  
 

 
   
AJK WATCHES/WARNINGS/ADVISORIES
 
 
PUBLIC...HIGH WIND WARNING FROM 10 PM THIS EVENING TO 6 AM AKDT TUESDAY  
FOR AKZ023-026-027.  
STRONG WIND FROM 1 AM AKDT TUESDAY THROUGH TUESDAY MORNING FOR  
AKZ021-022.  
STRONG WIND FROM 10 PM AKDT THIS EVENING THROUGH LATE TONIGHT  
FOR AKZ028.  
WINTER WEATHER ADVISORY UNTIL 1 PM AKDT TUESDAY FOR AKZ018.  
HIGH WIND WARNING FROM 6 AM TO 4 PM AKDT TUESDAY FOR AKZ017.  
MARINE...STORM WARNING FOR PKZ052.  
GALE WARNING FOR PKZ022-033-035-036-041>043-051-053.  
SMALL CRAFT ADVISORY FOR PKZ021-031-032-034.  
 

 
 

 
 
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