828  
FXAK67 PAJK 232255  
AFDAJK  
 
SOUTHEAST ALASKA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE JUNEAU AK  
255 PM AKDT SUN APR 23 2017  
   
SYNOPSIS
 
BROAD AREA OF LOW PRESSURE CENTERED ALONG THE CENTRAL  
ALEUTIANS IMPACTS THE GULF OF ALASKA WITH A TROUGH EXTENDING OVER  
GULF TO THE BRITISH COLUMBIA COAST. HIGHER PRESSURE OVER NORTHERN  
CANADA WILL WEAKEN AS THE CENTER MOVES EAST TOWARDS HUDSON BAY.  
 

 
   
SHORT TERM
 
/ SUNDAY NIGHT TO TUESDAY NIGHT / AN OLD TROUGH  
EXTENDING OVER THE GULF AND HAIDA GWAII HAS CLOUDS AND LIGHT  
RAIN/SHOWERS MOVING NORTH AND WEST ACROSS THE SOUTHERN PANHANDLE  
SUNDAY AFTERNOON. EXPECT TO SEE THE LIGHT RAIN TO CONTINUE TO  
WORK ITS WAY NORTHWARD THROUGH THE PANHANDLE TONIGHT. IT ISN'T  
UNTIL DURING THE EARLY DAY MONDAY WHEN THE TROUGH HAS MOVED NORTH  
TO THE NORTHERN GULF THAT POP GET MORE THAN LOW CHANCE LEVELS.  
WINDS OVER THE NORTHERN COASTAL MARINE ZONES ALSO INCREASE UP TO  
20 KT, AS THE THROUGH APPROACHES.  
 
ANOTHER SHORT WAVE/SURFACE WILL BE DEVELOPING AND INCREASING IN  
STRENGTH AS THE FEATURE MOVES EAST NORTHEAST OF THE PACIFIC  
TOWARDS THE HAIDA GWAII REGION LATER MONDAY WITH A CLOSED SURFACE  
LOW PATTERN GO BE ABOUT 200 NM SOUTHWEST OF THE ISLAND MIDDAY  
TUESDAY. THE OPERATIONAL MODELS ARE GENERALLY AGREEING ON THE  
FEATURE ALTHOUGH HAVE PRESENTLY FAVORED THE MORE EASTERN/WEAKER  
SOLUTION PAIR OF THE NAM/EC. THE LOW SHOULD BE CURVING NORTH INTO  
THE SOUTHEAST GULF WEST OF PRINCE OF WALES ISLAND BY EARLY  
WEDNESDAY MORNING. THIS TRACK AND STRENGTH SEEMS TO BE A NEW PATH  
FOR THE SOLUTIONS FROM PREVIOUS THINKING, SO BLENDED INTO THE  
WEDNESDAY FORECAST PERIODS.  
 
THE NEW LOW WILL SPREAD A NEW FRONT NORTH INTO THE SOUTHERN  
PANHANDLE AND HELP TO DRY OUT THE PRECIPITATION FROM THE NORTHERN  
AREAS TUESDAY, AND THEN THAT FRONT WILL START TO SPREAD THE RAIN  
NORTHWARD.  
   
LONG TERM
 
/TUESDAY MORNING THROUGH SATURDAY/ ISSUED 5 AM SUNDAY  
- THERE IS NOT MUCH CHANGE IN THE OVERALL SYNOPTIC PATTERN  
THROUGH NEXT WEEK. THE POLAR JET WILL REMAIN OVER THE CENTRAL  
PACIFIC AND THIS WILL KEEP THE STORM TRACK SOUTH OF THE FORECAST  
AREA THROUGH MID WEEK. THERE WILL BE A STRONGER LOW PRESSURE  
SYSTEM THAT WILL LIFT NORTH OUT OF THE NORTH PACIFIC ON WEDNESDAY  
AND MOVE INTO THE EASTERN GULF. THERE ARE SOME DIFFERENCES WITH  
THE TRACK OF THIS LOW BUT THE LATEST FEW MODEL RUNS SEEM TO BE  
PICKING UP ON THIS FEATURE. AS THE LOW SLOWLY LIFTS NORTHEAST  
THROUGH THURSDAY THE THREAT OF PRECIP WILL INCREASE FOR THE  
SOUTHERN HALF OF THE FORECAST AREA. THE NORTHERN AREAS RIGHT NOW  
WILL SEE A CHANCE OF RAIN. FOR LATE WEEK INTO THE EARLY NEXT  
WEEKEND THERE IS INCREASED ONSHORE FLOW FROM THE SOUTHWEST AND  
WITH THAT A CHANCE OF RAIN WITH CLOUDY SKIES SEEMS LIKELY.  
 
WIND WISE...THE INNER CHANNELS WILL SEE RELATIVELY LIGHT WINDS  
FROM THE NORTH THROUGH WEDNESDAY NIGHT WITH WEAK NORTHERNLY  
PRESSURE GRADIENT. AS THE LOW MOVES INTO THE EASTERN GULF WINDS  
WILL INCREASE TO 20 KT OVER MARINE WATERS WITH 15 MPH OVER LAND  
FROM FREDRICK SOUND SOUTH. THE WINDS WILL COME AROUND TO THE  
SOUTH LATE IN THE WEEK AS A RIDGE BUILDS OVER THE NORTHERN PANHANDLE  
AS THE LOW MOVES INTO CANADA ON FRIDAY.  
 
OVERALL THERE IS AVERAGE FORECASTER CONFIDENCE FOR TUESDAY AND  
WEDNESDAY BUT LOWER CONFIDENCE AFTER THAT DUE TO THE DIFFERENCES  
WITH THE LOW MOVING OUT OF THE NORTH PACIFIC AND SPREAD IN THE  
ENSEMBLES. CHANGES IN THE LONG TERM WERE MODIFIED USING THE 00Z  
NAM AND 12Z EC THROUGH DAY 4 THEN WPC FOR LATE IN THE WEEK INTO  
THE WEEKEND.  
 

 
   
AVIATION
 
WE BEGAN THE PERIODS WITH VCSH IN THE SOUTHERN ZONES,  
AND ONLY ADDED CHANGE GROUPS WHERE CEILINGS FLUCTUATED THROUGH THE  
NIGHT AND INTO MONDAY. THE NORTHERN SITES WE ADDED EVENING CHANGE  
GROUPS AS CHANNEL BREEZES FALL AND THEN EVEN THOUGH VCSH MAY OCCUR  
LATE TONIGHT, WE DELAYED ADDING UNTIL MVMC CONDITIONS ARRIVED  
LATER MONDAY. NO IMC CONDITIONS ARE FORECAST THROUGH THE NEXT 24  
HOURS.  
 

 
   
MARINE
 
WINDS PRIMARILY 20 KT OR LEST THROUGH THE PART OF NEXT  
WEEK THOUGH WILL NEED TO WATCH THE LOW DEVELOPMENT TUESDAY FOR  
THE SOUTHEAST GULF. SEAS AND SWELLS FOR THE COASTAL AREAS 5 TO 7  
FEET TONIGHT AND INTO MONDAY. A LOCALIZED BUOY IS REPORTING 8  
FEET, HOWEVER I SUSPECT THOSE WILL SUBSIDE THROUGH THE EVENING.  
 

 
   
AJK WATCHES/WARNINGS/ADVISORIES
 
 
PUBLIC...NONE.  
MARINE...NONE.  
 

 
 

 
 
BEZENEK/JWA/ABJ  
 
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