967  
FXAK67 PAJK 062303  
AFDAJK  
 
SOUTHEAST ALASKA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE JUNEAU AK  
303 PM AKDT MON APR 6 2020  
   
SHORT TERM
 
/SUNDAY EVENING THROUGH WEDNESDAY/ ACTIVE SHORT TERM  
PERIOD WITH SHOWERS ACROSS THE PANHANDLE THROUGH TUESDAY THEN A  
POWERFUL STORM SYSTEM MOVES INTO THE GULF TUESDAY NIGHT AND  
WEDNESDAY BRINGING THE NEXT ROUND FOR HEAVY PRECIPITATION AND  
GUSTY WINDS.  
 
WESTERLY FLOW OVER THE GULF MADE ITS WAY EASTWARD INTO THE  
PANHANDLE WEDNESDAY AFTERNOON WITH GUSTS OVER 40 MPH OBSERVED IN  
YAKUTAT AND GUSTAVUS. GUSTY WESTERLY WINDS ARE EXPECTED TO  
DIMINISH THROUGH THE EVENING HOURS ACROSS THE NORTHERN PANHANDLE.  
THE WEST WINDS ALSO BROUGHT MUCH COOLER AIR WITH IT CHANGING RAIN  
OVER TO SNOW THROUGH THE EVENING. TEMPERATURES AT 850MB DROPPED  
FROM AROUND -6C IN THE MORNING TO AS LOW AS -12C. THE COLDER AIR  
ADVECTING IN STEEPENED LOW LEVEL LAPSE RATE ENOUGH TO INCREASE  
SHOWER ACTIVITY ALONG THE COAST AND IN THE CENTRAL PANHANDLE.  
THESE CONVECTIVE SHOWERS MAY PRODUCE BRIEF PERIODS OF HEAVY  
SNOWFALL, EVEN IN AREAS WHERE SURFACE TEMPERATURES ARE IN THE  
LOWER 40S DUE TO MUCH COLDER AIR ALOFT. EXPECT SHOWERS TO PERSIST  
THROUGH MONDAY WITH THE OUTER COAST AND WEST FACING SLOPES  
EXPERIENCING THE MOST SHOWER ACTIVITY. LIGHT SNOWFALL  
ACCUMULATIONS POSSIBLE MONDAY NIGHT IN AREAS THAT RECEIVE HEAVIER  
SHOWERS AS THE BOUNDARY LAYER COOLS SOME; HOWEVER NO SIGNIFICANT  
ACCUMULATIONS EXPECTED.  
 
SLIGHT RIDGING BUILDS IN AT THE SURFACE TUESDAY AHEAD OF A STRONG  
STORM SYSTEM FORMING IN THE SOUTHWESTERN GULF. TUESDAY WILL BE THE  
CALM BEFORE THE STORM AS RIDGING WILL BRIEFLY SHUT OFF MOST OF THE  
SHOWER ACTIVITY ACROSS THE PANHANDLE. IN FACT, WITH ENOUGH DRY AIR  
IN PLACE ACROSS THE NORTH, A FEW AREAS MAY EVEN SEE SOME SUN  
BEFORE CLOUDS BEGIN STREAMING IN FROM THE SOUTHWEST.  
   
..WINTER STORM TUESDAY NIGHT THROUGH WEDNESDAY
 
 
A DEEPENING TROUGH MOVES INTO THE NORTHERN GULF TUESDAY NIGHT  
WITH A 110+ KT JET STREAK SLAMMING INTO THE PANHANDLE ON  
WEDNESDAY. AT THE SURFACE, A STRENGTHENING AREA OF LOW PRESSURE  
JUST OFF THE COAST OF KODIAK ISLAND TUESDAY EVENING MOVES  
NORTHEASTWARD TOWARDS THE YAKUTAT AREA BY WEDNESDAY AFTERNOON. AS  
THE LOW APPROACHES THE NE GULF COAST, IT WILL SWING A STRONG FRONT  
WITH HEAVY PRECIPITATION INTO THE PANHANDLE LATE TUESDAY NIGHT.  
WITH 850MB TEMPS STARTING OFF AROUND -6 TO -8C AND THICKNESS  
VALUES BELOW 1290M TUESDAY NIGHT, EXPECT THE PRECIPITATION TO  
START OFF AS SNOW EVERYWHERE. AS THE FRONT PUSHES INTO THE  
PANHANDLE WEDNESDAY MORNING, EXPECT SNOW TO CHANGE TO RAIN PRETTY  
FAST AS THICKNESS VALUES AND TEMPERATURES QUICKLY RISE. THIS WILL  
BE THE FIRST HEAVY RAIN PRODUCER IN A WHILE FOR THE ENTIRE  
PANHANDLE. REMAINING SNOW PACK ON THE GROUND AT SEA LEVEL MAY  
EXPERIENCE SIGNIFICANT MELTING DUE TO ALL OF THE RAIN EXPECTED.  
GFS AND THE GFS ENSEMBLES SHOW IVT VALUES OF 300-500 KG/M/S MOVING  
INTO THE REGION WITH STRONG FORCING AND PW VALUES UP TO TWO  
STANDARD DEVIATIONS ABOVE NORMAL ALONG THE COAST. PRECIPITATION  
TOTALS OF 1 TO 2 INCHES OF RAIN EXPECTED AT THE SURFACE WITH  
HIGHER AMOUNTS LIKELY AT HIGHER ELEVATIONS.  
 
DUE TO THE HEAVY SNOW POTENTIAL AS THE FRONT APPROACHES THE  
REGION, MULTIPLE STATEMENTS HAVE BEEN ISSUED. A WINTER STORM  
WATCH HAS BEEN ISSUED FOR YAKUTAT, THE HAINES HIGHWAY AND THE  
KLONDIKE HIGHWAY FOR LATE TUESDAY NIGHT THROUGH LATE WEDNESDAY  
MORNING. SIGNIFICANT ACCUMULATIONS ARE POSSIBLE BEFORE THE  
CHANGEOVER TO RAIN OCCURS. AT HIGHER ELEVATIONS ALONG THE KLONDIKE  
HIGHWAY, PRECIPITATION MAY REMAIN SNOW THROUGH THE DURATION OF  
THE EVENT. CURRENTLY HAVE 5 TO 8 INCHES OF SNOW IN THE FORECAST  
FOR YAKUTAT AND THE HAINES HIGHWAY AND UPWARDS OF A FOOT OF SNOW  
FOR WHITE PASS. LOCATIONS AT SEA LEVEL WILL SEE LOWER SNOW TOTALS  
AND THEREFORE HAVE NOT ISSUED ANY PRODUCTS FOR THESE AREAS YET.  
WOULD NOT BE SURPRISED TO SEE ADVISORIES ISSUED FOR JUNEAU AND THE  
ICY STRAIT CORRIDOR AS HEAVY SNOW MAY PUT DOWN OVER FOUR INCHES  
OF SNOW IN A SHORT AMOUNT OF TIME LATE TUESDAY NIGHT. WAS NOT  
CONFIDENT JUST YET ON SNOWFALL TOTALS TO ISSUE ADVISORIES. THIS  
WILL BE SOMETHING LATER SHIFTS WILL HAVE TO CLOSELY MONITOR OVER  
THE NEXT 24 HOURS.  
 
OVERALL FORECAST CONFIDENCE IS MODERATE THROUGH THE PERIOD.  
   
LONG TERM...WEDNESDAY THROUGH MONDAY...AS OF 9 PM SUN
 
THE  
PERIOD BEGINS WITH AN ATMOSPHERIC RIVER IMPACTING THE REGION.  
OPERATIONAL MODELS CONTINUE TO FLUCTUATE ON THE TRACK OF THE LOW  
ASSOCIATED WITH THIS SYSTEM BUT GEFS AND ENS IN FAIRLY GOOD  
AGREEMENT AS AR MAKES LANDFALL AROUND 08/12Z AROUND CROSS SOUND  
AND PUSHES S THROUGH THE PANHANDLE THROUGH THE DAY. IVT VALUES  
REMAIN AROUND 300-500 KG/M/S, WHICH IS 3-4 STANDARD DEVIATIONS  
ABOVE NORMAL. THIS DEEP MOISTURE WILL COMBINE WITH FAVORABLE SE  
LOW LEVEL FLOW RESULTING IN A 6-12 HR PERIOD OF HEAVY PRECIP.  
PARTIAL THICKNESS VALUES AND LOW LEVEL TEMPERATURE PROFILES  
SUPPORT ACCUMULATING SNOW MAINLY N OF FREDERICK SOUND WED MORNING.  
MODELED SNOW AMOUNTS OF 1-3 FEET SEEM EXCESSIVE, BUT EXPECT MOST  
OF THE N PANHANDLE TO WAKE UP TO 2-4 INCHES BEFORE PRECIP  
TRANSITIONS TO RAIN BY AFTERNOON. WIDESPREAD QPF OF 1-2 INCHES  
WITH LOCALIZED AMOUNTS TO 3 INCHES IN OROGRAPHICALLY FAVORED AREAS  
EXPECTED ACROSS THE REGION WITH THIS SYSTEM. PRECIP CHANCES WILL  
DIMINISH THU WITH MODELS IN FAIR AGREEMENT ON UPPER RIDGE BUILDING  
OVER THE W GULF MAINTAINING DRY AND COOL WEATHER IN NWLY FLOW  
PATTERN INTO NEXT WEEKEND. MODEL SOLUTIONS COMING INTO BETTER  
AGREEMENT WITH ANOTHER SYSTEM APPROACHING THE SE GULF WITH  
INCREASING PRECIP CHANCES HEADING INTO NEXT WEEK.  
 

 
   
AJK WATCHES/WARNINGS/ADVISORIES
 
 
PUBLIC...STRONG WIND UNTIL 6 PM AKDT THIS EVENING FOR AKZ019-020.  
WINTER STORM WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY  
MORNING FOR AKZ017-019.  
STRONG WIND UNTIL 4 PM AKDT THIS AFTERNOON FOR AKZ018.  
WINTER STORM WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY  
AFTERNOON FOR AKZ018.  
MARINE...GALE WARNING FOR PKZ022-043-052.  
SMALL CRAFT ADVISORY FOR PKZ012-013-021-031-033>035-041-042-051-  
053.  
 

 
 

 
 
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