575
FXAK67 PAJK 122153
AFDAJK
SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
153 PM AKDT SUN JUL 12 2020
SHORT TERM
RIDGE OF HIGH PRESSURE MOVED ONSHORE AND IS EXPECTED
TO STALL ALONG THE COASTAL RANGE SUNDAY NIGHT. SCATTERED RAIN
SHOWERS, MAINLY UNDER A WAVE RIDING NORTH OVER THE RIDGE, WILL
DIMINISH THROUGH THE EVENING, JUST IN TIME FOR ANOTHER SYSTEM TO
MOVE IN WITH MORE RAIN. FOR NOW KEPT FOG OUT OF THE FORECAST DUE
TO EXPECTATION OF LINGERING CLOUD COVER, HOWEVER WITH THE
DIMINISHING SHOWERS AND A FEW BREAKS COULD SEE MORE RADIATIONAL
FOG DEVELOPMENT TONIGHT. AN EASTWARD TRACKING LOW SOUTH OF THE
ALEUTIANS WILL JOIN AND BE INVIGORATED BY AN UPPER LEVEL LOW
MOVING FROM NEAR NORTON SOUND SOUTH TOWARDS KODIAK ISLAND. THE
SURFACE LOW WILL DEEPEN TO NEAR 1000 MB AS IT MOVES INTO THE
NORTHERN GULF. THE RAIN ASSOCIATED WITH THIS LOW/FRONT WILL
SPREAD INTO THE AREA MONDAY AND MONDAY NIGHT. A SECOND WAVE IS
EXPECTED TO DEVELOP ON THE TRAILING COLD FRONT AND THEN MOVE TO
THE SOUTHERN HALF OF THE PANHANDLE BY TUESDAY. THE SURFACE LOW
WILL BEGIN TO WEAKEN AND DISSIPATE TUESDAY NIGHT. STILL SOME
TIMING DIFFERENCES ON THE FRONT, WITH NAM BEING THE FASTEST
SOLUTION.
ATMOSPHERIC RIVER WILL CLIP THE SOUTHERN PORTION OF THE PANHANDLE
WITH THE SECOND WAVE. LONG FETCH OF MOISTURE FROM CONNECTION TO
THE MID TROPICS ADVANCING ACROSS THE NORTH PACIFIC WILL BRING IN
PERIODS OF HEAVY RAIN. THE FORECAST RAINFALL NUMBERS HAVE SO FAR
REMAINED THE SAME WITH ROUGHLY 1.0 TO 2.5 INCHES INTO TUESDAY
NIGHT.
LYNN CANAL WINDS BUMPED TO SMALL CRAFT SUNDAY EVENING. COASTAL
WATER WINDS UNDER THE ADVANCING FRONT WILL INCREASE TO 30 TO 35
KT, POSSIBLY 40 KT BY MONDAY EVENING. STRONGEST WINDS WILL BE
OVER THE NE GULF. SOUTHERN INNER CHANNEL WINDS WILL INCREASE WITH
THE SECOND WAVE BY EARLY TUESDAY MORNING.
WITH THE TIMING DIFFERENCES IN THE FRONT LIMITED FORECAST
CHANGES. DID INCREASE WINDS WITH SOME GFS/GEM AND NUDGED POP TO
SREF FOR BIT MOVE COVERAGE. ABOVE AVERAGE CONFIDENCE IN THE
RAIN/BREEZY FORECAST BUT STILL LOWER CONFIDENCE ON EXACT TIMING.
LONG TERM
/TUESDAY THROUGH NEXT SATURDAY/ AS OF 8PM SATURDAY.
BY TUESDAY MORNING THE FRONT DISCUSSED IN THE SHORT TERM PERIOD
SHOULD BE CAUSING WIDESPREAD RAIN OVER MAJORITY OF THE PANHANDLE.
THIS PORTION OF THE FORECAST HAS THE HIGHEST CONFIDENCE IN A
WET/CLOUDY DAY. DESPITE MODELS HAVING DIFFERENT TIMING/PLACEMENT
OF THE PARENT LOW ALL WEEK, THEY AGREE THAT MOST OF THE DAY WILL
SEE RAIN. THE DIFFERENCES IN LOW PLACEMENT STILL HAVE AN AFFECT
ON WIND DIRECTIONS HOWEVER. IF THE LOW IS A BIT FURTHER SOUTH,
THEN WINDS THROUGH SOME OF THE NORTHERN INNER CHANNELS WILL TURN
OUT OF THE NORTH. HAVE INCREASED WIND SPEEDS WITH THE FRONT TO
25KT IN A LARGER SWATH AND OUT OF CROSS SOUND AND UP CLARENCE
STRAIT. GUSTY WINDS ARE ALSO LIKELY IN PLACES LIKE KETCHIKAN AND
PORTIONS OF POW.
THE LOW WILL WEAKEN TO A TROUGH LATE TUESDAY NIGHT OR WEDNESDAY
MORNING, BUT MODELS DIFFER ON WHETHER THAT WILL BE OVER THE GULF OR
IF IT WILL CONTINUE EAST OVER THE SOUTH/CENTRAL PANHANDLE. EITHER
WAY, EXPECT RAIN TO BECOME MORE INTERMITTENT ON WEDNESDAY THAN
TUESDAY. BEYOND WEDNESDAY IS LESS CERTAIN. THE ECMWF HAS
CONSISTENTLY SHOWN A RIDGE BUILDING OVER THE GULF THURSDAY WITH
REDUCED CHANCE OF PRECIP. THE OFFICIAL FORECAST ALSO SHOWS THAT
IDEA, BUT OTHER MODELS BRING A NEW LOW OVER THE SOUTHERN HALF OF
THE AREA, SO THINGS COULD CHANGE. AS OF NOW, THERE IS AGREEMENT ON
A LARGER SYSTEM APPROACHING FROM THE SW NEXT SATURDAY.
THE GFS CONTINUES TO BE THE OUTLIER WITH PLACEMENT OF THE TUESDAY
LOW AND HAS A MUCH MORE ACTIVE PATTERN THAN OTHER MODELS BEYOND
THAT TIMEFRAME. WPC NOTED THIS AS WELL AND USED MORE OF THE 12Z
ECMWF AND I FOLLOWED SUIT. FORECAST CONFIDENCE DECREASES FOR THE
SECOND HALF OF THE WEEK DUE TO MODEL SPREAD.
AJK WATCHES/WARNINGS/ADVISORIES
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ052.
SMALL CRAFT ADVISORY FOR PKZ012-042-043-051.
PRB/FERRIN
VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page