251
FXAK67 PAJK 172234
AFDAJK
SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
234 PM AKDT THU SEP 17 2020
SHORT TERM
A RELATIVELY NARROW FRONT LIES ACROSS THE CENTRAL
GULF WITH CLOUDS SEEN ON SATELLITE BETWEEN PWS AND MT.
FAIRWEATHER. S-SE WINDS WITH GUSTS TO GALE FORCE HAVE BEEN
OBSERVED SO FAR AT THE CAPE SUCKLING BUOY AND EXPECT THE BARRIER
JET TO CONTINUE IN THAT REGION THROUGH MOST OF THE NIGHT. VERY
LIGHT RAIN HAS BEEN FALLING IN YAKUTAT ALL DAY OUT OF A FAIRLY
HIGH CLOUD DECK, AROUND 7KFT. EXPECT THE RAINFALL RATES/AMOUNTS TO
INCREASE THROUGH THE EVENING AS THE FRONT SLOWLY MOVES EASTWARD
SINCE UPWIND AREAS OF VALDEZ AND CORDOVA HAVE BEEN REPORTING
MODERATE RAIN ALL DAY.
EXPECT RAIN TO REACH THE SITKA TO JUNEAU AREAS BY EARLY FRIDAY
MORNING, THEN CONTINUE E-SE THROUGH THE AFTERNOON. THE FRONT LOOKS
TO WEAKEN AS IT CROSSES THE REGION, SO AMOUNTS WILL BECOME LIGHTER
OR EVEN SHADOWED BY THE TIME IT REACHES THE SOUTHERN INNER
CHANNELS. THE WEAKENING TREND APPLIES TO WINDS AS WELL, SO THE
WIND SPEED FORECAST HAS BEEN DECREASED.
SATELLITE IMAGERY SHOWS A SHARP BACK EDGE TO THE FRONT SO SOME
SUN IS POSSIBLE POST-FRONT FRIDAY AFTERNOON/EVENING ACROSS THE
NORTH. CAA BEHIND THE FRONT WILL CHANGE THE RAIN TO SHOWERS AND
SWLY ONSHORE FLOW FRIDAY NIGHT THROUGH SATURDAY WILL KEEP THE
POTENTIAL FOR ISOLATED/SCATTERED SHOWERS IN THE FORECAST. A
POSITIVELY TILTED RIDGE PUSHING IN OVER THE GULF BETWEEN SYSTEMS
WILL ALLOW FOR SOME SUNNY BREAKS ON SATURDAY. THIS IS ESPECIALLY
TRUE FOR THE SOUTHERN INNER CHANNELS SATURDAY AFTERNOON AS THERE
WILL BE NWLY FLOW ON THE LEE SIDE OF THE RIDGE. GENERALLY THE
PRESSURE GRADIENT WITH THE BRIEF RIDGE LOOKS WEAK, SO WINDS WERE
DECREASED WITH THAT AS WELL. THEN SATURDAY NIGHT, A LOW MOVING
INTO THE CENTRAL GULF WILL INCREASE THE THREAT OF SHOWERS AGAIN AS
FRONTAL BANDS MOVE INTO THE NORTHERN GULF COAST.
LONG TERM.../SATURDAY THROUGH THURSDAY NIGHT/
AS OF WEDNESDAY
EVENING. A LOW WILL BE LOCATED SOUTH OF KODIAK AND A SURFACE
RIDGE WILL EXTEND FROM THE EASTERN GULF NE ACROSS THE PANHANDLE
AND INTO CANADA AT THE START OF THIS LONG RANGE FORECAST PERIOD.
THE LOW WILL MOVE SLOWLY TO THE EAST AND DISPLACE THE RIDGE SOUTH
AND EAST ON SUNDAY, THEN BEGIN TO WEAKEN AND DISSIPATE MONDAY
EVENING. AT THAT TIME, A MUCH STRONGER LOW WILL BE LOCATED SOUTH
OF THE PENINSULA AND HEADED EAST. THIS LOW WILL FILL THE GULF WITH
A CIRCULATION THAT EXTENDS AS FAR NORTH AS THE CENTRAL INTERIOR
AND AS FAR SOUTH AS CALIFORNIA. IT WILL BEGIN WEAKENING WEDNESDAY
EVENING, ONLY TO BE REPLACED BY ANOTHER LOW SLIGHTLY LESS INTENSE
AND A BIT FARTHER SOUTH IN THE GULF BY THE END OF THIS FORECAST
PERIOD FRIDAY MORNING.
EACH OF THESE LOWS WILL PUSH A FRONT ACROSS THE GULF WITH
INTENSITIES COMMENSURATE TO THE STRENGTH OF THE PARENT LOWS. THE
SECOND FRONT IS LOOKING MORE AND MORE LIKELY TO FEATURE HEAVY RAIN
FOR ALL OF SOUTHEAST ALASKA ON WEDNESDAY. THIS SECOND FRONT WILL
ALSO PRODUCE A GALE FORCE WINDS OVER THE EASTERN GULF AND SMALL
CRAFT WINDS OVER MANY OF THE INNER CHANNELS. THIS SECTION OF THE
LONG RANGE FORECAST GOT THE MOST ATTENTION TONIGHT WITH MOST OF
THE WORK DONE TO INCREASE MARINE WINDS. MODEL AGREEMENT THIS FAR
OUT INTO THE FUTURE IS NOT VERY GOOD AND SOME OF THE LONG RANGE
MODELS ARE SUGGESTING STORM FORCE WINDS. FOR NOW, WIND GRIDS OVER
THE EASTERN GULF HAVE BEEN INCREASED TO MARGINAL GALE STRENGTH. IF
MODEL SOLUTIONS CONVERGE, STRONGER WINDS WILL BE NECESSARY AND
STRONG WINDS ON THE OUTER COAST WILL BECOME LIKELY TUESDAY GOING
INTO WEDNESDAY.
AJK WATCHES/WARNINGS/ADVISORIES
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ052.
SMALL CRAFT ADVISORY FOR PKZ022-043-051-053.
FERRIN/FRITSCH
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