Area Forecast Discussion
Issued by NWS Juneau, AK

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601
FXAK67 PAJK 122241
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
241 PM AKDT Sun May 12 2024

.SHORT TERM...

Key Points:
-Increasing marine winds by Monday morning as a front approaches
 the area, reaching Small Craft Advisory for inner channels by
 Monday afternoon.

Discussion:
No significant changes to the short term forecast at this time. A
weakening system has pushed inland from the Northern Gulf this
afternoon, bringing a wide swath of post-frontal on-shore winds
and scattered rain showers across the AOR. Anticipating this soggy
and unsettled pattern to continue to kick off the work week as a
mid-lvl low traverses over southcentral Alaska with a deepening
low over the northern Gulf keeping persistent southwesterly flow
over the area. As this low traverses eastward, it will push
another front across southeastern Alaska, bringing another round
of rain and elevated winds. Main concern through the short term
will be for N/S oriented inner channels by Monday afternoon as
southerly winds increase up to 25kts as another system and front
pushes into the area with Small Craft Advisories for Stephens
Passage and Chatham Strait.

As for temperatures, continuing cloud cover will prevent low
temperatures near sea level from reaching freezing tonight, with
expected lows in the low 40s to upper 30s. By tomorrow afternoon,
high temperatures should warm up to the upper 40s to low 50s under
mostly cloudy to overcast skies.


.LONG TERM...
The primary feature of the mid range forecast is a weak
atmospheric river (AR) for the southern panhandle Tuesday into
Wednesday. Ensemble guidance continues to be in two camps for how
this system will proceed: The first, mainly held by the GEFS and
GEPS, is a slower progressing trough which will increase rain
totals for the southern panhandle. With this solution, 80% of
ensemble members indicate rainfall rates of up to a half inch
every 6 hours with totals of up to 2 - 2.5 inches over 48 hours.
The EPS and deterministic EC continue to prefer a progressive
trough, which will push the heavier rates south of the southern
panhandle, near Haida Gwaii. At this time, there is good
confidence that a low end AR will occur, mainly due to the
duration of the event, but overall rainfall rates do not look
impressive to support any major impacts.

One tidbit of information to add is the 80-100 knot jet
associated with this weak AR at 500 mb. Naturally, high vorticity
advection and lift exist, meaning that there is the possibility of
a rapidly developing surface low feature near the southern
panhandle. LREF progs have trended up wind speeds, with the spread
of gusts varying wildly between 25 mph and 60 mph at the 10th and
90th percentile respectively around Metlakatla, Ketchikan, and
southern PoW Island. While the chances are still low, the general
progression towards a more windy system is definitely something to
keep in mind as more details become clear.

&&

.AVIATION...MVFR conditions persist tonight, with IFR under more
robust showers into late Monday morning. Widespread rain and some
LLWS begin to impact the coast near 20z Monday, moving east over
Monday night, reducing CIGS and VIS.

&&

.MARINE...Post-frontal on-shore precipitation and southwesterly
winds up to Moderate Breeze will continue through tonight for the
Gulf and outer waters with wave heights up 7-9ft. Main concern
will be for N/S inner channels by Monday afternoon as southerly
winds increase up to Fresh to Strong Breeze as another system and
front pushes into the area with Small Craft Advisories for
Stephens Passage and Chatham Strait. Winds decrease by Tuesday
morning.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ012-031>033-641>644-651-652-661>664-
     671-672.

&&

$$

SHORT TERM...NM
LONG TERM...NC
AVIATION...AP
MARINE...NM

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