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FXAK67 PAJK 181339
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
539 AM AKDT Thu Jul 18 2024

.SHORT TERM...A contrasting forecast is in store for SE AK, as
two separate weather patterns result in sharply differing
conditions across the panhandle. Across much of the northern half
of the area including locations like Juneau, Sitka, and Angoon, an
interlude of drier weather will be present through much of the
day on Thursday. The band of precipitation responsible for the
rainfall on Wednesday has moved into the southern panhandle as it
continues to weaken and synoptic NW flow behind it has resulted
in some clearing of the main stratus deck across the area.
Overnight, many areas with otherwise clearer conditions saw fog or
low level stratus decks develop as light winds and saturated
soils combined with cooling temperatures. Anticipate that the fog
will largely dissipate through the morning hours on Thursday, with
much of the low level stratus deck which developed in the wake of
the departing system following suit. This will clear the way for
significant breaks in the clouds and subsequently warmer
temperatures, for the northern half of the panhandle through the
day on Thursday.

The southern panhandle will feature a sharply different pattern
as chances of rain and a layer of stratus continue to remain
courtesy of the aforementioned decaying band of precipitation.
Although QPF totals will be substantially lower today than they
have been through the past few days, still anticipate that as much
as 0.25 to 0.5 inches of rain could fall in some locations. The
cloud deck will inhibit daytime heating, and so high temperatures
will likely be cooler than across the N half of the panhandle for
many locations.

Thursday evening and night will see a pattern reversal, as the
band of precipitation moves N, bringing chances of rain and
widespread cloud cover back to the N half of the panhandle, while
drier conditions and some breaks in the clouds become possible for
the southern panhandle. Chances of rain will continue on Friday
as moderate mid-level support helps fuel a shortwave which will
move into the area from the S as it orbits around a broad area of
low pressure in the Gulf.

The primary changes made to the forecast were to decrease high
temperatures for the southern half of the area on Thursday, and
to increase categorical precipitation coverage in conjunction with
the band of precipitation currently over the southern half of the
panhandle. Wind speeds were increased in a few of the inner
channels, but the forecast continues to remain largely on track.



.LONG TERM.../Friday through Wednesday/... Overview: A relatively
quiet weather period is likely for SE AK. Friday will see
additional moisture being funneled up from the south, which will
then be followed by drier air from the south. An easterly, wet
wave is possible late in the weekend and into next week.

With the 500 mb low in place flow pattern will move a low extending
from a deeper system over the far SW Gulf northward into the SE Gulf
by Friday. For now winds around the low expected to be in the 20 kt
range with lighter winds to the north. Light rainfall amounts
move in with the system with most models keeping precip over the
south with diminishing rates as the low moves northward. By late
Saturday this low will have dissipated, but the main low remains
in place into next week and thus can keep pushing precip bands
over the panhandle. The southerly flow and weather breaks will let
day time highs pick back up into the upper 60s to low 70s.

Looking towards late weekend and into next week, there is
increasing confidence of an easterly wave making it over the
mountains. Areas of interest include communities in the northern
panhandle and possibly Juneau at this time.

&&

.AVIATION...Early this morning, impacts to aviation can be split
between two very different areas.

South of Frederick Sound, continued rain streaming in from the
south is keeping the lowered clouds and visibility in place.
Clouds as low as a few hundred feet and visibility as low as a
couple miles. For this area, not expecting much in the way of
improvement today but some improvement is possible later tonight
as this area of rain pushes northward. So generally expecting
overall IFR to low-end MVFR today with some improvement tonight.

Areas north of Frederick Sound, the clearer skies that moved in
caused foggy conditions to develop. Reported visibilities
overnight have bounced around from the full 10SM to 1/4SM. Going
forward, once the fog fades out later this morning, expecting VFR
conditions through today. Tonight, the incoming rain and clouds
from the south would lower flying conditions to generally MVFR.

&&

.HYDROLOGY...Rivers across the northern inner channels are largely
on their way down or expected to be begin falling later on
Thursday, with the possible exception of the Chilkat River which
continues to rise as of the time of writing. Hydro issues should
improve over the next few days as much less rainfall is expected
over the area.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Dense Fog Advisory until 8 AM AKDT this morning for AKZ325.
MARINE...None.

&&

$$

SHORT TERM...GFS
LONG TERM....NC
AVIATION...GJS

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