Area Forecast Discussion
Issued by NWS Juneau, AK

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232
FXAK67 PAJK 222247
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
247 PM AKDT Mon Jul 22 2024

.SHORT TERM...Overview:  An easterly wave pushes into SE AK from Canada, bringing
widespread showers, moderate to heavy rainfall, and a noticeable
bump up in winds on Tuesday.

A vertically-stacked low in the Gulf of Alaska remains the main
catalyst of weather for Southeast Alaska through the rest of Monday.
The upper level system continues to shift eastward and elongates,
continuing a brief rain reprieve for the Panhandle outside of
isolated showers. Winds are still expected to increase late this
afternoon, with southerlies picking up from warm temperature in
Canada, up to 15 knots.

For Tuesday, easterly flow from an upper level low offshore from
Haida Gwaii will help bring in additional continental moisture
eastward over the Coast Mountains and into mainly the central
portion of SE AK, from Wrangell up through Juneau and over to Elfin
Cove and Sitka. Mainly a potential flooding risk, see the Hydrology
section for more on this system.

Winds will also increase up to around 25 knots in the northern half
of the inner channels with the passing of this front. In somewhat
unusual fashion, southerly winds will kick up to 25-30 knots with
gale force gusts for N-S channels, then pass out into the gulf,
transitioning the higher wind speeds to E-W facing channels such as
Icy Strait and Peril Strait. As this system transitions to the gulf
and diminishes, there is the potential for Lynn Canal to diminish
down to light winds or N 10 knots.

.LONG TERM.../Wednesday through Monday/...
Overview: Quiet weather period for the latter half of the week. A
return to wetter weather pattern for the weekend as a low moves
into the NE Gulf followed by additional short waves into next week.
No significant weather events anticipated at this time.

Mid level low originally over the AK Gulf will have dropped south of
Haida Gwaii as a high pressure moves over the area.  This ridge
remains in place through Friday before shifting east as another low
tracks over the NE Gulf then into NW Canada this weekend into next
week. Showers begin to dissipate Wednesday as the surface low that
brought in the strong easterly wave progresses to the SE. The
weather break lasts Thursday into early Friday for most of SE AK.
Onshore flow has potential to keep bit more cloud cover of the area.
Friday night into Saturday getting a pretty standard NE Gulf front
moving in. Some moderate rainfall for the Yakutat area otherwise
climatological normal amounts expected. Ensembles keep a wet
pattern continuing into next week while operational models have more
detail depicting individual lows/fronts with breaks in between.
However lots of spread on location and timing between these models.

&&

.AVIATION...Mostly VFR conditions today (exceptions Yakutat and
clouds hugging the terrain) will give way to MVFR/IFR conditions
tonight as an easterly wave moves over the region. Showers with
moderate to heavy rain are expected late tonight over the northern
and central panhandle reducing visibilities to MVFR, possibly IFR
in the heaviest showers. Ceilings will also lower and gusty winds
can be expected near the heavier showers. For the southern
panhandle, showers will be less intense, so conditions will be
slightly better. Expect the lower conditions to persist through
Tuesday.

&&

.HYDROLOGY...Juneau & Skagway will be hit the hardest from this upcoming Tuesday
system, with precipitation ranging from 1.5 to 2.5 inches over a 18
hour period around Skagway, and up to 2 inches near Juneau. Flashy
creeks and rivers are expected to rise with this system around the
Juneau area, but are currently expected to stay within bankfull
conditions. Biggest uncertainty on the flooding front is the Taiya
River, as there is uncertainty on how far moisture will push
northward from within Canada, and how much cold air aloft will push
in behind the main warm front around the Taiya Basin. At this time,
current thinking is additional cold air will move in around the 400
mb level, which will encourage some convective rainfall. With PW
valuing around 1.00 - 1.25 inches and training showers for at least
3 hours during the afternoon, there is the possibility to see rain
rates up to 0.25 inches per hour. While this likelihood is on the
lower end, the threat is still present. This amount of rainfall
would result in quicker than expected rises on the Taiya River.

Furthermore, how far those rain showers move westward into the
Chilkat River basin remains in question. Current forecast may
perhaps be overly pessimistic, but river levels regardless are
expected to stay above minor flood stage for the duration of the
present advisory.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ012-013-032-644-652-663-664-671-672.

&&

$$

SHORT TERM...NC
LONG TERM....PRB
AVIATION...BFL

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