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000
FXAK67 PAJK 092238
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
238 PM AKDT Tue Apr 9 2024

.SHORT TERM...Minor changes to the ongoing forecast for tonight through tomorrow
night. Main ideas are still in play: Westerly flow and showers today
from a transient ridge will push eastward and make way for another
frontal feature overnight tonight. Overall rainfall does not look
impressive from a return interval or IVT perspective. The big
question with today`s forecast is any additional mesoscale low
pressure systems that will spin up from 60 knot westerly winds
aloft. Deterministic models seems to agree on the idea that a
modestly strong system will develop near the triple point of the
parent low. As for the track of this new low, most guidance
including high resolution ensemble data seem to indicate that this
low will pass south of the panhandle, somewhere in Dixon Entrance.
However, if the low does pass into the southern panhandle, then
gusts near the Ketchikan area could be as high as 50 mph. Did not
include this possibility in the forecast, but the chance is
definitely there. Otherwise, expect a southerly push in the inner
channel marine waters to maximize around 25 knots in the central and
southern panhandle. Lax pressure gradients will keep winds lighter
in the Lynn Canal area for a majority of the frontal passage, but
will increase in the post frontal environment.

For snow potential, the likelihood is not high for any substantial
accumulations. Precipitation type probabilities have lent themselves
towards a mix on the onset of precipitation and transitioning to
mainly rain during the main frontal passage. In the post frontal
environment, showers beginning as rain will have increased
likelihood of snow with little accumulation over time as cold air
aloft works its way into the panhandle.

.LONG TERM...
Guidance has been running consistent with the
previous discussions; a 522-decimeter closed low will be
transiting southeast across the Gulf Thursday, with a ridge
sliding across the Panhandle into the evening. Simply put,
Thursday is looking like a fantastic spring day. As mentioned
previously, the big unknown is the formation and penetration of a
marine layer, but with respect to winds and swell/seas, not a lot
of concerns.

The main feature focused on the long-range discussion is an
upstream longwave trough lifting through the Bering Strait into
western Alaska Thursday, with the Jetstream moving into the
western Gulf by the afternoon. Increased amounts of IVT near the
Aleutian Islands associated with this Jetstream will shear apart
by Friday, which will help decrease precipitation amounts and
concerns; however, will still see widespread stratiform rain/snow.
Main threat is an increase of southerly winds and seas across our
waters as a surface low lifts into the Kenai Peninsula. For
timing, expect near-gale force winds west of Cape Suckling by
Thursday afternoon, moving east through the night. For the inner
channels, expect southerly winds to ramp up through Thursday
evening, with elevated 20-30 knot winds in the inner channels into
Friday afternoon before dissipating early Saturday. As mentioned
before, guidance consensus is about 25 knots sustained winds, but
if the surface low forming off the Alaskan Peninsula is able to
deepen further than anticipated, we could see closer to 30 knot
winds through some central and northern inner channels. Stay
tuned.

For the weekend, cluster analysis of the various ensembles
indicates a similar theme; the surface low that brought us the
active weather Friday will weaken as it stalls near Prince
Williams, before the parent trough aloft slides across the western
seaboard, bringing the low with it. Guidance struggles with the
timing and location of the eastward movement but the main forecast
notes are the pressure gradient looks weak with breezy, but
lighter winds than Friday in the inner channels, some low clouds,
and stratiform precipitation becoming showery, moving across the
Panhandle through Monday morning.

One note is we will likely see some outflow winds coming out of
Cook Inlet Sunday into Monday bringing some elevated 12-14ft
northwesterly seas in the western gulf. This feature is not fully
captured by wave guidance so something to watch.

&&

.AVIATION...Some shower activity across Southeast Alaska this
afternoon with conditions at or above 3000/5. The situation will
change overnight with the arrival of the next front and lowering
CIGs & VSBY. Lowest conditions down to 1000/3 or less expected
near the Canadian border along the Coast Mountains and much of the
northern Panhandle east of Glacier Bay. Sustained wind shear and
turbulence expected along the outer coast with a 4-6 hour stretch
of time in the morning where conditions will be rough on the
inside as well.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind until 6 PM AKDT this evening for AKZ318.
MARINE...Small Craft Advisory for PKZ036-641>644-651-652-661>664-671-672.

&&

$$

SHORT TERM...NC
LONG TERM....AP
AVIATION...Fritsch

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