Storm Warning 19, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
302 PM AKDT Sun Oct 8 2023

.SHORT TERM.../Through Monday night/...Another round of heavy rain
is forecast for Southeast Alaska, with the heaviest rain expected
tonight. Precipitation totals for tonight ranging from 1/2 inch to
nearly 2 inches. Greatest accumulations forecast for Prince of
Wales Island, Ketchikan, the eastern shore of Baranof Island, and
Juneau. The system for tonight is assessed to be of Storm force
strength and will pass closer to the outer coast than the previous
low. Have issued a high wind watch for Prince of Wales Island and
the Metlakatla areas for these potentially high winds. Ketchikan
will be close, but have not included that town as of yet. Strong
wind gusts between 40 and 50 mph are forecast for several of the
remaining public zones from tonight through Monday night. Brief
periods of storm force winds offshore of Prince of Wales Island
and the outer coast north of Cape Edgecumbe tomorrow afternoon. On
the inside, gale force winds will develop over the southern
inner channels and progress north, keeping pace with the low
offshore. Winds will diminish from south to north beginning Monday
afternoon with small craft conditions gone by late Monday night.

.LONG TERM.../Tuesday through Saturday/...Long story short, an active pattern
will persist throughout the week. 'Break' period is the early part
of the midrange forecast, days Tuesday and Wednesday. On these days,
may possibly see some glimpses of sunlight but expect these to be
very brief. With onshore flow and vorticity advection present aloft,
expect to see periods of rain for this time frame. The gulf of the
discussion; however, for the long range, is the system moving in on
late Thursday and continuing possibly through the weekend.

Looking at the setup, a digging trough aloft will set up multiple
waves moving up from the south into the panhandle. Each of these
waves will bring enhanced precipitation and a healthy dose of winds
to the panhandle.

Starting out with wind, there is good confidence that the initial
wave of this system will consist of moderate gales along the outer
coast and small craft winds in the inside channels, particularly in
the central and southern panhandle. Uncertainty lies in the duration
of these winds and how many additional waves will push up from the
south along a relatively stationary boundary. Furthermore, there is
uncertainty regarding how far westward the boundary will be set off
the panhandle. If set too far west, than most of the winds will
simply bypass the inner channels and be directed along the
coastline. Finally, the number of waves pushing up from the south
will determine how long the plume of moisture will be directed at
the panhandle.

Precipitation, like winds, looks to be enhanced during this time
period. With moderate to heavy rain falling over the panhandle for
this upcoming storm and little chances to dry out in-between the
early week system and late week system, chances are soils will still
be very saturated. On first look, model guidance seems to be
indicating that a majority of the precipitation will hit the
southern panhandle and outer coast. NBM, ensemble EC, and GEFS are
hinting at a 50% likelihood of greater than 2 inches in 24 hours on
the initial wave for the central and southern panhandle. Somewhat
conflictingly, however, is the extreme forecast index showing the
location for most out of the ordinary QPF is near the northern
panhandle. While these are derived from normal precipitation for
that area during this time, it does show a moderate difference.
Regardless, rivers will likely rise for this system throughout the
panhandle.

&&

.AVIATION...Widespread VFR to MVFR conditions this afternoon with
some periods of IFR CIGs. A front is lifting through the S Panhandle
this afternoon and will bring moderate rain and windy conditions.
Expect some LLWS between 30-40 kts through the southern inner
channels tonight before progressing northward through Monday
morning. Along the S outer coast, LLWS around 60 kts is possible
late tonight into early Monday morning.

&&

.HYDROLOGY...Heavy rain last night prompted multiple flood
advisories which have been expiring through the day. Remaining
trouble spots include the Chilkat near Haines, the Salmon near
Gustavus, Mendenhall Lake, and the Antler River near Berners Bay.
More heavy rain expected tonight will likely cause additional
hydrology issues as most SEAK creeks, streams, and rivers are
already running high. Late in the shift the decision was made to
issue a flood advisory for Mendenhall Lake based on in situ
observations made by NWS personnel. Similar actions may become
necessary for the above mentioned trouble spots.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind from 1 AM AKDT Monday through late tonight for
     AKZ323-329.
     Strong Wind Monday afternoon for AKZ323.
     Strong Wind Monday afternoon for AKZ325.
     High Wind Watch from 7 PM AKDT this evening through Monday
     morning for AKZ328.
     Strong Wind Monday afternoon for AKZ329.
     Strong Wind from late tonight through Monday afternoon for
     AKZ330.
     High Wind Watch from late tonight through Monday morning for
     AKZ332.
MARINE...Storm Warning for PKZ641-643-663.
     Gale Warning for PKZ013-031-033-035-036-642-644-661-662-664.
     Small Craft Advisory for PKZ012-021-022-032-034-651-671.

&&

SHORT TERM...Fritsch
LONG TERM....NC
AVIATION...CC

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