High Wind in Alaska, November 21, 2022

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
609 AM AKST Mon Nov 21 2022

.SHORT TERM...Gale force low moving into the SE Gulf early Monday
brining more heavy rain and high winds to the region, especially
over southern areas. As the low track northward and dissipates,
winds and precipitation will also diminish through overnight.
Inner channel winds already nearing gale force with overland
gusts of 40 to 60 mph by the afternoon. Rainfall totals of 1 to 2
inches expected through tonight. With temps already in the low to
upper 40s precip will be all rain with the exception of Hyder and
higher elevations. Winter Weather Advisory for the Klondike
highway remains in effect until 6 pm. Hyder should be switching
to rain as temps warm as winds shift. For the rest of the
panhandle temps will have little variation with max temps
occurring this morning then staying steady or slowly dropping
overnight. Low tonight will only be a few degrees lower than this
mornings max temps.

Track of the current low had some differences with a few of the latest
model runs where it was weakened to an open wave trough by this
afternoon which would result in winds diminishing earlier. not
enough confidence in this analysis with current increase in
surface winds so left forecast mostly as is.

.LONG TERM...A return to an active pattern is in full force
during the long term forecast, as a full-fledged resurgence of
the Pacific Storm Season will see system after system advance into
the panhandle. This includes what will likely be a strong storm
system impacting SE AK on Nov 23 and 24 which would bring with it
a significant amount of wind, rain, and for some areas possibly
snow.

Operational guidance has come into good agreement on the idea of a
rapidly developing low moving along the front which was already
over the area before recurving off to the NW a short distance
offshore of the panhandle through the day on Monday. Anticipate
that this will provide a respectable amount of precipitation for
the area, as well as gale force winds across many of the inner
channels. High end gale force winds are anticipated across the
outer coastal waters and eastern Gulf through the day on Monday,
and strong winds will be present across many land based areas as a
front associated with this low rapidly advances through the
panhandle. At this time, the system looks to primarily be a rain
maker with the possible exception being for the Klondike Highway
and to a lesser extent the Haines Highway, where snow will likely
prove a factor. A weaker system will arrive on Tuesday, bringing
with it additional moisture, and keeping parts of the area fairly
saturated.

These systems will prove to be the harbinger of a more powerful
storm system which will arrive on the eve of Thanksgiving and
impact the panhandle through Thanksgiving Day. A brief period of
upper level ridging in the wake of the previous system which built
along the eastern flank of the longwave will give way to the W
flank of the longwave trough which will deepen into a more narrow
and well- defined upper level trough. N flow in the lower levels
will be encouraged by a strong system forming on the E flank of
this trough. Individual ensemble members across the GEFS, GEPS,
and ECMWF ensembles show some differences in the exact track of
the low but there is better agreement on the center approaching
the NE Gulf coast by late Thursday. There is also broad consensus
that the accompanying moisture support and associated winds with
this system will be significantly more substantial than with the
previous ones. Combined with divergence aloft, the panhandle will
be favorably situated to see a respectable amount of precipitation.
The critical question is whether or not this precipitation is
rain or snow, especially in locations near sea level. Although 850
mb temperatures of -3C to -5C would normally be less than
favorable, a potentially very strong front advancing almost
directly out of the S could offer the potential for an
undercutting event to take place. Guidance oftentimes struggles
with forecasting undercutting events-given the general tendency of
warm air advection to successfully mix out cooler air near the
surface. Should an undercutting event take place, advancing cooler
air in the lowest levels of the atmosphere will successfully
force the warm air advection moving N aloft, setting the stage for
a potential snow event for parts of SE Alaska. At this time, the
possibility of a snow event would more likely than not primarily
effect the far N panhandle, with far lower confidence in the
possibility of a significant snow event for areas further S or in
the Icy Strait Corridor. Any snow event however would likely be a
low confidence event barring the Klondike and Haines Highways.
Changes in frontal orientation, the strength and location of the
low, and timing of the system, will all have significant impacts
on whether or not the system proves to be a snow-maker of note or
a rain- producing event. Regardless, respectable QPF totals are
anticipated with this system, with possible river rises, alongside
the potential for significantly elevated winds as the system
advances into the area.

The other big component of this system, alongside the
precipitation, will be the wind. The impressive frontal band
advancing N will see significantly elevated winds across most of
the panhandle and the associated maritime areas. Storm force winds
are anticipated across the outer gulf, outer coastal waters and
the Dixon entrance as the frontal band races N on Wednesday, with
gale force winds and small craft winds likely to be associated
with the system through much of Thursday. Significantly elevated
winds across many land based areas will also take place, and it is
possible that the wind forecast may need to be further increased
across some locations as guidance comes into better agreement on
the exact timing of the initial frontal band and the associated
dynamic support from the main low itself.

Beyond Thursday, ensemble guidance begins to steadily diverge.
There may be some chance for a break in some locations through
parts of Friday and Saturday. The overall pattern will continue to
be general troughing over the E gulf and the panhandle, which
would help favor continued chances of precipitation overall.

&&

.AVIATION...SE winds of 50-65kt are being measured by the Biorka
Island radar near Sitka as of 1445z between 1-3kft. Those winds
are not fully mixing down to the surface yet, so LLWS is in most
TAF sites. Peak winds and heavy rain will arrive with the front
through noon. A wind shift to the SW will occur behind the front
with a sharp decrease in speeds, reducing the LLWS threat heading
into the evening. Despite the widespread moderate (occasionally
heavy) rain, winds are keeping CIG/VIS VFR to MVFR. After the
front passes, rain will let up and become more
showery/intermittent.

&&

.MARINE...Gale force tracking over the SE gulf Monday bringing
strong gales to the E gulf and gales south of Frederick and Cross
Sounds with strong breezes through the rest of the inner channels.
Winds and seas will ease late Mon into Tue as this system
dissipates. Focus then shifts to a weakening hurricane force low
moving from NE Pac into SE gulf Wed into Thu. This will bring
storm force winds to the gulf with gales expected for most inner
channels.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory until 6 PM AKST this evening for AKZ318.
     Strong Wind through this afternoon for AKZ323.
     Strong Wind from 9 AM AKST this morning through this afternoon
     for AKZ325-326.
     Strong Wind through this afternoon for AKZ327.
     High Wind Warning from 7 AM this morning to 5 PM AKST this
     afternoon for AKZ328-330-332.
     Strong Wind from 6 AM AKST this morning through this afternoon
     for AKZ329.
MARINE...Gale Warning for PKZ013-021-022-031>036-041>043-051.
     Small Craft Advisory for PKZ011-012-052-053.

&&

SHORT TERM...PRB
LONG TERM....GFS
AVIATION...Ferrin

Visit us at http://www.weather.gov/Juneau