Storm Warning 11, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
304 PM AKDT Fri Oct 28 2022

.SHORT TERM...Cold core upper low is traversing the Panhandle
early this afternoon. Widespread showers are accompanying this
low. Steep lapse rates underneath the cold pool aloft combined
with weakening boundary layer flow has allowed snow to mix in with
the heavier showers in a few areas and this should continue into
the early evening hours with no accumulation expected. The
exception will be White Pass where and additional 2 inches or so
of snow is possible through early evening.

Attention then turns to the developing storm force low seen on
satellite pushing quickly eastward across the AK Peninsula this
afternoon. This low will take up residence in the central Gulf by
Saturday morning and then slowly move eastward and weaken through
Sunday. As the occluded front swings north into the northern Gulf
Saturday morning, storm force winds will be widespread over the
outside waters with near gale to gale conditions spreading across
the inner channels along and south of Icy Strait. This storm will
have significant cold advection on the south side of the low
center and thus expect strong SW winds to impinge on the southern
outer coast by Saturday night.

To the north, the surface pressure gradient across the far
northern Lynn Canal communities of Haines and Skagway will favor
north winds during the short term period. Snow levels are
currently less than 1000 ft over this area and should lower to sea
level by Saturday morning as at least some cooler boundary layer
air gets drawn south from the Yukon. As the front lifts northward
on Saturday, SE overrunning flow in the 925 to 850mb layer will
yield a pattern favoring the Haines area and the highway for snow
accumulations through Saturday night. Have some concern over just
how cool the sea level communities can get as we dont yet have a
true arctic airmass in place. Thus went with a Winter Weather
Advisory for the Haines Highway where temps are currently hovering
near freezing and should continue to through the event. Should
cooler air be able to be drawn into Haines proper, snow totals
will need to be adjusted upward but for now will hold with an
advisory for 3 to 6 inches of new snow.

.LONG TERM.../Sunday through Friday/...The storm force low from
Saturday will move into the NE AK Gulf where it will remain quasi
stationary while rapidly weakening Sunday into Monday. By Tuesday
weak riding will replace the low before the next system tracks
from the west Wednesday into Thursday. Lots of uncertainty on this
mid week low track and the weather pattern for the rest of the
week.

Secondary wrap over the southern AK Gulf weakens as jet support
moves to the south. Still some breezy conditions over the southern
panhandle and high end gales over the gulf but mainly coastal waters
and southwestern shores will be dealing with high seas due to
westerly swell. Overall trend will be a decrease in winds and seas
by Monday. What was looking like an outflow wind event for mid week
isn't looking as favorable due to the low remnants lingering in the
NE gulf keeping any East-West gradient down.

Showers over the Panhandle last a bit longer into Monday due, once
again, to the remaining low in the NE Gulf. No much QPF with these
showers overall but may see some locally higher amounts where flow
enhances orographic lift. More breaks in showers Monday night into
Tuesday. The next front have large timing issues between operational
models as larger spread on main low that moves over the Bering.
Ensembles have some heavy precip with this front so expect the
precip, just not sure on timing.

Cold air advances in as we move into the week as start of an arctic
front moves down from the Yukon. Since the ridging is not as
pronounced not likely to see as much of this cold air get over the
region as when the NE gulf low was previously forecast to be further
south. The cold air will lead to more snow or rain-snow showers
especially for the central and northern locations. But for now not
much snow accumulation is expected.

Operational models trended toward the previous days GFS solution but
GFS still keeps a deeper low in place much longer. Used a blend of
GFS/ECMWF initially then kept with an WPC ensemble solution for the
rest of the mid range.

&&

.AVIATION...MVFR conditions are expected across Southeast Alaska
for the next 24 hours with lower CIGs and reduced VSBY in rain
showers. Persistent pattern of layered clouds from 1500 feet up
to the flight levels into this evening. Conditions look to
improve a bit during the overnight hours before the next storm
starts to move into the area tomorrow morning bringing conditions
back to MVFR/IFR with widespread rains moving in along the next
front. Low level wind shear has calmed down during the day but
looks to return in the morning tomorrow with the next approaching
system.

&&

.MARINE...Attention is once again focused on outer coast tide
gauges. Astronomical high tide for the next few days will
coincide with strong southwesterly winds. This combined with the
waxing crescent moon and associated spring tides will cause tides
to be higher than they would otherwise be. Highest high tides
will occur in the early afternoon and particular attention is
being paid to the tidal predictions and surge at Sitka and Port
Alexander. In both locations, the combination of the astronomical
tide and predicted storm surge will result in water levels close
to the highest astronomical tide, or HAT. Water levels will reach
higher than normal levels, so individuals should remain vigilant
and take precautionary actions if needed.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind Saturday afternoon for AKZ317.
     Winter Weather Advisory until 7 PM AKDT this evening for AKZ318.
     Winter Weather Advisory from 6 AM Saturday to 1 AM AKDT Sunday
     for AKZ319.
     Strong Wind from Saturday morning through Saturday afternoon for
     AKZ323-330.
     Strong Wind from Saturday morning through Saturday afternoon for
     AKZ327.
     Strong Wind from Saturday morning through Saturday afternoon for
     AKZ328-329.
MARINE...Storm Warning for PKZ043-051-052.
     Gale Warning for PKZ022-031-034>036-041-042-053.
     Small Craft Advisory for PKZ012-013-021-032-033.

&&

SHORT TERM...DEL
LONG TERM....PRB
AVIATION...JG/SEF
MARINE...Fritsch

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