Gale Warning 199, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
627 AM AKDT Sat Sep 26 2020

.SHORT TERM...Patchy fog is once more a possibility in parts of
the N half of the panhandle through early Saturday morning as a
few breaks in the cloud deck allow parts of the area to reach
saturation. The system responsible for the waves of convective
showers moving over the panhandle is finally beginning to pull N,
and will depart the area by the end of Saturday. Though this may
give many places lower rain chances through the afternoon and
early evening hours, any possible respite will not last. Model
agreement continues to remain good on the movement and location of
the approaching 965 mb sfc low and its associated front.
Atmospheric dynamics continue to remain conducive for this event.
In the upper levels, a well-positioned jet streak of 160kt
is progged to support the system along with substantial divergence
aloft. In the mid-levels, abundant vorticity is evident across
all of the operational runs. In all levels, moisture and moisture
transport is evident. Integrated Water Vapor Transport Values
remain impressive, and Q vectors are indicative of plenty of
upward motion.

The end result of all of these ingredients will be a mixture of
heavy rainfall and strong winds. Rainfall amounts remain similar
to previously expected totals, and am still anticipating amounts
ranging from 1.5 inches to 3 inches across the panhandle. The
highest rainfall amounts will be in the southern panhandle, with
lower amounts expected for the central and northern areas. Given
the favorable ingredients, still think that the heaviest rainfall
will take place late Saturday night through Sunday. Lingering
rain in the northern panhandle and along favorable mountain slopes
Sunday night could push totals in certain locations a bit higher.

The other big impact of this storm will be the wind and waves.
Given the tight pressure gradient, am expecting this system will
reach storm force in the gulf and the more northerly outer
coastal waters beginning Saturday evening. The associated waves
in these places could reach in excess of 30 ft. The inner channels
will be a little bit calmer, with gale force or small craft
strength winds expected, depending on the channel. Strong winds
are expected across the coastal and southern parts of the panhandle
beginning on Saturday night. Wind shear will be a concern for
aviation interests with winds between 60 to 70 kt expected between
2000 to 3000 ft above ground level in the southern panhandle and
Sitka. Other parts of the panhandle could see wind speeds at
similar heights reaching up to 50 kt.

The system will be steadily weakening by Monday, though it will
continue to encourage rain across much of SE Alaska. Temperatures
will continue to remain less than impressive with lows hovering in
the mid to upper 40s and highs reaching into the 50s as cloud cover
minimizes the diurnal curve. The NAM and GFS were the models of
choice for adjustments made to the forecast. Forecaster confidence
is average.

.LONG TERM...Tuesday through Friday...As of 9 PM Fri...Period
begins with front pushing through the region. Models continue to
show some spread but continue to show ridging building into the
panhandle from the SE. The upper pattern of a long wave trough
over the AK pen and upper ridge anchored over W North America.
This will focus majority of precip into the NE gulf coast, but
with the active pattern and S-SWly mid level flow through the
extended kept mention of precip and normal to above normal temps.
Overall forecast confidence remains about average.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind from late tonight through Sunday morning for AKZ022-
     024-026>028.
     Strong Wind Sunday afternoon for AKZ022-023.
     Strong Wind from late tonight through Sunday morning for AKZ023.
     Strong Wind from late tonight through Sunday morning for AKZ021.
     Strong Wind from Sunday morning through Sunday afternoon for
     AKZ017.
MARINE...Storm Warning for PKZ043-051-052.
     Gale Warning for PKZ036-041-042.
     Small Craft Advisory for PKZ021-022-031>035-053.

&&

GFS/BC

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