Winter Storm Warning 1, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
310 PM AKST Tue Jan 2 2018

.SHORT TERM.../ Tuesday night to Thursday night / High pressure
over British Columbia towards the Yukon will persist through the
middle of the week while a front band with a several waves moving
along it through Thursday. A general area of low pressure will
continue to dominate the Bering Sea.

We have a low and short wave moving northward over the central
gulf and the northern panhandle this evening. Expect the rain band
to spread into the northern and central panhandle overnight and
then retreat west as another wave on the front move north just
east of 140 W longitude. This system is also pulling moisture
from the mid tropics northward so expect a fair bit QPF values
from it along with a slight rise of temperature to above normal.
Some cooler temperatures near the border of the Haines Road and
Klondike Highway so Winter Weather Advisory and Warning are being
issued for tonight.

The low with the second wave looks pause west of the Haida Gwaii
region and will rotate about there as the next waves moves north.
With the lows stalled however think the that Northeast gulf may
start dry out as rain/snow is held to the panhandle, for about a
day.

Think the last of the waves will be pulling northward but will
move into the southern Hecate Strait area for Thursday night and
then into the southern panhandle and along the coast mountains on
Friday. Also late Thursday there is long front moving into the
western Gulf of Alaska from a new low moving into the Bering Sea
area.

Only needed small changes to the forecast package today, and we
were using a blend of the NAM and GFS for the minor adjustment.

.LONG TERM.../Thursday through Monday night/ Not much change
overall in the long range today as large scale pattern remain
mostly unchanged from yesterday. Upper ridge over the US West
Coast and trough over the Bering sea producing SW flow aloft with
embedded shortwaves. The embedded trough on Fri is still giving
the guidance troubles though not to the same extent as yesterday.
The ECMWF has become more progressive moving the feature through
the area compared to yesterday. Meanwhile the GFS was still rather
progressive until its 0z run this evening which decided to slow
the feature up almost to the point of where the ECMWF was
yesterday but not bringing as much warm air north. Agreement
continues to suffer from there as various other shortwaves form
and dissipate. Timing and position of which vary depending on
which model and/or run you are looking at. Overall pattern
continues to be somewhat warm and active for the area into early
next week.

At the surface, overall changes were not that drastic with main
changes being an increase in winds over the gulf Fri night into
Sat to account for a front that is moving N at that time in the
18z GFS and Canadian (the 0z GFS is not as strong). Otherwise
overall message remains the same with a somewhat damp forecast
with warm temperatures overall but a slight cool down for Fri into
Sat. 18Z GFS and some nam used for updates early on as 0Z GFS
departed from what previous runs have suggested. WPC used for
later periods where needed as inclusion of more of the ensemble
guidance was needed given the uncertainty in the operational
models that far out.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Winter Weather Advisory from 6 PM this evening to 6 AM AKST
     Wednesday for AKZ019.
     Winter Storm Warning from 9 PM this evening to 6 AM AKST
     Wednesday for AKZ018.
     Strong Wind until 3 PM AKST this afternoon for AKZ018.
MARINE...Gale Warning for PKZ041>043-051.
     Small Craft Advisory for PKZ012-013-021-022-031-032-034>036-052-
     053.

&&

Bezenek/EAL

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