Area Forecast Discussion
Issued by NWS Juneau, AK

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FXAK67 PAJK 012355
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
255 PM AKST Mon Mar 1 2021

.SHORT TERM.../Monday night Through Wednesday/...An area of low
pressure at the surface will pass just north of Yakutat. As it
moves northward, it will swing a front into the panhandle tonight.

This front will bring precip to much of the panhandle. Confidence
on QPF amounts tonight is moderate due to the decent agreement
among the ensembles. Areas along the northern gulf coast are
expected to get around a half to three-quarters of an inch of
moisture. Farther south along the coast, amounts look to be around
a quarter to half inch. The central and southern inner channels
are expected to get around a quarter to half inch as well with
some isolated spots getting a little more due to topography. The
northern inner channels are looking to get around a quarter to a
third of an inch.

The temperature forecast for the lower elevations tonight will
play a big part in what type of precip will fall. The going
forecast is calling for low temperatures in the mid to upper 30s
for areas south of the Icy Strait Corridor. Along and north of the
Icy Strait Corridor looks to see lows around freezing or a few
degrees colder. If these forecasted temperatures play out, then
expect rain or a rain/snow mix for the south with rain, snow, and
rain/snow mix likely for the north.

Accumulating snow is possible for the higher elevations and for a
few spotty locations along and north of the Icy Strait Corridor.
But with the low liquid-to-snow ratios, the type of snow is
expected to be the sloppy/wet kind of snow. The Yakutat area
could see an additional one to two inches of snow. The Juneau area
could see up to one inch. The northern highways could get around
one to three inches in the higher elevations. Less than one inch
amounts are looking possible for Haines, Skagway, Gustavus, and
Hoonah.

While the wind forecast for tonight has calming winds, the wind
will be on the strong side to start tonight with some Strong Wind
headlines this evening.

Tuesday brings a broad area of low pressure in the gulf, which
would keep onshore flow and precip chances in the forecast.

But due to the unorganized nature of the pattern, confidence in
the QPF forecast is on the low end. Broad-brush estimates Tuesday
through Wednesday are around a quarter to half inch of moisture
with some isolated spots getting a little more due to the
topography.

High temperatures tomorrow will be in the 30s to near 40. Cold
air will begin to filter back into the northern regions Tuesday
night so forecasted lows north of Icy Strait are in the 20s to
lower 30s. Lows in the mid to upper 30s are still expected for the
central and southern areas.

And with those colder forecasted temperatures Tuesday night, some
snow is possible but for now, amounts look to be around one to
two inches.

.LONG TERM.../Wednesday through Monday night/..."Variety`s the
very spice of life, that gives it all its flavour." according to
William Cowper`s "The Task" (1785), and the long term looks to
deliver plenty of variety as the progressive pattern continues with
more than a few dashes of uncertainty to keep the forecasters on
their toes. As has been the case recently, there will be some rain,
snow, wind, waves, with a break possible at the very end of this
timeframe. Of note, temperatures do not appear to warm or cool
substantially during the long term. Temps will add their spice to
the forecast by just hanging uncomfortably close enough to
freezing to make snow a consideration in at least some portion of
the forecast area.

Models are in good agreement Wednesday and Thursday with a digging
upper level trough with the trough axis bisecting the Gulf of AK
Wednesday night. At it`s maximum amplitude, the base of the trough
extends all the way to 35N latitude in the central Pacific. At
the surface models are also in decent agreement with a broad low
in the gulf, and disturbances rotating around the system bringing
periods of precipitation and wind to the panhandle. Precipitation
type and the timing and strength of the impulses will be the
forecast challenges. There appears to be one rather weak impulse
that will impact the coast Wednesday afternoon bringing showers
and possible small craft advisory winds for some of the channels.
Deterministic and ensemble models are showing a stronger surface
low approaching the panhandle from the southeast and riding up the
coast throughout the day on Friday, but there are differences in
both timing and track. Model trends will need to be watched on
this system as it could bring more impactful winds, possibly
gales, and precipitation, including snow, depending on the exact
track. After the Friday system passes, yet another weak system is
modeled to form in the gulf Saturday and approach the southern
panhandle, this time from the west, and exits quickly to the
southeast. Sunday and Monday look be the best chance for a break
from the active weather, but with model disagreement present as
early as Friday, confidence is low for the extended period.

To conclude on the subject of variety, an array of models were
used to construct the long term forecast. For the first two days,
a blend of the GFS, Canadian, European, and NAM were used due to
the very good agreement. For Friday and Saturday, the European
appeared to have the best handle on the Friday system so a blend
favoring the European model was used. Beyond that the operational
blends were leveraged (WPC, NBM).

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind from 6 PM this evening to midnight AKST tonight for
     AKZ025.
     Strong Wind until midnight AKST tonight for AKZ019.
     Winter Weather Advisory until 6 AM AKST Tuesday for AKZ018.
     Strong Wind through late tonight for AKZ018.
     Winter Storm Warning until 9 PM AKST this evening for AKZ017.
MARINE...Gale Warning for PKZ012-051-052.
     Small Craft Advisory for PKZ011-013-021-022-031>036-041>043-053.

&&

$$

GJS/BFL

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