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FXAK67 PAJK 161452
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
552 AM AKST Sat Feb 16 2019

.SHORT TERM...Today through Sunday night...High amplitude upper
ridge over the gulf and extending into mainland AK will slowly
shift eastward Saturday. Northerly flow along the east side of the
ridge will keep most of southeast AK clear and dry through the
day and tonight. Pressure heights will continue to rise through
Saturday as well. Progressive shortwave currently near the central
Aleutians will move into the eastern Gulf Sunday morning. Weak
surface low develops in the NW gulf Sunday afternoon with
associated warm front lifting towards the northern gulf coast.
Ridge aloft will weaken as it is pushed further eastward into W
Canada. Upper vorticity wave will in turn weaken and be stretched
as it is forced up against the ridge and moves across the
panhandle.

Main forecast concerns in the short term deal with the specifics
of the front entering the gulf Sunday and impacting the NE gulf
coast late Sunday morning through Sunday night. The ridge
continues to slow the progress of the system according to model
guidance this morning. Accordingly, have pushed the POP back
another few hours, especially from entering the northern inner
channels until Sunday evening. Temperatures will remain cooler
than normal, so most precip will likely start out as snow. Warmer
air will advect in behind the warm front Sunday night along the
outer coast. The biggest challenge will be with the precipitation
type in the Yakutat area as snow levels rise, but precipitation
intensity is also anticipated to increase. Expect temperatures to
remain steady around 35 Sunday night. Possible that the heavier
rates will allow snow to fall there. For now have kept a mix of
rain/snow in the forecast during the Sunday night period. Thinking
that 2 to 4 inches of snow is possible in the Yakutat area.
Elsewhere, light snow is expected to commence across the northern
inner channels Sunday evening and gradually progress southward.

Northerly outflow winds will continue to diminish through today,
and eventually all hazards will go away late Saturday night
throughout the panhandle. Surface high across NW Canada will move
south today which will shift the pressure gradient to a more
easterly direction. The gradient will continue to slacken over
the panhandle Sunday. Strong winds will persist in the downtown
Juneau and Douglas areas through Saturday morning. Along the
northern gulf, expect a gale force barrier jet to set up Sunday
along the front.

Overall can expect a cool but sunny Saturday across southeast AK.
Decreased low temperatures for Saturday night into Sunday morning
in a few locations as lighter winds and clear skies are expected.
The southern panhandle should continue with mostly sunny
conditions through most of Sunday as well. Preferred GFS and NAM
model guidance to make a few minor adjustments to the inherited
forecast.

.LONG TERM.../Monday through Saturday as of 10 pm Friday/
Longwave pattern will generally keep ridging over the NEPAC with
troffing over the N-central PAC and the Bering Sea. However, there
will be several shortwaves, some on the strong side, that will
flatten the ridge as they move through during the week. Still some
timing and strength differences to resolve amongst the models
however. These systems will have sfc lows/fronts moving in with
them, again with models showing differing timing and strength.

First system will already be into the area by Mon morning. This
will be a weakening occluded front that moves onshore by late Mon
morning, then falls apart across the inner channels Mon afternoon.
Expect some light precip with this feature as it passes through,
with snowfall amounts up to 3 inches possible by midday Mon. This
system will likely cause outer coastal area to warm up enough to
become mainly rain by early afternoon.

A stronger system should move in for Mon afternoon into Tue.
Looks like a low will track across the N gulf with an occluded
front moving with it Mon afternoon and night. This system should
have more precip with it, but will also bring in some warmer air,
so the rain/snow line appears to move inland as this system moves
onshore. Still some differences in how much lower level cold air
hangs on over the more eastern and northern areas, so limited
any transition to a mix for most of those spots. It is possible
for advisory level snowfall during late Mon afternoon into Tue,
but this will depend on how long the precip can stay as snow.

There may be a break in precip threat beginning Tue night.
However, another system may move in for later Wed into Thu. Still
a lot of model differences though, so limited any POPs to likely with
this system. Once again, ptype will be tricky as that will depend
on whether any cold air might filter in Tue night into Wed. Still
a lot of model differences going into next weekend, with latest
GFS and ECMWF suggesting a colder airmass moving in with
sharpening ridge to the W, while Canadian model is flatter and
keeps cold air further E. Overall, forecast confidence is average
at best.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind until noon AKST today for AKZ025.
MARINE...Small Craft Advisory for PKZ012-013-021-022-031>034-041>043-052.

&&

$$

HARTSOCK/RWT

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