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FXAK67 PAJK 232225

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
225 PM AKDT Fri Mar 23 2018

.SHORT TERM...WV imagery this afternoon continue to show a closed
mid/upper low south of Haida Gwaii with sharp ridging extending
northward from the central Gulf into the central mainland of AK. A
weak shortwave over the AK Peninsula was making an attempt to
push into the mean ridge position while a second shortwave was
drifting southward from through the Yukon towards the NE Gulf.

A persistent band of light precip continues over the central and
southern Panhandle well north of the main upper low. This precip
has shown some banded structure and is most likely being driven
by an area of weak frontogenesis along a low to mid level shear
axis. Snow has been reported under the heavier precip rates today
and as much as 1.5 inches was reported at Petersburg early this
afternoon. Light rain or light snow will continue through the
evening hours as this band slowly sinks southward with little
additional accumulation.

Outflow winds have been on the decrease today and expect that
trend to continue tonight as the cold air advection ceases. By
Saturday morning expect small craft winds to be confined to
northern Lynn Canal with 15 kt or less across much of the inside

The Yukon shortwave will combine with the remnants of the wave
from the AK Peninsula to induce a weak surface low in the northern
Gulf Saturday and this low will track ESE into the southern
Panhandle by Saturday night. Kept cloudy skies with areas of
light rain or snow developing across southern areas by Saturday
night. To the north, skies will remain relatively clear behind
the mid level wave, and some weak CAA will ensue on Saturday
night. This will allow outflow winds to return to small craft
levels over all of Lynn Canal and Cross Sound by late Saturday
night, possibly continuing into early Sunday. Gradient rapidly
weakens on Sunday ahead of the next front approaching from the SW.

Models have trended slower with the next front progged to move
into the Gulf on Sunday and Sunday night. Both the GFS and
especially the Euro allow the front to take a more elongated and
southern approach. This may allow winds over the inside waters to
remain lighter and more northerly than the current forecast, so
trended in that direction. With the weak gradient, what precip
does fall on Sunday night into Monday especially north of
Frederick Sound may end up being snow with the continental airmass
in place, but due to some model differences did not make many
changes to precip type or amounts at this time.

.LONG TERM.../Monday through Thursday as of 10 PM Thursday/The
long term forecast continues to look wet. The primary concern in
the extended forecast remains a weather front that will track east
across the gulf Sunday. Precipitation still looks to begin as
snow or a rain and snow mix with this system before transitioning
to rain as warm air advection occurs. The far northern Panhandle,
specifically, the Haines and Klondike Highways may stay all snow
with this system. However, the bulk of heavier precipitation looks
to set up over the Southern Panhandle where it will fall as rain,
so snow accumulations remains low as a whole with about 1 inch
forecasted over the northern Panhandle. This system continues to
look quite wet with precipitatible water values in excess of 2
standard deviations above normal. Models have trended the heavier
precipitation further south so the largest rainfall totals are
expected south of Fredrick Sound currently. A brief break in
precipitation may occur after this front moves out, before another
low and its associated front move north over the gulf toward the
middle of the week.

Model agreement is average with poor run to run consistency
leading to lower forecast confidence. Not much change was made in
the extended forecast Sunday and Monday. Models are still
struggling with the timing of the system and precipitation totals;
however, they were diminished slightly and models have trended
precip totals downward with the exception of the GFS which
continues to be the wettest model. Primary guidance was a blend of
the ECMWF and Canadian to handle minor changes to the Sunday and
Monday timeframe with newest WPC being used beyond that timeframe
to add the midweek low to the extended forecast.


.AJK Watches/Warnings/Advisories...
MARINE...Gale Warning for PKZ012.
     Small Craft Advisory for PKZ013.




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