Area Forecast Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
000
FXAK67 PAJK 232341
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
341 PM AKDT Thu Mar 23 2017

.SHORT TERM...While one short-wave lifts northward across the
Panhandle, spreading rain and snow showers with it, another
follows it spreading stratiform precipitation into the southern
Panhandle tonight and spreading northward into the central
Panhandle Friday.

More snow was observed today than originally thought, but impacts
were low. Ketchikan probably received around a half-inch before
showers moved northward. Juneau and points around the central
Panhandle got just a dusting. These showers, now spreading into
Haines and Yakutat will progress north and westward through
tonight. By late tonight breaks around Juneau and Gustavus may
allow for some patchy fog formation.

For the south, fair skies this afternoon will quickly begin
darkening from the south as rain/snow moves in late. The forecast
for Ketchikan and points around the southern Inner Channels and
Prince of Wales Island is probably the most difficult. Temps at
850 warm to around -4 C which suggest rain. But surface gradient
orientation suggest a northerly wind that may help dry the
boundary layer sufficiently to allow for column cooling. This
would help keep snow mixing in with rain. Precipitation rates, if
high enough would further keep snow mixing in. We have opted to
keep the rain/snow for Ketchikan, but our confidence is low, as
they are low for all the above points. Farther north, precip
should begin as all snow around Petersburg with maybe a mix for
Wrangell that will change to rain later in the day. Juneau and
points north and west will stay out of the main precipitation
shield Friday but will see increasing clouds.

Small craft winds were added for the low around Dixon Entrance and
were kept for northerlies tonight in Lynn Canal. Also, we added 30
mph gusts for Downtown Juneau Friday morning in support of a weak
outflow event ahead of the system to the south. GFS/NAM were used
for any changes needed. Confidence is good, except over the
southern areas for precipitation type tonight.

.LONG TERM...Models have trended a little slower and further W
with a low for Fri night and Sat. A weak N-S oriented trof and
mid-level deformation zone will develop over the inner channels,
which will enhance the precip potential over most of the inner
channels except the far NW part Fri night into Sat morning. Some
of this precip will fall as snow especially over the more eastern
areas, and an inch or 2 of snow could fall by Sat morning in some
areas. Upper trof will sweep across the area Sat which should
push this precip out of the area by early to mid-afternoon, but
onshore flow will keep some showers going later on. The NE gulf
coast will likely remain dry Fri night into Sat morning as
offshore flow continues, but they will become onshore Sat
afternoon and increase threat for showers in the afternoon.

Later on, looking like another system will move in for Sun. Models
differ some on track of main low center and supporting shortwave
aloft, but looking like system will get into the eastern gulf at
least. More systems should move in next week but timing and track
differ somewhat on the models. Still, overall pattern will be
active so may end up with some precip during most of the week,
with a possible break Wed/Thu as larger scale ridge tries to build
over the area before shifting E ahead of a much larger system for
late Thu and Fri.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ012-041.
&&

$$

JWA/RWT

Visit us at http://www.weather.gov/Juneau



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.