Area Forecast Discussion
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FXAK67 PAJK 240013 CCA
AFDAJK

Southeast Alaska Forecast Discussion...CORRECTED
National Weather Service Juneau AK
413 PM AKDT Fri Jun 23 2017

.SYNOPSIS...A weather front approaching from the southwest will
reach the outer coast of the panhandle by Saturday morning then
spread inland through the day. The associated low pressure system
will slowly weaken over the SE gulf on Sunday as a ridge builds in
front the west.

&&

.SHORT TERM...Clouds assoc with the triple point ahead of
tomorrows system have already started to move into the southern
outer coast late this afternoon. Echos are showing up on the radar
with these clouds, but likely only virga so far. On the contrary,
a band of clouds moved over the Skagway/Haines valleys this
afternoon from the east, and this caused some showers up the
Chilkat Valley. These showers seem to be moving relatively quickly
to the west and thus expect clouds to decrease going into the
evening up north. Other clouds over the Juneau to Hoonah have
been noted this afternoon with some gravity waves due to winds
aloft flowing over the mountains.

The system mentioned above will cause increasing clouds overnight
from SW to NE and rain will spread inland Saturday morning. Expect
rain to reach as far inland a Juneau in the mid to late morning,
but some models would suggest even earlier. The extreme northern
and southern portions of the panhandle are progged to receive the
least rainfall with this system while the Sitka and Icy Strait
corridor could have some moderate rainfall. The assoc low
pressure center will move into the eastern gulf during Saturday
and cause rain to transition to showers in the late afternoon
behind the main front. Expect bands of showers to continue
wrapping around the low and affecting the panhandle through much
of Sunday. However the low should weaken going into the evening as
it is pushed E-SE by a building ridge to the west. Therefore,
expect numerous showers to become scattered to isolated from north
to south through Sunday afternoon/evening.

Relatively light winds today at the surface have taken until late
afternoon to be more sea breeze driven. Expect some variable winds
of around 10 kt to turn out of the SE overnight as the low/front
take over as the synoptic driving force. Overall SELY winds will
prevail, but on the light side the further away from the low
center you get. Near the low and out of Cross Sound have winds
increasing 25-30kt tonight. Once the low weakens on Sunday and the
ridge builds in from the west, will see winds largely turn around
to the NW.

Models were in good agreement through the short term so only minor
adjustments were needed.

.LONG TERM...Monday through Friday...As of 930 PM Thu...Period
begins with models in fairly good agreement depicting an upper low
over the central gulf drifting E across the central panhandle
into Mon. As expected, there are minor differences in position
and/or timing of this feature moving inland, but overall agreement
minimizes impacts of these differences on the fcst. This feature
is relatively weak as only the SREF mean SLP indicates a closed
SFC circulation while all other guidance depicts an open wave just
off S Baranof Mon Morning. Chc PoPs will persist Mon before he
upper low pushes E of AOR Tue. Although the low will be inland,
expect enough instability on the back side of it to see some ISOLD
showers Tue over E CWA. Ridge will build over the gulf and push E
over the panhandle Tue into Wed. Model solutions continue to
diverge by mid week, mainly with the strength and timing of the
system pushing into the W gulf. How long the ridge persists over
SE will depend on this next system`s approach. Expect dry weather
to continue Wed before increasing sky cover and precip chances
late next week. Temps will be slightly below normal Mon then
slightly above normal mid next week as supported by NAEFS low
level T standard dev swinging from 1-2 below to 1-2 above normal
during the first half of the week. Given model spreads in the
extended it`s difficult to determine how long the ridge will
maintain dry wx across SE. Therefore, elected to stay close to WPC
guidance for the latter half of next week with cooling temps and
increasing precip chances. Inherited forecast represented this
well with very little change before trending toward WPC.

&&


.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ022-042-043-051-052.

&&

$$

Ferrin/BC

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