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617
FXAK67 PAJK 252315
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
315 PM AKDT MON JUL 25 2016

.SHORT TERM...An upper-level shortwave trough is currently
pivoting northeastward toward the central gulf, and is forecast to
reach the panhandle by 12Z Tuesday. Vertical motion associated
with this feature combined with PW values near 2 standard
deviations above climo will aid in moderate rainfall rates that
will develop over the northern/central panhandle late
tonight...and then develop southward across the southern panhandle
by mid-day. In addition, a minor surface wave is forecast to lift
north toward the northern gulf tonight. As this occurs, an
easterly barrier jet is forecast to develop from marine zone 43 to
marine zone 52...which has prompted the inclusion of a small craft
advisory through Tuesday morning. Meanwhile, gusty southerly winds
continue to occur over northern Lynn Canal, Haines, and Skagway
Monday afternoon. However, the surface pressure gradient is
forecast to relax during Monday evening, which will result in
weakening winds with time.

No change was made to inherited pressure grids. Wind speeds over
the gulf were nudged toward the hi-res ARW/NMM. High temperatures
for Tuesday were manually tweaked downward several degrees for
area communities. POP values were bumped slightly upward tonight
and tomorrow, and ECMWF and hi-res guidance was used for QPF.

.LONG TERM...Onshore flow will prevail through the work week with
rain in the forecast each day. On Wednesday a low center will
develop along the moisture plume already affecting the region and
move into the north central gulf. This looks to enhance the
rainfall over the area as it taps into more subtropical moisture.
Expect heaviest rainfall to be over the north/central panhandle,
especially along S-SW facing slopes, but the whole region will see
measurable rain. Winds with this system look to increase 25-35kt
over the outside waters midday Wednesday. On Thursday the greatest
lift will be over the southern panhandle as the front moves
through.

On Friday the surface ridge over the panhandle will start to
flatten then shift over the gulf. All the long range models show
an upper level trough of low pressure dropping south across the
region Friday night. This will cause a change from the wet pattern
going into the weekend. Flow will turn offshore and should allow
for a break in the rain and some sunny breaks over the far
northern inner channels on Saturday. This break may be short-
lived however as some models were showing a new low affecting the
area with rain Sunday night/Monday, while others are dry a little
longer.

Warm moist onshore flow and cloud cover will keep low temps
moderated through the week with a fairly small diurnal range in
max/mins. Offshore flow and some sunshine on Saturday will warm
things up.

Models were in very good agreement through the week so a blend of
models was used for most fields and a nudge to the GFS for others.
Forecast confidence is above average for wet the next couple days.

&&

.HYDROLOGY...Several creeks, streams, and rivers are near bankfullacross
the panhandle. With rainfall potentially reaching moderate
intensity Monday night and Tuesday, and again Wednesday and
Wednesday night, water levels will likely rise, especially over
the central and northern panhandle, where rainfall will be
heaviest. Hydrological conditions will be monitored closely
through midweek.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ043-051-052.
&&

$$

Garner/Ferrin

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