Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 211034

Area Forecast Discussion
National Weather Service Medford OR
334 AM PDT Sat Apr 21 2018

.DISCUSSION...Upcoming high temperatures forecast in the 70s and
80s will be quite a contrast to the highs earlier this week in the
40s and 50s.

In the short term, a weak cold front will skirt the area with
much of its influence felt near and north of the Umpqua Divide
with additional clouds and a few degrees of cooling. Another weak
disturbance will follow Sunday morning with temperatures similar
to Saturday but a little cooler Sunday morning.

The warmup will begin Monday as high pressure builds and
temperatures flirt with 80 degrees in the Oregon western inland
valleys with the lower to mid 80s for the lower Klamath River

In the long term, both the GFS and EWMWF models are in agreement
on a large cut-off low pressure area meandering west of 130W
which is far enough away for a significant warmup to occur Tuesday
through Thursday. The warmest days look to be Wednesday and
Thursday with highs well into the 80s across the inland western
valleys and the 70s east of the Cascades.

Some instability could develop late Thursday with a slight chance
of thunderstorms over the favored higher terrain but enough
moisture is questionable. Cut-off low positions are difficult to
predict, especially in the spring, so there will likely be
changes in the forecast for late next week depending on when and
where the low moves toward the West Coast. The latest GFS model
just available was now showing this low diving farther south
toward central California next Friday so there is greater
uncertainty in the forecast for next Friday into the weekend.


.AVIATION...21/12Z TAF CYCLE...At the coast, an 80 mile wide band
of low clouds will continue to push onshore early this morning.
Mainly MVFR conditions will occur within this cloud band with
local IFR conditions. The back edge of the low cloud band will
reach the coastal mountains by 18z. The low clouds will lift and
become more scattered between 18z Saturday and 00z Sunday. Mainly
VFR conditions will follow with a drier offshore flow.

For inland areas VFR conditions will continue, except near and north
of the Umpqua Divide where MVFR conditions will spread inland toward
the western Cascade foothills through 18z with local obscurations.
After 18z, the low clouds will lift and become more scattered. VFR
conditions will follow tonight although local IFR conditions may
develop late tonight in the Umpqua Basin.


.MARINE...Updated 800 PM PDT Friday 20 April 2018...Calm weather
will continue through tonight. A weak front will dissipate as it
moves onshore early Saturday morning. Offshore high pressure will
build and strengthen west of the waters Saturday morning. At the
same time a thermal trough will develop and strengthen along the
coast. This will result in increasing north winds and steep wind
driven seas developing late Saturday morning then lasting through
Sunday evening. There`s good agreement winds will be strongest from
about Gold Beach south, but low end gales are still expected just
south of Bandon and beyond 10 nm from shore, thus affecting the
southern portion of Zone 370. Elsewhere small craft advisory
conditions are expected. Please see MWWMFR for more details.

Winds and seas will gradually lower Sunday evening, especially over
the northern waters. However, steep wind driven seas will persist in
the southern waters, and it is not until Sunday night that they are
expected to diminish below gale force.

The general consensus is for the thermal trough to build north and
weaken Sunday night through Monday. This will result in diminishing
winds and seas. This pattern is not expected to change much Tuesday
and Wednesday, therefore conditions should be calmer during this
time. -Petrucelli




Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT Sunday for
     Gale Warning from 2 PM this afternoon to 11 PM PDT Sunday for

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