Area Forecast Discussion
Issued by NWS Medford, OR
FXUS66 KMFR 252055 CCA
Area Forecast Discussion...CORRECTED
National Weather Service Medford OR
155 PM PDT MON JUL 25 2016
Updated to add Fire Weather discussion.
.DISCUSSION...25/12Z NAM/GFS/EC in.
Mostly clear skies this afternoon over the Medford CWA...except
for some areas of marine stratus over the coastal waters and along
the coast north of Cape Blanco. There are also a few cumulus
popping over the ridges.
Flow aloft remains nearly westerly this afternoon. Nearly zonal
flow will persist through Wednesday as weak troughs and ridges
parade onshore...with little in the way of short wave activity
over our area.
Low level flow will turn easterly...and the ridges of the coast
range will be dry and breezy during the overnight hours due to low
to moderate...but persistent...easterly low level flow. The
thermal trough is also supporting strong winds over the coastal
Temperatures will change little through Tuesday. Highs in the
Umpqua Basin will be near normal. Inland highs over the remainder
of the area will be 5 to 10 degrees above normal. One exception
will be the Brookings area...where easterly low level flow will
allow high temperatures to warm to 10 to 15 degrees above normal
Tuesday...and Wednesday looks to be even hotter there.
A strong high over the four corners area will gradually retrograde
through the week...and the ridging will build into the Pacific
Northwest Wednesday into Thursday. This will bring hotter
temperatures to the area. Inland highs Thursday will warm to
around 10 degrees above normal over Oregon and 10 to 15 degrees
above normal over northern California.
The ridge will begin to weaken Thursday into Friday as short waves
embedded in the westerly flow move through...but inland
temperatures will keep on warming. Friday highs will be similar
to the Thursday highs over northern California and east of the
Cascades...but the thermal trough will move over the west
side...and highs there will be 2 to 3 degrees higher than the
Thursday highs. In general...Friday will be the hottest day of
the stretch. The models also hint at convection on Friday...but
this will likely not occur as there will not be sufficient
moisture yet. Some cumulus may sprout on the ridges though.
The ridge will weaken further Saturday as more short waves move
through and a long wave trough approaches from the west. That
trough will move onshore Saturday night. At this time Saturday
looks to be the most favorable day for thunderstorm activity due
to a bit more moisture and cooling aloft...but the increasing
southwest winds aloft will push the most favored area to the south
and east. Another concern is those winds...the east side will
likely see strong gusts Saturday.
Inland areas will cool down next weekend...and by Sunday inland
highs will be near normal to 5 degrees above normal. Monday will
be cooler still and the highs at some locations may drop to just
below normal. Another trough will be approaching the Pacific
Northwest by that time...so temperatures will not rebound early
.AVIATION...25/18Z TAF cycle...Mostly low MVFR ceilings are
affecting the coast and coastal valleys late this morning. Low
clouds are clearing from the Umpqua Valley now. Clouds along the
coast will likely continue through the day, and then the stratus
will push inland to the Umpqua Basin this evening, remaining there
through early Tuesday morning. Elsewhere, VFR conditions will
persist with mostly clear to clear skies. -DW/SK
.MARINE...Updated 100 PM PDT Monday 25 July 2016...A persistent
thermal trough along the coast and high pressure offshore will
continue to produce strong north winds and steep to very steep
wind driven seas through the weekend and possibly into next week
as well. Gales will continue south of Cape Blanco beyond roughly 5
NM from shore with small craft advisory level conditions
elsewhere. Winds will be strongest and seas will be steepest
during the afternoons and evenings.
Surface pressure gradients tighten considerably tomorrow through at
least Thursday, and winds just above the surface increase to as much
as 50 kt. As a result, the area of gales expands, and there may be
occasional storm force gusts over a small area west of Brookings
between approximately 15 and 40 NM from shore. At that time, gales
may also occasionally affect the waters north of Cape Blanco but not
to enough of a degree to warrant expansion of the Gale Warning north
of the Cape. -Wright
.FIRE WEATHER...Updated 130 PM PDT Monday 25 July 2016.
Hot and dry weather will trend hotter and drier into Friday.
The long-duration surface thermal trough will continue to bring
periods of breezy northeast overnight winds and moderate to locally
poor humidity recoveries through the week in high terrain of Curry
and Western Siskiyou Counties. Moderate humidity recoveries are also
expected east of the Cascades. Wednesday and Thursday morning look
to be the windiest and poorest recoveries of the week for the high
terrain in Western Siskiyou and Curry counties with east to
northeast wind gusts to 30 mph.
Instability is expected to be weak and produce a few buildups on
Friday then increase on Saturday for a slight chance of
thunderstorms in Siskiyou, Modoc, southern Klamath and Lake
counties. Current data does not suggest a very favorable pattern
for thunderstorms and coverage of thunderstorms should be isolated.
However, given very dry fuels following this hot and dry episode,
any lightning could start fires, and West winds will turn gusty on
Saturday and Sunday as an upper trough approaches from the west.
Additionally, it appears that any thunderstorms that do form won`t
bring much rain with them.
Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT
Friday for PZZ350-356-370.
Gale Warning until 11 PM PDT Friday for PZZ356-376.
Small Craft Advisory until 11 AM PDT Tuesday for PZZ376.