Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Medford or
805 am PDT Monday Jul 25 2016
Discussion...25/12z NAM in.
Clear skies this morning over the Medford County Warning Area...except for some
areas of marine stratus over the coastal waters...along the
coast...and in the Umpqua basin.
Flow aloft remains nearly westerly this morning. 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
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...25/12z taf cycle...stratus with coastal IFR and
local MVFR ceilings along the coast has spread MVFR ceilings into
the Umpqua valley...including krbg. Stratus will erode back to the
coast but persist at the coast today. Stratus is expected to make
another surge into the Coquille and Umpqua valleys tonight.
Elsewhere, VFR conditions will persist with mostly clear to clear
Marine...updated 500 am PDT Monday 25 July 2016...a thermal
trough along the coast and high pressure offshore will produce
strong north winds and steep to very steep wind driven seas through
the week. Gales are certain over the waters 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.
On Tuesday, surface pressure gradients tighten considerably, 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 a small area
over the southern outer waters where winds approach storm force.
This also the most likely time when gales could affect a small part
of the northern zones as well. Winds in the outer waters south of
Cape Blanco are expected to continue at mainly the high end of gale
strength through Friday evening. -Wright/dw
Fire weather...updated 600 am 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 at the coast and in
western Siskiyou County. Recoveries will be poorest in the Curry
County mountains. Moderate humidity recoveries are also expected
east of the Cascades. Wednesday morning 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 from Siskiyou County across much of
the east side. -Sk/dw
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.