Wildfire in California, August 1 to 20, 2020

Area Forecast Discussion
National Weather Service Medford OR
840 PM PDT Fri Jul 31 2020

.DISCUSSION...8:30 PM Satellite imagery is showing a band of
clouds associated with a dry cool front moving through the area.
This band of clouds will not bring any precipitation to the area
(maybe a little bit of drizzle at the coast), but conditions
tomorrow will be a little bit cooler and more humid.

We allowed the red flag warning to expire at 8 PM with humidity
increasing as part of the humidity recovery process. Tomorrow will
be quite similar to today, but slightly cooler with slightly
higher humidity. Will allow the overnight shift to assess the
situation and make any further decisions regarding the critical
nature of the forecast. For now, no changes are needed. -Schaaf

&&

.AVIATION...For the 01/00Z TAF Cycle...Over the coastal waters and
along the coast IFR/LIFR cigs/vsbys in low clouds and fog will
become widespread this evening and persist through Saturday morning.
The marine layer will spread a bit into the coastal valleys and
portions of the lower Umpqua northwest of Roseburg tonight through
Saturday morning.

Over the inland areas...VFR conditions will prevail through tonight.
There will be some MVFR vsbys in smoke near active fires such as the
recent Worthington fire in Jackson county, which may reduce
visibility at KMFR at times. Other fires affecting the region are
the July complex near the Siskiyou/Modoc county boundary and the Red
Salmon fire, near Somes Bar, in southwest Siskiyou County. -CC

&&

.MARINE...Updated 800 PM PDT Friday 31 July 2020...Relatively calm
seas and light northerly winds will prevail through this weekend. A
weak front will move onshore Sunday night. A thermal trough will
develop near the coast Monday night into Tuesday. This will bring
gusty north winds and steep seas to the area, especially for areas
south of Cape Blanco. These conditions may continue through late
next week. -CC

&&

.PREV DISCUSSION... /Issued 235 PM PDT Fri Jul 31 2020/

DISCUSSION...Clear skies prevail across the forecast area this
afternoon. The exception being some lingering coastal stratus
along the capes and south of Gold Beach as well as hazy/smoky
conditions due to local wildfires. Quiet conditions with a slight
cooling trend will continue through the weekend and into Monday.
The upper level ridge responsible for the triple digit heat has
shifted east. Current temperatures are trending a few degrees
lower than this time yesterday, but it's still hot outside.
Afternoon breezes will be enhanced today and these winds combined
with low relative humidities will bring another round of critical
fire weather conditions to portions of the area. Please see the
Fire Weather Discussion below for more details. Hazy conditions
will continue across the area due to wildfire smoke.

Expect conditions through the weekend to be similar to today, albeit
slightly cooler and with slightly weaker afternoon breezes. On
Monday, a shortwave trough will move through the area, and this will
be the "coolest" day of the forecast period. Considering the fairly
dry air mass this trough will be moving into, it's not likely for
any precipitation to be squeezed out of this system. There may be
some sprinkles along the coast north of Cape Blanco, but any mention
of measureable precipitation has been removed from the forecast.

After Monday, broad upper level troughing moves into the area and
lingers for much of next week. This will moderate temperatures,
keeping them within a few degrees of normal. Thunderstorm potential
increases next week (Tues-Thurs), however, confidence is not high
enough to introduce chances into the forecast. Much will depend on
the actual track of any shortwaves moving through the area.
Currently, thunderstorm parameters are weak, but the favorable areas
look to be east of the Cascades. Stay tuned as details become more
clear. /BR-y

FIRE WEATHER...Updated 200 PM PDT Friday 31 July 2020...Critical
fire conditions are expected in terms of winds and low relative
humidity and to some extent instability (haines 5). Thus, a Red Flag
Warning remains in effect through early evening for gusty winds and
low relative humidity for portions of fire weather zones (FWZs) 624
in Oregon and 284 and 285 in California. This includes the Caldwell
Fire. Please see RFWMFR for more details. We've also issued a Red
Flag Warning for portions of the Rogue and Bear Creek Valleys in FWZ
622 because humidity values are trending lower than 24 hours ago,
and with the expected gusty winds this afternoon, we expect
conditions to again become critical this afternoon.

Tomorrow begins a period where we expect temperatures to trend lower
and humidity to trend higher. Winds will trend lower tomorrow as
well, compared to today. Marginal cooling will start today west of
the Cascades and tomorrow east of the Cascades. Temperatures will
still be above normal with dry afternoons and breezy conditions, but
we don't expect Red Flag criteria to be met.

Models are hinting at a chance of thunderstorms entering the picture
on Tuesday as a disturbance moves into Northern California from the
west. Probabilities of lightning aren't high enough to introduce
them into the forecast, and there is still some variability in model
solutions, so we'll keep an eye on it for now and communicate the
potential via discussions at this time. Keene

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.

CA...None.

Pacific Coastal Waters...None.