Wildfire in Oregon, July 21 to 26, 2024

Area Forecast Discussion
National Weather Service Medford OR
301 PM PDT Sun Jul 21 2024

.DISCUSSION...Another round of showers and thunderstorms are
developing along the eastside...generally confined to Lake and the
eastern half of Modoc county as of 2:30 pm Sunday. As of
now...there have been no ground strikes...however this is likely
to change in the next hour...with the best chance of thunderstorms
(25% to 40% chance) over mainly Lake county. We did expand out the
potential for an isolated thunderstorm (around a 15% chance)
westward into central Klamath county...however confidence is low.
This activity is expected to increase into the early evening
hours before starting to dissipate around 10 pm...dissipating
completely around midnight.

Not much change in the overall weather pattern through early next
week as an upper level ridge of high pressure dominates the desert
southwest with an upper low currently in the Gulf of
Alaska. This upper low is expected to move slowly southwest
toward the British Colombia coastline Tuesday into Wedensday. All
of this will result in slight chances of thunderstorms over
portions of far eastern Lake and Modoc counties through at least
Wednesday.

Temperatures across the area will generally be near normal for the
middle to end of July. The one exception will be Tuesday...when
the upper ridge nudges northwest into central CA...bringing us
daytime high temperatures between 5 and 10 degrees above normal.

Otherwise...another big issue for much of the forecast area will
be smoke. There is a LOT of uncertainty in the smoke forecast from
day to day given our overnight thunderstorms on the west side and
what if any fires were started. Either way...the only places in
the forecast area that might totally escape from the smoke/haze
will be Coos and western Douglas counties. All other locations are
expected to experience intermittent smoke/haze for at least the
next few days.

-Riley

&&

.AVIATION...21/18Z TAFS...Marine stratus, mainly IFR with patches of
drizzle will impact portions of the coast through this evening, and
the coastal valleys will see these impacts this morning. The stratus
will lift and thin a bit during the day today, but will likely
remain for the coast.

Elsewhere, VFR conditions will prevail through this evening with an
exception. The exception will be in the vicinity of the cluster of
fires in eastern Douglas County, and across northern portions of
Klamath and Lake counties, where visibility could occasionally lower
to 3-5 miles in smoke/haze. Hazy skies are likely across more of the
area than recent days as well, including in portions of Jackson
County, including Medford, and near Klamath Falls. Visibility could
be briefly MVFR.

Thunderstorms are possible again on the east side this afternoon
into this evening. There is an outside chance (5 to 10%) that
Klamath Falls will see lightning, and have added thunderstorms to
the vicinity, with the best chances just to the east of Klamath
Falls Airport. -Schaaf

&&

.MARINE...Updated 200 PM Sunday, July 21, 2024...A thermal
trough will strengthen through Tuesday. Moderate north winds and
steep seas will be present south of Port Orford are expected
increase with stronger, gale force winds and very steep, hazardous
seas are expected to develop later this afternoon and continue into
Tuesday evening. The thermal trough is expected to weaken slightly,
then persist for the remainder of the week with Advisory strength
northerly winds likely south of Cape Blanco. -Schaaf/Hermansen

&&

.FIRE WEATHER...Issued 200 PM Sunday July 21, 2024...Scattered
thunderstorms are expected this afternoon and evening east of the
Cascades in portions of FWZs 624 (especially eastern) and all of
625. As such, we have a Red Flag Warning in effect through 11 pm PDT
for abundant lightning on dry fuels in those areas. Any
thunderstorms in these areas will have the ability to produce
numerous cloud to ground lightning strikes as well as gusty outflow
winds (40+ mph). Isolated thunderstorms are also expected into this
evening for portions of the Modoc (FWZ285) and the rest of 624 up to
around the Cascade Crest, just east of Diamond Lake. After the action
wanes and moves off to the north and east by late this evening, the
remainder of tonight into Monday morning will be dry.

Along the coast and into the Umpqua Valley, increased onshore flow
will maintain some cloud cover and higher humidities there tonight.
Similar to last night, RH recoveries will also be better than they
have been recently in the NW CA/SW OR mountains (generally moderate
to good in the 50-70% range).

Most areas remain dry in west-southwest flow aloft Mon-Wed, but
lingering mid-level moisture and instability near the Sierra
will extend northward to around SE Modoc and SE Lake counties
where an isolated thunderstorm or two could pop up each
afternoon/evening. Heights rise slightly, so it will turn
hot again Tue-Wed with widespread temperatures in the 90-100F
range, except in the higher mountains and along the immediate
coast, where it will be cooler. Fairly typical diurnal breezes
are expected as well through mid week.

Then, a deep upper trough and low pressure over the Gulf of Alaska
will move eastward into western Canada around Wed-Thu. This will
bring increasing mid-level flow across the area with some gustier
afternoon/evening winds expected. While some west side valleys like
the Rogue and Shasta Valley will also have a slight uptick in winds,
the strongest winds will occur over the east side (generally 20-25
mph with peak gusts of 30-35 mph). Afternoon minRH values are
forecast to be down around 15% during this time, so both Wed/Thu
afternoon could see some areas near critical wind/RH thresholds.
Right now, however, these areas do not look widespread enough for a
Fire Weather Watch. We'll maintain a headline in the Fire Weather
Planning Forecast.

Late in the week into next weekend, models are showing a closed low
off the California coast, which gets absorbed into the WSW flow
aloft and eventually cruises across NorCal Fri/Sat. Normally,
we'd be concerned about more thunderstorms, but by this time, best
mid-level moisture will move off to the east and thunder risk is
low. What this should will do is lower temperatures to levels that
are more typical for this time of year (highs in the low to mid 90s
for west side valleys and in the upper 80s east of the Cascades).
-Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory until 11 PM PDT this evening for ORZ025>031.

     Red Flag Warning until 11 PM PDT this evening for Orz024.

     Red Flag Warning until 11 PM PDT this evening for ORZ025.

CA...Heat Advisory until 11 PM PDT this evening for CAZ084>085.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT Tuesday
     for Pzz350-356-370-376.

     Gale Warning until 11 PM PDT Tuesday for Pzz350-376.

&&