Wildfire in Oregon, July 17 to 31, 2024

Area Forecast Discussion
National Weather Service Medford OR
319 AM PDT Wed Jul 17 2024

.DISCUSSION...The shirt wave trough will finally push north of the
area this morning. Dry air has already wrapped in behind the
system, quickly clearing most of the region of clouds and showers
at this time, with the exception of some residual showers over far
eastern Lake and Modoc counties. Meanwhile, a strong marine push
is occuring along the coast, with low clouds pushing into all of
the coastal valleys, and pouring in to the Umpqua Basin and
potentially the lower Rogue and Applegate valleys by sunrise.
These clouds should burn back to the coast through the day, but
some areas along the immediate coast may not fully clear before
clouds return late this evening and tonight.

Strong ridging remains centered on the Four-Corners region, and
will maintain control over most of the western half of the country
for the foreseeable future. Meanwhile, general troughing
continues over Alaska and extending south into the northeast
Pacific. This places the Pacific Northwest under the southwest
flow between the two features. While in general the area will
remain very warm and dry throughout the entire forecast period, a
few shortwaves will pass through this southwest flow, possibly
bringing a few periods of interesting weather, much like we have
seen these past two days.

The first of these troughs will pass through Thursday night into
Friday, but it looks like the bulk of the energy and moisture will
remain well to our northwest. Therefore, there shouldn't be any
impacts from this shortwave in our forecast area, unless there is
a major and unexpected shift in the track of the wave. The next
shortwave, however, could be more troublesome as it passes through
the area Saturday into early next week. Most model solutions
depict the wave arriving in a very similar fashion as the impulse
that just passed through the area, and as a result, thunderstorms
may once again be a concern this weekend. Convection with these
types of systems are very difficult to nail down until only a day
or two beforehand, so details on the forecast are uncertain. That
being said, we have introduced a slight chance (15-20 percent) for
showers and thunderstorms mainly east of the Cascades, with very
low chances (only 5 to 10 percent) elsewhere. Truthfully, at this
time, it is possible for thunderstorms to develop anywhere within
the forecast area, but hopefully we can narrow down the threat
area over the next several forecast cycles, especially once the
high resolution convection models begin to resolve the event. -BPN

&&

.AVIATION...17/12Z TAFS...A mix of MVFR and local IFR marine stratus
is widespread along the coast and into the coastal valleys,
including the lower Umpqua Valley to near Sutherlin. The stratus
will gradually diminish after sunrise, but may locally persist at
the coast into this afternoon. A similar situation with mainly MVFR
and local IFR is expected to quickly return to the coast and coastal
valleys early this evening into Thursday morning. Otherwise, VFR
will persist with mainly clear skies and breezy afternoon winds.
-DW

&&

.MARINE...Updated 230 AM Wednesday, July 17, 2024...Low pressure
offshore has disrupted the thermal trough pattern. Weak winds and
low seas will persist into Friday morning. A weak thermal trough is
expected to return Friday, then strengthen this weekend, with the
strongest winds south of Cape Blanco. Advisory strength northerly
winds and steep seas are possible Saturday, then gales and steep to
very steep seas are possible early next week. -DW

&&

.FIRE WEATHER...Issued 200 AM Wednesday July 17, 2024...

A dry and stable southwest flow sets up over the area today through
Friday with no concerns for thunderstorms. However, afternoon
relative humidities will trend lower for most interior locations
with values in the single digits for portions of the East Side
Wednesday, Thursday, and Friday along with the typical gusty
afternoon and early evening breezes. This will result in near
critical conditions for portions of Fire zones 624, 625 and 285, but
at this time were not expecting the combination of wind and RH to
result in Red Flag conditions.

This weekend will warrant close watching. Some evidence is pointing
towards another upper low moving up from the south on the backside
of the four corners high and could tap into some monsoonal moisture
as early as Saturday, overall much like the event of the past two
days. Therefore, there is an increasing concern for thunderstorms
through the weekend. The details remain uncertain, so this is
something that we'll monitor. Stay tuned. -Petrucelli/BPN

&&

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

CA...None.

PACIFIC COASTAL WATERS...None.

&&