530
FXUS66 KMFR 171610
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
910 AM PDT Thu Jul 17 2025

.DISCUSSION...The main story today will be how ongoing smoke in
the area impacts thunderstorm development this afternoon and
evening. Satellite shows a thin blanket of smoke across much of
southern Oregon and northern California which is noticed on the
ground with hazy skies and air quality monitors showing some
degradations of air quality around the area. Smoke can
traditionally keep temperatures from reaching the "convective
temperature" (meaning the temperature needed for air at the
surface to rise and eventually turn into a thunderstorm) among
influencing other stability terms. That being said, it`s not
always a guarantee that this will happen, especially if the smoke
layer is very thin. The HRRR smoke model seems to indicate our
west winds pushing smoke away from the area (except for
immediately downwind of our areas fires). As a result, the 10-15%
chance for a thunderstorm forecast this afternoon and evening for
portions of Siskiyou County and the East Side remains relatively
on track. For more information, please read the previous
discussion below. -Schaaf


&&

.PREV DISCUSSION... /Issued Issued by National Weather Service Eureka CA/

DISCUSSION...

We are fortunately going to see a trend of slightly cooler temperatures
starting today, and we will likely be back "down" to near normal
highs by this weekend. Temperatures are expected to "cool off"
today, but we will still see highs around the upper 90s through
Friday. Otherwise, we are going to see haze/smoke impacts for the
next few days as nearby wildfires continue. Lastly, while its a
low end chance (10%-20%), we will see a potential for thunderstorms
the next couple afternoons (today through Friday). Smoke will
likely add to inhibit these storm chances, so we will need to
monitor smoke/haze trends through these next few afternoons.

Generally speaking, we have a northwesterly flow pattern aloft over
the PacNW with slight high pressure to the south of us. Model
agreement has a 500mb low strengthening over the Pacific around 37N
and 135W Wednesday night into early Thursday morning. This will
cause some disruption to the general NW flow and may introduce
some upper level dynamics over the forecast area the next few
afternoons. As we hit convective temperatures each afternoon
(today through Friday), we will have a very small chance for
thunderstorms each afternoon. This will be primarily for northern
California and areas east of the Cascades. These weak forcing
events are tough to forecast, but the smoke and haze in the area
does further confidence that thunderstorms are generally going to
struggle to mature. Most likely is we have towering cumulus that
struggle to develop into a thunderstorm. However, one cannot rule
out an isolated storm or two, with a chance (15-25%) this afternoon
or evening. There is better instability (~300-500 J/kg), and
better upper level dynamics as the aforementioned H5 low brings
PVA over the forecast area, albeit weak forcing. Not expecting
severe weather but lightning and gusty winds will be possible with
any thunderstorm that develops.

The northwesterly flow pattern will essentially be unchanged through
the next several days. Interior temperatures are expected to remain
slightly above normal with a downward trend forecast for this
weekend. By Sunday, we will likely be close to normal temperatures.
For example, Medford is normally around the low/mid 90s this time
of year, and we are forecasting 92 which is 1 degree below normal.
By Monday, there is a chance for westside valleys to be below 90
with Medford currently forecast to be 89. These cooler temperatures
might be a nice welcoming for some folks after this stretch of
hot weather we have had.

While wind speeds are expected to be breezy (sustained 15-25 mph)
for some areas and in very typical diurnal fashion, we are not
seeing any days where wind speeds are expected to be strong.

AVIATION...

17/12Z TAFs...Along the coast and over the marine waters, LIFR
conditions under the marine layer will persist into this morning.
Ceilings should lift with improved vsby this afternoon with a slightly
deeper marine layer. IFR along the coast will likely redevelop
this evening. Inland, expect VFR conditions to prevail through the
TAF period, though wildfire smoke/haze will bring reduced
visibility at times to Klamath Falls. Guidance suggests the bulk
of the near surface smoke should push out of the region later this
afternoon, but expect generally hazy conditions to continue with
limited reductions in visibilities to be in the vicinity of
wildfires. More cumulus buildups are expected this afternoon, with
better chances (15-25%) of showers/thunderstorms east of the
Cascades and across northern California.

MARINE...

Steep seas persisted across all waters through the night. As wind
waves transition to fresh swell through early this morning, there
may be a brief period of improved conditions starting today and
going through at least Friday. That said, a weak thermal trough
could return over weekend. Though winds are expected to be weaker
than the previous event, steeps seas and advisory level winds
could return south of Cape Blanco over the weekend.

FIRE WEATHER...

A short wave trough will move in and bring another slight chance
of thunderstorms Thursday afternoon and evening which is
headlined in the fire weather forecast. Winds and relative
humidities will also bring some concerns in the eastern portions
of our forecast area. Our local MOS guidance is suggesting some
wind gusts up to 30 mph over the exposed RAWS sites east of the
Cascades with near single digit minimum humidities. This will
remain headlined in our fire weather forecast text product.

Friday is another day to watch out for as pressure gradients
tighten. High pressure in the Pacific and generally lower pressure
farther to the east should allow for some gusty winds east of the
Cascades. There is very little change in humidities, so concerns
remain elevated for fire weather conditions in south central Oregon.

There should be gradual improvement in fire weather conditions
Saturday and Sunday with a bigger improvement by Monday as minimum
humidities about 5 percent higher compared to what we`ve been
observing. The hot dry windy index also shows this trend with fire
weather conditions improving into the extended period.

&&

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

CA...None.

PACIFIC COASTAL WATERS...None.

&&

$$