864
FXUS66 KMFR 040548
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1048 PM PDT Thu Jul 3 2025

.DISCUSSION...Today through Saturday night...Another shortwave
trough is approaching the region this afternoon. This will pass
through the region overnight tonight into Friday while merging
with an upstream shortwave, resulting in a broad low pressure over
the Pacific Northwest for the Fourth of July holiday. Overall,
this will bring near to slightly below normal temperatures today
through Saturday. On the other hand, isolated to scattered
thunderstorms will persist over the region through Friday evening.
Much like recent days, the focus for thunderstorm activity today
will mostly be across eastern Klamath, Lake and Modoc counties,
though isolated thunderstorms are possible farther westward into
western Siskiyou County and the Cascade Foothills of
Jackson/Douglas Counties.

Heading into the overnight hours, the incoming trough takes on a
negative tilt as it moves overhead, and this combined with
sufficient moisture and instability will lead to showers and
thunderstorms continuing tonight into early Friday morning. The
focus for activity looks to be along the Cascades north of Lake of
the Woods and areas eastward into Klamath County generally north
Klamath Falls towards Chemult/Fort Rock area. While moisture and
instability are more limited for areas west of the Cascades, there
are some members of the high resolution suite of models that show
some activity firing up across portions of eastern Jackson/Douglas
Counties before quickly shunting off to the north and east. As such,
we`ve included a slight chance (10-20%) mention of thunderstorms for
areas generally east of Grants Pass/Shady Cove/Steamboat.
Shower/thunderstorm activity continues into the early morning hours
of Friday across northern portions of Klamath and Lake Counties
before activity wanes around 9-10am or so. Though activity will
wane, the break will be short-lived with another round of
showers/thunderstorms developing Friday afternoon across northern
portions of Klamath and Lake Counties.

Aside from the thunderstorm threat on Friday, the Fourth of July
holiday should be a rather pleasant one across the region with
temperatures being the coolest of the forecast period. In fact,
afternoon highs on this July 4th will hover around 5 to 10 degrees
below normal, with up to 15 degrees below normal in some places.
There will be some lingering cloud cover around west of the
Cascades, but overall, mostly to partly sunny skies are expected.
We`ll finally get a break in this persistent thunderstorm pattern on
Saturday as a brief period of ridging develops and afternoon highs
trend warmer by about 5 to 10 degrees.

This break will be short-lived, however, as another low pressure
develops off the coast of California and lingers there into next
week before finally moving off to the northeast around mid-week. The
position of this trough looks farther north than the one from
earlier this week, and this will have implications on where the best
moisture/instability line up. Current guidance maintains a dry
forecast through this time period, but pattern recognitions would
say that there will be at least slight chance of thunderstorms at
some point between Sunday-Wednesday. An isolated thunderstorm or two
could develop as early as Sunday across western Siskiyou, but
moisture looks too marginal for any significant activity, and
cumulus buildups are the more likely scenario. Heading into early
next week, however, moisture increases and storms look more
plausible for Monday afternoon. By Tuesday, the best
moisture/instability/dynamics look to be farther north of the area.
As the trough passes overhead on Wednesday, this would be another
opportunity for increased thunderstorm activity in the area. Stay
tuned as details on location and timing of this trough become more
clear over the coming days. In the meantime, guidance shows the
return of hot temperatures as strong high pressure over the Desert
Southwest retrogrades westward and exerts more influence over the
region. /BR-y

&&

.AVIATION...04/06Z TAFs...Thunderstorm activity has waned this
evening, but isolated to scattered showers and thunderstorms are
still possible through the overnight and into Friday primarily from
the foothills of the Cascades eastward. Most active areas will be
across northern Klamath and Lake counties through Friday afternoon.
While VFR will prevail in these areas, IFR/MVFR
ceilings/visibilities are expected near any storms as well as gusty
outflow winds and even hail.

VFR will prevail inland west of the Cascades tonight into Friday,
but MVFR has already returned to coastal areas and expect this to
persist through the night into Friday morning. Some clouds will
likely also fill into the Umpqua Basin around Roseburg toward
morning. MVFR ceilings become VFR Friday afternoon, but the lower
conditions return to coastal areas during the evening. -Spilde

&&

.MARINE...Updated 800 PM PDT Thursday, July 3, 2025...Conditions
have improved this evneing, and should remain relativle ycalm
through Saturday mroning. The thermal trough pattern returns late
Saturday, bringing the return of gusty north winds and steep seas.
This will likely result in conditions hazardous to small craft
returning by Saturday afternoon and persisting into early next week.
/BR-y

&&

.FIRE WEATHER...Updated 200 PM PDT Thursday, July 3, 2025...
Thunderstorms continue to be the main concern. There will be another
round of thunderstorms this afternoon and evening, focusing on FWZ
625 into eastern FWZ 624. This is where the Red Flag Warning is in
effect through 11 PM tonight. These storms will be moving north
through the evening. Some storms could be dry.

Keep in mind, lightning strikes outside of the precipitation cores
are possible. Due to the prolonged period of dry and warm to hot
weather, lightning efficiency will be high to very high for fire
starts. We also have to be mindful of gusty and erratic outflow
winds near and away from the core of thunderstorms.

Many models are still supporting convection continuing tonight into
Friday morning. Any overnight storms are much more likely to be high-
based, and would then have much more likelihood of being dry. While
most guidance, and the typical pattern, shows showers and
thunderstorms during this time still concentrating on Klamath and
Lake counties (and a bit into Modoc), one or two models have a band
of convection running up the Cascades from Mount Shasta to Bend late
this evening into tonight. This is the outlying solution, thus
unlikely, but something to consider. A Red Flag Warning will be in
effect from 11 PM tonight through 7 AM tomorrow for the risk of
abundant lightning on dry fuels. This area includes northeastern 623
north of Highway 140, 624 north of Highway 140, and far northern 625
north of Summer Lake.

An area of low pressure will bring another chance of thunderstorms
Friday afternoon with the main concerns in Klamath and Lake
counties. However, a Red Flag Warning will be in effect tomorrow
afternoon for the northern half of FWZ 625 as this is the area that
the thunderstorms will focus on which will bring a risk for abundant
lightning on the dry fuels.

Fortunately, it does appear that the trough will exit by Saturday,
and it appears that this will be the first day with no thunderstorm
chances anywhere within the forecast area. This break in the action
may be short-lived, however, as another upper level trough arrives
late in the weekend, and convective chances may once again return
Sunday into Monday. The deep southerly moisture flow should have
ended by that time, so with the lack in moisture, convection may not
be as widespread or as active, if it occurs at all.

Otherwise, the forecast will be for continued near to slightly above
normal temperatures, seasonal humidities, and the typical diurnal
wind patterns, although general east flow late this weekend into
early next week could lead to drying, especially across the
ridgelines, where poor to moderate recoveries are possible. -
BPN/Hermansen

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 11 PM PDT this evening for ORZ623>625.

CA...Red Flag Warning until 11 PM PDT this evening for CAZ285.

PACIFIC COASTAL WATERS...None.

&&

$$