951
FXUS66 KMFR 020547
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1047 PM PDT Tue Jul 1 2025

...Updated the Aviation section...

.AVIATION...02/06Z TAFs...Along the coast, from Cape Blanco north,
IFR/LIFR ceilings and IFR/MVFR visibilities are expected through
Tuesday morning. Then, expect clearing to mainly VFR with patchy
lingering IFR/MVFR Tuesday afternoon into the early evening. Strong,
gusty north winds are expected (up to ~30kt) again Wednesday
afternoon, strongest south of Cape Blanco.

Inland, VFR will continue to prevail. Coverage of showers and
thunderstorms will be less on Wednesday, but scattered activity is
expected along a line from around Mt. Shasta to Klamath Falls to
Fort Rock and eastward during the late afternoon and evening.
Strong, gusty erratic outflows of 30-50 kts are possible with these
storms along with hail. Lightning probabilities are around 15% in
Klamath Falls late Wednesday. -DW

&&


.MARINE...Updated 800 PM PDT Tuesday, July 1, 2025...Gales and very
steep seas will continue through this evening south of Cape Blanco,
with small craft advisory winds and seas to the north. Conditions
will very gradually improve into Friday, with gales ending tonight,
but gusty north winds and steep seas continuing through Wednesday.
After a period of reduced winds and light seas Thursday into Friday,
the thermal trough returns this weekend into next week. It will
result in strong north winds and steep to very steep seas, with the
strongest winds south of Cape Blanco. -BPN/DW

&&

.PREV DISCUSSION... /Issued 425 PM PDT Tue Jul 1 2025/

DISCUSSION...Low pressure near the SF Bay area continues to send
moist, southerly flow northward into NorCal and SW Oregon.
Instability is increasing this afternoon due to daytime heating
and we`re seeing thunderstorms initiate now. These will increase
in coverage through the afternoon and into this evening. As
mentioned earlier today, steering flow for storms is on the weak
side, so storm motion should be slow (5-15 mph), in a general SE
to NW fashion, but with more of a bending toward the SW in
southern portions of the forecast area (Siskiyou County). Storms
that initiate farther north along the Cascades or in the Highway
97 corridor in Klamath County should propagate more toward the
north. Focus for lightning will be in Siskiyou and western
Modoc/Lake Counties, but also northward into Klamath County and up
the Cascades through about 9 pm or so this evening. Lightning
risk isn`t negligible west of the Cascades, but convective
inhibition of 100-300 J/KG should be a limiting factor as to just
how much can really get going and how far west. As it stands,
there is a low probability (~20% chance) of a thunderstorm nearby
the Rogue Valley late this afternoon/evening, but storms are more
likely to affect eastern portions of Jackson County and remain in
the Cascades/Foothills and closer to Butte Falls/Prospect. Main
storm risks through this evening will be strong, gusty outflow
winds due to dry sub-cloud layer and DCAPE in the 1000-1500 J/KG
range as well as small hail and numerous cloud to ground flashes.
With more lightning expected, expect new fire ignitions. Fire
weather discussion below will cover the specifics.

After sunset this evening, the atmosphere will begin to stabilize
and thunderstorms will transition to showers, gradually ending
overnight into Wednesday morning.

The low that is moving into California will continue to move
slowly inland Wednesday afternoon south of Lake Tahoe. This should
bring more of WSW flow aloft from the Cascades westward to end
the risk of lightning in those locations. It will also result in
some gusty afternoon upvalley NNW breezes (15-25 mph) and a drying
air mass. However, the trough axis to the north of the low will
still move through areas east of the Cascades. As such, we are
expecting another round of showers and scattered thunderstorms
over there, primarily from eastern Klamath/Siskiyou counties to
Lake and Modoc counties (just east of Klamath Falls and also
probably just east of Mt. Shasta, though instability could cause
one or two to pop up back to northern Trinity County). A Red Flag
Warning has been issued and should also be detailed in the Fire
Weather section.

Thursday through the 4th of July, another couple of short wave
troughs will swing through in westerly flow aloft. The first will
push onshore into NorCal late Thursday and Thursday night with the
second moving quickly into Oregon behind it on Friday.
Instability and moisture will remain highest in NE Cal and areas
east of the Cascades. So, we have maintained a chance of showers
and thunderstorms for portions of Klamath/Lake and Modoc counties.
It should remain dry though west of the Cascades. Could be some
marine cloudiness each morning/night near the coast. Overall,
with cooler air aloft, most areas should see high temperatures
those days within a few degrees of normal. This means highs in the
low to mid 80s for the valleys west of the Cascades and in the
upper 70s to low 80s over the East Side.

We should be between systems on Saturday. Temperatures edge back
to slightly above normal levels. However, yet another disturbance
will move toward the area. Moisture and instability are modest at
best with this system, so most guidance is not showing any
precipitation. But, we may need to adjust should future model
runs increase these parameters.

Next week, models show a trough (weak closed low?) hanging around
Monday/Tuesday near/just off the NW California coast, but then
the Four Corners high strengthens and retrogrades mid-late week.
This should bring a return of hotter weather with NBM guidance
showing mean high temps in the upper 90s and lower 100s for the
valleys west of the Cascade. -Spilde

FIRE WEATHER...Updated 230 PM PDT Tuesday, July 1, 2025...
Thunderstorms continue to be the main concern. After nearly 1000
cloud to ground strikes yesterday, we expect to see another round of
thunderstorms this afternoon and evening, mainly along and east of
the Cascades, followed by more thunderstorms Wednesday afternoon and
evening, again mainly east of the Cascades. A Red Flag Warning
remains in effect for FWZs 280, 281, and 284 today, but areas east
still remain in moderate fire danger, so no warnings have been
issued there for today. However, these areas will be going to high
fire danger at midnight tonight, so a Red Flag Warning has been
issued for FWZs 284, 285, 624, and 625 due to the next round of
lightning Wednesday afternoon and evening.

We picked up a few more lighting strikes in Klamath and Lake
counties this morning, but conditions have calmed over the last few
hours, with Radar showing only showers as of this writing. We still
expect thunderstorms to develop in just a few more hours, aligning
with max heating this afternoon and evening. Storms today should
behave much like yesterday, with storms early this afternoon perhaps
not producing much of any precipitation to start, then the chance
for wetting rain could increase mid to late this afternoon and
evening. The main reason for the increase chance in wetting rain is
steering winds will be light and high moisture content throughout
the column of the atmosphere. Thus, storms will be slow movers
providing the bigger window of opportunity for storms to produce
locally moderate to heavy precipitation. However, that does not mean
that all storms will produce wetting rain. Some could also produce
little to no rain, because of the dry sub layer below.

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.

A few models suggest that some isolated thunderstorms could continue
into the late evening or overnight hours, but as is typical for
these types of situations, confidence on this is low and it will be
something that we`ll need to monitor as it occurs.

It should be noted that any residual cloud cover from nightime or
morning convection, much like we have seen across some of the area
east of the Cascades today, could easily reduce thunderstorm chances
by blocking solar heat and therefore reducing instability. This is
not easily predictable until it occurs, and would be the primary
reason the forecast may not turn out as expected.

Although the trough responsible for these past several days of
convection will kick off to the east by Wednesday night, the concern
for thunderstorms could carry over into Thursday as an upper trough
approaches the area from the west. The best chance for storms
Thursday would be along and around the Warners in Lake and Modoc
counties. -BPN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from 2 PM to 8 PM PDT Wednesday for ORZ624-625.

CA...Red Flag Warning from 2 PM to 8 PM PDT Wednesday for CAZ284-285.

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT Thursday
     for PZZ356-376.

     Small Craft Advisory until 11 AM PDT Wednesday for PZZ350-370.

     Gale Warning until 11 PM PDT this evening for PZZ356-376.

&&

$$