977
FXUS66 KMFR 291757
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1057 AM PDT Sun Jun 29 2025

.Updated AVIATION Discussion...

&&

.AVIATION...29/18Z TAFs...Skies are clear across the region this
morning leading to widespread VFR conditions. There is a thin layer
of marine clouds just offshore north of Cape Arago, spreading
southward, and this could bring some temporary LIFR ceilings to the
immediate coast if it drifts inland at all through this afternoon.
Overall, however, expect VFR conditions to prevail for all areas
through this evening with the typical diurnal breezes. Another day
of gusty winds in the 25-30 kt range along the coast is expected
this afternoon. Patchy cumulus buildups are expected this afternoon
into the evening, over the higher terrain from the Cascades eastward
and into northern California. This is particularly so in western
Siskiyou and eastern Modoc Counties where an isolated
shower/thunderstorm will be possible.

Later this evening, expect marine stratus to return to the coast
north of Cape Blanco and into the Coquille Basin, resulting in LIFR
conditions that will persist into Monday morning. /BR-y

&&

.PREV DISCUSSION... /Issued 857 AM PDT Sun Jun 29 2025/

DISCUSSION...An update was sent this morning to include a slight
chance (10-20%) of showers/thunderstorms for southeastern Modoc
County along the Warners for this afternoon. Low pressure will
develop off the coast of California today, turning the upper level
flow to southerly and begin pumping monsoonal moisture into the
region this afternoon. This will begin a stretch of time with
persistent thunderstorm chances through mid-week, and this will be
the focus of today`s efforts in updating the afternoon forecast
package. The other weather item of note for today and tomorrow
will be the hot temperatures expected. Upper 90s to triple digits
are expected across the region, and this will lead to a moderate
risk of heat related illnesses. For more details, see the previous
discussion below. /BR-y

PREV DISCUSSION... /Issued 429 AM PDT Sun Jun 29 2025/

SHORT TERM...Currently marine stratus is developing near Bandon
and is stretching north toward Coos Bay. Other than the regular
cold spots east of the Cascades, looking at 50s and low 60s for
morning temperatures today.

More heat is on the way to finish out the weekend. Today is looking
to be the warmest of the week for areas west of the Cascades with a
slight increase Monday east of the Cascades. The probability for
Medford to see 100 degrees today and Monday has increased to 70-90%
and with clear skies forecast today, looking to reach that this
afternoon. For now, keeping the triple digit high tomorrow for
Medford in the forecast, but with increasing moisture and a low
pressure system to the south impacting our area, more cloud cover
could hinder warming that much Monday. Elsewhere west of the
Cascades you can expect low to mid-90s. Either way, this heat will
bring a moderate risk for heat related illnesses the next two
afternoons for most inland locations. Please take the proper
precautions by staying hydrated and in the shade if you need to be
outside during peak heating hours. Although there will be a slight
cooldown into the middle of next week due to an increase in moisture
and areas of low pressure passing, temperatures will still overall
be 3 to 10 degrees above normal.

Thunderstorm chances return to the forecast this afternoon as an
area of low pressure builds in California and brings monsoonal
moisture to the area. Today`s thunderstorm chances will be into
southern Siskiyou County near the Trinity Horn as today`s heat and
additional moisture could produce a few isolated
showers/thunderstorms there. The chance for more locations west of
the Cascades to see thunderstorms is Monday. I have extended the
PoPs into eastern Josephine County Monday afternoon as the northward
track of the rain could clip this area. There could also be a
continued chance for showers/thunderstorms east of the Cascades in
northern Klamath and eastern Lake County. The movement of these
storms Monday is expected to be slower and with PWATs nearing 0.75"-
1.00" across Northern California and east of the Cascades, this
could bring a higher chance for moderate to heavy rain while it
moves slowly. Please see the long term discussion to hear more about
the thunderstorm potential that starts for Tuesday onward.
-Hermansen

LONG TERM...There is much more confidence on thunderstorms reforming
Tuesday afternoon, although with the eastward progression of the
trough, the best dynamics and support would then be over northern
California and along and east of the Cascades. Other than location,
storm behavior and character should be very similar to Monday. One
fly in the ointment to consider will be the amount of cloud cover
around on Tuesday, especially if convection continues through the
previous overnight hours. With this much moisture entering the area,
and with the widespread convection expected Monday, there may be
extensive cloud cover over the area Tuesday limiting incoming solar
energy, keeping temperatures lower, and limiting instability. If
this is the case, thunderstorm coverage would be significantly less
than what is currently expected. Stay tuned as this time frame
becomes resolved by high-resolution convection allowing models
(CAMs) and we are clued in to a better picture of expectations.

At this time, we aren`t expecting much in the way of severe weather
given the weak winds aloft, but as always with thunderstorms, gusty
outflow winds and deadly cloud to ground lightning are always
elements to be concerned about. If you have outdoor plans during
this time frame, stay weather aware and have a plan for shelter
should a thunderstorm develop nearby.

Wednesday through the Fourth of July holiday weekend...By Wednesday,
the upper level low responsible for all the instability shifts far
enough east to limit thunderstorm chances to far eastern Lake and
Modoc Counties. Temperatures will have trended cooler compared to
this weekend, returning to near seasonal normals. Guidance shows
another low pressure affecting the region late Thursday into Friday,
but coming through in westerly flow and positioned farther north
than the one expected early next week. One positive to this, is that
temperatures would remain near normal for the Fourth of July holiday
and thus no heat waves for the holiday. The flip side to that,
however, is that thunderstorm chances could return to the forecast
during the holiday weekend. Given that this is a different
pattern/trajectory of the low pressure, thunderstorm coverage would
likely be less, but stay tuned as we get past the upcoming event and
details on the next become more clear. /BR-y

MARINE...Updated 300 AM PDT Sunday, June 29, 2025...A thermal
trough along the south Oregon coast has resulted in moderate to
occasionally strong winds. The thermal trough will persist into the
early next week. The net result will be a long duration of
persistent moderate to strong winds, and very steep wind-driven
seas, especially south of Port Orford where gales are likely.
Meanwhile, Small Craft conditions will expand over the rest of the
waters. Because of the above mentioned, the Small Craft Advisory and
Gale Warning continue through Tuesday evening. Please see MWWMFR for
more details. -Petrucelli/Hermansen

FIRE WEATHER...Updated 315 AM PDT Sunday, June 29, 2025...The
main concern through the weekend will be the warming temperatures
and drier conditions. Temperatures will have a larger jump in most
locations with highs 5 to 15 degrees above normal. Min RH`s today
will trend to the ~15% range in the afternoon. However, winds
under the ridge will still be lighter, so not looking at both
critical fire weather conditions to be met. This afternoon an
upper low will form in California, and this will bring monsoonal
moisture into Northern California. With that, there is a chance
for an isolated shower or two near the Trinity Horn. However,
guidance is showing there is a 75-90% probability for portions of
Northern California to have CAPE values of 250 J/kg Sunday
afternoon, so a thunderstorm could also be a potential.

After the heat comes more thunderstorm chances early next week. The
monsoonal moisture continues as the upper low to the south builds.
Rain chances come into the forecast starting early Monday morning
for portions of the Cascades, the Trinity Horn and the Curry County
coast. As daytime heating continues, the increase in thunderstorms
comes Monday afternoon near the Trinity Horn and along the Cascades
before spreading into FWZ 625 later in the day. Forecast soundings
show PWATs near 0.75"-1.00" for Northern California and FWZ 624/625.
Soundings also support a slower flow while the rain moves in from
the south. Heavier rainfall could be possible in spots due to the
additional moisture available and slower movement. DCAPEs are
nearing 750-1,000 J/kg Monday afternoon, bringing a threat for gusty
winds in some storms as well. Due to the prolonged period of dry and
warm weather, higher lightning efficiency for fire starts will be
present Monday afternoon. A Fire Weather Watch has been issued for
portions of Siskiyou County, please see RFWMFR for more details.

The lighting threat Tuesday will be in similar areas besides west of
the Cascades, so the threat of abundant lightning on dry fuels is
possible then as well. Wednesday`s threat shifts farther eastward
into Lake and Modoc counties and is lower than previous days at
15- 25%. Please continue to look out for any Fire Weather
Watches/Warnings this week due to the lightning risk. -Hermansen

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...Fire Weather Watch from Monday afternoon through Monday evening
     for CAZ280-281-284.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT Tuesday
     for PZZ350-356-370-376.

Gale Warning until 11 PM PDT Tuesday for PZZ356-376.

&&

$$