845
FXUS66 KMFR 082351
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
451 PM PDT Tue Jul 8 2025

.Updated AVIATION Discussion...

&&

.AVIATION...09/00Z TAFs...IFR/MVFR ceilings will persist along the
coast today, lowering back down to IFR/LIFR with IFR/MVFR
visibilities this evening through Wednesday morning. Low pressure
persists off the northern California coast today, maintaining a
threat for thunderstorms this afternoon. Today`s activity is focused
east of the Cascades across far norther Klamath/Lake Counties, but
there remains about a 10-15% chance of a storm across Jackson,
Josephine, and Siskiyou Counties, including at Medford (KMFR). Gusty
outflow winds are possible with thunderstorms today. Otherwise,
expect typical afternoon breezes today that will ease after sunset.

As low pressure moves inland late tonight into early Wednesday, the
marine layer will deepen and push into portions of the Umpqua Basin.
If ceilings make it to Roseburg (KRBG), low end VFR conditions are
expected, and should improve by the late morning. LIFR/IFR
conditions along the coast will improve to IFR/MVFR later Wednesday
morning, but ceilings will likely persist into the afternoon hours
and later. /BR-y

&&

.PREV DISCUSSION... /Issued 243 PM PDT Tue Jul 8 2025/

DISCUSSION...This afternoon holds another lightning risk for similar
areas as yesterday. The largest threat area is in northern Klamath
and Lake counties at 25-35%. An area of 15-25% extends to the
southwest through central Josephine County and western Siskiyou
County.

Yesterday afternoon`s sounding at Medford had MU CAPE at 333
J/kg. Forecast soundings this afternoon show forecast MU CAPEs
between 300- 400 J/kg, which shows another potential for portions
of the Rogue Valley to have thunderstorms with this energy.
Through 11 PM tonight the area of northern Lake and Klamath
counties will still be under a 25-30% chance for thunderstorms and
the same area will be under a 15- 25% risk for thunderstorms as
CAPE will remain elevated during that time.

Past 11 PM, there will be a 5-10% chance for another isolated storm
in portions of western Siskiyou and southern Jackson and Josephine
counties. Surface CAPEs are forecast to remain at 100-250 J/kg, so
this would be enough to keep the potential going later into the
night. However, forecast soundings in the area are showing drier air
in the lower atmosphere, so these would be dry thunderstorms
overnight.

Tomorrow an upper low near San Francisco will be moving towards
Southern Oregon, and this will bring breezier conditions in the
afternoon, especially east side. With this upper low there will also
be near normal temperatures the next two days.

The last thunderstorm chance of this string comes tomorrow and will
be concentrated in central and southern Lake County and eastern
Klamath County. Forecast CAPE values in this region will be near 250-
350 J/kg.

In the long term, ridging will start to build into the weekend,
and this will bring a return of heat to the area. There is
currently a 50-70% probability to see 100 degrees in Medford from
Friday through early next week. For now, dry conditions are
forecast during that time frame. -Hermansen

MARINE...Updated 200 PM PDT Tuesday, July 8, 2025...Conditions
have improved for all areas and will continue through tomorrow.
The thermal trough returns into Thursday and will build steeps
seas Thursday morning south of Port Orford. The steep seas will
likely expand to the rest of the waters Thursday afternoon with
hazardous seas possible south after. -Hermansen

FIRE WEATHER...Updated 200 PM PDT Tuesday, July 8, 2025...
Isolated to  scattered thunderstorms (15 to 30% chance) are expected
to develop this afternoon/evening as the low off the coast of
northern California edges closer. East Side areas north of the
Sprague River Valley and NW of Abert Rim (northern sections of FWZs
624/625) have the highest probabilities of thunderstorms (25-30%),
so a Red Flag Warning (2-11 pm PDT) remains in place, but isolated
activity (15% chance) may develop to the SW across the Southern
Oregon Cascades, into Jackson, Josephine and western Siskiyou
County. Strong, gusty outflows  are possible near thunderstorms
today (generally 30 to 40 mph but up to 55 mph near strong storm).
Models show the convection beginning in our area, then lifting north
into Deschutes County this evening.

Overnight, as the upper low moves into northwest California, models
are indicating an elevated unstable layer with marginal moisture for
thunderstorms to develop. This will bring a low chance (5-10%) for
overnight/early morning thunderstorms into western Siskiyou County
and the Siskiyou mountains. Given the weak moisture signal,
confidence is low in storms developing. We will continue to monitor
this.

By Wednesday, the low will move inland across northern California.
This will maintain a slight chance to chance of thunderstorms across
eastern portions of the forecast area, including eastern Klamath,
Lake and northern Modoc counties. Models are continuing to highlight
eastern Klamath and Lake counties as well as areas to the east as
having the best chance (15-20%) for thunderstorms. Additionally,
with elevated bases and relatively low precipitable water values,
these storms may be on the dry side.  We have upgraded the Fire
Weather Watch to a Red Flag Warning for eastern portion of FWZ 624
and FWZ 625 (2-9 pm PDT) for abundant lightning on dry fuels. The
trough axis pushes east of the area fairly quickly Wednesday evening
and convection is expected to diminish after 9pm.

Following the trough passage, drier westerly flow aloft moves in
Wednesday night and the thunder risk ends. Expect slight cooling
Wed/Thu over inland areas, but northeast winds provide warmer
weather to the south coast by Thursday. A return of hotter weather
is expected Friday into the weekend with fairly typical late-day
summertime breezes, but also dry afternoon humidity. Offshore
northeast flow over the coastal mountains and Siskiyou mountains may
result in moderate to locally poor RH recovery at night.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 11 PM PDT this evening for ORZ624-625.

     Red Flag Warning from 2 PM to 9 PM PDT Wednesday for ORZ624-625.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory from 5 AM to 5 PM PDT
     Thursday for PZZ356-376.

&&

$$