978
FXUS66 KMFR 081030
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
330 AM PDT Sun Jun 8 2025

.DISCUSSION...The skies remain clear over much of the area this
morning, with the exceptions of the coast and the near-shore waters,
where an extensive layer of marine stratus has pushed up to the
western slopes of the coastal ranges once again. Just like
yesterday, these clouds should burn back offshore through the
morning, with mostly clear skies then expected along the coast
this afternoon. Mostly clear skies are expected inland as well,
although some clouds are expected to form this afternoon due to
some developing instability this afternoon. More on this below.

The strong upper ridge is moving overhead today, and the thermal
trough has shifted inland. Afternoon highs across the area will
be 15 to 25 degrees above normal for this time of year, and some
of the West Side valleys, especially those in Josephine, Jackson,
and Siskiyou counties, could easily reach triple digits,
today and again Monday. Highs yesterday were 1 to 3 degrees above
forecast, and today and tomorrow`s highs have been adjusted up
slightly to correct for this, given that conditions are expected
to be very similar. A Heat Advisory remains in effect for the
West Side valleys, where moderate Heat Risk values are expected.
Details can be found at PDXNPWMFR.

It will be dry most of the time and for most locations for the
majority of the forecast area, however, we are keeping a sharp eye
on the potential for thunderstorms as monsoonal moisture begins
to enter the area today. The weak upper low drifting offshore of
California will provide a route for moisture to stream up from the
south, and when combined with the hot daytime temperatures,
moderate instability is expected to develop this afternoon, mainly
over Siskiyou and Modoc counties (and perhaps just a bit north of
the state line as well). The high-resolution CAMs support this,
although the synoptics, and the NBM, do not. Isolated
thunderstorms may result in northern California this afternoon
and evening, most likely over Siskiyou County. Any convection that
does develop will die off after sunset.

Instability then returns, spreading farther north into portions
of southern Oregon by Monday afternoon, and farther still by
Tuesday. Tuesday afternoon may be especially troublesome, when an
approaching weak upper level impulse would provide the best
chances for lift. There`s some evidence pointing towards storms
lingering into the overnight hours Tuesday, but they are likely to
be isolated and confined to portions of Lake and Klamath County.

Today and tomorrow afternoons, instability will be marginal, with
CAPE values of up to 1000 J/kg and LIs of no less than -2. By
Tuesday, some models are bringing CAPE up to 2000 J/kg, with most
unstable LIs as low as -4. Also of note, precipitable water values
will steadily increase through Tuesday, reaching a peak of about
1.2 inches by Tuesday afternoon. With all this in mind,
thunderstorms are likely to remain sub-severe for much of the
three day event, although a few strong storms are possible with
the potential for gusty winds and small hail. Gusty winds are
especially a concern given the dry low levels and downdraft CAPE.
The best dynamics, lift, and moisture are available Tuesday, and
this would be the day with the best chances for more widespread
thunderstorms, and we cannot rule out an isolated near-severe
storm or two. Given the higher moisture content, some storms
could also produce very heavy rain, should the precipitation
punch through the dry lower levels. Stay tuned in to the latest
forecast updates as this event evolves.

Ensemble means continue to suggest that some form of upper level
troughing will remain overhead for the latter half of next week,
with a strong majority of ensemble members showing a large upper
level low or open trough moving into the area Fathers Day weekend.
This would result in cooler temperatures and additional chances
for showers and thunderstorms during the remainder of the
forecast, especially next weekend. -BPN


&&

.AVIATION...08/12Z TAFs...The marine stratus is bringing IFR/LIFR
ceilings to the coast, coastal valleys, and the coastal waters again
this morning. These areas will burn back offshore by this afternoon,
but are likely to return again this evening. Elsewhere, VFR
conditions will prevail.

This afternoon, showers and isolated thunderstorms are possible over
Siskiyou and Modoc County. PWATs are nearing 0.75"-1.00" tomorrow
afternoon, but forecast soundings keep dry air in the lower levels.
That means that although heavy downpours are possible, they will be
isolated, and gusty outflow winds are likely around any stroms that
do develop. -BPN/Hermansen

&&

.MARINE...Updated 200 AM Sunday, June 8, 2025...North of our
area, a broad area of gusty north winds will build north-northwest
fresh swell that will move into the area today. This will result in
steep seas across the southern Oregon coastal waters by this
evening, and continuing through the day Monday. Gusty northerly
winds will develop over the area Monday, with the highest speeds
south of Cape Blanco. Areas of very steep and hazardous seas are
possible on Tuesday especially south of Cape Blanco as the thermal
trough returns. Gusty north winds then continue through the rest of
the week with very steep seas possible south of Cape Blanco.
-BPN/DW

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory from 11 AM this morning to 8 PM PDT Monday for
     ORZ023-024-026.

CA...Heat Advisory from 11 AM this morning to 8 PM PDT Monday for
     CAZ080-081.

PACIFIC COASTAL WATERS...Small Craft Advisory from 5 PM this
     afternoon to 5 PM PDT Monday for PZZ350-356-370-376.

&&

$$