932
FXUS66 KMFR 041735 AAA
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1035 AM PDT Fri Jul 4 2025

...Updated aviation section...

.DISCUSSION...The overnight thunderstorms in our area, almost
exclusively in Klamath and Lake counties, have been prolific
lightning producers, but otherwise have been weak as regards wind
speeds and hail production. This isolated to scattered activity
will continue this morning, and increase again this afternoon
into the early evening from the Cascades and Shasta Valley
eastward, with the focus of activity still in Klamath and Lake
counties. The Red Flag Warning for abundant lightning remains in
effect for south central Oregon early this morning and Lake County
this afternoon and evening.

Two other noteworthy aspects of today`s weather will be:  the
slow erosion of low clouds that are presently at the coast into
the coastal valleys, Umpqua Valley, and locally in the Illinois
Valley. Secondly, while it is reasonable to expect another episode
of at least slightly below normal temperatures later this summer,
it is not far-fetched that today`s cooler temperatures could be
the coolest high temperatures inland until after Labor Day. A
strong warming trend starts Saturday with readings of 5 to 15
degrees above normal expected to be common from Sunday for at
least the following 10 days. This will result in a lengthy
episode of west side valley highs from the lower 90s to around 100
with east side valley highs around 90 to 95.

An upper level low has reached the Oregon coast this morning and
will continue across Oregon through early Saturday morning.
Shortwaves rotating around the low will continue the
aforementioned thunderstorm activity today. On a brighter note, a
ridge will follow on Saturday with a stable air mass. Our chances
are very good for another day without thunderstorms on Sunday,
though with the next trough tracking southeast toward San
Francisco weak diffluence aloft should support some cumulus
buildups over northern California. Perhaps a weak cell or two
could develop, but activity would be a far cry from the prolific
lightning of yesterday and today.

The latest model data is continuing to trend toward increasing
instability for Monday and Tuesday afternoons with the trough
beginning to move north-northeast up the northern California
coast on Monday and across far northern California on Tuesday. But,
the extent of thunderstorm development may be hindered by only a
moderate amount of mid-level moisture.

Model confidence is lower beyond Tuesday, but the general picture
is for an active pattern that will keep the notable heat from
getting extreme while producing mostly modest thunderstorm risks
from day-to-day.

&&

.AVIATION...04/18Z TAFs...Isolated to scattered
thunderstorms be the main concern again this afternoon and evening
along and east of the Cascades, mainly for Lake and eastern Klamath
counties. Isolated showers and storms may extend all the way to the
Shasta Valley in northern California. IFR/MVFR ceilings/visibilities
are expected near any storms as well as gusty outflow winds and even
hail.

Also, a mix of IFR and MVFR at the coast extends into the coastal
valleys. Expect slow improvement into the afternoon. But, the lower
conditions return to coastal areas during the evening. Elsewhere,
VFR will continue. -BS

&&


.MARINE...Updated 200 AM PDT Friday, July 4, 2025...The main update
was to issue a Small Craft Advisory that will start Saturday morning.
First, conditions will remain relatively calm today. The thermal
trough pattern returns Saturday, bringing gusty north winds. This
will result in conditions hazardous to small craft south of Cape
Blanco. The region of steep seas will likely expand early Sunday,
reaching all of the waters during Sunday evening, while very steep
seas will be possible south of Gold Beach during Sunday afternoon
into Monday. Steep seas then are likely to persist into Tuesday
morning. The outlook is for a brief improvement in conditions
Tuesday into Wednesday. -DW

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 8 AM PDT this morning for ORZ623>625.
     Red Flag Warning from 2 PM until 8 PM PDT today for ORZ625.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory from 8 AM to 11 PM PDT
     Saturday for PZZ356-376.

&&

$$