269
FXUS66 KMFR 211119
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
419 AM PDT Thu Aug 21 2025

.DISCUSSION...Updated Aviation section...

&&

.AVIATION...21/12Z TAFs...VFR prevails across the area and will do
so through the TAF period. The chance for a thin marine layer along
the coast north of Cape Blanco is looking smaller, so clear skies
continue for the forecast this morning. Gusts near 20 to 30 knots
will be found this afternoon at the coast as the thermal trough is
in the area. Inland sites near the Umpqua Basin could see afternoon
gusts nearing 20 knots as well. /BR-y/Hermansen

&&

.PREV DISCUSSION... /Issued 340 AM PDT Thu Aug 21 2025/

DISCUSSION...Satellite shows clear skies everywhere, even at the
coast tonight. If anything, there could be some stratus that
develops near the Coos County coast between 3 to 6 am range, so
this will be watched for. Otherwise, the clear skies will help
most spots see lows in the 40s and 50s this morning.

The main areas of concern in the forecast are the return of heat and
rain/thunderstorms this weekend. As the ridge builds around the four
corners in the next few days, the heat will come first. 80s and
90s will return to more locations by this afternoon. Morning
temperatures will trend slightly warmer by Friday morning with
more west side lows back in the 60s. The higher heat risk will
come Friday with 90s east side and upper 90s to low 100s west.
Heat Advisories and Extreme Heat Warnings have been issued
starting Friday afternoon for most areas except the coast as they
will be reaching the 70s for the most part. The heat will continue
for the next several days with triple digit highs in the forecast
for the Rogue Valley through Tuesday. Precautions need to be made
to protect yourself from the heat. Drink plenty of water, avoid
peak heating between 10 AM and 4 PM, and stay in an air-
conditioned room as much as possible. Please see NPWMFR for more
details.

The other piece is the rain/thunderstorm chances this weekend. This
has a better chance to begin Sunday as monsoonal moisture is making
its way in from the south with disturbances to the west. This
chance will mainly be into areas east of the Cascades Sunday and
a 15-20% chance of thunder will be present in far eastern Modoc
and Lake counties. Monday afternoon chances expand farther west to
include most of Northern California and the Cascades with a
15-25% chance for showers. This trend continues each afternoon
through at least Thursday. This will be monitored as models are
not in as much agreement yet this far out.

MARINE...Updated 200 AM PDT Thursday, August 21, 2025...The
thermal trough will maintain gusty north winds and steep wind driven
seas across the waters through the end of the week. Moderate to
occasionally strong north winds and brief periods of very steep seas
are expected south of Cape Blanco. Winds ease over the weekend,
hovering near advisory criteria, but seas are likely to remain steep
through the weekend and into early next week. /BR-y/Hermansen

FIRE WEATHER...Updated 200 AM PDT Thursday, August 21, 2025...
High pressure developing over the Four Corners area looks to build
an upper ridge over the area starting Thursday and remaining in
place through at least the weekend. The most immediate effect will
be temperatures rising 5-15 degrees above seasonal norms. An Extreme
Heat Warning has been issued for Friday afternoon through Monday
evening, affecting multiple FW Zones. A Heat Advisory is in place
for Friday afternoon into Saturday night for other inland areas.
Individuals in these zones who are not prepared for these hazardous
conditions may experience heat-related illnesses.

Dry conditions continue for more west side locations today through
the weekend as well. Overnight recoveries look to be generally
moderate, but periods of easterly flow overnight could bring locally
low recoveries to area peaks and ridgelines. This looks especially
true for terrain in western Siskiyou County, and may affect Curry
County coastal ranges as well.

Monsoon moisture looks to move over the area on Saturday morning.
With ample surface heating expected, convective thunderstorm
development will be possible east of the Cascades ann in northern
California starting on Saturday afternoon and evening. In general,
the best chances look to be in easternmost Lake and Modoc counties,
with lesser chances over other areas east of the Cascades and
possibly into Siskiyou County as well. Additional instability
remains absent from the forecast, although this could change as
information gains detail. Without additional instability, convective
thunderstorms tend to be isolated to locally scattered in coverage.
Winds aloft look to be light, which may limit storm motion. With the
amount of moisture anticipated, any thunderstorms that develop may
be wet which would help reduce the threat of fire starts. -TAD

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Extreme Heat Warning from 1 PM Friday to 8 PM PDT Monday for
     ORZ024-026.

     Heat Advisory from 1 PM Friday to 8 PM PDT Saturday for ORZ023-
     025-027-029>031.

CA...Extreme Heat Warning from 1 PM Friday to 8 PM PDT Monday for
     CAZ080-081.

     Heat Advisory from 1 PM Friday to 8 PM PDT Saturday for CAZ084-
     085.

PACIFIC COASTAL WATERS...Small Craft Advisory until midnight PDT
     Friday night for PZZ350-356-370-376.

&&

$$