595
FXUS66 KMFR 021025
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
325 AM PDT Sat Aug 2 2025

.DISCUSSION...Low pressure remains in the Gulf of Alaska with high
pressure centered over the southwestern US, leaving the region in
southwest flow aloft. With the ridge far enough to the south, the
upper trough has more influence over the region, sending
shortwaves through the southwest flow aloft and maintaining near
normal temperatures through the weekend and likely well into next
week. We`ve got a few more days of thunderstorms in the forecast
through the weekend as additional shortwaves pass through the
area. Then, it looks like a more stable air mass arrives for next
week, and we`ll finally get a break from this persistent
thunderstorm pattern.

After another day of wetting thunderstorms yesterday, 24 hour
rainfall totals resemble those of recent days with quite a few
reports of 0.50"-0.75" across northern California and east of the
Cascades, with some sites even reaching up to or just over 1.00"!
Another day of thunderstorm activity is expected today, but with a
weaker shortwave passing through, forcing will be weaker and storm
coverage will be comparatively less than the last few days. Isolated
storms are expected across central/western Siskiyou County
northeastward into Klamath/Lake Counties. Storms should stay out of
the West Side Valleys today, but a stray storm could clip the
southern end of the Rogue Valley today (south of Ashland).

On Sunday, a more defined open trough approaches the region.
Guidance has slowed down the progression of this trough, but
thunderstorms are still expected Sunday afternoon/evening.
Thunderstorm coverage increases with this trough compared to what`s
expected today, but the focus will be along and east of the Cascades
and across northern California. Additionally, this trough will bring
cooler than normal temperatures to the region, with high
temperatures on Sunday expected to be around 10 degrees cooler than
normal. Expect some increased winds in the area on Sunday with this
trough passage. Sunday night into Monday, there`s some potential for
shower activity and maybe a stray thunderstorm to carry on during
the overnight hours, but confidence is low in this. If this were to
occur, the best chances would be over portions of northern
Klamath/Lake Counties.

The pattern transitions on Monday. We`ll see another day of below
normal temperatures though a few degrees warmer (mid-upper 80s (70s)
for West (East) Side locations) than Sunday. With the open trough to
the northeast, westerly flow will bring a drier and more stable air
mass into the region, and for the first time in many days, we`ll see
thunderstorm chances drop out of the forecast. This stable pattern
will persist through the week, so at this time, we don`t expect
thunderstorms to return to the forecast through the week. There will
be a few shortwaves/weak fronts to pass through Tuesday and maybe
Thursday, but these will be in west to northwesterly flow, resulting
in continued stable conditions. With zonal to northwesterly flow
persisting through week, temperatures will remain near seasonable
norms with typical daily breezes and periods of enhanced breezes.

Towards the end of the forecast period (Friday 8/8) and into the
following weekend, guidance is hinting at a potential warm-up with
high pressure strengthening over the Pacific Northwest. High
temperatures could reach back into the upper 90s/low 100s (upper
80s/low 90s) for areas west (east) of the Cascades next weekend.

&&

.AVIATION...02/12Z TAFs...Marine stratus will remain along the
southern Oregon coast, maintain IFR and LIFR conditions through this
evening, except for patchy breaks during the late morning into the
early evening, around 19Z through 02Z. Gusty winds will be strongest
in the afternoon, and south of Cape Blanco at 15 to 25 kt.

VFR conditions are expected for inland areas through the TAF period.
Compared with Friday, thunderstorm activity is expected to be
slightly diminished today with isolated storms expected for
Siskiyou, Klamath, and Lake counties. Lightning and gusty/erratic
winds with small hail and locally moderate to heavy rainfall are
expected with any storms today.

&&

.MARINE...Updated 200 AM PDT Saturday, August 2, 2025...A weak
thermal trough will maintain gusty north winds south of Cape Blanco.
This is bringing low end advisory level winds and seas south of Port
Orford that will persist through Sunday morning. Conditions will be
relatively improved through much of the week, though winds could
briefly reach advisory levels between Port Orford and Gold Beach
during the afternoons/evenings. Seas are expected to remain at or
below 5 ft through much of the week with a slight increase as a
light northwest swell (4-6 ft @ 10-12 seconds) moves into the waters
around mid-week.

&&

.FIRE WEATHER...Updated 200 AM PDT Saturday, August 2, 2025...A few
more days of isolated to scattered thunderstorms are in the forecast
for the weekend. The overall upper level pattern hasn`t changed all
that much, and we`ll continue to see shortwave disturbances pass
through the region in southwest to westerly flow. Today`s shortwave
will be weaker compared to recent days, and this will limit storm
coverage to isolated for this afternoon/evening across
western/central Siskiyou County and Klamath/Lake County (highest
chances - 25% - across northern areas).

On Sunday, a more pronounced trough approaches the region and is
likely to kick off another round of isolated to scattered
thunderstorms during the afternoon and evening. Storms should be in
the more typical areas, firing off around the Shasta Valley,
northeastward into Klamath/Lake Counties. Scattered coverage is most
likely over the northern portions of Fire weather zones 624/625.
However, given the ample moisture that has accompanied storms over
the last several days, ERCs in those zones are running below average
for this time of year. Additionally, fuel conditions are noted to be
a moderate fire weather risk per the Wildland Fire Assessment System
(WFAS) with even some low risk noted in some areas. Given the fuel
conditions and the lack of ignitions notably gaining a foothold over
the last few events, will continue to headline the scattered
potential in the Fire Weather Planning Forecast.

Guidance has slowed the progression of the trough through the region
until Sunday night/Monday morning, and this should help mitigate the
gusty wind potential that typically comes with an upper level trough
passage this time of year. Even still, expect some enhanced
afternoon breezes on Sunday along with a notable cooling trend
compared to this afternoon`s temperatures. Below normal temperatures
are expected Sunday into early next week. With the trough passing
overhead during the overnight hours, there was some concern for
overnight convection. Current guidance isn`t too keen on it at this
time, but it can`t be completely ruled out. If this were to
materialize, best chances would be east of the Cascades in portions
of Klamath/Lake Counties.

Otherwise, from Monday onward, conditions will finally stabilize for
the week. Thunderstorm chances drop out of the forecast for the
remainder of the week as a drier and more stable air mass moves in
under a west to northwesterly flow pattern. Below normal
temperatures continue through Tuesday with a warming trend expected
for the latter half of next week.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 8 AM PDT Sunday
     for PZZ356-376.

&&

$$