720
FXUS66 KMFR 011713
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1013 AM PDT Fri Aug 1 2025

...Updated AVIATION forecast for 18Z TAFs...

.DISCUSSION...

We`ll see yet another round of thunderstorms this afternoon as
another disturbance moves through the atmosphere. There will be
plenty of lightning as the lightning probabilities for one cloud
to ground flash within 20km of a point is about 80% over the
Cascades, which is yet again on the high side for our area.
Another thing that caught our eye this morning was valley fog
south of Chemult, which is indicative of how much moisture is on
the ground east of the Cascades. Otherwise, no major changes to
the forecast except for cutting out thunderstorms for some
locations west of the Cascades.

-Smith

&&

.AVIATION...01/18Z TAFs...Marine stratus remains along the Oregon
coast, keeping IFR and LIFR levels in place. A break in the layer
and periods of gusty winds remain in the forecast in the early
afternoon, with winds calming and stratus rebuilding into the
evening.

Inland areas generally look to remain at VFR levels through the day.
Rain showers and thunderstorms are expected to develop this
afternoon across most of the area. Coos, Curry, and western Douglas
county may not see activity develop. Isolated to scattered
thunderstorms are possible through the afternoon and evening, with
activity decreasing into the night. Thunderstorms can present
hazardous conditions, including lightning strikes, gusty and erratic
winds, and small hail or locally moderate to heavy rainfall. -TAD


&&

.MARINE...Updated 800 AM PDT Friday, August 1, 2025...A thermal
trough will maintain gusty north winds south of Cape Blanco through
at least Sunday morning. This will result in low end advisory level
conditions south of Port Orford and within 30 nm of shore. Winds
will be strongest and seas will be steepest during the afternoons
and evenings this weekend. There may be some improvement to sub-
advisory conditions for the early part of the week, but the thermal
trough pattern returns for the latter half of next week, with
stronger north winds and higher seas possible.

&&

.FIRE WEATHER...Updated 300 AM PDT Friday, August 1, 2025...The main
concern will be isolated to scattered thunderstorms during the
afternoon and evening hours through the weekend. Storms will be wet,
with moderate to heavy rain expected with these storms.
Additionally, gusty erratic outflow winds are also a concern near
thunderstorms. A more stable air mass is expected on Monday, and
thunderstorms finally drop out of the forecast through the rest of
the week.

There`s good agreement for another slightly negatively tilted
shortwave to pass through the region today during the time of max
heating and instability. The general consensus among several pieces
of data suggest the bullseye of thunderstorms mid to late Friday
afternoon into Friday evening will be in portions of Fire zones 280,
623 and 624. However, PWATS are around an inch or higher and storm
motion is expected to be weak, meaning storms that develop will be
slow movers. This will provide the opportunity for storms to produce
wetting rains, some of which could be moderate to heavy. Therefore
despite the expected frequent lightning, the threat for ignitions
should be mitigated for the reasons just mentioned above. Storm
motion will be more southwesterly today, so storms that develop
along the Siskiyous could move up into portions of Josephine/Jackson
Counties today.

Storm activity will be diminished on Saturday with isolated activity
confined to portions of Fire zones 280, 281, 624 and 625 late in the
afternoon and early evening. A stronger upper trough moves into the
area on Sunday which could trigger thunderstorms along and east of
the Cascades and northern California. This upper trough will also
bring enhanced winds east of the Cascades Sunday afternoon into
Sunday evening. At this time, it looks like RHs will be just high
enough to preclude any critical winds/RH overlap Sunday afternoon,
but near critical conditions will be possible, which could result in
increased fire activity for new or existing fires.

A dry and more stable flow is likely for the first half of next week
resulting in dry weather and ending the threat for thunderstorms.
Temperatures will cool down some with values near or slightly below
seasonal norms.

&&

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

CA...None.

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

&&

$$