183
FXUS66 KMFR 130552
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1052 PM PDT Mon Aug 12 2024

.DISCUSSION...An update to the forecast is not necessary this
evening. A few thunderstorms earlier this evening produced around
8 lightning strikes east of the Cascades. It was breezy and warm
today, but temperatures were generally a few to several degrees
below normal, which was a few to several degrees cooler than
yesterday. A trough dominated upper level pattern will continue
this episode of breezy afternoons with slightly cooler than
normal conditions with night and morning low clouds for the coast
and coastal valleys.

A stable air mass will be in place on Tuesday, and likely during
the early part of next week. In between, Wednesday through
Saturday, there will be some modest/very slight possibilities of
showers and thunderstorms with the highest probabilities, around
10-15%, for Klamath and Lake counties on Thursday
afternoon/evening, and then closer to the Cascades (central and eastern
Siskiyou, eastern Jackson, eastern Douglas, and Klamath counties)
on Saturday.

&&

.AVIATION...13/06Z TAFS...Marine stratus along the coast will be the
main concern this evening along with some ceilings in the Cascades.
Overall, MVFR ceilings seem most likely, although periods of IFR
ceilings remain possible along the coast tonight based on the latest
satellite data. Smoke from the fires seems to have settled in
northern Lake and Klamath Counties based on air quality data, so IFR
visibilities are likely in those areas.

Otherwise, some isolated showers are possible overnight east of the
Cascades.

Smoke will continue to impact the same locations as mentioned above
on Tuesday with VFR ceilings spread across other locations in the
forecast area.

-Smith

&&

.MARINE...Updated 130 PM Monday, August 12, 2024... High pressure
is weakening in the Pacific. Benign wave conditions will persist
through most of the week with no thermal trough condition. A weak
northerly short period swell will glide through the waters this
week.

&&

.FIRE WEATHER...Issued 200 PM Monday August 12, 2024...Temperatures
will trend cooler through next week with increasing onshore flow,
improving humidities, and breezy afternoon winds as upper level
troughing settles in and remains over the Pacific Northwest.

Another relatively strong marine push is expected tonight into
tomorrow, with extensive stratus and fog decks west of the Cascades
that may even push into the Rogue Valley by daybreak Monday.
Afternoon breezes could be gusty as well in the afternoon, but not
as strong as Monday afternoon.  Despite these winds, rising
humidities should keep us well outside of any critical thresholds.

With the shortwave passing just south and eats of the area this
afternoon and tonight, some instability is expected to develop this
afternoon. Instability is marginal at best, and mid level moisture
is lacking, therefore the threat for thunderstorms is low. The most
likely scenario will be cumulus build ups over the Cascades, higher
terrain east of the Cascades, and in northern California, and one or
two of these could develop into a mature storm. While the threat for
thunderstorms is low, the threat for strong outflow winds is very
high and will be a concern for any ongoing or new fires. Note that
outflow winds could initialize from the more robust cumulus fields
as well, although the resulting winds would not be as strong.

Then, with the trough remaining overhead through the week, we can
not completely rule out additional afternoon convection,
particularly Wednesday and especially Thursday afternoons and
evenings as additional shortwaves pass through the region. Again, we
only expect isolated storms should any develop, and confidence is
pretty low across the board, especially given that wildfire smoke
has a tendency to suppress convective development.

Models are showing the potential for a much stronger, broader trough
arriving and setting up over or very near the area late this week
into this weekend. This will maintain our cooler temperatures and
higher humidities, and may also produce more widespread chances for
showers and thunderstorms Friday into Saturday. While wetting rains
are very unlikely, we will keep a close eye on how the system
develops, as cooler temperatures, higher humidities, and even a
small amount of rain will be very welcome to fire concerns. -BPN


&&

.PREV DISCUSSION... /Issued 230 PM PDT Mon Aug 12 2024/

DISCUSSION...An upper trough over the Pacific Northwest brought
cooler temperatures to the area...with most locations currently
running between 5 and 10 degrees cooler compared to yesterday at
this time. Cumulus clouds are developing in eastern Siskiyou and
Klamath counties as well as Lake county...all locations where the
short term models are indicating the possibility of
showers/thunderstorms. According to the short term
models...showers and the possibility (around 15% chance) of
thunderstorms increases between 00z and 03z. Any activity that
does develop is expected to move northeast out of the area by 09z
tonight.

As far as smoke goes...the greatest impact for smoke will be over
Lake...Klamath...eastern Douglas...and northern Jackson counties
through at least Wednesday. An air quality advisory was issued by
the Oregon Department of Environmental Quality. Please see
https://oregonsmoke.org for more information.

We will continue to be in a trough pattern through the
week...with temperatures below normal...and a slight chance of
thunderstorms/showers most days through Thursday. The one day we
may have a break in the action will be Tuesday. The best chance
for showers and thunderstorms will be generally along the east
side. There is still quite a bit of uncertainty in the extended
forecast as far as timing of precipitation...but we do know that
we will stay in this cooler weather pattern through the forecast.

CCR

&&

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

CA...None.

PACIFIC COASTAL WATERS...None.

&&

$$