121
FXUS66 KMFR 170623
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1123 PM PDT Sun Aug 16 2026

...Updated the Aviation and Marine Sections...

.AVIATION...17/06Z TAFs...VFR will persist through Monday evening,
with extensive high level clouds. Except, LIFR will return to the
coast and coastal valleys from around 07Z this evening to around
18Z late Monday morning.

&&

.MARINE...Updated 830 PM PDT Sunday, August 16, 2026...There will be
brief, slight improvement overnight. But, due to gusty north winds,
the Small Craft Advisory in effect for most of the area south of
Cape Blanco (excepting near shore south of Brookings) has been
extended to cover all of the southern waters Monday afternoon
through Wednesday evening. The strongest winds are expected during
Tuesday afternoon and evening. Conditions are expected to improve
late in the week.

&&

.PREV DISCUSSION... /Issued 149 PM PDT Sun Aug 16 2026/

KEY MESSAGES...

* Low chances of thunderstorms in the high central Cascades this
  afternoon and again on Monday.

* Temperatures trend slightly warmer mid week as high pressure
  builds.

* An upper level low will move up the coast on Friday with a low
  chance of showers and thunderstorms across the state of Oregon.

* Seasonal temperatures for most of the week.

DISCUSSION...

We`re watching more cumulus build ups over the higher Cascades
this afternoon as some moisture and upper level energy are
present in the atmosphere. We have a 5-10% chance of
thunderstorms in the high Cascades near Crater Lake this
afternoon. Again, model guidance isn`t too ambitious about
thunderstorms, although the FV3 model is predicting some echos
late this afternoon. Convective available potential energy(CAPE)
is modest around 500 J/kg with 20 to 25 knots of shear. It looks
like we are missing some stronger lifting mechanisms in this
environment, so perhaps thats why thunderstorm coverage isn`t
higher.

By tonight, the marine stratus will likely make another push into
the Umpqua Basin based off data from the REFS. The probability of
low clouds is about 60% with low stratus and fog continuing to
cover the Oregon coast.

Moving further into Monday, some upper level energy will shoot up
into Oregon with the low chances(~5%) for thunderstorms
continuing around Crater Lake and northern Klamath County with
similar 500-750 j/kg CAPE values. Again, the upper air pattern is
messy with 500 mb vorticity and a broad and shallow short wave
riding over the ridge just to the east. If storms do form, they`ll
be isolated and fairly brief based on guidance from the convective
allowing models.

Heading into the remainder of the week, The ridge begins to build
into Oregon and California with heights rising slightly, although
a cut off low remains out over the Pacific off the central
California coastline. Historically, these lows will give us a
chance at thunderstorms around northern California, however that
isn`t the case this week. The national blend of models is keeping
us very dry through the middle of the week. About 3 out of the 50
ECMWF ensemble members are predicting convection around the
Wednesday and Thursday timeframe, so just a small chance.

The best chances for precipitation arrive on Friday when the low
off the California coast moves northwards providing deeper lift
over our area. The NBM has a 20% chance of precipitation over the
Cascades Crest at this time. However, the 12Z ECMWF ensemble is
not as ambitious with shower and thunderstorm activity during
Friday. In fact, it looks like things have trended drier based
off the latest data.

As this low moves north, the cloud cover and potential cold front
will push temperatures lower here in Medford with a high around 88
on Friday and 89 on Saturday. That should be right around normal
for the end of August.

Overall, thunderstorms and showers are the biggest weather
feature to watch through the week. Nothing stood out on the
extreme forecast index(EFI) product over the next 7 days, so
minimal weather impacts for the region.

-Smith

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT
     Wednesday for PZZ356-376.

&&

$$