113
FXUS66 KMFR 281130
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
430 AM PDT Fri Jun 28 2024

.UPDATE...Updated aviation section for 12z TAFs.

DISCUSSION (Today through Thursday)...

Overview:

Potential impacts through this forecast include the triple digits
next week, in addition to the potential for fire weather given the
continued drying trend with further dry/windy conditions possible
next week. This stretch may lead to many areas near 100 degrees
across our westside locations. During the middle part of next
week, this heat may be accompanied by breezy winds and low RH, so
we could see fire weather conditions arise Tues-Thurs. Lastly,
there is a small chance for thunderstorms Sunday afternoon and
evening across the far eastern portions of Modoc and Lake
counties. Although widespread severe weather is not expected,
lightning will be a concern across far eastern portions of the
forecast area.

Further Details:

We will transition from a mostly zonal flow pattern aloft today to
more southwesterly flow by Saturday as a closed low pushes south of
the Gulf of Alaska into southwest Canada. Depending on how the
moisture and forcing phase together, there is a chance for
thunderstorms on Sunday with both the GFS and EC indicating around a
couple hundred J/kg of MUCAPE. Its not the best setup, but there was
enough evidence to warrant at least a mention of thunderstorms, but
more than likely most of the area will miss out on thunderstorms.
Depending on how the low develops out of the Gulf of Alaska, we may
have a chance for thunderstorms on Saturday as well, but chances are
even less compared to Sunday`s potential. Moisture is the limiting
factor here for this setup.

As the aforementioned low pushes east, an area of high pressure over
the southern CONUS will break down and slide east. This will
allow for high pressure over the Pacific ocean to slide over the
west coast. The high is progged to setup over central California,
and this will allow for the heat to settle in for several days
starting Tuesday. By Wednesday, and more so Thursday, the
probability for 100 degree days will be on the rise, especially
for our typical warmer locations like our westside valleys. For
example, the Rogue Valley and Shasta Valley will approach a 50-60%
chance of reaching 100 degrees or greater late next week through
the weekend. In other words, some sort of heat risk is shaping up
mid/late next week.

Unfortunately, much of the forecast area has not received much--if
any--rainfall in quite a while now, and this trend is only forecast
to continue. Given the drying trend, fuels are likely to cure
further, and the risk for fire danger will likely increase next
week. This will be most notable starting Tuesday, as overnight
recoveries are not that great, and we will be going into some hot
afternoons near 100 degrees. Western parts of Siskiyou county in
particular could have critical fire weather conditions arise mid
week with RH values around 10 percent in the afternoon coupled with
breezy wind speeds. In fact, elevated to critical fire weather
conditions look possible for much of mid/late next week.

-Guerrero

AVIATION. 28/12Z TAFS...IFR ceilings have built in around Brookings
and across much of Coos County. As higher level clouds move out,
this low cloud bank is expected to expand. There is low confidence
that it will expand into the central Umpqua valley, impacting
Roseburg; but some development across western Douglas County is
expected and already seen on satellite. However, some models do show
some MVFR/IFR ceilings at Roseburg right around sunrise, so it can`t
totally be ruled out. Otherwise, VFR conditions are expected tonight
across the region and through today.

In addition during this afternoon, strong gusty north winds (20-35
knots) will develop across the coast and over the Pacific, strongest
south of Cape Blanco. Afternoon breezes will also be present this
afternoon. Then there is the wildfire smoke. The main impact will be
from the fire south of Bend, OR near La Pine, which is projected to
produce a smoke plume that will locally reduce visibility below 3
SM, as well as send a plum of smoke to the southeast across Lake
County.
-Miles

MARINE...Updated 1215 AM Friday, June 28, 2024...A return
of gusty northerly winds is present today, with steep seas affecting
areas south of Cape Blanco. Winds and seas will peak late Friday
afternoon and evening, with steep seas continuing south of Cape
Blanco into early Saturday morning.

Winds and seas lower Saturday afternoon into Sunday for most of the
area. However, areas from Pistol River south within about 15 NM of
shore could observe brief and isolated advisory level seas as winds
peak in the afternoon, generating a steep wind wave. These
conditions will likely be too short lived and localized to warrant
needing a warning, but you`ll want to watch Buoy 27 to monitor
conditions in this area to be safe before heading out.

Then, a very strong thermal trough is expected to develop next week
beginning on Monday and lingering towards the end of the week. The
peak should be either Tuesday or Wednesday evening, but there is
some spread in the forecast and uncertainty here. As for the wind
speeds expected during the peak of the thermal trough, the chance
for gale force wind gusts south of Cape Blanco is 70% or greater
(90% plus south of Pistol River) and this will drive very steep
waves. There is also a moderate (20-40%) chance that gale force
winds develop over the waters north of Cape Blanco.

-Miles

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT Saturday
     for PZZ356-376.

&&

$$