921
FXUS66 KMFR 102347
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
447 PM PDT Wed Jul 10 2024

.Updated Aviation Discussion.

.DISCUSSION...

Temperatures are trending lower compared to what we`ve seen the
last few days. We`ve yet to hit 100 degrees here at the airport as
of writing this AFD at 2pm and this relatively cooler trend will
continue for most of our Oregon zones through the remainder of the
week. However, the NWS HeatRisk algorithm remains in the major
category for parts of Siskiyou County around the Shasta Valley as
high temperatures are still about 20 degrees warmer than normal
for this time of year. In addition, low temperatures will be
around the mid 60`s to upper 60`s in sections of northern
California.

A push of cooler air or a cold front will move into the forecast
area around Friday. BUFR soundings show steep lapse rates up to 10
C/km up to 600 mb ahead of the front. This will result in some
gusty conditions east of the Cascades with wind gusts up to 35 mph
or perhaps even higher if we do indeed mix that deep.

Heading into the weekend, a closed low will approach from the
south, which will introduce a risk of thunderstorms across our
forecast area. The highest risk areas will be east of the Cascades
in Lake and Klamath counties. We also considered adding sections
of western Siskiyou County in the risk area, although many of the
upper level soundings didn`t show enough CAPE. Some of the
soundings did show a small surge of moisture at the mid levels on
the other hand.

The storm threat will persist into Sunday as an upper level wave
moves through into the forecast area. However, the threat of
lightning significantly decreases Sunday night as the wave moves
eastwards.

-Smith

&&

.AVIATION...11/00Z TAFS...Along the coast and just offshore,
satellite image shows marine stratus from about Bandon north, and
just to the west of the North Bend airport. The marine stratus
should return at North Bend by 2z. Visibility could also drop later
tonight to 4 miles or even less at North Bend.

South of Cape Blanco, marine stratus should remain offshore beyond 5
nm from shore int tonight, the exception will be south of Gold Beach
where marine stratus with IFR ceilings could return late this
evening.

Inland, west of the Cascades, VFR conditions will continue through
the TAF period with gusty breezes into early this evening, and again
Thursday afternoon. The exception will be MVFR visibility in the
vicinity of the Salt Creek and Shelly Fires, and in Medford tonight
as the smoke from the Salt Creek Fire could drift into the airfield.

East of the Cascades, VFR conditions will continue through the TAF
period. However, smoke from the Salt Creek fire could get
transported into the area resulting in visibility lowering to 5
miles. -Petrucelli

&&

.MARINE...Updated 200 PM Wednesday, July 10, 2024...A thermal
trough will strengthen through Thursday resulting in stronger north
winds and increasingly hazardous seas. Small Craft Advisory
conditions with moderate north winds and steep wind-driven seas are
expected through this afternoon for areas south of Cape Blanco, with
Small Craft Advisory conditions spreading into the northern waters
this evening as north winds and seas increase which will last
through Thursday. Meanwhile, gales and very steep, hazardous seas
develop this evening from Gold Beach south. Moderate to strong north
winds and steep to very steep seas continue Friday. Then, winds and
seas are expected to gradually lower Saturday and Sunday.

-Petrucelli

&&

.FIRE WEATHER...Issued 300 PM Wednesday July 10, 2024...

...Near critical fire weather conditions possible through at least
this weekend...

Hot, breezy, low humidities, and occasional unstable afternoon
conditions will persist through this weekend, and this will lead to
near critical fire weather conditions. Additionally, we have a
chance for thunderstorms this weekend, mainly across the eastside.

Wind speeds are not too impressive this week, but they certainly
will be on the breezy side around 10-20 mph, with speeds becoming
more of a concern for Red Flag conditions by Friday over the
eastside and parts of Siskiyou County. Single digit RH values are
also forecast this week during the afternoon hours across the
eastside and some isolated westside valleys like Northern
California. These factors, on top of this prolonged drying stretch
will result in elevated to critical fire weather conditions nearly
every day this week. This afternoon and tomorrow afternoon may fall
just short of actually reaching those critical thresholds due to the
wind. While no official warnings are out now, it will be very
borderline today and tomorrow afternoon for fire weather conditions,
so the threat is there even if we aren`t hitting "criteria".
Conditions worsen as the week progresses, and we will likely see Red
Flag Warnings coming to fruition as early as Friday.

For the thunderstorm potential, it should be noted that the trend
stay the same from yesterday for both Saturday and Sunday. We were
seeing slight increases early in the week, but those trends have
flatlined. A lot will depend on how a ridge of high pressure sets up
over the Four Corners region as this will direct monsoonal moisture
northward. There is about a 10-20 percent chance for isolated
thunderstorms both Saturday and Sunday.

-Guerrero

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning until 9 PM PDT this evening for ORZ024-
     026.

     Heat Advisory until 9 PM PDT this evening for ORZ029>031.

CA...Excessive Heat Warning until 9 PM PDT this evening for
     CAZ080>082.

     Heat Advisory until 9 PM PDT this evening for CAZ083>085.

PACIFIC COASTAL WATERS...Small Craft Advisory until 8 PM PDT Friday
     for PZZ356.

     Small Craft Advisory from 8 PM this evening to 8 PM PDT Friday
     for PZZ350-370.

     Gale Warning from 8 PM this evening to 8 PM PDT Friday for
     PZZ356-376.

     Small Craft Advisory until 11 AM PDT Thursday for PZZ376.

&&

$$