837
FXUS66 KMFR 041601
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
901 AM PDT Thu Jul 4 2024

.DISCUSSION...Satellite imagery is showing some stratus quickly
dissipating along the Coquille Basin, and persisting offshore.
Meanwhile, smoke from the Shelly Fire can be seen moving east
along Sawyers Bar Highway indicative of a strong high pressure
system. Meanwhile, observations are starting to show the winds
relaxing a little bit, but remaining easterly along the coast
range. We have allowed the current Red Flag warning in the
Kalmiopsis to expire, but we will continue to see very dry
humidities. The question will be whether the winds will become
typically breezy this weekend and so we will be evaluating further
potential for additional red flag products.

In addition, temperatures will be very hot today for most inland
locations. It is worth noting that the low temperature at the
Brookings airport was 75 degrees, and current observations in the
Chetco basin are already showing temperatures in the mid 80s.
Guidance is suggesting another day of temperatures pushing into
the mid to upper 90s before the winds come from the ocean giving a
quick cooldown. Have issued a heat advisory to account for this.
Interestingly this is confined to largely the Chetco Basin as
there is a Brookings Agrimet station showing temperatures in the
upper 50s with weak winds coming from the ocean. This suggests
that Crescent City may be a good place to go to escape the heat
today. -Schaaf

&&

.MARINE...Updated 830 AM Thursday, July 4, 2024...Winds and seas
will gradually improve later today as the thermal trough pushes
inland and expands northward. North to northeast winds will ease
some at this time, but seas and winds will remain hazardous to
small craft with hazardous warning level seas lingering through
this evening for the outer waters south of Cape Blanco. Conditions
improve further on Friday as winds continue to weaken, but seas
will remain steep due to fresh swell and ongoing wind waves.

A period of improved conditions is expected over the weekend with
sub-advisory conditions likely for at least the inner waters on
Saturday, and possibly all the waters on Sunday. Strong high
pressure aloft will disrupt the thermal trough pattern, keeping
winds in the 10 to 15 knot range. Swell will be low and seas will
remain dominated by fresh swell. The thermal trough rebounds early
next, and hazardous conditions are likely to return at that time.
-Schaaf/BR-y


&&

.PREV DISCUSSION... /Issued 432 AM PDT Thu Jul 4 2024/

DISCUSSION...As stated in the previous AFD, here is information on a fire in
southwest Siskiyou County--A wildfire [is] growing within the Marble
Mountains southwest of Shelly Lake near the PCT in south west
Siskiyou County. Siskiyou County Emergency management is requesting
hikers along the PCT to be aware of and avoid this fire.

Overnight satellite shows the hot spot in this area of the new fire
with stratus riding along the central Oregon coast. The lower cloud
deck is starting to reach parts of Coos County this morning,
including Charleston. There are clear skies elsewhere and this will
continue today.

A ridge is present off the coast and will be moving inland towards
southern Oregon the next few days. This will bring the warmest
temperatures of the week to the area. The Chetco effect will be
present this afternoon with highs in the mid-90s near Brookings. On
average, highs will be 5-15 degrees above normal this afternoon.
This translates to 90s with triple digits in more valley locations
west of the Cascades as the heat expands to more west side locations
including the Illinois Valley and Umpqua Basin. Winds will overall
be lighter, so please plan accordingly with these temperatures in
mind before going out to the fireworks.

The heat will be the worst Friday and Saturday. The probability of
reaching highs of 110 degrees in Medford is near 70-80% Friday and
Saturday afternoons. There is also a ~35% probability to reach 115
Saturday in Medford. For reference, 115 is the hottest high on
record for Medford. There will also be a factor of low temperatures
west side only falling to the low to mid-60s Friday and into the
weekend. With this in mind, it is crucial that precautions are taken
to prepare and deal with the heat. With the heat concerns for the
coming days, an Excessive Heat Warning and Heat Advisory exists for
most locations (with an emphasis on valleys) this morning through
Monday evening.

Early next week the ridge will move farther east and temperatures
will fall from the weekend peak, although it will still be warm with
highs in the triple digits for the Rogue and Illinois valleys. -
Hermansen

AVIATION...04/12Z TAFS...VFR will prevail through the TAF period.
The exception to this is in the Coquille Basin where stratus is
spreading this morning. Gusty breezes at the coast and in the Umpqua
Basin will be present tomorrow.

Smoke from the wildfire in western Siskiyou county has settled into
the valleys tonight, locally lowering ceilings and visibility. Any
smoke tomorrow during the day is expected to be blown generally
south.
-Miles/Hermansen

FIRE WEATHER...Updated 300 AM Thursday, July 4, 2024...

..Near critical fire weather conditions possible in the afternoons
and evenings through the weekend for much of southern Oregon and
northern California...

..RED FLAG WARNING REMAINS IN EFFECT UNTIL 8 AM PDT THIS MORNING
FOR EAST WIND WITH POOR OVERNIGHT RH RECOVERY FOR FIRE WEATHER ZONES
619 AND 620...

Fire weather concerns will remain elevated through the weekend. A
strong thermal trough remains along the coast this morning. This is
resulting in moderate to poor RH recoveries for the upper slopes and
ridges, along with gusty northeast winds of 15-25 mph with gusts 30
to 40 mph. Critical fire weather conditions are occurring for
portions of FWZ 619 and 620 and a Red Flag Warning remains in effect
until 8 AM this morning.

The pattern will transition today as the thermal trough expands
northward and northeast flow weakens. Strong high pressure aloft
will move over the region today and linger overhead through the
weekend. Very hot temperatures (100-110 degrees) and very low (low
teens/single digit) daytime humidities are expected during this time
away from the immediate coast. Recoveries will improve some along
the coast, but will remain in the moderate to poor range across the
area through the weekend. Afternoon breezes will be slightly weaker
than normal today and then fairly typical for Friday. With the heat
and very dry conditions, however, even typically breezy afternoon
conditions could result in dangerous weather that is favorable for
the rapid spread of fire. Near critical conditions are possible for
West Side Valleys for the remainder of the week.

We`re keeping an eye on a disturbance expected to move into the
region from California on Saturday and Sunday. While the atmosphere
will be too dry for thunderstorms, this may enhance the afternoon
breezes on those afternoons. This combined with very low daytime
humidities in the low teens and single digits could lead to some
widespread critical fire weather conditions this weekend, including
the Rogue/Applegate Valleys, the Cascades, western and central
Siskiyou County and portions of the East Side. We`ll continue to
monitor this development and evaluate the need for any products in
upcoming shifts. /BR-y

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning until 9 PM PDT Monday for ORZ023>026.

     Heat Advisory until 9 PM PDT Monday for ORZ022-029>031.

CA...Excessive Heat Warning until 9 PM PDT Monday for CAZ080-081.

     Heat Advisory until 9 PM PDT Monday for CAZ084-085.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT Friday
     for PZZ350-356-370-376.

     Hazardous Seas Warning until 11 AM PDT this morning for PZZ356-
     370-376.

&&

$$