NWS Medford, OR wrote its last area forecast discussion before the first event at Jul 9, 10:04 AM PST, 2 hours 56 minutes earlier.
Area forecast discussion, Jul 9, 10:04 AM PST, 2 hours 56 minutes before
Area Forecast Discussion
National Weather Service Medford OR
1104 AM PDT Fri Jul 9 2021
Updated AVIATION Section
.SHORT TERM...A thermal trough is centered along the coast and a
high pressure ridge is over the region today. Heat and smoke will
be the main concerns into this weekend and early next week. Also
today, a weak shortwave will move up into the area in the late
afternoon and evening. Weak instability and weak mid level
moisture may allow some cumulus clouds to develop, especially in
southeast Modoc County. However, current model forecasts do not
support any thunderstorms.
With the thermal trough in place today, expect breezy to gusty
north winds along the coast and into areas west of the Cascades
this afternoon, followed by northeast winds over the coastal
mountains overnight. East of the Cascades, hot and dry conditions
are expected today with afternoon breezes.
The thermal trough will strengthen along the coast into the
weekend with a flat upper level ridge over the region. This will
result in hot temperatures across inland areas in southwest
Oregon through at least Sunday, with lingering hot temperatures
into Monday over northern California. These hot temperatures will
bring increased heat risk concerns for inland areas. An excessive
heat warning remains in effect for central/western Siskiyou
County with heat advisories for Jackson, Klamath, Lake and Modoc
Counties. Please see the NPWMFR for the latest details. Meanwhile,
at the coast, expect cooler conditions with gusty north winds
each afternoon and evening. Of note, along the southern Curry
coast, expect a mild warming effect with highs in the mid 70s to
near 80 this weekend.
Smoke from area wildfires will continue to affect many inland
areas through Monday. The Bootleg fire in eastern Klamath County
has grown significantly in the last 24 hours and the Jack fire in
eastern Douglas continues to produce significant smoke as well. An
air quality alert (AQAMFR) is in effect for eastern Douglas,
Jackson, Klamath and Lake Counties. Areas of smoke will also
affect portions of Siskiyou and Modoc County at times.
&&
.AVIATION...For the 09/18Z TAF Cycle...MVFR/IFR marine
stratus/fog continue to hug portions of the immediate
coastline north of Cape Blanco, but also south of Port Orford.
These may temporarily lower conditions at North Bend in the
next hour or so, but should not be much more than a mile or so
inland. This will change later this afternoon and evening as
the marine layer (IFR) is expected to push back onshore, impacting
most of the lower Umpqua and Coquille valleys overnight into
Saturday morning. This will push into about Elkton, but will
probably stay north and west of Roseburg.
VFR will prevail inland, but other concerns will continue to be
gusty afternoon and evening westerly winds, and thick smoke from
area wildfires, especially near the Jack fire in the upper Umpqua
Basin, and the Bootleg fire, northeast of Klamath Falls.
Visibilities will be reduced in the vicinity of these fires and in
much of the area from the Cascade foothills eastward, especially
during the late night and morning hours. Visibilities generally
improve away from the fires as winds increase during the afternoon.
-Spilde
&&
.MARINE...Updated 800 AM PDT Thursday, 8 July 2021...The thermal
trough will strengthen into Sunday and remain strong well into early
next week. Gusty north winds and steep wind-driven seas south of
Cape Blanco will spread across much of the waters through this
morning. Winds will increase further this afternoon, and seas will
become very steep south of Gold Beach this afternoon through Saturday
morning. As the thermal trough continues to strengthen, gales and
very steep seas are likely Saturday afternoon through at least
Tuesday afternoon for portions of the waters from Port Orford south,
with gusty north winds and steep seas north of Port Orford. -BPN/AV
&&
.PREV DISCUSSION... /Issued 329 AM PDT Fri Jul 9 2021/
DISCUSSION...Near infrared (IR) and shortwave IR satellite
imagery show the Bootleg and the Jack fires remaining relatively
active overnight. The nearest observational site near the Bootleg
Fire, Calimus, is showing poor humidity recoveries overnight (38
percent at the time of writing this AFD) with breezy winds from
the northwest 10 mph with gusts to 15 mph. More remarkably, the
Jack fire seems active despite much better recoveries at Toketee
Falls (82%) and Grandad (69%) respectively. These fires, as well
as the Lava, Tennant, and Juniper fires will bring some smoke into
portions of southern Oregon and northern California at times as
winds cycle around due to the area of high pressure and thermal
trough beginning to come ashore. As a result, an air quality alert
has been issued for portions of southern Oregon east of Interstate
5 (excluding Josephine County.) It is worth noting that despite no
air quality products existing in California, smoke will likely
impact much of northern California as well. Now is a good time to
dig out those N95 masks if you have them. Please see the AQAMFR
for more details.
This thermal trough means that we will remain hot and dry for the
next several days as it is slow to move through the area.
Temperatures in valleys west of the Cascades (and south of
Douglas County) will reach into the triple digits once again.
Additionally, most of the east side will see temperatures reach
into the upper 90s with a few locations reaching the century mark.
As a result, a heat advisory exists for most of the valleys in
southern Oregon and Modoc County away from the Coast and the
Umpqua Valley. In Siskiyou County, California, overnight low
temperatures will be a bit warmer than their normal low, prompting
the excessive heat warning issued on Wednesday. It is worth
mentioning that guidance suggests that temperatures in Medford
could be a little higher than what we are forecasting, but these
guidance do not take smoke into account. Expect a little bit in
the Rogue Valley, which is why temperatures are not as high as
guidance. Should smoke stay out of the Rogue Valley, expect highs
to be a few degrees warmer than what we are forecasting. Please
see the NPWMFR for more details.
Regardless, this pattern will continue over the weekend and well
into next week with no rain in the forecast. The coast will be the
coolest spot, despite being a few degrees above normal for this
time of year. Additionally, the coast will also be the area to
escape the smoke.
FIRE WEATHER...Near the Jack Fire in Douglas County, we are
seeing the valleys experience good recoveries with moderate
recoveries on the ridges. The marine push typically associated
with the Umpqua basin is expected to remain well west of I-5, and
more likely to remain near the coastal valleys. Elsewhere,
including the Bootleg, Lava, Tennant, and Juniper fires, poor to
moderate recoveries are ongoing with east winds beginning to take
hold in Modoc County 285.
Overall, expect dry conditions and breezy winds in many places.
With critical conditions possible across eastern portions of fire zone
284 and most of 285 in northern California. This includes the
Juniper fire. The line of thought at the moment is that the
critical conditions will only occur briefly, and therefore a red
flag warning is not necessary. That being said, expect moderate
(5) to high (6) Haines indices in addition to the hot, dry, and
breezy conditions over many of these locations, including the
Juniper, Lava, and Tennant fires in northern California, and the
Bootleg Fire and the Jack Fire in southern Oregon Note, the Jack
Fire will be mainly Haines 5 while the Bootleg will see
possibility of 5's and 6's. This amount of instability can cause
additional plume-dominated fire growth and could cause safety
concerns for firefighters later today.
East winds are expected to continue as the thermal trough pushes
inland over the weekend, and this will keep overnight recoveries
at moderate to locally poor for the upper slopes and ridges,
particularly east of the Cascades and Kalmiopsis wilderness.
The hot, dry, and breezy conditions will also continue over the
weekend. Although today will be the day with the most widespread
high Haines indices, the weekend looks to stay at majority
moderate with local areas of high haines, keeping the area
generally unstable with some plume-dominated fires possible,
particularly in the late afternoon in the hottest parts of the
day. This overall pattern could break as early as Wednesday next
week, but conditions will likely remain hot, dry, and somewhat
breezy through the end of next week. -Schaaf
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory from 2 PM this afternoon to 8 PM PDT Sunday for
ORZ029>031.
Heat Advisory from 2 PM this afternoon to 8 PM PDT Sunday for
ORZ024-026.
CA...Excessive Heat Warning from 2 PM this afternoon to 9 PM PDT
Monday for CAZ080>082.
Heat Advisory from 2 PM this afternoon to 9 PM PDT Monday for
CAZ083>085.
Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT Monday
for PZZ356-376.
Gale Warning from 11 AM Saturday to 5 AM PDT Monday for
PZZ356-376.
Hazardous Seas Warning from 2 PM this afternoon to 11 AM PDT
Saturday for PZZ356-376.
Small Craft Advisory until 5 AM PDT Monday for PZZ350-370.
CC/MAS