Wildfire in Oregon, July 19 to 21, 2023

Area Forecast Discussion
National Weather Service Medford OR
244 PM PDT Wed Jul 19 2023

.DISCUSSION...

Warmer than normal temperatures are anticipated to continue across
the forecast area. Heat risk, which measures the public's ability
to withstand heat illness, remains moderate through most of the
week. This is probably due to temperatures pushing towards 100
degrees and lows being able to drop down into the upper 50's and
lower 60's. The cooler overnight temperatures are what is likely
dropping the heat risk in this case. Those susceptible to heat
illness are most at risk over the next few days.

Other than the warm temperatures, smoke from the Flat Fire will
remain an issue through the forecast period and likely most of the
summer. We'll see winds shift from slightly offshore to onshore
later this evening as the surface pressure gradient becomes west
to east. The winds aloft are not all that strong, so the smoke
will make a 10 knot crawl eastwards. However, it seems reasonable
most valleys west of the Cascades will see more smoke Thursday
into Friday. Concentrations don't appear that bad at this time
relative to previous years, although that could change if the fire
burns hotter or there are more burnout operations.

Outside of the smoke and temperature concerns over the next few
days, an upper level low will approach the Washington coast
sometime around the Sunday or Monday. This will result in heights
lowering and temperatures trending lower into the extended
forecast. The high in the Medford on Monday is anticipated to be
91, which is slightly below normal for this time of year. There
could be an increase in cloud cover as well as moisture between
the boundary layer and 500 mb is 60 to 70 percent. Thunderstorms
are not out of the question either as the NBM has a 10 percent
chance of thunderstorms east of the Cascades Monday and Tuesday.

Beyond Tuesday, ensembles are not as clear on the synoptic
evolution in the Pacific Northwest. It doesn't appear a strong
ridge will be build in. NBM High temperatures in the 75th
percentile for Medford remain at or below 100 degrees into late
next week. Outside of ongoing Flat Fire, this is pretty typical
weather for the region.

-Smith

&&

.AVIATION...19/18Z TAFs...Marine stratus from Cape Blanco
northward will prevail throughout the TAF period even during
daylight hours making IFR and MVFR ceilings the rule. Surface
visibilities should remain VFR during daylight hours but will lower
to MVFR with local IFR conditions overnight. Local VFR conditions
along the coast are likely from Cape Blanco to Gold Beach due to
weak offshore flow there but marine stratus will resume from Gold
Beach southward to OR/CA border.

VFR ceilings will prevail for the rest of southern Oregon and
northern California. The only exception is smoke from the Flat
fire will have a large impact on visibility in Curry County, and it
could be thick enough to produce ceilings. Eventually the smoke will
settle in parts of Josephine County including the Chetco River
Drainage and Illinois Valley, reducing visibilities down to 1 mile
at times.  -Sargeant

&&

.MARINE...Updated 200 PM PDT Wednesday, July 19, 2023...The thermal
trough responsible for hazardous conditions and steep seas,
especially in the southern waters, will weaken tonight as an upper
level trough enters our region. This weakening, in conjunction with
minimal swell heights from the outer Pacific entering our area,
should create overall calmer seas from tomorrow afternoon through
this weekend and into early next week. -Sargeant

&&

.FIRE WEATHER....Updated 200 PM PDT Wednesday, July 19,
2023...The overall pattern will not change much for the next 10
days. We'll continue to experience hot, dry and windy conditions,
especially for the interior westside valleys with the typical
gusty afternoon and early evening breezes Thursday into the
weekend.

The thermal trough along the coast is will weaken, and move just far
enough inland where we'll see a weak to moderate onshore flow over
fire zones 619, western 620, and western 616. The net result will be
improving overnight recoveries in these areas including the Flat
Fire. However, this will also result in gusty afternoon and evening
northwest breezes, especially near and at the ridges near and over
the Flat Fire starting Thursday and could last into the weekend.

Meanwhile, unstable conditions are expected this afternoon and
evening, and Thursday afternoon near and over the Flat Fire. The
latest guidance puts a solid HAINES 5 over the Flat fire, but with
an expected increase in fire activity, we could see the HAINES
increase to a 6 both this afternoon and evening and again Thursday
afternoon and evening.

Therefore, the Red Flag Warning remains in effect for the Flat fire
for HAINES 6 conditions this afternoon into the evening, and we
upgraded the Fire Weather Watch to a Red Flag Warning for Thursday
afternoon and evening also for a HAINES 6 for the Flat Fire. Please
see the RFWMFR for more details.

The general dry and breezy winds will lead to a minor risk for
elevated fire weather conditions east of the Cascades, but winds are
expected to remain below criteria. This pattern of hot, dry, breezy,
and unstable will continue through next week. -Petrucelli

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 9 PM PDT this evening for ORZ619.

     Red Flag Warning from 1 PM to 9 PM PDT Thursday for ORZ619.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 PM PDT this
     afternoon for PZZ350-370.

     Small Craft Advisory until 5 AM PDT Thursday for PZZ356-376.

&&