Wildfire in Oregon, July 22 to 31, 2023

Area Forecast Discussion
National Weather Service Medford OR
1110 AM PDT Sat Jul 22 2023

.Updated Aviation Discussion.

.DISCUSSION...The latest visible image shows marine stratus along
the coast and Coquille Basin dissipating quickly and it should
clear out in these areas within the hour. However the marine
stratus from about Pistol River south is expected to persist
through the morning, then clearing out in the afternoon.

Areas of smoke exist near and around the Flat Fire with hazy
conditions from the illinois Valley northeast to Union Creek.
However, it's showing signs of dissipating.

Adjustments were made to the forecast to add some detail to the
sky cover and location of smoke and haze, otherwise the forecast
is on track. -Petrucelli

&&

.AVIATION...22/18Z TAFs...Marine stratus has burned off along the
coast, with VFR conditions lasting through 0z. The marine stratus
will likely return along the coast, north of Cape Blanco and from
about Pistol River south with IFR ceilings along with reduced
visibility, including at North Bend.

Inland, VFR conditions will continue through the TAF period. The
exception will be near and south of the Flat Fire where visibilities
could be restricted due to the concentration of smoke. -Petrucelli

&&

.MARINE...Updated 830 AM PDT Saturday, July 22, 2023...A thermal
trough will persist near shore. The thermal trough will be of
moderate intensity, with winds remaining strongest south of Cape
Blanco. This thermal trough will dissipate Sunday night as a weak
upper level trough moves over the waters. A stronger upper trough
will move into the waters Monday and will bring intermittent light
showers mainly north of Cape Blanco late Monday morning into Monday
evening. Wind should be from the south and seas for all areas are
forecast to be below advisory criteria. A thermal trough returns on
Tuesday. -Miles/Petrucelli

&&

.PREV DISCUSSION... /Issued 502 AM PDT Sat Jul 22 2023/

..Updated AVIATION discussion...

DISCUSSION...Going into the weekend, an upper level trough will
continue to influence conditions across northern California and
southern Oregon. This pattern will continue to keep any active
weather away from the area, resulting in clear skies and above
seasonal temperatures through Saturday and Sunday. Coastal areas
will see temperatures in the 70s today, while west side valleys
and northern California counties will be in the mid to high 90s.
Lake and Klamath counties will be in the low to mid 90s. Triple
digit temperatures are not generally expected, with Medford
having a 20% chance of seeing 100 degrees today and a 10% chance
Sunday.

With the ridging pattern remaining in place, smoke from the Flat
Fire will continue to head in two directions. Lower level northerly
winds will push smoke along the coast and higher level southwest
flow will push smoke to the northeast. Coastal areas south of Port
Orford and inland valleys (excluding the Umpqua Valley) may see
some smoke through the day, but HRRR guidance is not showing any
severe accumulation. The combination of warm temperatures and
possibility of decreased air quality is worth considering,
especially for vulnerable individuals.

On Sunday evening, a low pressure system over the Gulf of Alaska
will start to move eastward, moving the upper ridge to the east as
well. With a trough moving over the area, temperatures will drop
down to near seasonal norms. Widespread precipitation is not
expected, but there's a slight (15-25%) chance for coastal areas
north of Cape Blanco to see some light rain216 showers Monday
evening. A very slight (5%) chance for thunderstorms over northern
California and east of the Cascades is also present Sunday and
Monday evening. While not a significant percentage, any increase in
thunderstorm chances is notable.

Looking at Tuesday and beyond, upper troughing looks to remain as
the guiding pattern. Temperatures are expected to remain at seasonal
levels. Ensemble guidance is generally against precipitation through
the rest of next week, and slight thunderstorm chances look to
return across the east side in the evenings. -TAD

&&

FIRE WEATHER...Updated 110 AM PDT Saturday, July 22, 2023...We are
still looking at a dry end to the month with no precipitation in the
forecast for the foreseeable future. The one caveat is Monday/Monday
night when showers/thunderstorms may pass just to the north of the
forecast area. Overall, the general theme going forward is hot, dry,
and breezy afternoon/early evening winds.

Only slight fluctuations in the thermal trough are forecast through
the weekend and into early next week, and this should allow for
onshore flow (west winds) each afternoon in addition to breezy winds
in the afternoon and early evening. The onshore flow should help
moderate RH values slightly, especially into the coastal valleys and
Umpqua. However, we are generally expecting RH values which could
yield elevated fire weather conditions for a good chunk of the area
in the afternoons, especially east of the Cascades where values may
actually be in/close to critical thresholds (FWZ-624, especially).
For westside valleys, winds will be at critical speeds during the
afternoon, while humidities are currently forecast to remain in the
upper teens. The key for us going forward is pinpointing those days
when critical values do overlap. Current thinking/analysis suggest
Sunday could result in isolated Red Flag conditions east of the
Cascades. Monday, Red Flag conditions are forecast to be more
widespread east of the Cascades.

-Guerrero/Miles

&&

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

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 2 PM PDT Sunday
     for PZZ356-376.

&&