961
FXUS66 KMFR 242357
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
457 PM PDT Mon Jun 24 2024

.Updated AVIATION Discussion...

&&

.AVIATION...(25/00Z TAFs)...VFR conditions prevail across the region
this afternoon with gusty afternoon breezes. IFR conditions in
marine stratus are expected to return to coastal areas late this
evening and overnight, especially north of Cape Blanco and south of
Gold Beach. VFR conditions are expected to prevail through the TAF
period for inland locations. /BR-y

&&

.PREV DISCUSSION... /Issued 232 PM PDT Mon Jun 24 2024/

DISCUSSION...

Monday and Tuesday will be warm and dry, but the overall heat
risk will not climb above minor, despite being about 10 degrees
above normal; and this is due to the overnight lows cooling
efficiently.

A feature we are tracking is an area of moisture with tropical
origins near Baja. It is currently offshore near central-Cal and
is already electrified. A sign that it can support nocturnal storm
activity. This blob of moisture will make its way north and by
Tuesday night, be exiting NorCal in Modoc/Lassen County and moving
into south-central Oregon around Lake County early Wednesday
morning. This is a low confidence forecast, but with most hires
models supporting the moisture moving in this direction,
instability aloft being resolved and the implications being
concerning, we thought it was best to include it. So, a 10-20%
chance for thunderstorms was added to the forecast Tuesday night
into Wednesday morning for portions of Modoc, Lake, and Klamath
Counties. These storms are expected to be dry and if the storms
can break through the dry lower layers, most models aren`t showing
more than 0.1" of rain breaking through, which would still be
close to the formal definition of dry lightning.

The implication of the nocturnal lightning is that if it occurs
and fire starts result, a period of dry and windy conditions will
lead to critical fire weather conditions east of the Cascades.
This would provide the weather variable to support the new fire
starts spreading.

West of the Cascades though, Wednesday will offer around a 10
degree swing towards cooler temperatures as the front moves
through a the trough ushers in a cooler airmass. In Coos and
Douglas County, a chance for precip/drizzle will steadily rise up
to 20-40% by the evening as a strong marine push banks up clouds
against the mountains.

Thursday should be a fine sunny and cool day, if perhaps a bit
windier in the afternoon. The cold air moving Thursday night in
also favors temperatures nearing freezing across the northern
portions of Lake and Klamath Counties. Certainly, if you have any
cold sensitive plants or animals, you`ll want to track this part
of the forecast so you can take action.

Then this cycle repeats of a brief warmup, followed by another
weak trough and slight cooldown.

-Miles

MARINE...Updated 145 PM Monday, June 24, 2024...The thermal trough
continues today, and gusty north winds will maintain steep seas
south of Cape Blanco into early Tuesday morning, with very steep and
hazardous seas south of Pistol River through this evening. The
approach of another front then disrupts the pattern with improving
conditions tonight into early Thursday. The front is expected to
provide a deep layer of low clouds and a slight chance of showers
Wednesday night. A return of the thermal trough pattern is expected
Thursday into at least Friday night, with steep seas possible south
of Cape Blanco.

/BR-y

FIRE WEATHER...

Overall, warm (above normal) and dry conditions are forecast
through this week with only a slight break Wednesday and then
slightly more on Thursday. However, even with the cool down, we
are still expecting elevated to critical fire weather conditions
nearly every day going forward this week. Lastly, great humidity
recoveries are expected both Thurs and Fri mornings when at least
70% overnight RH is forecast for most of the area these mornings,
but afternoons still remain on the dry side.

The overlap of low RH (<20%) and breezy winds (>15mph) will be
notable tomorrow across parts Modoc, Klamath, and Lake counties
where we have flipped over the watch to a Red Flag Warning. Fuels
are of course tricky this time of year in transition to summer,
and this may be the limiting factor regarding fire weather
conditions until fuels transition over to "high". We are leaning
on fuels experts for these decisions during this transition
period, and have coordinated these headlines.

Wednesday will be another day where we get a period of stronger,
gusty WSW winds in combination with low humidity, especially east of
the Cascades. For most of the area, guidance is showing a drop in
temperature and an increase in humidity to help mitigate this
threat, but areas farther east in Lake and Modoc counties are more
susceptible. We have issued a Fire Weather Watch to account for this
threat. We will have to evaluate Siskiyou County further because
there are signs of critical fire weather conditions possible,
especially around the outskirts of Scott Valley. We will headline
this threat for now, but we may want to consider a warning for parts
of Siskiyou County on Wednesday. The one caveat for Wednesday
(and perhaps Tuesday night) is the thunderstorm potential. We will
have to watch how this upper low tracks as the moisture fetch
will be key, but right now its not the most favorable setup for
thunder with the lack of instability. There are some signs of
nocturnal thunderstorms Tuesday night into Wednesday afternoon,
but confidence is low at this time for thunder with the potential
less than 10% at this time.

-Guerrero

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from noon to 8 PM PDT Tuesday for ORZ624.

     Fire Weather Watch from Wednesday afternoon through Wednesday
     evening for ORZ624-625.

CA...Red Flag Warning from noon to 8 PM PDT Tuesday for CAZ285.

     Fire Weather Watch from Wednesday afternoon through Wednesday
     evening for CAZ285.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT this
     evening for PZZ356-376.

     Hazardous Seas Warning until 11 PM PDT this evening for PZZ356-
     376.

&&

$$