134
FXUS66 KMFR 250537
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1037 PM PDT Mon Jun 24 2024

.UPDATE...Updated the aviation section.

&&

.AVIATION (25/06Z TAFs)...VFR conditions prevail across the region
this evening. IFR conditions in marine stratus are expected to
return to coastal areas overnight into early Tuesday morning,
especially north of Cape Blanco and south of Gold Beach. These low
clouds are expected to dissipate after sunrise, with VFR by 18Z.

VFR conditions are expected to prevail through the TAF period for
inland locations, with breezy afternoon and evening westerly winds.
Winds will be strongest east of the Cascades with gusts up to 25 kt.
/DW

&&

.MARINE...Updated 800 PM Monday, June 24, 2024...The thermal
trough continues with steep seas for much of the waters south of
Cape Blanco into Tuesday morning, except very steep and hazardous
seas south of Pistol River through this evening. The approach of
another front then disrupts the pattern with improving conditions
Tuesday into early Thursday.

The front is expected to provide a deep layer of low clouds and a
chance of showers Wednesday night. A return of the thermal trough
pattern is expected Thursday into Friday night, with steep seas
possible south of Cape Blanco. Another front and deep marine layer
are likely to disrupt the pattern, with improved conditions for the
weekend.
/DW

&&

.PREV DISCUSSION... /Issued 840 PM PDT Mon Jun 24 2024/

DISCUSSION...The forecast remains on track for tonight. Clear
skies and stable weather continue over northern California and
southern Oregon. Temperatures west of the Cascades will warm by
about 5 degrees with little change to the east during the day
Tuesday.

Please see the previous discussion for more details about the
short- and long-term forecast. -TAD


FIRE WEATHER...Updated 200 PM Monday, June 24, 2024...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

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

&&

.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 AM PDT
     Tuesday morning for PZZ356-376.

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

&&

$$