082
FXUS66 KMFR 151129
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
429 AM PDT Mon Jul 15 2024

.DISCUSSION...

Just a few echos on the radar scope this morning in Modoc county
as some high based showers move through that area this morning.
Not a whole lot has change over the last few days as plenty of mid
level moisture remains planted over southern Oregon and northern
California and an upper level low remains situated to our south
west.

The one thing that was notable this morning was how warm
temperatures were around midnight and the expansive cloud cover
over the forecast area. With temperatures warming up just a tad,
we felt it appropriate to issue a heat advisory. The NWS HeatRisk
algorithm us picking up on spots of major heat risk in the Rogue
and Illinois Valleys today and Tuesday. This is likely due to the
warmer low temperatures in the area and the heat lasting for
about 48 hours. Temperatures trend a few degrees lower by
Wednesday and that will lower the heat risk in the region.

Thunderstorms remain in the forecast today as some mid level
moisture persists. High resolution guidance is most excited about
western Siskiyou County, although an isolated storm could pop up
in Lake County later this afternoon as the HisRes ARW is
forecasting some potential instability and simulated reflectivity
in that area. Otherwise, nothing too much of a concern except for
the potential for new fires starts because of the storms.

Finally this upper level low sitting off the California coast will
eject towards the north on Tuesday. We`ll see an increase in
southerly winds across the forecast area with smoke plumes from
active fires traveling almost due north based on the upper level
winds. The upper level wave will become negatively tilted, which
usually implies a little more energy and lift ahead of the wave.
One can see models parameterizing convection Tuesday afternoon in
the northern sections of our forecast area in northern
Lake/Klamath and Douglas Counties.

Potential instability isn`t all that great looking at forecasting
soundings, although CAPE values are high enough to support
thunderstorms. Most of the activity will occur to our north
Tuesday night as the wave ejects northwards.

By Wednesday, temperatures trend a few degrees lower with some
weaker onshore flow developing along our coast. Even with this
relatively cooler flow, the westerly flow won`t be enough to
bring Medford some below normal high temperatures this month,
something that has remained elusive all month.

Towards the end of the week, another short wave will probably
swing through southern Oregon and northern California. The end
result will be another quick round of thunderstorms sometime
around Saturday or Sunday.

-Smith

&&

.AVIATION...15/06Z TAFS...VFR prevails over inland areas late this
evening after convective activity from earlier this evening has
waned. We can`t completely rule out an isolated cell popping up here
or there in SE sections overnight, but the probability is 15% or
less.

Meanwhile, coastal IFR/LIFR marine stratus/fog is present
north of Cape Blanco this evening, including at North Bend with
patchy IFR/LIFR near Brookings. Expect the lower conditions in the
north to prevail through the overnight into Monday morning, while
areas of stratus/fog fill more coastal locations south of Gold
Beach. All lower conditions peel back to the beaches again between
16-18Z Monday with gusty north winds 25kt developing Monday
afternoon.

Expect another round of isolated to scattered thunderstorms Monday
afternoon/evening in the same general areas and with the same
weather risks as today (cloud to ground lightning and outflow
winds). However, cells could reach farther to the NW into portions
of Jackson/Josephine counties, which may graze portions of the Rogue
Valley.

Smoke from the Shelly fire in western Siskiyou County could bring
visibility reductions in the immediate vicinity of the fire with
MVFR visibility 15-25 miles away, especially to the NE (toward
Montague) as S-SW winds carry the main plume in that direction.
-Spilde

&&

.MARINE...Updated 230 AM Monday, July 15, 2024...Breezy north
winds will continue over most of the waters today and tonight with
steep, choppy seas. These will gradually diminish as the thermal
trough weakens Tuesday with continued light winds and seas through
Thursday. The thermal trough will restrengthen Friday into the
weekend with possible advisory strength northerly winds and steep
seas. -Spilde/CC

&&

.FIRE WEATHER...Issued 300 PM Sunday July 14, 2024...Thunderstorm
potential remains the focus of the forecast efforts through at
least Tuesday. Strong high pressure will linger over the Great
Basin region into next week and a weak low pressure will move
northward just offshore of the California coast. This is a pretty
classic thunderstorm pattern for this area as the flow turns more
southerly and moist unstable air moves into the region.

As we head into Monday, storms look more isolated east of the
Cascades compared to today while the threat for areas west of the
Cascades has increased. We`ve decided to cancel the watch for FWZs
285/284/282 and upgrade FWZ 280/281 while also adding in FWZ
621/620/622. High resolution convection models are showing some
storms moving north from western Siskiyou County into Jackson and
Josephine Counties tomorrow afternoon. There is some concern for
nocturnal convection Monday night into Tuesday as low pressure
starts to move closer to the region. Confidence is rarely high for
these scenarios as models just don`t handle elevated convection
well. However, pattern recognition raises some concern for overnight
thunderstorms, potentially even West Side activity Monday night. Due
to low confidence, have left the mention of thunderstorms out of the
forecast for now, but it should be noted that the chance is not
zero.

For Tuesday, moisture is shifting northward and thunderstorm
activity will shift northward as well. The best chances for Tuesday
look to be across northern areas, but timing will be key as the
trough gets closer to the region. We`ll be in a bit of transition
pattern as drier air moves up from the south. The trough will be
taking on a negatively tilted orientation which is a common wind
maker pattern for us well. Strong gusty south winds are possible
across northern California and this could combine with low daytime
RHs to result in near critical to critical fire weather conditions.
for Tuesday afternoon. This could potentially include the Rogue
Valley, but confidence in thunderstorm potential limits confidence
in the strong winds/low RH potential as well.

Tuesday night into Wednesday, low pressure finally swings through
and out of our region. Given the negative tilt of the trough, it
could kick off some nocturnal storms again, but it looks more like a
situation where storms develop along the Douglas/Lane County border
and then moves north out of our area. Moisture looks to be well
north and east of the region on Wednesday, so thunderstorm chances
drop out of the forecast after Wednesday afternoon. /BR-y


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from 11 AM this morning to 9 PM PDT this
     evening for ORZ620>622.

     Heat Advisory until 8 PM PDT Tuesday for ORZ024-026.

CA...Red Flag Warning from 11 AM this morning to 9 PM PDT this
     evening for CAZ280-281.

     Fire Weather Watch from Tuesday afternoon through Tuesday
     evening for CAZ281.

PACIFIC COASTAL WATERS...Small Craft Advisory until 2 AM PDT Tuesday
     for PZZ350-356-370-376.

&&

$$