FXUS66 KMFR 080522
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1022 PM PDT Sat Sep 7 2024

Updated AVIATION Section

.DISCUSSION...Current Satellite imagery is showing some cloud
cover across much of southern Oregon and northern California. In
addition, RADAR has shown a few showers and thunderstorms this
afternoon, mainly to the north of Lake and Klamath Counties.
However, there were several plumes of smoke visible from the
radar, and the most prominent plume of smoke was from the
Firestone fire which created a Pyrocumulonimbus and lightning
strikes downwind (north of the fire) in Pendleton's area of
responsibility.

Luckily, the lightning stayed north of our area, and our Red Flag
Warning for abundant lightning will not verify. We are perfectly
happy with this. Have cancelled that red flag warning as sunset
has limited the thunderstorm activity. As the low pressure system
moves away from our area, we'll return to hot and dry conditions.
For more information about the forecast, please see the previous
discussion below. -Schaaf

&&

.AVIATION...08/06Z TAFS...Along the coast and over the marine
waters, stratus and fog will result in continued IFR/LIFR ceilings
for all areas, including North Bend for most of the TAF period.
Satellite imagery is showing the stratus pushing into the lower
Umpqua Valley near Scottsburg/Elkton late this evening. These clouds
will make a run at Roseburg around daybreak Sunday. At this point,
it's a 50/50 chance ceilings go BKN at 1500' around 13Z and last for
a few hours, but for now will just have it as SCT, since we
think it will stop short. We'll monitor how it progresses overnight.
Conditions should improve to MVFR along the coast or even break up
to VFR Sunday afternoon, but it should be short-lived as onshore
flow will bring stratus back onshore quickly around or even a little
prior to sunset.

Elsewhere, VFR conditions will continue through the TAF period.
Numerous fires are burning in the area. At this time, we don't think
they'll bring reduced visibility to the terminals, but MVFR
visibilities are possible in smoke in the immediate vicinity of the
fires. -Spilde

&&

.MARINE...Updated 830 PM Saturday, September 7, 2024...Low clouds,
areas of dense fog and even some drizzle will impact the marine
waters overnight into early Sunday morning, despite improved wind
and sea conditions. However, north winds and steep wind-driven
seas will return late Sunday morning south of Cape Blanco, then
across most of the southern Oregon coastal waters Sunday night and
Monday. Conditions improve again Tuesday night into Wednesday as
weak low pressure moves into the region. North winds are then
expected to return late in the week. -BPN/Spilde


&&

.PREV DISCUSSION... /Issued 639 PM PDT Sat Sep 7 2024/

DISCUSSION...Satellite shows sunshine across areas east of the
Cascades with cumulus moving northward in Siskiyou County and from
the Cascades west. There is also marine stratus that is reaching
into parts of Coos County. The HRRR smoke model is taking out the
smoke in Jackson County sooner than anticipated for the evening,
so added this to more of the area this afternoon.

Radar shows that the showers in northeastern Lake County have moved
farther north. A 15% probability of thunderstorms will be present
with gusty outflow winds possible in the strongest storms with
expected DCAPEs near 1,000 J/kg this afternoon and evening.

Temperatures will still be overall 5-10 degrees warmer than normal
through the rest of the weekend and Monday. After, a trough begins
to reach the Pacific Northwest and near normal temperatures will
return. This means by Tuesday afternoon 80s are in the forecast, and
it will drop from there with 70s possible for highs west of the
Cascades and 60s east Wednesday afternoon.

The troughing will bring the next rain chance to the area later
Tuesday night into Wednesday starting near the coast. Although the
latest model runs are in better agreement that there will be rain
Wednesday, there still are still unknowns on timing and amounts. The
probability to see 0.25" of rain between 5 AM Wednesday- 5 AM
Thursday has increased west of the Cascades to 40-60%. The Euro is
bringing the system in earlier and is forecasting for the low to
keep PoP chances through Thursday whereas the GFS finishes sooner.
For now, have shown a drying trend through the day Thursday with the
last spots in Douglas and Klamath counties to become dry. For
thunderstorms, Tuesday night's computed CAPEs are nearing 150-300
J/kg near the Coos County coast, and with the west to east movement
of the rain, added a probability of thunder ~10% there. Computed
CAPEs also show 250-500 J/kg Wednesday afternoon east of the
Cascades, so have added a 5-15% probability of thunder for that
area. -Hermansen

AVIATION...08/00Z TAFS...Along the coast and over the marine
waters, stratus and fog will result in continued IFR/LIFR ceilings
for all areas, including North Bend for most of the TAF period.
MVFR/IFR conditions are expected to return to the coastal valleys
tonight as well. Conditions should improve a bit to MVFR along the
coast or even break up to VFR Sunday afternoon, but it should be
short-lived as onshore flow will bring stratus back onshore quickly
around sunset.

Elsewhere, VFR conditions will continue through the TAF period.
Stratus will make a run at Roseburg around daybreak Sunday. At this
point, it's a 50/50 chance ceilings go BKN at 1500' around 13Z and
last for a few hours, but for now will just have it as SCT, since we
think it will stop short. We'll monitor how it progresses overnight.
Numerous fires are burning in the area. We don't think they'll bring
reduced visibility to the terminals, but MVFR visibilities are
possible in smoke in the immediate vicinity of the fires. -Spilde

FIRE WEATHER...Issued 200 PM Saturday, September 7, 2024...Hot, dry,
and unstable conditions will continue into this weekend. Isolated
to scattered thunderstorms remain a concern for today. Additionally,
gusty winds and low humidities may result in brief or local critical
conditions for areas in the Scott and Shasta Valleys and east of the
Cascades.

Current models show the upper level disturbance along southwest
Oregon  coast today, gradually moving inland tonight and east on
Sunday. This is allowing for isolated to scattered showers and
thunderstorms to develop over eastern portions of the area,
including Lake and northern Klamath Counties. This is also a low
(15%) chance for storms into eastern Douglas County this
afternoon/evening. Storms are expect to be mainly isolated, except
for a potential for scattered storms in northern Klamath and Lake
counties. Thunderstorms may have little rain with them and gusty
outflows up to 40 to 45 mph are possible nears storms.

Gusty south to southwest winds and dry humidities are also expected
this afternoon and early evening, for the Scott and Shasta Valleys
as well as for some areas east of the Cascades into southeastern
fire weather zone 624, southern 625 and eastern 285. Conditions may
near critical RH/wind levels in these areas. A headline is in the
forecast for these potential conditions.

Tonight, winds lower but expect areas of moderate recoveries over
the ridges, mainly in southeast 625, southern 625 and northern
California zones (280-285).

Sunday and Monday, temperatures are expected to trend less warm as
another upper trough approaches the region. However, humidities will
remain dry. On Monday, there is also a potential for some breezy
afternoon conditions in Modoc and Lake counties. The trough and
associated front will then move through Tuesday and Wednesday,
resulting in chances for light rain showers and isolated
thunderstorms, cooler temperatures, and a potential for breezy to
gusty winds. Confidence is low on the strength of this trough and
how much rain will arrive, but there is a chance (20-40%) for
wetting rainfall (0.25"+) on Wednesday for areas from the Cascades
west. The thunderstorm potential is current low (10-20%) and is
focused on Wednesday for areas east of the Cascades, mainly in Lake
and Modoc counties.

-CC

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Small Craft Advisory from 2 AM Monday to 11 AM PDT Tuesday for
     ORZ021.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory from 2 AM Monday to 11
     AM PDT Tuesday for PZZ350-370.

     Small Craft Advisory from 11 AM Sunday to 11 AM PDT Tuesday for
     PZZ356-376.

&&

$$