Damaging Wind in Oregon, September 6, 2024

Area Forecast Discussion
National Weather Service Medford OR
528 PM PDT Fri Sep 6 2024

Updated AVIATION Section

.DISCUSSION...Geocolor shows mid and high clouds moving northward near
and west of the Cascades and a haze is present across southern
Oregon and Northern California from wildfires. The marine stratus
is hugging the coast and is in Coos Bay, and this will continue
through tomorrow morning.

Temperatures in the 80s will turn to 90s and triple digits later
this afternoon. A Heat Advisory is in effect for this heat, and
there is high confidence for cooler temperatures tomorrow so the
Heat Advisory will expire this evening. Temperatures are still on
track to see lows in the 50s east of the Cascades with 60s and upper
50s west for the next few mornings.

Ridging is moving east today while an area of low pressure off the
coast moves westward. Isolated to scattered thunderstorms will be
possible in the afternoon. Most of the thunderstorm chances are for
the Cascades and Klamath County. DCAPEs across southern Oregon have
a high probability (80-100%) of reaching over 1,500 J/kg, and a
range of 1,000-1,500 J/kg in forecast soundings favor gusty outflow
winds in the strongest cells. Although storms could bring locally
heavier amounts, overall a tenth of an inch or less is forecast
tomorrow.

Looking into the weekend afternoon temperatures, they should
gradually cool to be 5-10 degrees above normal. Lows will overall be
in the 50s/low 60s west side and 40s/low 50s east side. The next
timeframe to watch will be mid-week with the next trough moving in.
This will not only cool temperatures to 5-10 degrees cooler than
normal, but it will also bring a return of rain chances. The latest
ensembles are supporting a 20-30% prob to see a quarter of an inch
of rain west of the Cascades through Wednesday. There is still a lot
of variability in the temperatures and rain chances with this
system. Trends are leaning towards a more showery pattern rather
than stratiform rain which could introduce thunder potential next
week. This will need to be monitored. -Hermansen

&&

.AVIATION...07/00Z TAFS...Isolated thunderstorms are developing
in an arc from near Willamette Pass southward to Winter Rim and
in the vicinity of the Warner Mtns in southern Lake and eastern
Modoc counties this evening. Gusty erratic wind gusts can be
expected in and near and thunderstorms. These will continue to
lift northward and eventually weaken/dissipate with the loss of
instability late this evening.

Wildfire smoke will continue to be present, limiting visibility in
the immediate vicinity of the fires, but mostly just producing haze
elsehwere.

Along the coast and over the marine waters, stratus and fog will
bring IFR/LIFR ceilings and fog tonight into Saturday morning for
all locations, including North Bend. These will push into the
lower Umpqua and Coquille valleys by morning, but will stay north
and west of Roseburg. Ceilings will lift a bit at North Bend on
Saturday (to MVFR), but onshore flow will probably keep them from
breaking out completely.

Medford/Klamath Falls will remain VFR despite some mid and high
level clouds over the next 24 hours. -Spilde

&&

.MARINE...Updated 200 PM Friday, September 6, 2024...The main update
was to extend the small craft advisory for steep seas in the outer
waters into Saturday evening, with a combination of moderate west-
northwest swell, and moderate north winds that will not quite reach
advisory strength.

Moderate north winds will continue steep seas in the outer waters,
beyond 10 nm, into Saturday evening. Steep seas could also briefly
reach the inner waters on Saturday. Winds will decrease and seas
will subside Saturday night into early Monday. A brief increase in
wind dominated seas is likely on Monday. There are signs of wind-
built steep seas developing near the end of next week in waters
south of Cape Blanco with no expectation of anything more intense.
-TAD/DW

&&

.FIRE WEATHER...Issued 200 PM Friday September 6, 2024...Hot, dry,
and unstable conditions will continue into this weekend. Isolated
dry thunderstorms remain a concern for today. Additionally, gusty
winds and low humidities may result in brief or local critical
candidness for areas in the Scott and Shasta Valleys and east of
the Cascades.

For this afternoon and evening, a primary concern is  the potential
for dry thunderstorms with gusty outflow winds. An upper level
disturbance off  northwest California and bringing limited moisture
into the region. Satellite imagery from early this afternoon shows
cumulus developing over the Cascades and to the east. Moisture
and instabily will result in a chance (15-25%) for thunderstorms for
many inland areas, mainly from the Southern Oregon Cascades eastward
and into Modoc county.  Storms are expected to develop this
afternoon and evening, then lift north overnight. Confidence remains
highest for storms developing in the Cascades north of Lake of the
Woods, in eastern Umpqua forest, in Klamath county north and east of
Chiloquin and in northwest Lake County. There is also a slight
chance for storms farther south and southwest. This includes in
northwest Jackson County and Modoc County. Any storms that develop
will likely be dry with little or no rainfall and there is potential
for gusty outflows (up to 50 mph). A red flag warning (RFWMFR)
remains in effect for eastern fire weather zone 617, fire weather
zone 623 (north of Lake of the Woods), fire weather zone 624 (north
and east of Chiloquin) and northwestern fire weather zone 625 due to
isolated or scattered dry thunderstorms.

Additionally, breezy to gusty south winds are expected this
afternoon and evening for areas east of the Cascades and in the
Shasta and Scott Valleys. Local or brief critical RH/wind
conditions are possible in the Scott and Shasta valleys today. The
upper level disturbance gradually moves inland Saturday and
expect low (5-10%) chances for thunderstorms over the south-
central Oregon Cascades. Gusty south to southwest winds and dry
humidities are expected again on Saturday 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.

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 (10-20%) 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...Heat Advisory until 10 PM PDT this evening for ORZ021-023-024-
     026.

     Red Flag Warning until 9 PM PDT this evening for ORZ617-623>625.

CA...Heat Advisory until 10 PM PDT this evening for CAZ080.

PACIFIC COASTAL WATERS...Small Craft Advisory until 8 PM PDT Saturday
     for PZZ370-376.

&&