NWS Medford, OR wrote its last area forecast discussion before the first event at Sep 5, 1:21 PM PST, 39 minutes earlier.
Area forecast discussion, Sep 5, 1:21 PM PST, 39 minutes before
Area Forecast Discussion
National Weather Service Medford OR
221 PM PDT Thu Sep 5 2024
.DISCUSSION...Geocolor shows mostly clear skies, although a haze
is present across southern Oregon and Northern California from
wildfires. The marine stratus is starting to extend northward into
Gold Beach and Port Orford and is expected to return to Coos
County into Coos Bay later this evening. High clouds are starting
to form in Siskiyou County and will be moving northward into
Klamath County this afternoon.
With ridging over the Pacific Northwest, today's afternoon
temperatures are going to be the warmest of the forecast period.
Temperatures are already in the 90s in west side valleys and will
continue warming into the triple digits, and a Heat Advisory is in
effect for these areas due to the heat this afternoon. The record
high at Medford is in jeopardy because the record is 103 from 1975
and the forecast is 105.
With only a 25-35% probability to see low temperatures reach 45 or
greater to the northeast of Crater Lake into Chemult the next few
nights, have lowered temperatures slightly. Minor changes were also
made to the high temperatures as the widespread smoke will make it
harder to see as much warming in the coming days. Even with these
tweaks there is still enough confidence to see dangerous heat in
west side valleys, so the heat advisory continues through tomorrow
afternoon.
An area of low pressure will be moving in tomorrow and isolated to
scattered thunderstorms will be possible in the afternoon. Most of
the thunderstorm chances would be 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 1,500-2,000 J/kg
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 temperatures should gradually cool to
only be 5- 10 degrees above normal. Lows will overall be in the
50s/low 60s west side and 40s 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 20-40% prob to see a quarter of an inch of rain
west of the Cascades through Wednesday. The GFS has a more
southward movement, meaning more spots in Northern California
could see rain, whereas the Euro is hugging the Oregon/California
line and keeps more of the rain north of the border. This is too
far out and models are not in agreement with the placement of the
low, so this will need to be monitored. -Hermansen
&&
.AVIATION...09/05/24...18Z TAFS...VFR prevails this morning, except
for patchy lingering LIFR at the coast south of Cape Blanco. This
marine stratus will gradually erode through the afternoon. This
evening, LIFR/IFR will return to the coast and persist into Friday
morning. Improvement will be slower than today, but is still
expected during Friday afternoon. Inland, aside from patchy smoke
and haze from wildfires, it will remain VFR through Friday morning.
Instability will develop Friday afternoon with isolated
thunderstorms possible for eastern Douglas and northeast Jackson
counties, north of Lake of the Woods, and eastward across northern
Klamath and Lake counties. -DW
&&
.MARINE...Updated 200 PM Thursday, September 5, 2024...There
will be mostly light north winds today with a moderate west-
northwest swell. North winds increase a bit Friday, with steep seas
expected to develop Friday afternoon and then continue through
Saturday. A small craft advisory has been added over the outer
waters (beyond 10 NM from shore). Steep seas could also reach the
inner waters Friday night, but confidence in this occurring is a bit
lower, so will allow future shifts to assess this potential. North
winds persist the remainder of the weekend, but should be lighter
with lower seas.
-Spilde/Hermansen
&&
.FIRE WEATHER...Issued 200 PM Thursday September 5, 2024...
Hot, dry, and unstable conditions will continue into this weekend.
Moderate to poor overnight recoveries are expected over the ridges
tonight and Friday morning. A headline is in place for these
conditions. This afternoon/evening winds are expected to be below
critical levels. An exception may be in the southern Shasta Valley
and southern Scott Valley, where a brief period of gusty southerly
wind and critically dry humidities are possible this
afternoon/evening.
On Friday, the concern shifts to thunderstorms. An upper level
disturbance will approach northwest California and send limited
moisture into the region. This will bring a chance (15-30%) for
thunderstorms for many inland areas. Storms are expected to develop
mainly in the afternoon and evening, then lift north overnight.
However, cannot rule out an isolated storm or two in the late
morning over the Cascades. Friday afternoon and evening, confidence
is 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 further south and southwest. This includes
in northwest Jackson County, far southern Josephine County, western
and northeast Siskiyou County and Modoc County. 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) is 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, on Friday, breezy to
gusty south winds are expected in the afternoon and evening for
areas east of the Cascades and in the Shasta Valley. This
disturbance will gradually move inland Saturday and expect low (5-
10%) chances for thunderstorms over the south-central Oregon
Cascades.
Sunday and Monday, temperature are expected to trend less warm as an
upper trough approaches. This trough and associated front will then
move into the region Tuesday and Wednesday, resulting in chances for
rain, 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. Additionally, we are monitoring for any potential
of embedded thunderstorms. We will continue to update as details
become available. -CC
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory until 10 PM PDT Friday for ORZ021-023-024-026.
Red Flag Warning from 1 PM to 9 PM PDT Friday for ORZ617-
623>625.
CA...Heat Advisory until 10 PM PDT Friday for CAZ080.
PACIFIC COASTAL WATERS...Small Craft Advisory from 11 AM Friday to 11
AM PDT Saturday for PZZ370-376.
&&