NWS Medford, OR wrote its last area forecast discussion before the first event at Sep 2, 7:59 AM PST, 3 hours 50 minutes earlier.
Area forecast discussion, Sep 2, 7:59 AM PST, 3 hours 50 minutes before
Area Forecast Discussion
National Weather Service Medford OR
859 AM PDT Fri Sep 2 2022
.SHORT TERM...The forecast is on track today with warm, dry and
windy conditions expected ahead of an upper trough. The main
concerns are with gusty winds and low humidities, resulting in
increased fire danger. A red flag warning remains in effect for
portions of Josephine, eastern Douglas, Jackson, Siskiyou,
Klamath, Lake and Modoc Counties today.
Smoke will continue to affect areas west of the Southern Oregon
Cascades today, mainly due to the smoke from the Rum Creek Fire.
However, with increased winds from the west, expect many areas
west of the Southern Oregon Cascades to see a decrease in smoke
late today into Saturday morning and this could result in an
improvement in air quality. However, a lot will depend on how
these winds impact fire activity and resultant additional smoke
output. An air quality alert (AQAMFR) remains in effect for
Curry, Josephine and Jackson Counties until further notice. Other
areas in far western Siskiyou County may also see a decrease in
smoke but expect haze and smoke to affect central and eastern
Siskiyou. Meanwhile from the Cascades eastward, especially across
Klamath County and northern Lake County, expect to see a increase
in haze along with some areas of smoke. Most notable is that there
has been an increase in fire activity overnight on the Cedar
Creek Fire in far eastern Lane County and models indicate smoke
from this fire will move east to southeast today and Saturday and
may affect portions of northern Klamath and Lake County.
Along the coast, fog and low clouds are present this morning.
Expect low clouds to persist today into Saturday morning with
moist, onshore flow. Also expect a slight chance for light rain
or drizzle along the coast in the morning and overnight hours
through Saturday.
&&
.AVIATION...02/12Z TAFs...Along the coast and into the coastal
valleys, IFR to LIFR ceilings will continue early this morning.
Ceilings will gradually lift later this morning to mainly IFR with
local MVFR as a weak cold front moves across. Clouds will thicken
this evening with IFR expected and patchy drizzle or light showers
possible into early Saturday morning.
Farther inland, lower visibilities due to smoke from active fires
remains the main hazard. Visibilities will likely decrease in
southwest Oregon into sunrise with patchy MVFR. Gusty low level
westerly winds in southwest Oregon this afternoon and early evening
will greatly aid mixing with improved visibilities, although a
broader area of haze/smoke aloft will persist over southwest Oregon
and expand across Siskiyou County and the Cascades into Klamath
County. Otherwise, it will be VFR into this evening. During the
evening, mainly MVFR stratus with patchy IFR will spread into the
Camas Valley and Umpqua Valley, including Roseburg. By early
Saturday morning, patchy MVFR is also expected to make it over the
Umpqua Divide into Josephine County, including the Rum Creek Fire.
-DW
&&
.MARINE...Updated 230 AM PDT Friday 02 September 2022...
Light winds and seas are expected to prevail into Saturday morning.
A thermal trough is expected to develop Saturday afternoon with
winds increasing near Brookings. The thermal trough will strengthen
along the coast Sunday into Monday with increasing northerly winds,
and seas that may become steep to very steep. Winds will be
strongest south of Cape Blanco. The outlook is for the thermal
trough to push farther inland Tuesday into Wednesday with winds
weakening slightly. -DW
&&
.PREV DISCUSSION... /Issued 414 AM PDT Fri Sep 2 2022/
DISCUSSION...A strong upper ridge is centered over the Great
Basin this morning with an upper trough offshore out around 135W.
This puts our forecast area in a broad south to southwest flow
aloft. The upper ridge will hang on east of the Cascades today, so
it will get quite hot there again this afternoon. Strengthening
surface pressure gradients as the upper trough offshore approaches
the coast will lead to some gusty winds across a good portion of
the forecast area this afternoon/evening. Given the very dry air
mass in advance of this trough, critical fire weather conditions
are expected today due to the combination of the winds and very
low relative humidity. We have Red Flag warnings up for much of
the area, details of which can be viewed at RFWMFR. Please
continue to heed all fire restrictions today to minimize risk of
new fire starts. One less spark, one less fire.
It'll be sunny where wildfire smoke isn't present, but much of
the Rogue/Illinois/Applegate valleys and also portions of Douglas
County will continue to have smoke impacts with moderate to
unhealthy air quality. The air quality product issued by Oregon
DEQ can be viewed at AQAMFR. Winds are likely to push out a good
deal of the mid and upper level smoke late this afternoon through
tonight and this could result in an improvement in air quality.
Of course, a lot will depend on how these winds impact fire
activity and resultant additional smoke output. We'll be up around
100F here in Medford today.
The upper trough itself does not have much moisture associated
with it. CAMs have been showing some radar reflectivity
developing over the far east side late tonight/Saturday morning,
but surface conditions remain extremely dry, so the likelihood of
any precipitation reaching the ground over there is quite small.
We won't be surprised to see some echoes on radar early Saturday
morning, but most of this will likely be virga.
Most of the area will cool down by several degrees on Saturday
with a marine push into the west side late tonight and into
Saturday morning. Areas of fog and perhaps even some light
rain/drizzle are expected along the coast. Clouds will push into
the Umpqua Basin, but moisture probably won't be deep enough to
spill much over into the Rogue. Could be some clouds, but more
certain is an uptick in humidity. Clouds eventually break for all
but the coast Saturday afternoon. A high of 90F here in Medford
will feel "cooler" than it has been, still a bit above normal
though for this time of year. East side areas will also be cooler,
but gusty afternoon winds (not as windy as today) will continue
along with low humidity. For this reason, we have added a fire
weather watch to portions of Modoc County. Overall, winds will
ease Sunday into early next week, but we'll maintain a dry
forecast with no thunderstorms in sight. It remain above normal
with highs generally in the low to mid 90s here in Medford
creeping back up toward 100F by Tuesday.
The next upper trough will likely bring another round of strong,
gusty winds and low relative humidity around the middle of next
week. So, be on the lookout for that. This should be followed by
another cool down with NBM MaxTs next Thursday showing 84F here in
Medford. -Spilde
FIRE WEATHER...Updated 340 AM PDT Friday 2 September 2022...A dry
cold front will move onshore today. The main concern will be
strong afternoon and evening winds in most of Siskiyou county, the
Cascades, all of the east side, as well as most of Jackson and
Josephine counties including the Rum Creek fire. This, combined
with very low relative humidities, will create Red Flag conditions
across much of the area with Red Flag Warnings in effect. In the
higher elevations of the far east side gusty ridge winds could
continue through the overnight hours, occasionally dropping to
lower elevations. A marine push is expected behind the front, and
thus higher humidities and improved recoveries are expected west
of the Cascades. Temperatures will decrease a few degrees on the
west side Saturday. However, it will remain hot and dry east of
the Cascades and over northern California. Winds won't be as
strong as they are today, but still strong enough with low enough
humidity for a fire weather watch in portions of Modoc County.
This has been added with the morning forecast. We'll remain above
normal into next week with temperatures trending upward again,
especially toward Tuesday. The next upper trough will then
approach the area resulting in another round of strong, gusty
winds and low rh. This is most likely Tuesday into Wednesday.
-Spilde
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 11 PM PDT this evening for ORZ617-620>625.
CA...Red Flag Warning until 11 PM PDT this evening for CAZ280>282-284-
285.
Fire Weather Watch from Saturday afternoon through Saturday
evening for CAZ285.
Pacific Coastal Waters...None.
&&
CC/CC/CC