763
FXUS66 KMFR 050547
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1047 PM PDT Fri Oct 4 2024

...Update the aviation section...

.AVIATION...05/06Z TAFS...Coverage of IFR and LIFR will expand
overnight. Patches are now present at the coast north of Cape
Blanco, and into the Coquille and lower Umpqua valleys. Also, a more
solid band of IFR covers southern and eastern Douglas County. This
band will gradually cover more of the Umpqua Valley overnight into
Saturday morning, through around 18Z. VFR will persist into Saturday
eveninf for other inland areas.
-DW

&&

.PREV DISCUSSION... /Issued 918 PM PDT Fri Oct 4 2024/

DISCUSSION...SW Oregon and northern California, I find myself
saying many times (especially this time of year), is the place
where fronts come to die. Now, I`m not saying today`s front didn`t
cause any weather hazards, because, as I`m sure residents in
NorCal and from the Cascades eastward can tell you, it sure was
windy out there today. Surface observations of gusts peaked in the
35-45 mph range in most areas and some exposed RAWS out over the
eastern deserts (Wagontire) topped out above 50 mph. Wind
advisories expired a little over an hour ago. But while the mid-
level winds associated with the front were strong, upper jet
support was lacking and, as such, precipitation with the front
basically fell apart as it crossed our forecast area. It was also
running into an extremely dry air mass in place, as evidenced by
humidity readings in the single digits in some places across
NorCal this afternoon. The low humidities in combination with the
strong winds led to critical fire weather (Red Flag Warning)
conditions for several hours as well. Those warnings also expired
at 8 pm. All we could muster here in Medford was some visible
clouds on the NW horizon at times and, of course, some gusty
afternoon breezes. The thin clouds did make for a nice sunset.
Roseburg didn`t get any rain, but there was a cooling cloud deck
most of the day, only allowing temperatures to briefly touch 70F.
Rainfall that did manage to make it into rain gauges was mostly in
Coos County where amounts were generally less than 0.10 of an
inch. (Charlotte Ridge RAWS was the winner with 0.17 of an inch).
Now, the front is hard to find, a shell of its former self, strung
out across NorCal this evening. Some fog and/or low clouds will
impact the coast and also portions of interior Douglas County
tonight into Saturday morning, but it will remain mostly clear
elsewhere.

Tomorrow and Sunday, high pressure will return. In areas that
were cooler today, it will warm up, and in the areas that were
warm today, it will remain warm. Temperatures will be above normal
(by about 10F). That means highs in the mid to upper 80s in the
west side valleys and in the upper 70s to low 80 east of the
Cascades. Dry weather will persist into at least Tuesday of next
week, when, you guessed it, another front will likely meet its
demise across the area. Shall I dub SW Oregon/northern California
the "fall-frontal wasteland"? Maybe next Tuesday. -Spilde

MARINE...Updated 800 PM PDT Friday, October 4, 2024...Seas are
expected to remain below advisory conditions through Wednesday.
Moderate northerly winds will develop tonight and persist through
the weekend with weak high pressure offshore and a weak thermal
trough inland. Seas will be closest to becoming steep this weekend
in the inner waters near Port Orford, and south of Pistol River.

Long period swell will arrive early Monday morning and build through
the morning, increasing surf and breaking action around bars. The
swell period will then gradually decrease, with moderate swell
dominated seas through midweek. -DW

PREV DISCUSSION... /Issued 228 PM PDT Fri Oct 4 2024/

DISCUSSION...A strong, but decaying front is pushing through the
region today. The main impact with this front is strong west to
southwest winds out ahead of it. Surface observations show wind
gusts in the 25 to 30 mph range is common across northern
California and east of the Cascades. The strongest winds so far
are gusting to 40 to 45 mph across the high terrain of Lake
County. Even in the absence of surface observations, the dust
plume coming off Summer Lake in Lake County would be enough to say
there are strong winds over there. This dust could reduce
visibilities at times along Highway 395 this afternoon. A look at
webcams in that area does show the dust being lofted into the air,
but ODOT webcam on Highway 395 doesn`t show any reductions to
visibilities at this time. It`ll be something that needs to be
monitored until the winds ease this evening. There is a Wind
Advisory in effect for portions of Lake County through this
evening, and details can be found at NPWMFR. The other concern
with these strong winds is the low relative humidities expected
this afternoon. The combination of the two will lead to critical
fire weather concerns for much of the East Side, and details can
be found in the fire weather discussion below.

Radar does show a weakening band of precipitation moving inland at
this time, but we don`t expect rain to make it much farther inland
than Roseburg. Even then, amounts are expected to be fairly light
with only a few hundreths recorded so far along the coast and into
western Douglas County. Otherwise, afternoon temperatures will trend
slightly cooler today, most notable north of the Rogue-Umpqua
Divide. For the remainder of the area, instead of high temperatures
reaching 10 to 15 degrees above normal, they will peak around 5 to
10 degrees above normal today (low 80s (upper 70s) West (East)
Side).

Today will largely be a hiccup in the overall pattern and trend of
dry conditions with seasonably cool mornings that warm up to late
summer like temperatures. High pressure quickly returns on Saturday,
and once lingering cloud cover dissipates later in the morning, dry
and warm conditions will return. It`ll be another breezy day across
the region, especially east of the Cascades, but not as strong as
today. 700 mb winds today are maxing out around 35 to 45 kt, while
700 mb winds are more along the lines of 25 to 35 mph. Winds will
trend weaker on Sunday, and above normal temperatures will continue
through at least mid-week next week. Through then, the daily weather
pattern will generally be rinse and repeat.

The next blip in the pattern comes Tuesday as a weak shortwave
trough passes through the region. There could be a weak front
associated with this trough, which would once again bring some
slight chances of light precipitation to the coast, but models are
in good agreement that much of the region will remain dry.
Temperatures will trend cooler on Tuesday, and this looks like the
start of an overall cooling trend that could continue through the
end of the week. The question comes to any precipitation chances for
the latter half of the week. Models generally agree on a trough
pattern Thursday into Saturday, but there are differences in timing
and any associated moisture. Precipitation chances have trended
downward with recent model runs, now showing around a 30-40% chance
across the region on Friday. Looking into the ensembles, confidence
is higher for coastal locations to see some rain during this time,
but that confidence decreases heading inland. The EC and it`s
ensembles are the least optimistic in terms of precipitation chances
for inland locations, with the GFS and it`s ensembles are in better
agreement. At this time, if precipitation does occur, it doesn`t
look to be much with a 30-50% chance for 0.10" over a 48 hour period
ending Saturday morning for areas west of the Cascades, and a 15-30%
chance for areas east of the Cascades. Stay tuned as details become
more clear over the coming days. /BR-y

FIRE WEATHER...Issued 200 PM Friday October 4, 2024...The main
concern today is strong winds and low relative humidity east of the
Cascades and the Red Flag Warnings for those areas remains in effect
until 8 pm pdt this evening. Surface observations are already showing
winds increasing east ofthe Cascades with a few location like Timber
Mountain, Juniper Creek and Devils Garden already hitting Red Flag
conditions due to winds and low humidity. Satellite image also shows
mountain wave cloud formation as the front pushes inland which is
typically an indicator of strong winds aloft. The stronger winds
aloft will have a good chance to reach near or at the surface this
afternoon. Precipitation, if any will be mainly confined to Fire
Zones 615, 616, and northern 617 into early this evening, otherwise
we`ll remain dry with the best chance and higher precipitation
amounts remaining north of our area.

In addition, conditions are beginning to reach Red Flag conditions in
portions of Fire Zone 622 and with still 3-4 more hours of mixing,
it`s becoming more likely Red Flag conditions will be met and a Red
Flag Warning has been issued for portions of Fire Zone 622.

Winds will drop off pretty quickly early this evening as the mixing
heights decrease and low level inversion takes over. Skies will
likely be clear and this will allow temperatures to drop off pretty
quickly given how low the surface dewpoints will be. This should
result in pretty good overnight recoveries for most locations,
especially in the valley bottoms. Meanwhile mid slopes and ridges
could experience moderate overnight recoveries.

After today, no Fire weather concerns are expected. However, on
Saturday, there is a low level jet that will move into the area
resulting in moderate winds east of the Cascades that could result
in brief periods of critical conditions in fire zones 624, 625 and
285 Saturday afternoon. Humidity`s in these areas will be similar to
today, but the winds are not expected to be as strong. As such,
we`ll headline the winds and low relative humidity for east of the
Cascades Saturday afternoon.

Dry weather is likely Saturday into at least the middle of next
week.

Looking out further into next week, there`s some evidence suggesting
the upper ridge shifting east with an upper troughing approaching
the Pac NW towards the middle of next week. The flow aloft will be
from the southwest and the operational models hint at a front
approaching our area. However, the front will be nearly parallel to
the upper flow. In this type of situation, the front will basically
will have little or no southeastward progression into our area, thus
odds are it will remain dry. There will be some cooling for the
interior, but afternoon temperatures will still be above normal.

The combination of clusters, ensemble means (ECMWF and GFS), and
operational models show more pronounced upper troughing over our
area towards the end of next week, leading to an increased chance of
precipitation and cooler temperatures. -Petrucelli

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.

CA...None.

PACIFIC COASTAL WATERS...None.

&&

$$