O Brien, Oregon Weather Forecast Discussion

431
FXUS66 KMFR 161130
AFDMFR
Area Forecast Discussion
National Weather Service Medford OR
430 AM PDT Tue Sep 16 2025
...New Aviation Section...
.AVIATION (12Z TAFs)...
Expecting a southerly surge of low clouds to expand northward
which may impact North Bend later today through tonight into
tomorrow morning. This could (~60% chance) bring IFR/LIFR
conditions to the terminal for low ceilings. Inland, expecting
quite the opposite with plenty of sunshine expected through this
cycle resulting in widespread VFR conditions.
-Guerrero
&&
.PREV DISCUSSION... /Issued 329 AM PDT Tue Sep 16 2025/
DISCUSSION (Today through Monday)...
Overview:
Overall, expecting minimal impacts through this forecast. Today
will be a warm day across the area as temperatures will be roughly
5-10 degrees above normal under mostly clear skies. Tomorrow will
be another similar warm day with well above normal temperatures
albeit slightly cooler. Thursday onward temperatures will be near
normal. The next few days will also be accompanied by a drying
trend which could lead to more receptive fuels across the area.
Lastly, we will keep an eye on potential for showers and
thunderstorms late this week through the weekend. At this time,
the signal is not the greatest for our area, but will continue to
monitor this threat as thunderstorms could pose a risk for fire
weather after this drying trend.
Further Details:
Current water vapor imagery depicts a fairly dry airmass as high
pressure continues to build in over the region. The ridge axis
will be centered over the area today which will lead to the
warmest day in the forecast. This axis of high pressure will shift
east tomorrow which will result in another warm day. Thereafter
an upper level trough will help break this ridge down, and the
result will be a cooler airmass Thursday onward with temperatures
closer to normal. At the same time, we will see remnants of
Tropical Storm Mario influencing the upper levels Thursday as it
gets absorbed into the mean. Deterministic models are struggling
to resolve the upper level pattern as seen with different areas of
low pressure over the Pacific. The result is a lack of confidence
in the extended with regards to the upper levels; as a result,
precipitation chances are in question later this week and through
the weekend. At this time, not expecting much in regards to
precipitation across the area outside of very isolated areas.
Looking ahead, ensemble members are somewhat split with regards
to precipitation through the end of this month. There is a signal
for the upper levels to bring a trough into the region which could
result in more widepsread chances for rainfall to end the month.
The Climate Prediction Center is calling for above normal
precipitation chances to end the month.
-Guerrero
AVIATION (06Z TAFs)...
VFR prevails area wide late this evening with low-level offshore
flow (east winds) expected overnight allowing VFR to continue for
most areas through Tuesday.
However, a coastal eddy is expected to develop off Pt. St. George
and the flow will turn onshore at the coast Tuesday (starting in
the morning south of Cape Blanco, then becoming more pronounced at
all coastal locations in the afternoon). Some marine stratus
could develop, with soundings showing it very shallow (at or below
500 ft) and mostly over the marine waters initially. However,
expect some of the stratus to begin affecting the beaches during
the afternoon, eventually spreading onshore Tuesday evening,
including at North Bend.
-Spilde
MARINE...Updated 200 AM PDT Tuesday, September 16, 2025... A
thermal trough will continue to bring gusty northerly winds and
steep seas through this morning. Below advisory seas are expected
later today through Wednesday afternoon. Then gusty northerly
winds with possible gale gusts across the outer waters south of
Cape Blanco are forecast to build Wednesday night into Thursday.
Winds may ease on Friday, with northwest swell possibly building
through the weekend.
FIRE WEATHER...Updated 200 AM PDT Tuesday, September 16,
2025...A sharp warming and drying trend is underway today with an
upper level ridge and thermal trough inducing easterly flow
through early Wednesday. Moderate to locally poor recoveries are
expected through Wednesday morning, with recoveries expected to be
lowest this morning. Winds will weaken tonight, but as drier air
spreads eastward, more areas will see moderate to locally poor
recoveries on Wednesday morning as well. Current guidance bottoms
out RH recoveries in the 30-40% range (down to 25% for some of the
higher peaks), with winds gusting to 15-25 mph. This doesn`t
quite reach criteria for watch/warning products, and typically it
needs to be at least a few nights in a row to get the RHs to
really drop low enough. As such, we`ll be maintaining a headline
for this event in the Fire Weather Planning Forecast (FWFMFR).
Meanwhile, daytime humidities will trend lower with teens/low 20s
common across the region. Min RHs bottom out this afternoon, and
if winds align with favored valleys (namely the Illinois Valley),
winds/RH values could near critical conditions on this afternoon.
Overall, RHs will trend higher Wednesday into Thursday, slowest to
improve east of the Cascades.
Another upper level trough will approach the region tomorrow and
this may result in some enhanced afternoon breezes for inland areas
with temperatures trending less warm tomorrow into Thursday. There
could be another round of northeasterly winds tomorrow night into
Thursday morning, but recoveries will continue the improving trend
compared to early in the week. The approaching trough looks to stall
offshore in response to the remnants of Tropical Storm Mario moving
northward along the California coast, then gets swept into the main
flow late week and into the weekend. This pattern could bring the
return of thunderstorms Thursday into Friday. There`s some
uncertainty in how far north and west this moisture gets. As the
moisture moves northward, thunderstorms could return to portions of
northern California as early as Thursday, then potentially into
portions of the East Side on Friday. It`s far too early and there is
plenty of uncertainty in the details to pinpoint timing and location
of potential thunderstorms, so have left them out of the forecast
for the time being. Will see how future model runs evolve before
adding details to the forecast, but this will be a time period worth
watching.
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...None.
PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT early
     this morning for PZZ350-356-370-376.
&&
$$

NWS MFR Office Area Forecast Discussion