Merrill, Oregon Weather Forecast Discussion

617
FXUS66 KMFR 240537
AFDMFR
Area Forecast Discussion
National Weather Service Medford OR
1037 PM PDT Tue Sep 23 2025
.Updated AVIATION Discussion...
&&
.AVIATION...24/06Z TAFs...VFR conditions will prevail through the
TAF period, with continued offshore low-level flow and a
strengthening subsidence inversion. Patchy shallow fog could develop
near the coast or just offshore tonight, including at North Bend,
mainly between 07z-14z. Any lower conditions will improve by
Wednesday morning. Gusty north winds will return to the coast north
of Cape Blanco with gusts 25-30 kts Wednesday afternoon. /BR-y
&&
.PREV DISCUSSION... /Issued 416 PM PDT Tue Sep 23 2025/
DISCUSSION (Today through Monday)...
Overview:
Overall, weather hazards/impacts continue to be low based on a scale
of low/moderate/high. Notable items include the hot temperatures
today and tomorrow with records in jeopardy for westside areas.
These temperatures are around 15 degrees above normal for some
locations. This week will also be noted by a drying trend. Tonight
in particular will experience poor overnight RH recoveries with
breezy winds, but generally speaking this week will be noted by
overall dry conditions. Please see the Fire Weather discussion below
for more details on these concerns. Lastly, a pattern change could
occur Sunday into early next week with more seasonable temperatures
and rainfall chances, but uncertainty does exist on some details.
Further Details:
The stagnant pattern we have been talking about is shaping up
today as a low continues to slide south over the Rockies and into
the Central/Southern Plains. This will set the stage for an Omega
Block type of pattern over the CONUS, while a westerly jet stream
will be noted over much of southern Canada. This Omega Block
pattern will be noted by an H5 low over the west coast as well as
an area of low pressure aloft over the east coast with high
pressure in between. This pattern will stick around through Sunday
before an area of low pressure moves into the PacNW which could
break this blocking pattern down. In the meantime, this week will
be noted by mostly high pressure over the forecast area, above
normal temperatures, and dry conditions. In fact, some records may
be in jeopardy today and tomorrow as we flirt with triple digits
over westside areas. For example, the record for Medford is 100
today and 99 tomorrow, and we are forecasting a high of 97 both
days. The normal temperature for Medford this time of year is 82
degrees.
After this week of dry and above normal temperatures, our attention
will turn towards a potentially strong upper level low which could
bring widespread rainfall to the forecast area. There is a lot of
uncertainty with regards to rainfall amounts and areal coverage.
However, confidence is high for more seasonable temperatures.
Cluster analysis indicates high confidence for a trough impacting
the region starting Sunday, but the finer details are what is
currently in question like rainfall and potential breezy/gusty
areas. Ensemble members are still showing a split of dry solutions
and very wet solutions and a mix in between these two. This doesn`t
boost confidence for rainfall, and we will likely need a few more
days before some semblance of confidence arises. Highest
confidence is for temperatures to be more seasonable early next
week. For potential wind advisory and rainfall amounts, these
details are very much in question. Early signs point towards
widespread rainfall and breezy/gusty wind speeds over the eastside
and areas near/along the coast as a very dynamic low enters the
area. The GFS in particular is showing a 155kt jet stream at 300mb
which could go right over the forecast area. Stay tuned as we
continue to analyze this potential pattern change.
-Guerrero
MARINE...Updated 100 PM PDT Tuesday, September 23, 2025...A
thermal trough continues along and near the coast. This is
resulting in gusty north winds and steep seas across outer waters.
These conditions are expected to persist overnight into tomorrow
morning. Thereafter, wind speeds are expected to increase across
area waters, which will result in steep seas across all waters, as
well as very steep and hazardous seas beyond 10 nm south of Cape
Blanco. These conditions will likely continue into Thursday night,
but steep seas could linger longer across all waters. The
strongest winds are expected Thursday and Thursday night
potentially lingering into Friday. During this time, the
probability for wind speeds of 22 knots or greater is about 80
percent for areas south of Cape Blanco. However, the probability
for wind speeds of 30 knots or greater drops down to around 5-10%
for the same area.
-Guerrero
FIRE WEATHER...Updated 200 PM PDT Tuesday, September 23,
2025...Dry and hot weather will continue through Wednesday. Late
last night into early this morning, a few locations near and at
the ridges along the Cascades, coastal mountains and Fire zone 280
that experienced brief periods of critical conditions.
Were expecting moderate to poor overnight recoveries again
tonight for the same locations as last night/early this morning.
Some of the guidance suggest overnight recoveries could be less
tonight compared to last night/early this morning. However the
winds are expected to be weaker. Despite the weaker winds, it`s
not out of the question there could be brief periods of time where
the critical conditions could be met near and at the ridges in
portions of Fire zones, 280, 617, 619, 621, and 623.
We`ll keep the headline as is at the top of the Fire Weather
Planning Forecast for the locally gusty east winds and poor RH
recoveries during this period. High temps Wednesday will be in the
mid-upper 90s west of the Cascades, and in the 80s over the East
Side (about 10-15F above normal). So, those out on the landscape
this week should plan for the expected hot weather/unusual warmth.
Take breaks during the peak of the heat in the afternoons and
stay hydrated. The good news is that with the longer nights,
temperatures in the valleys will cool down shortly after sunset.
An upper trough will swing through the area Thursday morning with
a dry cold front moving through the area. In the wake of the
front, the pressure gradient will tighten up with gusty breezes
setting up along and east of the Cascades Thursday afternoon and
lasting into early Thursday evening. At the same time, relative
humidity will be low, but at this time the combination of the two
just aren`t quite there for critical conditions to be met. So for
now we`ll headline this and have the evening shift take another
look at this when new data comes in later this evening.
In the wake of the dry front there`s good agreement a thermal
trough will set up along the south Oregon coast and models are
showing rather robust northeast winds at 925 mb (15-20 kts) along
the southwest Oregon coast, and 15-20 kt at 850 mb in portions of
Fire zone 280, along with moderate to poor overnight recoveries.
Upper ridging will build in again Friday, but the ridge is not as
strong as what we are currently experiencing, therefore while
afternoon temperatures will be above normal, they won`t be as hot
when compared to today and Wednesday. as Upper ridging will weaken
and shift to the east in response to a large and rather strong
upper low sets up over the Alaska Panhandle, this will bring
cooler temperatures and slightly higher humidities to the area.
The above mentioned upper low could be a play maker for the
weather for early next week. The operational model, ensembles and
clusters all point to a change in the pattern towards cooler and
wetter and some of the guidance is suggesting a good shot of
precipitation for most areas along and west of the Cascades.
However, this needs to be taken with a grain of salt given it`s
still a ways out there and typically when there is a potential
significant change in the pattern often times models and ensembles
have some difficulty in resolving some of the details with
respect to timing and locations of high and lows. Stay tuned.
-Petrucelli
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...None.
PACIFIC COASTAL WATERS...Small Craft Advisory from 11 AM Wednesday to
     11 PM PDT Thursday for PZZ350-356-370-376.
Hazardous Seas Warning from 11 AM Wednesday to 11 PM PDT
     Thursday for PZZ370-376.
&&
$$

NWS MFR Office Area Forecast Discussion