Merrill, Oregon Weather Forecast Discussion

684
FXUS66 KMFR 230529
AFDMFR
Area Forecast Discussion
National Weather Service Medford OR
1029 PM PDT Mon Sep 22 2025
.UPDATE...Updated aviation and marine discussions.
&&
.AVIATION...23/06Z TAFs...Widespread VFR late this evening will
persist the next 24 hours beneath high pressure, offhsore low-level
flow and a strengthening subsidence inversion. Patchy IFR/LIFR
fog could develop very near the coast or just offshore north of Cape
Blanco in a very shallow marine layer (500 ft or lower). We think
most of this will stay to the west of North Bend due to low-level
N-NE winds, but can`t rule out some shallow 2-5 NM mist overnight or
first thing Tuesday before VFR prevails again. -Spilde
&&
.MARINE...Updated 800 PM PDT Monday, September 22, 2025...A thermal
trough continues along and near the coast. Gusty north winds and
steep to very steep, hazardous seas will persist overnight into
Tuesday. Winds trend slightly lower through Wednesday but steep
seas will continue, with strongest winds and steepest seas beyond 5
nm from shore. Winds may strengthen across the waters again Thursday
and Friday.
&&
.PREV DISCUSSION... /Issued 451 PM PDT Mon Sep 22 2025/
UPDATE...Updated aviation discussion.
AVIATION...23/00Z TAFs...Widespread VFR this evening will
persist the next 24 hours as offshore flow takes hold beneath high
pressure and a strengthening subsidence inversion. Patchy
IFR/LIFR fog could develop very near the coast or just offshore
north of Cape Blanco in a very shallow marine layer (500 ft or
lower), but we think this will stay to the west of North Bend due
to low-level N-NE winds.
Satellite imagery this evening is showing a fire between Lookout and
Adin which could lower visibility at times in its immediate
vicinity. -Spilde
PREV DISCUSSION... /Issued 213 PM PDT Mon Sep 22 2025/
DISCUSSION (Today through Sunday)...
Overview:
Overall, weather hazards/impacts continue to be minimal. Notable
items include the hot temperatures Tuesday and Wednesday with
records in jeopardy. These temperatures are around 15 degrees
above normal for some locations. This week will also be noted by a
drying trend. Tonight and tomorrow night in particular will
experience poor overnight RH recoveries with breezy winds which
will lead to elevated fire weather concerns. Please see the Fire
Weather discussion below for more details.
Further Details:
A rather stagnant pattern is shaping up tomorrow as a low slides
south from Canada 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 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 at least Saturday. This will result in
high pressure over the forecast area, above normal temperatures,
and dry conditions through much of next week. An area of high
pressure will be directly overhead tomorrow afternoon. Records
may be in jeopardy tomorrow and Wednesday as we flirt with triple
digits over the westside. For example, the record for Medford is
100 on Tuesday and 99 on Wednesday, and we are forecasting a high
of 97 both days. These records are certainly within reach as
temperatures will be about 15 degrees above normal for this time
of year. Technically not in this 7-day forecast period, but this
stagnant pattern may be followed by a trough moving through the
region early next week. However, uncertainty does exist as
ensemble members are split on rainfall amounts and areal coverage,
so confidence is not the greatest with regards to rainfall, but
confidence is high we will be more seasonable with regards to
temperatures being near normal for this time of year.
While probabilities are very high this week will be dry, we will
need to watch how the H5 low over California transitions through
mid/late week in this blocking pattern. Main reason for this is
due to the moisture associated with this upper low. Currently,
guidance shows higher probabilities for rainfall well to our
south, but if the low trajectory changes and pushes north we could
see that moisture advect over the forecast area. Thursday would
be the day for this chance if the trajectory changed, but again
want to drive home the fact chances are very high for a dry
forecast.
-Guerrero
AVIATION (18Z TAFs)...
Satellite image shows marine stratus burning off in the Umpqua
Basin, including Roseburg. Have gone with VFR conditions for the
start of the Roseburg TAF with the expectation that VFR conditions
will return around 18z. Otherwise VFR conditions will continue
through the TAF period, with gusty north winds at North Bend this
afternoon into early this evening. Offshore flow along with a very
dry air mass should be enough to keep marine stratus in check
along the coast and just offshore. Patchy shallow fog could form
for a brief period of time (hour or less) towards 12z tomorrow at
North Bend, but confidence is not high enough to include it in the
TAF.
-Petrucelli
MARINE...Updated 200 PM PDT Monday, September 22, 2025...A
thermal trough continues along and near the coast, bringing gusty
northerly winds to area waters. These winds will be strongest
south of Cape Blanco and will build steep seas in this area from
late tonight through Monday afternoon. Localized areas of very
steep and hazardous seas are possible south of Gold Beach late
this afternoon and through the overnight period. Gusty northerly
winds increase tomorrow evening, with current forecast showing
steep seas building as far north as Reedsport from Monday evening
through Tuesday afternoon. Winds trend slightly lower on Wednesday
but gusty north winds and steep seas will persist, with strongest
winds and steepest seas beyond 5 nm from shore. Winds may
strengthen across the waters Thursday and Friday.
FIRE WEATHER...Updated 200 PM PDT Monday, September 22,
2025...Upper ridging will build over the area today through
Wednesday with rapid warming and drying as a thermal trough takes
hold along the northern California and SW Oregon coast. We`ll have
another cool to chilly night in the valleys with the coldest
overnight lows east of the Cascades and valleys in Siskiyou
County. At the same time, the thermal trough will result in breezy
east to northeast winds near and at the ridges, especially in
Fire zones 619, 621, 623, and 280 along with moderate to poor
overnight recoveries tonight into early Tuesday morning. It`s not
out of the question there could be brief periods of time where the
fire zones mentioned above could get to critical conditions
tonight.
The dry air mass will be in place over the area through at least
midweek. We`ll likely have another night of moderate to poor
overnight recoveries Tuesday night into Wednesday morning. The
only difference is winds speeds should be less while overnight
recoveries could end up lower than tonight for the mid slopes and
ridges.
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 both Tuesday and
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.
The upper ridge should largely hold across southern Oregon and
Northern California through the week as a closed upper low wobbles
into the Great Basin. This should keep the thunder risk to the SE
of the area with probabilities generally 10% or less. Slight
cooling is expected later in the week into next weekend. It won`t
be quite as hot as earlier in the week, but still above normal.
-Petrucelli
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...None.
PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT Tuesday
     for PZZ350-356-370-376.
Hazardous Seas Warning until 5 AM PDT Tuesday for PZZ356-376.
&&
$$
MAS

NWS MFR Office Area Forecast Discussion