525
FXUS66 KMFR 031759
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
959 AM PST Mon Nov 3 2025

.DISCUSSION...Updated aviation discussion.


&&

.AVIATION...03/18Z TAFs...Low pressure will bring lowering clouds
and rain to the coast this afternoon. The rain and lowering ceilings
will spread inland this afternoon and evening. Expect areas of MVFR
with higher terrain obscuration and also increasing southerly winds.
The gusty south to southwest winds will be the most widespread
impact, which includes areas of low level wind shear across southern
Oregon and northern California through this evening, but lingering
over Lake and Modoc counties into early Tuesday morning. Both wind
speeds and areal coverage of low level wind shear will reach a peak
this evening. Later tonight into Tuesday morning, things should dry
out for most and post-frontal showers will continue along the coast
with lowering ceilings to a mix of IFR/MVFR. Breaks that develop
behind the front could lead to some fog/low stratus development in
the west side valleys around sunrise. A warm front will lift north
across the area Tuesday with light rain. Stronger south winds will
develop again during Tuesday afternoon, especially along the coast,
in the Shasta Valley and over the East side. A period of strong S-SE
winds is expected Tuesday night into Wednesday morning, affecting
North Bend, Medford and Klamath Falls and to a lesser extent,
Roseburg. Wind gusts of 35-40kt will be possible and wind shear will
again be likely leading up to the strong winds. -Spilde


&&


.PREV DISCUSSION... /Issued 637 AM PST Mon Nov 3 2025/

DISCUSSION...A series of frontal systems are expected to produce
wet and windy weather today through Friday. These will be warm
systems with snow levels remaining above the major passes, in a
range from 6000 to 8000 FT MSL. The heaviest rain is expected
Tuesday afternoon into Wednesday afternoon, and Thursday afternoon
through Friday morning ...especially for Curry, Josephine, and
Siskiyou counties. Also, totals in Coos County will not be far
behind.

The term `atmospheric river` applies well to both the Tuesday/Wednesday
and Thursday/Friday systems. There remains a healthy amount of
uncertainty in rain amounts, but weekly amounts of 3 to 7 inches
seem reasonable for areas from the Coast to Interstate 5.
Of note, the downslope influence of southerly wind episodes will
have the typical effect of diminishing totals for the Shasta
Valley, Rogue Valley, and (to a lesser extent) the Umpqua Valley.
1 to 3 inches of rain is expected east of Interstate 5, with the
lesser end of the range for valley areas of Lake and Modoc
counties.

For today, wind speeds will be more notable than rainfall amounts.
A High Wind Warning remains in effect for this afternoon and
evening for the Coastal Headlands and exposed terrain with gusts
up to 60 mph expected. Generally, winds will increase today into
this evening, then diminish overnight into Tuesday morning. Rain
will be light to moderate with highest amounts at the coast with
the frontal passage this afternoon and evening, tapering off after
midnight.

The most impactful system in the forecast is set to arrive late
Tuesday into Wednesday, with a intense front and a substantial
moisture plume bringing strong winds and heavy precipitation to
southern Oregon and far northern California. The surface low on
Monday has altered the pattern sightly with some of the downstream
systems, with some minor changes in timing and intensity, but
only slightly. With surface pressure gradients ranging roughly
between -6 and -8 mb across the area, and with 700mb winds of 50
to 70 kts, it still looks likely that wind headlines will be
necessary, especially along the coast, in the Shasta Valley, and
across the East Side. The negative tilt in the upper level trough
also suggests that that stronger winds could impact portions of
the West Side as well, including the I-5 corridor from Ashland to
Medford, and in some of the other roughly south/north oriented
valleys.

Meanwhile, moisture transport values for this front, as measured
by IVT, a function of wind and humidity, are expected to reach
values of 1000 to 1250 (a typical front would average about 500).
This would be considered a strong atmospheric river, or a rather
classic "Pineapple Express," as the moisture plume originates
from the tropics near Hawai`i. A substantial amount of rain is
possible for much of the area, especially along the coast and in
Siskiyou County. However, the front is a fast mover, and some
locations, such as the Rogue Valley near Medford and much of the
East Side, will see lesser amounts due to significant downsloping
winds off the Siskiyous and Cascades. While widespread flooding is
not expected at this time, we will likely see nuisance type
flooding with ponding on roadways and blocked drains due to
recently fallen leaves. Additionally, King Tides are expected Nov
5-7 (Wednesday through Friday) which could bring additional
impacts to the coast as this system enters the region, especially
with heavy rains putting additional water into area rivers and
estuaries.

Another robust front arrives Thursday, and although it looks
slightly weaker than the previous one, most model guidance suites
are again depicting potential for impactful winds and rain. This
storm, however, will coincide with the highest King Tides around
noon on Thursday. Ocean level models are depicting a small storm
surge with the event, along with high surf conditions which will
push water into local bays and estuaries, which will make tidal
influences even stronger. Some localized coastal flooding is
possible, particularly for low lying areas and roads around Coos
Bay, and erosion along area beaches will be a concern.

After a brief break Friday night into Sunday, we are seeing the
signs of another frontal system later Sunday into Monday. There
remains quite a bit of variation in model guidance regarding this
scenario, so confidence is low. Confidence remain high, however,
that an active storm pattern will resume next week.
-DW/BPN

AVIATION...03/12Z TAFs...Conditions early this morning are mainly
VFR, with patchy valley IFR. An approaching front will spread
increasing clouds into the area this morning with rain developing
along the coast. Rain, then spreads inland during the afternoon and
evening. This will bring areas of MVFR conditions, and also
increasing southerly winds. The gusty south to southwest winds will
be the most widespread impact. This includes areas of low level wind
shear across southern Oregon and northern California today through
this evening, lingering over Lake and Modoc counties into early
Tuesday morning. Both wind speeds and areal coverage of low level
wind shear will reach a peak this evening. Later tonight into
Tuesday morning, post-frontal showers will continue along the coast
with lowering ceilings to a mix of IFR/MVFR.

MARINE...Updated 200 AM PDT Monday, November 3, 2025...A series
of frontal systems will provide impactful conditions during the next
week, with advisory to gale force southerly winds, and high to very
high steep to very steep seas. This includes a slight chance to
chance of thunderstorms Tuesday night into Wednesday evening.

The first of these fronts will bring increasing southerly winds
today with gales during the afternoon and evening, and combined seas
building to a peak this evening. The strongest winds will be north
of Cape Blanco and within 30 nm of shore under a coastal jet. Winds
in this jet may exceed may exceed 45 kts. As the path of this low
has some variability and with near-gale to gale gusts forecast for
most waters, a Gale Warning has been issued to cover all area
waters. Those areas that do not quite reach gales will
still have very steep seas.

Conditions briefly improve early Tuesday morning before a
significant, stronger front approaches. Winds increase on Tuesday
afternoon and peak early Wednesday morning. Widespread gale gusts
are expected and may approach 50 kt in the outer waters.
Additionally, marine thunderstorms may develop Tuesday night into
Wednesday evening.

Southerly winds ease Wednesday night into Thursday morning, but very
steep and hazardous long-period west swell follows through the day.
Advisory level high surf is forecast, with current guidance building
22-26 ft surf heights. King Tides are expected on Thursday, which
may increase the impact of hazardous conditions. Bar crossings may
become especially dangerous and fishing infrastructure may be
vulnerable.

Another strong front may bring additional gales and very high seas
Thursday. High pressure brings improving weather late Friday into
the weekend. But, lingering swell is likely to support high, steep
to very steep and hazardous seas at least through Saturday. Active
weather may return early next week.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning from 1 PM this afternoon to 10 PM PST this
     evening for ORZ021-022.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 1 PM PST this
     afternoon for PZZ350-356-370-376.

     Small Craft Advisory from 10 PM this evening to 4 AM PST Tuesday
     for PZZ350-356-370-376.

     Gale Warning from 1 PM this afternoon to 10 PM PST this evening
     for PZZ350-356-370-376.

&&

$$

MAS/MAS/MAS