FXUS66 KMFR 030354
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
854 PM PDT Wed Apr 2 2025

.DISCUSSION...Updated Aviation Discussion.


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.AVIATION...03/03Z TAFs...Scattered light showers continue to move
across northern California and southern Oregon, but flight levels
have generally stayed at VFR across the area. A stray shower may
cause locally lower flight levels, but extended poor conditions are
not expected at area terminals in this TAF period. Showers will
decrease through the night. Roseburg may see a period of MVFR
ceilings tonight as well as a period of fog on Thursday morning, but
confidence is slight to moderate in these possibilities.

With dew points trending up at Klamath Falls, the chance of fog in
the Klamath Basin is also worth mentioning. High-res guidance has a
10% chance of IFR and LIFR visibilities moving over the Klamath
Falls terminal early Thursday morning. These conditions are only
present for a couple of hours in model guidance and dissipate in the
late morning hours. -TAD

&&

.PREV DISCUSSION... /Issued 500 PM PDT Wed Apr 2 2025/

DISCUSSION...A long wave upper trough is settling into the Great
Basin and moving slowly toward the Four Corners region. The PacNW
is currently on the back side of this upper trough with northerly
flow aloft. Some energy in the northerly flow aloft and
instability due to daytime heating is resulting in isolated to
scattered showers this afternoon, especially from the Cascades and
Siskiyous north and west, but also over Winter Rim and the
Warners. Some of these may contain brief gusty winds. An isolated
shower or two still could pop up outside those locations as well
through this evening. Coverage of showers should diminish
around/after sunset and cloud cover should also gradually break
up. While we're getting out of the time of year for fog formation,
there is a 20-30% chance some forms in the west side valleys
toward morning. This is most likely in the Umpqua Basin, where low
level moisture is highest. Low temperatures tonight will be a bit
below normal. So, it'll be chilly east of the Cascades with lows
largely in the 20s. West side valleys will bottom out in the 30s,
which could lead to patchy frost where it is clear long enough
(perhaps Illinois Valley).

High pressure offshore will build into the area on Thursday. There
is still just enough instability for a slight chance/isolated
rain/snow showers in far SE sections during Thursday afternoon,
but most areas will be dry and turn milder, though high
temperatures remain mostly below normal.

Chilly mornings and milder afternoons are expected Friday and
Saturday with a period of drying east winds Friday, which will
shift to southerly during Saturday. The warming trend continues
with high temperatures of 5-10F above normal west of the Cascades
Friday (near 70F west side valleys) and 10-15F above normal there
on Saturday (mid 70s). East side areas warm more gradually, but
still end up about 5-10F above normal on Saturday (generally
60-65F for highs).

Sunday will be a transition day as the next trough approaches the
coast. This will probably be the warmest day east of the Cascades,
but increasing cloud cover should result in slightly cooler
temperatures west of the Cascades. Expect an uptick in southerly
winds in the usual spots (along the coast, in the Shasta Valley
and over the East Side), but overall, just a breezy afternoon.
Rain chances increase along the coast and rain is likely there, if
if not late morning, then by afternoon. Most other areas escape
the day dry, but there is a chance of rain along I-5 (30-50%)
Sunday afternoon. A period of rain moves through most areas
Sunday night with snow levels around 7500 feet dropping to the
higher passes (5000 feet) by Monday morning. Post-frontal showers
continue Monday.

Flat ridging will build into the area Tuesday with the storm
track expected to shift far enough north to keep conditions dry,
except for the northwest part of the forecast area. Even then,
were only expecting a slight chance of rain. -Spilde


MARINE...Updated 200 PM Wednesday, April 2, 2025...Overall,
expect seas of 6 to 9 feet at 10 seconds with north to northwest
winds generally in the 10-20kt range into tonight. Northerly
winds increase once again on Thursday which will result in steep
short-period seas. We have issued a Small Craft Advisory out to
20 NM from shore off Cape Blanco, and extending to 60 NM from
shore off Pt. St. George. Then, another period of improving
conditions is expected Friday through Saturday. A building long
period (18-20 seconds) west swell is anticipated on Sunday, and
this will likely lead to steep seas once again. -Spilde

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

PACIFIC COASTAL WATERS...Small Craft Advisory from 11 AM Thursday to
     3 AM PDT Friday for PZZ356-376.

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