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196
FXUS66 KMFR 121144
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
444 AM PDT Wed Jun 12 2024

...New Aviation Section...


.AVIATION (12Z TAFs)...

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A tricky situation developing along/near the coast for North Bend
(KOTH) and Roseburg (KRBG) where low stratus is building in the
Umpqua Valley. Confidence was high enough to introduce MVFR
ceilings for KRBG as satellite indicates the valley filling in
with stratus. KOTH is a little trickier, but could not completely
rule out some stratus building in this morning; however, uncertain
about categorical changes at this time as VFR may prevail.
Otherwise, plenty of sunshine expected further inland for Medford
and Klamath with VFR conditions expected at these locations. It
will be a breezy afternoon, especially for KOTH, but inland TAF
sites will also see winds pick up this afternoon.

-Guerrero
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.PREV DISCUSSION... 
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/Issued 248 AM PDT Wed Jun 12 2024/

DISCUSSION...Stratus has returned in some coastal valleys and
across Douglas County northward in the foothills of the Cascades.
The fog is expected to expand overnight. With zonal mid-
tropospheric flow and a thermal trough still in place along the
coast, the winds generated in the afternoon should be strong
enough to ensure that the stratus erodes by the afternoon. The
forecasted north winds along the Coos County coast, especially,
have been increased, with gusts over 30 mph expected along the
Oregon coast as far north as Florence.

Afternoon humidities will be at their driest during this warm and
dry spell. Some single digit humidities are expected across NorCal
valleys and east of the Cascades in Oregon. Combined with the
afternoon winds, these critical humidities could lead to one or
two hours of red flag conditions in the Scott Valley of Siskiyou
County, and the hills surrounding this valley. That said, this
pattern is a typical one for summer and these conditions are not
uncommon. Elsewhere in Oregon west of the Cascades, humidities
will remain above critical values, but the diurnal afternoon winds
will be a bit stronger than normal and very similar to what
happened on Tuesday.

Thursday night through Friday, a trough will move off the British
Columbia coast, moving cooler air into this region. Beyond this
cooler air, the main impact will be the strengthening of the west-
east pressure gradient, increasing the afternoon west-northwest
winds. With humidities remaining mostly remaining above 15%, the
fire weather risk from these increasing winds should remain low.
The exception is along Winter Ridge and Summer Lake, where an hour
or two of critical conditions are possible. However, the chance
for this is low, as the air will have less time to dry as moister
air moves in.

That said about moister air, no rain is expected Thursday night
through Friday. However, this should produce a moderate onshore push
of the marine layer, generating fog and stratus across the coast and
Douglas County. The elevation where these clouds set up, could
observe some accumulating drizzle. But this far out, we are holding
off in including this in the forecast due to a lack of confidence.

The trough will remain parked off the west coast through Saturday,
before building southward Saturday night, and then beginning to move
inland Sunday into Monday. As the trough builds southward late ron
Saturday, a front will move onto the coast, which may have enough
moisture along it to bring a 10-30% for a hundreths of an inch of
rain to the Coos and Douglas County area. A more moist front is
expected when the low moves inland with a 10-40% chance for rain,
which might exceed 0.1" in some spots, becoming more wide spread
north of the Siskiyous and west of the Cascades.

With snow levels forecast to dip below 7kft, it`s not impossible
some of the higher peaks in the Cascades pick up some new snow as
the trough moves inland. There is also a big unknown with regards
to thunderstorms as this trough moves inland. Right now the model
data puts the chance at less than 10%, but this could quickly
jump up, especially east of the Cascades, if the trough builds
further south or a more organized front moves onshore than is
currently expected.

-Miles

AVIATION...12/06Z TAFs...VFR will prevail across much of the area
for the next 24 hours. The exception will be over portions of Coos
and Douglas counties where conditions may be locally MVFR due to
marine clouds. At North Bend, it`s been in and out of MVFR for the
last few hours and it might be this way through the first part of
the night, but it appears VFR will win out as some drier NNE flow
takes hold toward morning. Similarly, MVFR clouds may briefly impact
Roseburg early Wednesday, though confidence wasn`t high enough to
include in the TAF (SCT025). Either way, any clouds Wednesday
shouldn`t last much past mid-morning at the latest with VFR expected
in all areas by Wednesday afternoon. Gusty N-NW winds pick up again
Wednesday afternoon/evening, especially at North Bend where gusts up
to 35 kt are possible.

-Spilde

MARINE...Updated 245 AM Wednesday, June 12, 2024...North winds will
increase throughout the day and remain strong overnight into
Thursday morning before some relief comes. This will result in winds
and seas remaining hazardous to smaller crafts through at least
Thursday night. A thermal trough will help produce gale force winds
over the southern waters south of Port Orford along with high and
steep seas south of North Bend (combination of both gale and
hazardous seas warnings). Seas could reach up to 15 feet off Point
St. George this evening due to the strong gale force winds.
Conditions improve Friday morning onward through the weekend.

-Guerrero
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&&

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

PACIFIC COASTAL WATERS...Hazardous Seas Warning until 11 AM PDT
     Thursday for PZZ350-356-370-376.

Small Craft Advisory until 11 AM PDT Thursday for PZZ350-370.

     Gale Warning until 11 AM PDT Thursday for PZZ356-376.

&&

$$