990
FXUS66 KMFR 070540 AAB
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
940 PM PST Wed Nov 6 2024

...Updated AVIATION discussion for 06Z TAFs...

.AVIATION...07/06Z TAFS...Clear skies and visibilies continue to
support VFR levels across northern California and southern Oregon.
Satellite imagery shows hints of fog developing around the edges of
the Umpqua Valley, so fog remains in the forecast for Roseburg on
early Thursday morning. Warmer temperatures in the Rogue Valley are
making fog unlikely, but approximate possible timing remains in the
TAFs. Anything that does develop in either valley will likely be
cleared out before Thursday afternoon. -TAD

&&

.MARINE...Updated 800 PM PDT Wednesday, November 6, 2024...

Gusty northerly winds and steep seas south of Cape Blanco will lower
late tonight. Then, light winds and seas are expected Thursday and
Friday.

Two fronts will move through this weekend, one Saturday
afternoon/evening and another Sunday night into Monday. The first
front, the weaker of the two, will bring increasing south winds
Friday night into Saturday with building westerly swell. This will
likely result in conditions hazardous to small craft for much of the
waters as well as a potential for locally very steep seas. The
second front Sunday into Monday will be stronger with possible gales
and steep to very steep, chaotic seas. This system could then be
followed by another large, long period swell, peaking around next
Tuesday. Early indications are showing peak swells 17-21 feet with a
period of 15-16 seconds.

-CC

&&

.DISCUSSION...Our region is sandwiched between an upper level high
pressure over the Pacific Ocean and a deepening trough over the
Intermountain West. As this pattern evolves, high pressure will
nudge over the Pacific Northwest while the upper level trough will
dig southward and settle over the Four Corners Region. These two
features will remain rather stationary into the early part of
Friday before a more active pattern returns over the weekend and
into early next week. At the surface, a thermal trough along the
coast will push inland tonight and this will maintain a period of
northeast to easterly (offshore) flow. Under this pattern, dry
conditions will persist through the end of the week and strong
valley inversions will bring the nightly return of low clouds/fog.
These inversions and morning rounds of clouds/fog will keep
valley temperatures cooler than surrounding areas with plenty of
sunshine and warmer temperatures above the inversions. For areas
outside of the inversions, there will be a wide diurnal range of
temperatures. Lows will range from the teens/low 20s on the east
side to the 30s on the west side (except lower 40s at the coast).
High temperatures will be 5 to 15 degrees above normal through
Friday, with readings in the mid 50s to lower 60s on the east
side, and mostly in the mid 60s on the west side. The Chetco
Effect is making an appearance today, bringing the warmest
temperatures of the forecast period to the Brookings area. Highs
will reach into the upper 60s, maybe even low 70s on Wednesday.

With this pattern, we expect gusty northeast to east winds across
the higher terrain, even during the overnight period and this will
result in some low end moderate recoveries both Thursday and Friday
mornings, but especially Thursday morning. There will be poor mixing
in the valleys during this period, with the poorest mixing expected
on Thursday. Evaluated the need for an Air Stagnation Advisory, but
it doesn`t quite look to reach criteria with only one day of
conditions being met (need 48 hours to reach advisory criteria).
Will continue to monitor conditions for interior valleys and
evaluate future model trends.

Heading into the weekend, the upper level ridge axis buckles as the
pattern transitions to a more active one and the next front
approaches the region. As suspected, models have trended slower and
weaker with the arrival of this front, now holding off until later
in the day Saturday. We do expect another round of beneficial rain
and gusty winds across the area, but anticipated rainfall amounts
have significantly decreased as the front now looks to fall apart
over the area. Snow levels will be high (around 7000-8000 ft) so we
aren`t anticipating any winter impacts with this front. There still
looks to be a break between systems on Sunday (albeit short) before
the next, stronger, front moves through late Sunday into early next
week. Again, another round of beneficial rain with gusty winds is
expected and snow levels will lower down to around 4000 ft with the
next system. Guidance at this point does show the potential for some
strong winds late Sunday into Monday, so we`ll need to monitor this
period for potential impacts. Additionally, with the lowering snow
levels, winter impacts can be expected for the Cascades Passes, and
maybe even Siskiyou Summit. Stay tuned as details become clear over
the coming days. /BR-y

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 4 AM PST Thursday
     for PZZ356-376.

&&

$$

MNF/CZS/MAS