-- Discussion containing changed information from previous version are highlighted. --
853
FXUS66 KMFR 131137
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
437 AM PDT Mon May 13 2024

...Updated AVIATION discussion...

.SHORT TERM...Today through Tonight...
The last few showers in Lake County tapered off late last evening,
after isolated thunderstorms produced several dozen lightning
strikes in south central Oregon and our portion of northern
California.

The trough over the region, and its associated instability will
shift east, into far eastern Oregon and Idaho today. In its wake,
it will be slightly cooler today, most noticeable on the west side
of the Cascades with highs to be several degrees cooler than
yesterday. But, that will still mean high temperatures will be
several degrees above normal.

Inland, skies will be mostly clear to clear. The focus for the
new forecast issuance was on properly accounting for the influx of
marine stratus into the Coquille and lower Umpqua valleys, and
the southern Curry County coast. The stratus is expected to slowly
erode back to the beaches during the morning. More of a due
northerly rather than northeast low level flow near Brookings
should allow for a gradual breaking up of the low clouds with a
not overly warm, but still above normal high in the upper 60s to
near 70. Meantime, the longer duration of stratus should keep
temperatures north of Cape Blanco in the 50s to lower 60s.

Also of note, it be a bit breezy this afternoon, with strongest
winds out of the north at 10 to 25 mph with gusts up to 35 mph at
the coast. Inland, afternoon winds will be more on the order of 10
to 15 mph.

Tonight into Tuesday morning, stratus is expected to return to
the Coos and Douglas County coast, while developing northeast
winds keep the Curry County coast clear.

-DW


.LONG TERM...Tuesday through Sunday...
(From the previous discussion)

The longer term forecast begins with upper level, long-wave
ridging starting to move into the western U.S. from the Pacific.
The axis of the ridge will remain offshore, leading to northerly
flow aloft. Another thermal trough, an area of low pressure
induced by warm air, will continue to strengthen along the
southern OR/northern CA coast Tuesday into Wednesday. This is a
very similar pattern to the one that just ended, one which brings
higher than average temperatures to the area (more typical of
June than May), dry weather, and sunny skies.

At lower levels, northerly flow will start to shift NE to
easterly Tuesday through Wednesday. This will set off the Chetco
Effect, where air is funneled down the Chetco River Valley and
warms as its forced down towards sea level, which will result in
warm temperatures for Brookings and the surrounding southern Curry
County coast. Highs look to be in the high 70s to mid 80s through
Thursday, peaking Wednesday. Farther north, more of a due
northerly flow will continue night and morning stratus for the
beaches from Cape Blanco northward. Inland, we`ll continue to see
warm temperatures each day, especially in valleys. Highs in the
80s up to 90 degrees are expected in western, inland valleys,
peaking Wednesday, while east side locations will see high 70s to
low 80s, likely peaking Thursday. Finally, mountainous areas will
see highs in the 60s, warming slightly each day through Thursday.

Model differences increase Friday into the weekend, but generally
agree that the ridge will flatten and move east as a shortwave
trough approaches from the northwest Friday into Saturday. Only 5
to 10 percent of ensemble members indicate any precipitation, but
an eventual introduction to the forecast of some slight
probability of showers and thunderstorms is possible with this
pattern. The trough will help moderate temperatures Friday into
the weekend, though they`ll remain warmer than average in most
areas. A more progressive pattern with more troughs and transient
ridges looks likely beginning early next week.

-CSP/DW

&&

.AVIATION...
-- Changed Discussion --
13/12Z TAFs...IFR and LIFR ceilings remain along the
Oregon coast under persisting marine stratus. These clouds will
remain in place through most of the TAF period. Gusty northerly
winds may help to break the layer up this afternoon, but the clouds
will rebuild and return to IFR and LIFR levels in the evening as
winds calm.

Inland areas will remain at VFR levels under clear skies through the
TAF period. -TAD
-- End Changed Discussion --


&&

.MARINE...Updated 230 AM Monday, May 13, 2024...A thermal trough
will continue to develop today. Gusty northerly winds will spread
over all waters, bringing wind-built chaotic seas over all waters.
Additionally, gale-strength winds will be possible in waters
south of Coos Bay. A Gale Warning will be in place over these
waters starting at 2 PM this afternoon and remaining in place
until at least Wednesday afternoon, with a Small Craft Advisory
covering other area waters. These hazards are likely to be
extended through the week and possibly into the weekend. -TAD

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 2 PM PDT this
     afternoon for PZZ350-356-370-376.

Gale Warning from 2 PM this afternoon to 11 AM PDT Wednesday for
     PZZ350-356-370-376.

&&

$$