277
FXUS66 KMFR 070957
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
257 AM PDT Tue May 7 2024

.SHORT TERM...

Showers remain ongoing this morning with some surface stations
reporting light rain along the coast and the Umpqua Basin this
morning. Upper level energy will pass through this morning and
sinking motion in the mid levels will become more widespread
today. As a result, the probability of precipitation will
gradually decrease, although may linger in the Cascades into the
early afternoon. Temperatures will trend slightly warmer compared
to the last few days with plenty of solar heating towards the
afternoon.

By Tuesday night, we`ll have mostly clear skies with temperatures
dropping down into the lower and mid 30`s west of the Cascades
and lower 20`s east of the Cascades. The main concern here is
temperatures approaching freezing in valleys west of the Cascades,
although the duration of freeze should be fairly brief.

-Smith


.LONG TERM.../Issued 240 PM PDT Mon May 6 2024/

Upper level ridging will continue to build into the region from
the eastern Pacific on Wednesday, with a thermal trough developing
over California and far southwestern Oregon. The thermal trough
will then strengthen and extend northward along the coast through
Thursday night, creating generally east winds through the
remainder of the week. Meanwhile, the upper level trough that
passed over the area earlier in the week will retrograde, moving
back to the west and setting up over the Great Basin, just south
of the ridge, which by this time will extend across the Pacific
Northwest and into the northern Rockies, creating east winds aloft
that will correlate and enhance the east winds at the surface.
All of this will result in very warm temperatures through at least
the first part of the weekend, with a strong Chetco effect likely
along the southern coast near Brookings. This pattern begins to
break down over next weekend, which may allow a weak trough to
enter the area early next week.

With all of this in mind, many changes were made to the forecast to
adjust temperatures and winds to fit the expected pattern. The
Chetco Effect will begin Wednesday ,then peak on Thursday, with
highs in Brookings expected to reach the 80s (and a few models even
suggest 90 degrees is possible) Thursday afternoon and perhaps
Friday as well. When the thermal moves inland, the south coast will
begin to cool as the marine layer regains control, while
temperatures for most inland areas will reach their warmest Friday
afternoon or Saturday afternoon. For these areas, high temperatures
will be more in line with early July than early May. Forecast
temperatures were adjusted to fit this thinking, while also
considering the strong inversions and warm ridgelines that this
pattern typically produces during the overnight and early morning
hours.

Once the thermal trough moves inland, the prevailing flow will take
on a more westerly onshore component, and temperatures will begin to
gradually cool Sunday and Monday. Some models suites suggest the
possibility of a weak front arriving around this time, but given the
warm and dry conditions ahead of it, any frontal passage will most
likely remain dry. -BPN

&&

.AVIATION...07/06Z TAFs...VFR conditions are expected throughout
this cycle. The chances for MVFR conditions to develop are around 30-
40 percent through this cycle. This would be for mainly ceilings,
and really any of the terminals have this chance. Skies will
generally start to clear late tomorrow afternoon and furthermore
through the evening hours. Conditions may be breezy tomorrow
afternoon as well.

-Guerrero


&&

.MARINE...Updated 245 AM Tuesday, May 7, 2024...A thermal trough
will strengthen Tuesday afternoon; as a result, north winds will
become gusty and steep wind-driven seas will develop--highest south
of Cape Blanco. Wind speeds will peak during Wednesday
afternoon/evening, but gusty northerly winds will persist into
Thursday night. During this stretch (Wed-Thu), gale force winds are
likely (85% or greater) across our southern waters. Given these
conditions, a Gale Warning for areas from roughly Coos Bay southward
is in effect. The strength of the thermal trough has trended
stronger as new data comes in. Consequently, a Hazardous Seas
Warning is in effect for all remaining areas north of the Gale
Warning. The thermal trough will weaken Friday into next weekend
resulting in weaker north winds and lower seas.

-Guerrero/Hermansen


&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory from 2 PM this
     afternoon to 11 AM PDT Wednesday for PZZ356-376.

Gale Warning from 11 AM Wednesday to 5 AM PDT Thursday for
     PZZ356-376.

     Hazardous Seas Watch from Wednesday morning through late
     Wednesday night for PZZ350-370-376.

&&

$$