339
FXUS66 KMFR 150323
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
823 PM PDT Tue May 14 2024

.DISCUSSION...There are no changes to the forecast this evening.
An upper level ridge remains in place, supporting continued above
average temperatures and clear daytime skies through midweek. Low
pressure in Canada is expected to flatten the ridge and bring
cooler temperatures at the end of the week and into next week.

Please see the previous discussion for more details about the
short- and long-term forecasts. -TAD


&&

.AVIATION...15/00Z TAFs...VFR conditions will prevail through
Wednesday evening, with a couple of exceptions. Starting around 04Z
this evening, IFR ceilings are expected to return to areas north of
Cape Blanco and persist into mid-morning on Wednesday. Also, patchy
IFR ceilings are expected in the Umpqua Basin late tonight and could
potentially affect Roseburg for a brief period early Wednesday
morning (between 12z-17z). Otherwise, expect gusty winds near the
coast, strongest during the afternoon and evening hours with
similar strength as today during late Wednesday.  /DW

&&

.MARINE...Updated 800 PM Tuesday, May 14, 2024...A thermal trough
pattern will maintain gusty north winds and very steep and hazardous
wind driven seas for all areas through Wednesday night. Winds will
be strongest, reaching gales, and seas will be steepest south of
Cape Blanco and during the afternoons and evenings. North of Cape
Blanco, very steep and hazardous seas with strong winds are
expected, but below gale force.

The thermal trough pattern weakens some on Thursday and gales will
ease. Despite this subtle improvement, gusty winds and very steep
and hazardous seas will persist through the end of the week.
Conditions may improve overall over the weekend as the upper level
pattern transitions, though expect conditions to remain hazardous to
small craft for areas south of Cape Blanco as northerly winds
continue. /BR-y


&&

PREV DISCUSSION... /Issued 156 PM PDT Tue May 14 2024/

SHORT TERM...Tonight through Thursday...Strong high pressure
aloft and at the surface is centered well off the U.S. West Coast,
but will be the main player and influence on our weather for the
next couple of days. Satellite imagery is showing the high clouds
from this morning (and also the low clouds in the Umpqua Basin)
have largely dissipated or exited the area to the south. Bright,
sunny skies can be expected area wide the rest of this afternoon.
Inland areas will be warm with highs generally 10-15 degrees F
above normal.

A strong thermal trough is currently set up along the NorCal and
SW Oregon coast and this is leading to gale force winds and high
seas over the marine waters. On land, NNE offshore winds
originating in the coast ranges, are funneling down the Chetco
River valley and resulting in significant warming due to
compression. As such, temperatures early this afternoon are
already in the low to mid 80s in Brookings. With more of a
northerly wind component, areas farther north along the coast
won`t get to experience this effect and will remain cooler with
highs in the 60s (maybe low 70s for areas just a bit inland).
Breezy winds inland this evening will wane with the setting sun.

Expect mainly clear skies tonight, though some low clouds will
develop later this evening/overnight along the coast north of Cape
Blanco as north winds subside. In fact, some clouds are already
showing up near Cape Arago.

Wednesday`s weather will be mostly a repeat of today. Low clouds
along the coast north of Cape Blanco peel back offshore during the
mid-late morning; sunny skies prevail inland. Inland temperatures
probably top out at least a few degrees higher than today. Another
warm day is expected in Brookings as winds continue channel down
the Chetco valley.

A deeper marine layer is expected to develop Wednesday night, and
this should result in more cloud cover/patchy fog along the coast
north of Cape Blanco. The clouds could also push into portions of
the Coquille Valley and the Umpqua Basin. -Spilde

LONG TERM...Thursday May 16th - Tuesday May 21st...The upper level
ridge that lead to the warm temperatures earlier in the week will
start to flatten as a trough moves down the British Columbia coast.
This will help push a thermal trough (heat low) from along the
southern OR/NorCal coast inland. Typically, this leads to the
warmest temperatures of a stretch inland while coastal areas,
especially Brookings, cool off.

The trough then slides over the northwest U.S. Friday. Any
precipitation associated with this looks to remain well to our
north, so dry weather will continue in the region, but the resulting
cooler, northwesterly flow will result in temperatures dropping (by
more than 10 degrees in some areas) Friday afternoon compared to
Thursday. Breezy northwest winds at the surface will pick up in the
late afternoon into the evening, but not anything overly gusty.

While dry weather continues through the weekend, temperatures will
cool each day under continued northwesterly flow as another
shortwave trough starts to slide down from the northwest. This will
gradually dig far enough south by Monday that about 10-15% of
members of the National Blend of Models indicate some precipitation
is possible in northern Douglas and Klamath counties. Another
shortwave Tuesday will bring these chances further south and east,
though model differences in the strength and timing of this system
are numerous at this range. -CSP

&&

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

PACIFIC COASTAL WATERS...Gale Warning until 5 AM PDT Thursday for
     PZZ356-376.

Hazardous Seas Warning from 5 AM Thursday to 5 AM PDT Friday for
     PZZ350-356-370-376.

     Small Craft Advisory until 5 AM PDT Friday for PZZ350-370.

&&

$$