659
FXUS66 KMFR 082147
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
247 PM PDT Sat Jun 8 2024

.DISCUSSION...

.Short Term...Rest of Today through Monday Night...A trough will
approach the coast this afternoon and evening, move onshore
tonight, and pass over southern Oregon and far northern California
tomorrow. This trough is responsible for the cooler temperatures
today, and it will also be the lifting mechanism the atmosphere
needs to tap into some relatively significant instability in the
low to mid levels, while also providing enough shear to enhance
thunderstorm chances. A few convective cells have already formed
today, and activity is expected to intensify and become more
widespread through the afternoon, mainly along and east of the
Cascades and in northern California. Some of these storms could
be strong; while severe storms are not expected, they are not out
of the question, with around a 5 percent chance for any given
storm to produce strong winds and/or large hail.

Elevated instability is expected to continue through tonight and
into Sunday afternoon as the trough passes onshore. Convective
activity is therefore expected to continue all the way into Sunday
afternoon as well, although over time it will be concentrated more
to the east, ahead of the trough axis.

Ridging returns Sunday night into Monday, along with a
reintensifying thermal trough along the coast. This will dry
things out and bring an end to thunderstorm chances, and it will
also allow temperatures to bump back up, reaching about 10
degrees above normal for this time of year as we head into the
extended period. -BPN

.LONG TERM...Tuesday 6/11 through Saturday 6/15...The extended
forecast begins with zonal flow (west to east) at the middle levels
of the atmosphere. While weak disturbances will pass largely to the
north of the area, expect dry weather to continue across southern
Oregon and northern California through the extended period. However,
temperatures will be much slightly above normal with highs in the
upper 80s to low 90s east of the Cascades and lower 80s to upper 70s
east of the Cascades. The coast will be cooler with temperatures in
the 60s.

Then, for the weekend, the general flow pattern will turn to become
more unsettled as a low pressure system approaches the Pacific
Northwest. The general front ahead of the low will be relatively
weak and precipitation is not expected that far south. However, some
precipitation in showers will be possible within the low itself.
Ensembles do show some timing differences, but the general thought
is that temperatures will be even cooler over the weekend, winds
will be breezy, and that a slight showers will be possible largely
north of the Douglas/Lane County Border. However, this could change
as the details of this system become more clear. Have gone with the
National Blend of Models for this forecast package. -Schaaf


&&

.AVIATION...08/18Z TAFs...An isolated thunderstorm has already
popped up this morning ahead of an upper level wave and some modest
mid level moisture. Thunderstorm activity will pick up into the late
afternoon and early evening as the atmosphere destabalizes. The bulk
of the activity will develop east of the Cascades and in northern
California.

The thunderstorm threat will persist overnight east of the Cascades
and in the central Cascades as the upper level wave approaches the
Oregon coast. Some models also show a bulk of moisture around 7000
to 9000 feet above sea level, which could aid in initiating
convection overnight. Right now the threat of overnight
thunderstorms remains low, although these events are sometimes
underdone in the models.

Overall, be on the lookout for thunderstorms across the forecast
area, especially farther to the east through the TAF period. Lower
ceilings around 1000 feet are anticipated near the coast overnight
as high pressure begins to build. IFR ceilings are most likely,
although periods of LIFR ceilings also remain possible.

-Smith

&&

.MARINE...Updated 200 PM Saturday, June 8, 2024...Gusty north winds
will bring steep seas to areas south of Ophir and a few miles away
this evening. Then, a moderate west swell moves in tonight through
Sunday. During this time, the thermal trough will restrengthen,
bringing increasing north winds and steep to very steep seas Sunday
into early next week, especially south of Cape Blanco. Conditions
will at least remain hazardous to small craft south of Cape Blanco
through midweek.

Conditions could worsen again around Thursday as the thermal trough
builds strength.

-Smith

&&

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

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 AM PDT Monday
     for PZZ356-376.

     Hazardous Seas Warning from 5 AM Sunday to 11 AM PDT Monday for
     PZZ356-376.

&&

$$