FXUS66 KMFR 021544

Area Forecast Discussion
National Weather Service Medford OR
844 AM PDT Thu Jul 2 2020

.DISCUSSION...No changes to the forecast at this time.

Marine layer induced stratus is burning off in areas of Douglas
and Coos county. Expect cloudless skies, but mild temperatures.
Remember that at this time of the year the sun's intensity is
quite strong, so even if it doesn't feel hot, to take action to
prevent sunburn.

We are still anticipating afternoon breezes for inland areas, but
they should be weaker than the past few afternoons. Beyond this,
please refer to the previous discussion for expanded details on
the forecast.


.AVIATION...For the 02/12Z TAF Cycle...Areas of MVFR ceilings will
burn off quickly this morning. VFR will prevail for the remainder
of the TAF cycle.



.MARINE...Updated 840 AM PDT Thursday 2 July 2020... Gusty north
winds and steep to very steep seas will continue through this
evening as the thermal trough persists along the coast. The
strongest winds with very steep and hazardous seas will continue
south of Gold Beach. Winds and seas will remain highest during the
afternoon and evening hours.

Conditions will improve as the thermal trough weakens Friday, with
Small Craft Advisory conditions retreating to areas south of Cape
Blanco. Relatively calm conditions are then likely Friday night into
early next week, although a low, long period southerly swell is
expected later Friday through the weekend, which could result in
problematic bar conditions and increased sneaker wave risk. The
thermal trough will return next week, but models are showing it
taking up a more inland position. This would keep north winds in
place over the area, but at a much weaker strength than during a
typical event.



.PREV DISCUSSION... /Issued 450 AM PDT Thu Jul 2 2020/

DISCUSSION...Upper troughing will dominate our weather pattern into
next week, and weather impacts will be minimal through the next 7
days. Marine layer stratus has made its way into the Umpqua
Basin, and the coast, as is typical when the winds aloft (at about
5000 ft) turn more northerly, has at least partially cleared out
north of Cape Blanco. Expect any morning clouds to clear out later
this morning,

A warming trend is expected today (about 5 degrees warmer than
yesterday), and then temperatures should remain relatively steady
through the weekend. A sunny 4th of July weekend is expected with
temperatures near normal and typical afternoon breezes. Models show
a robust area of marine layer clouds over the Northeast Pacific
waters, so expect nighttime and morning low clouds to move inland to
the Umpqua Basin, then clear in the late morning/early afternoon.
For the immediate coastline, clearing is a little more uncertain,
but we do think that at least partly sunny skies can be expected in
the afternoons/early evening timeframe...before the marine stratus
moves back in late in the evening and overnight.

Midlevel winds (at about 10000 feet above sea level) dictate
much of the weather we experience in the summertime...and in the
wintertime to some extent. We've transitioned away from late
spring frontal-type thunderstorm activity that involves warming
surface temperatures due to increasing sun angle and the last of
cold air "pools" aloft behind cold fronts. Now through August,
thunderstorms are generally dictated by how much moisture can be
delivered into our forecast area. Summertime winds that are
generally from a westerly direction (northwest to southwest)
usually bring relatively dry and stable air to the forecast area.
This may seem strange, given that these winds are coming from the
ocean. However, the Northeast Pacific is a cold ocean, and the
colder the ocean the less evaporation of moisture into the
atmosphere. Summertime thunderstorms in our forecast area depend
on significant moisture, so any winds that come from our local
ocean waters typically do not provide sufficient moisture. When
deep layer winds shift more southerly, the moisture source can
shift to distant, warmer oceans like the Gulf of California and
Gulf of Mexico. This is when significant thunderstorm events
enter the picture. All this early-morning pontificating about
winds above the surface is to bring home the point that these
winds are so meaningful for our forecast area, and that regional
midlevel winds will remain southwesterly to westerly through
Wednesday at least, resulting in a stable air mass with no
thunderstorms expected.

As we move into late next week, there's some data that suggests as a
4-corners high develops in the Desert Southwest, midlevel winds may
shift to a more southerly direction. However, the consensus of the
model data keeps generally southwesterly flow aloft, so we're
keeping thunderstorms out of the forecast even late into next week.
We'll keep monitoring the evolution of this upper troughing

FIRE WEATHER...Updated 200 AM PDT Thursday, 2 July 2020...Gusty
northeast winds and moderate humidity recoveries are occurring
along the mid slopes and ridges in fire zones, 618, 619 and
western 620 this morning.

Aside from afternoon breezes, it's looking like a relatively
quiet fire weather pattern for at least the next 7-10 days. The
general pattern will feature troughiness over the area with a
stable northwest, then southwest flow. This typically results in
temperatures around or slightly below normal and no precipitation.
A warm up is expected through early next week. Even then,
afternoon temperatures are expected to be near normal for this
time of the year.

Thunderstorm chances are next to zero through the forecast period.
This is because of generally stable and dry northwest to southwest
flow aloft and drier mid level moisture. A upper trough will move
into the area by the start of next week with a weak trigger, but
once again mid level moisture is lacking, thus no threat of

Beyond next Monday the operational models, ensemble members and
cluster analysis all point to a similar conclusion. General
troughiness with continued dry and stable conditions.


OR...Frost Advisory until 8 AM PDT this morning for ORZ029>031.

CA...Frost Advisory until 8 AM PDT this morning for CAZ084.

Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT Friday for PZZ350-370.
Small Craft Advisory until 2 AM PDT Saturday for PZZ356-376.
Hazardous Seas Warning until 5 AM PDT Friday for PZZ356-376.

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