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Area forecast discussion 
National Weather Service Medford or
924 PM PDT sun Sep 14 2014

Discussion...with the winds decreasing before switching to a
southerly flow begins...as the upper trough continues to migrate
towards the coast...the stratus has filled the coastal waters and is
starting to intrude into the coastal valleys at this time. Have
adjusted forecast to account for this this evening...otherwise no
changes this evening.

Previous discussion...an upper ridge centered over our area this
afternoon will slide east tonight as an upper low currently centered
near 35n 135w moves our way. The weather will remain tranquil
through tonight even as middle level moisture gradually increases. The
upper trough opens up and becomes very negatively tilted as it moves
north along the coast tomorrow. Most of the dynamics stay offshore,
but middle level moisture coupled with modest instability, weak pva,
and weak directional shear will result in a slight chance of
thunderstorms over our area tomorrow. We're keeping the chance
slight across the area inland from the coast, but if we're to have
storms they're most likely over the Cascades. While we don't expect
a lot of storms (if any) fuels are so dry that any lightning strike
is liable to start a fire. So this is certainly a concern. At any
rate, low levels will remain very dry (inverted-v soundings) so
little to no rain is expected and conditions will remain critical at
the surface. We have decided to issue a Fire Weather Watch to
highlight the thunderstorm threat in the Cascades for Monday.

At the same time, more energy will dive down along 140w and carve
out a large trough off the coast. The resulting southwest flow aloft
will continue to send bits of energy our way Tuesday, but it doesn't
look like much will happen as a result. Temperatures will cool
Tuesday and humidities will rise, but we will also likely see
gusty south to southwest winds on the east side, which is another
fire weather concern. The main upper trough then approaches the
coast Wednesday and moves onshore Thursday. The energy is going to
split with a closed low then heading south into California and a
northern jet stream staying well north of US. But we will still be
looking at an increased chance of showers and slight chance of
thunderstorms from Wednesday through Thursday. There will be a lot
of clouds and cooler temperatures, so showers may be the
predominant weather maker, but still can't rule out thunderstorms,
especially from the Cascades east. Both Wednesday and Thursday
will also feature gusty southwest winds on the east side.

A ridge begins building over the pacnw Friday and continues to do so
through the weekend into next week. This will result in a return of
hot, dry weather for our area. -Wright

&&

Aviation...based on the 14/18z taf cycle...at the coast...locally
persistent stratus and fog with IFR ceilings and visible are hugging the
coast south of Cape Blanco and will persist through Monday morning
with minimal inland intrusion. Areas of smoke will affect western
Siskiyou County and north into Jackson and Josephine County,
including kmfr. This may produce occasional restrictions to
visibility, however conditions are expected to remain VFR away from
the fires. Elsewhere, VFR conditions are expected to continue
through Monday morning. Weak instability will develop Monday
afternoon with a slight chance of thunderstorms, mainly from the
Cascade foothills eastward. Sk

&&

Marine...updated 235 PM PDT Sat 14 Sep 2014... a weak thermal
trough will remain over the area through tonight with light
winds and seas. Areas of low clouds and fog are expected over the
waters through Monday, mainly in areas south of Cape Blanco.
Increased southerly winds are expected beginning Monday afternoon as
a weak low approaches the coast from the southwest and moves
northward...followed by another low pressure system on Wednesday.
Winds in the coastal waters associated with these lows are expected
to remain just below Small Craft Advisory levels...and models have
trended lower with the winds and seas over the past few days. Even
so...seas will gradually increase Monday into Tuesday with small
craft conditions for seas possible by Tuesday afternoon. The second
low will gradually move inland Thursday with winds lowering
Thursday night and becoming northwest as high pressure builds
offshore. Sk

&&

Mfr watches/warnings/advisories...
or..Fire Weather Watch from Monday afternoon through Monday
evening for orz617-623.

California...none.

Pacific coastal waters...none.

$$

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