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Area forecast discussion 
National Weather Service Medford or
620 am PDT Sat Jul 30 2016

Updated aviation, marine, and fire weather discussions.

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Discussion...the main forecast challenge for Saturday will be the
potential for thunderstorms. There will be less upper level
support for convection than there was Friday...but what support
there is will stretch from The Mount Shasta area northeast into
Modoc...southern Klamath...and Southern Lake County. Low levels
will be significantly drier than Friday with precipitable water
values Saturday afternoon around half what they were Friday
afternoon. On top of all this the model lifted indices are not as
bullish with the instability as they were on yesterday's runs.
Even with the more favorable conditions on Friday...only one cloud
to ground strike was recorded. Therefore...will drop any mention
of thunderstorms from the forecast for Saturday.

Temperatures will be cooler as ridging aloft weakens over the
area in response to a long wave trough approaching the coast well
north of the area. Inland high temperatures will be near normal
over the Umpqua basin...5 to 10 degrees above normal over the rest
of southern Oregon...and 8 to 12 degrees above normal over
northern California.

The main item of concern Sunday and Monday will be wind and very
dry conditions.

The winds will be generated by two troughs moving onshore to the
north of the area. The first one will be relatively weak and will
move through to the north Saturday night into Sunday. This will
bring some gusty winds to the east side Sunday. This combined with
very low relative humidities will create fire weather concerns at
that time...possibly red flag warning conditions. Sunday highs
will be cooler...around 5 degrees above normal over Oregon and 5
to 10 degrees above normal over northern California.

The second trough will move onshore Monday night into Tuesday
morning and this one will be much stronger. It will push a dry
front onshore Monday night...and winds will be strong and gusty
east of the Cascades Monday afternoon and evening. This...combined
with the very dry air already in place may once again make for red
flag warning conditions over the area. Monday highs will be
similar to the Sunday highs.

Tuesday through Thursday looks to be quiet weatherwise with
quasizonal flow aloft over the area.

The coolest day will be Tuesday. Inland highs will be near normal
over most of the area...and a bit below normal over the Oregon
west side.

Inland temperatures will warm a bit Wednesday...but just 2 to 3
degrees. Then they won't change much through Friday. It will
remain dry. An approaching long wave trough may bring another
round of winds to the east side Friday...but that is a pretty iffy
forecast this far out.

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Aviation...30/12z taf cycle...MVFR marine stratus clouds have
become focused in the coastal valleys and have left the
immediate coastline, and the marine layer has become less
pronounced per latest profiler data. Still, there is a possibility
of a brief period of MVFR conditions at koth before full clearing
later this morning. Moderate to strong and gusty north winds are
expected through this evening for most areas along the coast and
offshore. Scattered cumulus buildups are expected over the higher
terrain of northern California into south central Oregon this
evening, but no thunderstorms are expected. Expect that MVFR
ceilings will return to the coast late this afternoon through the
evening. Sk/btl

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Marine...updated 500 am PDT Saturday 30 Jul 2016...a thermal trough
along the coast and high pressure offshore will continue to produce
moderate to strong north winds and steep to very steep wind driven
seas into early next week. Hazardous warning level seas and gales E
expected mainly beyond 5 nm from shore today through today...mainly
for locations from Cape Blanco southward. However, an area of
hazardous seas warning conditions is expected to next extend
northward to just south of Cape Arago. Winds and seas should peak
this afternoon and evening. On Sunday, warning seas and
gales are expected from Cape Blanco south with Small Craft Advisory
winds and seas to the north. On Monday, winds may drop below gale
force across most the waters. However, hazardous warning level seas
remain possible from Gold Beach south on Monday. Winds are expected
to rise to gales again by Tuesday evening and continue into Thursday
of next week. -Cc/sk

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Fire weather...updated 6 am PDT Saturday, 30 July 2016...

With only one lightning strike yesterday and models showing
all parameters today as being less favorable for thunderstorms, they
have been removed from the forecast today. Some cumulus buildups
can still be expected in northern California into Southern Lake
and Klamath counties.

Hot, dry, and, in times and places, windy will be the theme
over the weekend and into early next week, especially for the Modoc.
Given the good agreement among models for sunday's low humidities
and gusty winds, we have upgraded the watch in fwz285 to a red flag
warning for Sunday afternoon and evening. The Fire Weather Watch
continues there for Monday. Critical fire weather conditions could
also affect the southeastern portion of fwz624, and given the
lower confidence there for conditions being met, we have a Fire
Weather Watch continuing there Sunday and Monday. Current data
suggests Monday will be the windiest day with gusts to 35 mph in
east side locations.

A slight cool down and a wind decrease is then expected Tuesday and
Wednesday. Generally seasonable temperatures are expected
late week into next weekend. Btl/sk

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Mfr watches/warnings/advisories...
or...Fire Weather Watch from Sunday afternoon through Sunday evening
for orz624.
Fire Weather Watch from Monday afternoon through Monday evening
for orz624.

California...Fire Weather Watch from Monday afternoon through Monday evening
for caz285.
Red flag warning from noon to 9 PM PDT Sunday for caz285.

Pacific coastal waters...Small Craft Advisory until 5 am PDT Monday for pzz350-356-370.
Gale Warning until 5 am PDT Sunday for pzz356.
Hazardous seas warning until 5 am PDT Monday for pzz356-376.
Hazardous seas warning until 5 am PDT Sunday for pzz350-370.
Small Craft Advisory from 5 am Sunday to 5 am PDT Monday for
pzz376.
Gale Warning until 5 am PDT Monday for pzz376.

$$

Nsk/jrs/nsk

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