Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 111055
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
355 AM PDT Tue Aug 11 2020

.DISCUSSION...Even though temperatures will trend a few degrees lower
today compared to yesterday, today will be a hot, dry and breezy
day across the forecast area. It will be hot in absolute terms
because we`re very close (just passed) to the hottest time of the
year, and also in relative terms because high temperatures are
expected to be about 5 degrees above normal for most locations. A
dry cold front will provide the "breezy" part of the day, with
many locations gusting into the 30s(mph) east of the Cascades, and
areas west of the Cascades will gust well into the 20s(mph). A
Red Flag Warning continues for this afternoon for portions of
Southern Klamath and Lake Counties while a Fire Weather Watch
continues for tomorrow afternoon for portions of Modoc and
Southern Lake Counties.

Model guidance is in pretty good agreement regarding thunderstorm
chances today, with most data pointing towards Modoc, southern Lake,
and far eastern Siskiyou Counties for the best chances for
lightning.

Winds will trend lower, along with temperatures, on Wednesday, with
the exception of areas well east of the Cascades where stiff
afternoon breezes are expected again. Wednesday will feature the
coolest temperatures of the week.

Cooler conditions will continue through Thursday (although afternoon
high temperatures will still be around normal).

On Friday a warming trend will begin as a large upper ridge of high
pressure builds over the Desert Southwest. At least a couple
afternoons with 100+ degree temperatures are expected in the Rogue
Valley. While hot conditions are very likely at this time, any
details on thunderstorm potential that tends to follow heat events
like this are fuzzy at this time. Thunderstorm chances could enter
the picture as early as Saturday, but latest model data doesn`t
provide enough confidence to add them to the forecast.  Stay tuned
as we try to hone in on the likely evolution of the pattern ahead of
us.

&&

.AVIATION...For the 11/06Z TAF Cycle...A marine stratus surge along
and near the Curry County coast from Brookings southward will result
in IFR to LIFR ceilings and visibilities mainly along and within
about 15NM through Tuesday morning. Similarly reducing conditions in
the northerly flow will expand along and west of the coast from Port
Orford northward tonight into the morning. Expect conditions to
improve to VFR for land areas in the 17-20Z time frame Tuesday
afternoon while the lower conditions linger through the afternoon
for a smaller portion of the coastal waters.

Tuesday afternoon and evening winds will be breezy to windy ,
strongest over the the southeastern portions of the area, where they
will be westerly. While breezy northwest winds are expected
elsewhere, they will be lesser than they have been along and near
the coast.

Smoke will continue to reduce visibilities near and downwind of the
Red Salmon Fire through the TAF period, generally to the northeast
and east of the fire in the afternoon and evening hours. ~BTL

&&

.MARINE...Updated 200 AM PDT Tuesday, 11 August 2020...The thermal
trough will continue to weaken today into Wednesday as an upper
level trough swings through the area and disrupts the pattern.
Conditions will gradually improve today, especially north of Cape
Blanco. However, winds and seas will remain hazardous to small craft
through tonight for areas south of Port Orford. Conditions will be
improved for all areas for a brief time early Wednesday morning and
afternoon.

The thermal trough rebounds Wednesday evening and strengthens into
Friday. Conditions hazardous to small craft will return south of
Cape Blanco by late Wednesday afternoon, with conditions
deteriorating further Thursday afternoon into Friday. Conditions
hazardous to small craft will likely spread north of Cape Blanco,
and a period gales will be possible south of Cape Blanco Thursday
afternoon into Friday. Winds and seas look to peak Friday with
conditions gradually improving Saturday into Sunday. By Sunday, the
thermal trough diminishes, resulting in weakened winds and lower
seas. /BR-y

&&

.FIRE WEATHER...Updated 4AM PDT Tuesday 11 August 2020...A weaker
thermal trough has set up at the coast this morning. This has
resulted in this morning`s humidity similar to slightly higher
than 24 hours ago. An approaching dry cool front will bring gusty
winds and continued low humidity this afternoon and again
Wednesday afternoon, and these are the two days we`re most
concerned with in terms of critical fire weather conditions this
week. Isolated thunderstorms are expected in Northern California
and southeast Lake this afternoon and a combination of dry/windy
conditions east of the Cascades both today and Wednesday,
resulting in critical fire weather conditions. West of the
Cascades humidity will be near critical, and gusty northwest winds
are expected.

Thunderstorms...Today there is higher confidence than yesterday for
isolated thunderstorms to develop over eastern Siskiyou, Modoc
and far southeast Lake Counties in the afternoon and evening. Any
thunderstorms that do develop may not produce much rainfall.

Dry Humidities and Gusty Winds...Ahead of the dry frontal passage
Today and Wednesday, gusty winds and low relative humidities are
expected east of the Cascades. A Red Flag Warning is in effect for
Oregon fire weather zones 624/625 for this afternoon and evening.
These conditions are expected to continue into Wednesday and a
Fire Weather Watch is in effect for zones 624/625 in Oregon as
well as 285 in California. Compared to today, conditions on
Wednesday look to be slightly cooler, but similarly dry and breezy
to windy. Minimum relative humidity east of the Cascades on both
days will generally be in the lower teens to as low as 8 percent
with 15 to 25 mph winds gusting as high as 40 mph.

A warming trend with dry weather will follow during the second half
of the week. -CC/Keene


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from 2 PM this afternoon to 9 PM PDT this
     evening for ORZ624-625.
     Fire Weather Watch from Wednesday afternoon through Wednesday
     evening for ORZ624-625.

CA...Fire Weather Watch from Wednesday afternoon through Wednesday
     evening for CAZ285.

Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT early this morning for
     PZZ350-370.
     Small Craft Advisory until 5 AM PDT Wednesday for PZZ356-376.
     Small Craft Advisory from 5 PM Wednesday to 5 PM PDT Thursday
     for PZZ356-376.
     Hazardous Seas Warning until 5 AM PDT Wednesday for PZZ356-376.
     Hazardous Seas Warning until 5 AM PDT early this morning for
     PZZ370.

$$


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