Small Craft Advisory 62, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
835 PM PDT Sun Jul 8 2018

.UPDATE...No major changes were necessary this evening. Only a few
updates were necessary, to bring the sky conditions into line
with recent satellite imagery, and to make some slight adjustments
to smoke coverage over Siskiyou and Klamath counties.

Expect another quiet night tonight, with mostly clear skies away
from the coast, and winds calming shortly after sunset. Along the
coast, thick marine layer clouds will remain, although some
erosion is possible south of Cape Blanco this evening.

For more information on the rest of the forecast, see the
previous discussion below. -BPN

&&

.AVIATION...For the 09/00Z TAFs...Along the coast and in the
Coquille Basin, MVFR ceilings are present with IFR/LIFR cigs
present south of Cape Blanco. The latest visible image shows the
marine stratus remains entrenched inland of Coos County. MVFR cigs
continue at North Bend this afternoon and could lower to IFR
tonight.

In the Shasta Valley and east of the Cascades, wildfire smoke will
continue to bring a reduction in vsbys and terrain obscurations
through the TAF period.

The latest visible image shows the smoke mainly concentrated
northeast of the wildfire near  Howard Prairie and smoke has pushed
into Klamath Falls. Satellite imagery also shows smoke has moved
into southern half of Klamath County.

VFR conditions are expected elsewhere through the TAF period.
FB/Petrucelli

&&

.MARINE...Updated 830 PM PDT Sunday 8 July 2018...Relatively calm
conditions will continue tonight with seas remaining below 5 feet
and northerly winds below small craft advisory levels. The thermal
trough will redevelop Tuesday. North winds will steadily increase,
with small craft advisory winds and seas likely late Tuesday
afternoon for areas south of Cape Blanco.

Winds and seas increase further Tuesday evening and Wednesday,
possibly reaching gales Wednesday afternoon beyond 5 nm from shore.
Meanwhile, gusty winds with steep to very steep seas are possible
north of Cape Blanco.

The thermal trough is expected to weaken Thursday afternoon with
winds and seas gradually diminishing. -FB

&&

.PREV DISCUSSION... /Issued 548 PM PDT Sun Jul 8 2018/

DISCUSSION...Confidence in the forecast through Thursday is high.
The changes in the short term were mainly fine tuning adjustments
to reflect the latest forecast data. Warming, drying, and gusty
winds will be the main features of interest during that time.

A Red Flag Warning remains in effect through this evening for the
eastern half of Modoc County and southern portion of Lake County,
which includes Alturas and Lakeview. Winds in that area have
become gusty during the past couple hours, including 29 mph at 3
PM in Alturas. Within the past hour, the plume of thickest near
surface smoke from the Klamathon Fire near Hornbrook has begun its
expected eastward push from the Jackson/Siskiyou/Klamath County
triple point. A higher concentration of smoke is still expected in
Klamath Falls early this evening...expanding toward Lakeview,
while a southwest flow aloft continues sending a lower
concentration haze across much of the southern Oregon Cascades and
east of the Cascades. Smoky skies also linger in the Shasta
Valley. The current and future trend in the amount of smoke being
produced is difficult to tell, and is the most important variable
in air quality. But, a similar scenario is expected Monday with
at least a slight decrease in east side smoke during the morning
then an increase in westerly low level winds during the afternoon.

Another notable aspect of the short term forecast has been the
stubbornness of coastal and Coquille Valley low clouds to erode.
Continued onshore flow is expected to continue these low clouds
into Monday morning with better progress in erosion during the
day, especially south of Cape Blanco. Further improvement with
increased mixing later in the day.

A dry trough is forecast to reach the coastal range Monday
afternoon then continue to weaken as it moves across the remainder
of our area Monday night. This will bring an increase of northwest
winds, with gusts to 30 MPH likely in the vicinity of the
Klamathon. But, the trough will also bring higher relative
humidity than today, trending higher by around 5%. The higher RH
will keep conditions from reaching critical thresholds.

Other aspects of note this week are easterly winds with drying at
ridge tops, and downslope warming at Brookings Tuesday through
Wednesday, a strong warming trend with the hottest temperatures so
far this season inland Wednesday at least into Thursday (into the
triple digits for many west side valleys and 90s for east side
valleys). The warming will develop with strong ridging behind
Monday's fast moving weak trough. The forecast probability for
thunderstorms on Thursday was low and now trended lower with
higher confidence in a slightly slower northward push of monsoonal
moisture up the spine of the Sierra Nevada. A thunderstorm from
south of our area might extend into southeast Siskiyou or
southern Modoc County late on Thursday.

There is a higher probability for thunderstorms Friday
afternoon/evening, but the locations to be in focus are still
highly uncertain. A blend was utilized between the GFS solution
that maintains stronger ridging late in the week and the ECMWF
that allows a deeper trough moving into western Canada to weaken
the ridge. The ridge position will be the major factor in
determining the resultant mid-level steering flow for monsoonal
moisture. By the weekend, the probability increases that lingering
instability will trend eastward, perhaps east of our area.

&&

FIRE WEATHER...Updated 230 PM PDT Sunday, 08 July 2018...
A dry airmass has moved over our area with RH values trending lower
compared to Saturday.  It's interesting to see a few clouds actually
develop over the eastside even with this drier airmass.  None the
less, we're still expecting red flag conditions this afternoon and
evening as RH's hit the single digits with wind gusts 20 - 25 mph
with some areas possibly seeing gusts to 30 mph.

After today,  Monday will be interesting with an upper level trough
and a dry cold front pushing through parts of Oregon. In general,
RH's will be trending upward by about 5% making it more difficult to
hit Red Flag Warning criteria.  It should also be noted this dry
cold front should produce some gusty conditions yet again east of
the Cascades and on the higher ridges and peaks.

The immediate concern was for the Klamathon fire burning along the
Siskiyous into the Soda Mountain Wilderness.  Some of the exposed
peaks up there can become pretty breezy without any weather moving
through.  With a trough and front moving through, we are thinking
gusts 20 - 30 mph on exposed peaks are probable. The dry cold front
will probably come onshore around 0z Tuesday and continue it's
eastward progression during the evening.

A thermal trough is expected to develop along the Curry County
coastline Tuesday night into Wednesday.  East winds are expected on
the coastal range, bringing drier and warmer air into the Brookings
area, and the surrounding coastal range.  Recoveries will start to
fall into the moderate range Wednesday night into Thursday morning
with the warmer and drier weather.

Finally, we'll see temperatures in the upper 90's to the mid 100's
Wednesday into Friday for the west side valleys.  These temperatures
are about 10 to 15 degrees above average for this time of year.  It
should be noted that an average high for Medford this time of year
is about 90 degrees. We'll also have a slight chance for
thunderstorms Friday into Saturday.  Read the discussion above for
more details on the heat and thunderstorms.

-Smith

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 9 PM PDT this evening for ORZ624-625.

CA...Red Flag Warning until 9 PM PDT this evening for CAZ285.

Pacific Coastal Waters...None.