Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 282140

Area Forecast Discussion
National Weather Service Medford OR
240 PM PDT Wed Oct 28 2020

.DISCUSSION...High pressure centered near 40N and 130W will
maintain dry weather over the area through Thursday. Tonight will
be clear and cold east of the Cascades, but it`ll also be mainly
clear and chilly in the valleys west of the Cascades. Dewpoints
are up from 24 hours ago along the immediate coast, the coastal
valleys and in the Umpqua Basin, so expect some low clouds and
fog to form again in those areas. After any morning clouds/fog,
Thursday will be sunny with another mild afternoon. Expect highs
largely in the 70s with some 80s in western Siskiyou County
valleys, but also some 60s in the mountains, along the coast and
in NW Douglas County.

By Friday, a fast-moving upper air disturbance and surface cold
front will push through the area. Moisture with this system is
limited, so we`re not expecting any precipitation, except for a
minimal chance of showers near the Douglas/Lane County border. It
will cause an increase in WNW winds during the afternoon/evening,
especially from the Cascades east. Model 700mb flow peaks around
40 kt, so there could be some gusts of 25-35 mph over the higher
terrain and more exposed locations of the east side. Temperatures
overall Friday will be about 5 degrees lower than on Thursday.

A brief period of offshore east winds is expected late Friday
night into Saturday as the upper ridge offshore becomes re-
established and a surface thermal trough redevelops, but
humidities should be up a bit as well. The upper ridge axis will
shift inland Sunday into Monday with a broad south to southwest
flow aloft developing early next week, but we are expecting dry,
mild weather to continue.

The next opportunity for precipitation still looks to be centered
on the November 3-4 time frame. Guidance continues to show the
first front reaching the coast around Tuesday, but with it largely
falling apart as it moves inland. The best rain chances with this
system will be along the coast, in the Umpqua Basin and eastward
to the Cascades. But, areas that tend to get downsloped under such
a flow, like the Rogue Valley, NorCal and the east side could end
up with little to no precipitation. A new axis of high pressure
is then likely to set up in the Gulf of Alaska. This is likely to
open the door for some frontal systems to arrive from the
northwest. Typically, a pattern such as that results in light to
moderate precipitation and near to below normal temperatures.


.AVIATION...For the 28/18Z TAFS... VFR conditions will prevail
through Thursday morning at most locations. The exceptions are the
coast/coastal valleys north of Cape Blanco and the Umpqua Basin
around Roseburg. This morning visibility lowered some in those
areas, and with more moisture in the low levels now compared to 24
hours ago, we expect better chances for IFR/MVFR visibility Thursday
morning. Any low visibility should improve to VFR late Thursday
morning. Keene


.MARINE...Updated 200 PM PDT Wednesday 28 Oct 2020...A thermal
trough is moving inland and winds and seas are gradually
diminishing. Calmer conditions are expected late tonight through the
end of the week with seas around 5 feet. A weak front will move
onshore late Friday and bring building northwest swell but
conditions are expected to remain just below Small Craft Advisory
criteria. Keene


.FIRE WEATHER...Updated 200 PM PDT Wednesday Oct 28 2020...Winds
will remain relatively weak through Thursday. Humidities will remain
much drier than normal, but not as dry as the past few days. Ridge
humidity recoveries will rise to above 30 percent in Siskiyou county
and extreme southwest oregon by Thursday night, with much better
recoveries Friday night. There will also be large temperature swings
from cool/cold overnight low temperatures to well above normal
afternoon highs. The models have continued to trend weaker with the
cold front late Friday into Friday night, and now does not look like
it will produce any rain in almost all of the region. It is likely
to simply produce a modest and brief improvement in humidity levels
and slight decrease in day-time temperatures. Southerly flow is
likely Sunday into Monday, which would bring warming and drying.
Forecast uncertainty is high beyond Monday, but a pattern shift is
likely. The medium range models suggest that several fronts may move
onshore between next Tuesday and next Friday, but confidence remains
low on the timing and strength of these systems with many ensemble
members not showing any precipitation.  Sven




Pacific Coastal Waters...Small Craft Advisory until 2 AM PDT Thursday
     for PZZ350-356-370-376.


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