Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 170356

Area Forecast Discussion
National Weather Service Medford OR
856 PM PDT Mon May 16 2022

.DISCUSSION...The forecast remains on track and no updates were
needed at this time as . Currently, some scattered fair weather
cumulus exists west of the Cascades. Humidities are also beginning
to recover since dropping into the upper-teens and lower-twenties
across NorCal and the east side this afternoon. Beyond this,
there exists a low possibility of patchy fog in west side valleys
but, NBM probabilities of ceilings below 3kft into Tuesday morning
are low, around 20%. So more likely just some valley stratus will
result, that get impacted against the valley walls.

The area will be influenced by periods of weak troughing and
ridging through the week, and we`re not expecting much in the way
of precipitation. Occasional gusty winds will impact the more
wind-prone areas (east of the Cascades). There is some potential
for frost west of the Cascades Friday morning. Please refer to
the previous discussion below for further details.   -Miles


.AVIATION...17/00Z TAFs...Along the coastal waters, coast, and
Umpqua Basin. Predominantly MVFR CIGS with a few isolated areas of
IFR CIGS possible will return tonight before lifting again Tuesday
morning. Over the remainder of the area...VFR conditions will
prevail through the TAF timeframe, with some breezy afternoon winds.


.MARINE...Updated 830 PM PDT Monday 16 May 2022...Offshore high
pressure and a thermal trough near the coast will weaken Tuesday
night. This will bring a period of gusty north winds and steep
choppy seas to areas south of Cape Blanco through the day tomorrow.
A weak front will move onshore Wednesday. Offshore high pressure and
a thermal trough near the coast will return Thursday, strengthen
through Friday evening, then weaken Friday night into Saturday. This
will bring a return of moderate to strong north winds and steep to
very steep wind-driven seas, mostly south of Cape Blanco. -Sven


.PREV DISCUSSION... /Issued 208 PM PDT Mon May 16 2022/

SHORT TERM...Today through Thursday night...Beautiful geocolor
satellite imagery this afternoon shows high clouds sweeping over
the eastern portions of the forecast area, while low clouds are
confined mainly to areas west of the Cascades. Temperatures are
trending about 10 degrees lower than yesterday at this time,
courtesy of the cooler air mass moving in behind the mainly dry
cold front. Weak upper troughing will continue through Tuesday
before a move significant trough moves through Wednesday into
Thursday. High temperatures Wed and Thu will trend significantly
cooler, 5 to 10 degrees below normals for this time of year.

Some precipitation will accompany the trough on Wednesday and
Thursday, but it will likely be confined to the coast, Umpqua Basin,
and Cascades from around Lake of the Woods northward. Winds will
become gusty Wednesday and Thursday afternoons, and Wind Advisory
criteria (gusts to 45 mph) may be reached in the most wind-prone
areas of Lake County.

Temperatures have been and will continue to be rather non-impactful
for much of the week. However, by Friday the air mass will be cool
enough to bring the potential for frost in some valleys west of the
Cascades. Latest model data suggests there won`t be much in the way
of cloud cover, and this could maximize the amount of cooling we
experience. Given all the backyard gardens that are being started
this time of year, we thought it would be prudent to highlight
Thursday night/Friday morning as potentially impactful in terms of
temperatures. Folks may need to protect frost-sensitive
vegetation. Stay tuned to the forecast for more updates.

LONG TERM...Friday through Monday...The general consensus among
the operational models (ECMWF and GFS) and ensemble members are
all pointing towards a relatively quiet and dry pattern from
Friday through next Monday.

Friday, the upper ridge axis remains offshore, but will slowly inch
towards the area and we`ll be a a northwest flow aloft as the upper
trough slowly departs. A dry cold front will have already moved
through the area with a dry air mass to follow. This will result in
mostly clear skies and a chilly start for most locations away from
the coast. Patchy to areas of frost are possible for portions of the
Rogue Valley, but the better chance of frost could end up in the
valleys in Siskiyou County. The afternoon will warm up with
temperatures near seasonal norms.

The upper ridge will build in Saturday with continued dry conditions
and warmer afternoon temperatures. Sunday will remain dry and warm,
although the ECMWF does flatten out the ridge some as a weak front
approaches the northwest part of the forecast area. If nothing else,
it will bring an increasing onshore flow which could result in more
cloud cover and slightly cooler temperatures north of the Umpqua
Divide, but the operational GFS, GEFS and ECMWF ensemble means show
more pronounced ridging. Thus, a higher confidence for dry and warm

The upper ridge axis is expected to flatten out by the start of next
week, but it will still be dry and rather quiet. -Petrucelli




Pacific Coastal Waters...
     Small Craft Advisory until 11 PM PDT Tuesday for PZZ356-376.

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