Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 241031
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
331 AM PDT Wed May 24 2017

.DISCUSSION...An upper level trough will track across southern
Canada today. The associated cold front is moving southeastward
across the area at this early hour and is bringing onshore flow
into northwestern sections of the CWA. The arrival of the trough
is deepening the marine layer and stratus is filling into
portions of the Umpqua Valley from the north. These clouds will
bank up against the Umpqua Divide this morning and may briefly
cause some light rain/drizzle in the Coquille Valley near Powers
eastward to Camas Mountain and perhaps over to near Canyonville in
the Umpqua Basin. Low clouds, fog and patchy drizzle will also
affect Brookings/Harbor this morning. This shouldn`t last too
long though as much drier air arrives and mixes the low clouds out
by mid-late morning.

Despite sunshine, inland areas will be about 10-15 degrees cooler
today compared to yesterday, and perhaps up to 20 degrees cooler
near Roseburg, where the low clouds will take some time to clear.
With high pressure situated offshore, a thermal trough along the
coast will bring strong northerly winds to the coastal waters and
adjacent beaches, while gusty north breezes occur in the west side
valleys this afternoon. Breezy west to northwest winds are
expected this afternoon/evening over the East Side.

Models continue to show some weak instability stretched out along
the southern border of the CWA this afternoon, from far southern
Siskiyou County eastward to extreme southern Modoc County.
Available mid-level moisture is shallow and only extends upward
to around 650mb, so while cumulus buildups are likely,
thunderstorm potential is low. Have left a slight chance in the
forecast, but the emphasis is on the word "slight".

An upper trough will dig southward across eastern Oregon
Wednesday night into Thursday keeping SW Oregon and northern
California in a dry northerly flow. Some cumulus will develop in
portions of eastern Klamath and Lake Counties, but any
shower/thunder chances will remain off to the northeast. Overall,
Thursday`s high temperatures will be similar to today.

The upper ridge offshore will begin to edge eastward Friday, so
expect it to warm up a bit, especially west of the Cascades. The
ridge will move into the area this weekend, so we`ll be looking at
temperatures getting back up into the upper 80s and lower 90s
here in Medford. Instability will increase from western Siskiyou
County northward to the Cascades, so expect some buildups to occur
there with at least a slight chance of thunderstorms each
afternoon through the holiday weekend. -Spilde

&&

.AVIATION...24/12Z TAF CYCLE...Along the coast and over the coastal
waters...An area of IFR cigs/vsbys near Brookings will clear to VFR
later this morning. The rest of the coast will be VFR through this
evening...then local MVFR cigs will move in. Over the Umpqua and
Coquille Basins...areas of MVFR cigs with higher terrain obscured
will clear to VFR by late this morning...but the lower cigs will
return Wednesday night. The remainder of the areas will remain
VFR through Wednesday night.

North winds will be a concern at KOTH with gusts to 30 knot possible
this afternoon and evening. Gusty winds and increased turbulence are
also expected east of the Cascades this afternoon and evening. There
is also a very slight chance of a thunderstorm or two over Southern
Siskiyou and Modoc Counties this afternoon and evening.

&&

.MARINE...Updated 200 AM Wednesday 24 May 2017...The thermal trough
will strengthen today...which will bring strong north winds and
choppy seas to the area. Seas will be steep to very steep into
tonight. Winds will be north gale force through tonight south of
Cape Blanco with gusty small craft advisory winds north of the cape.
Winds will decrease Thursday but there will still be some gale force
winds south of Gold Beach and hazardous seas south of Cape Blanco.
Winds will subside further Thursday night, but steep fresh swell
will persist into Friday south of Cape Blanco.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Hazardous Seas Warning until 5 AM PDT Thursday for ORZ022.

CA...None.

Pacific Coastal Waters...Hazardous Seas Warning until 5 AM PDT Thursday
     for PZZ350-370.
     Small Craft Advisory until 5 AM PDT Friday for PZZ350-356-370.
     Gale Warning until 5 AM PDT Thursday for PZZ356-370.
     Hazardous Seas Warning until 5 AM PDT Friday for PZZ356-376.
     Small Craft Advisory from 5 AM Thursday to 5 AM PDT Friday for
     PZZ376.
     Gale Warning until 5 AM PDT Friday for PZZ376.

$$

MAS/JRS/NSK



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