484 
FXUS66 KMFR 101059
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
359 AM PDT Wed Oct 10 2018

.DISCUSSION...An extended period of dry weather begins today
across the CWA as a long wave trough that brought the cooler
weather and showers to the area for the first week or so of
October finally begins to edge eastward. A piece of the trough
will break off, forming a closed low that will retrograde and
meander near the Southern California coast Friday through the 
weekend. Meanwhile, high pressure aloft positioned over the 
eastern Pacific will amplify and slowly move eastward, nosing 
into the Pacific Northwest. This is one of the more common 
blocking patterns, known as an omega block. This will ultimately 
prevent weather systems from reaching the West Coast and will 
likely take quite a while to break down. In fact, we expect 
ridging aloft to stick around right through next week. This will 
bring a transition from northerly flow to a dry east or 
northeasterly continental flow resulting in a significant drying 
of the air mass across SW Oregon and northern California along 
with a warm-up.

Today, some energy is still arriving from the north on the back 
side of the trough, so some higher clouds are moving through 
currently. There are also some low clouds and fog developing, but 
these won't last too long this morning. Clouds should thin out 
yielding mainly sunny conditions this afternoon. The air mass is 
still on the cool side, so high temperatures will remain a few to 
several degrees below normal. 

Tonight, with fewer clouds expected, typically colder spots in the
valleys west of the Cascades will have lows in the lower to mid 
30s. We're not expecting frost right here in Medford, but some 
areas of the Rogue Valley, like near Lakecreek, and also in 
portions of the Applegate/Illinois Valleys (Ruch, Cave Junction) 
will, so we have issued a frost advisory from 200-900 AM PDT. 

Expect periods of stronger east winds over the ridges, especially
west of the Cascades throughout the remainder of the forecast 
period. This will bring ridgetop drying with moderate to, at 
times, poor overnight humidity recoveries and general low minimum 
afternoon relative humidity. Chilly mornings will continue inland,
but afternoon temperatures will be comfortably warm. Southwest 
coastal areas near Brookings will also have some abnormally warm 
days with highs in the upper 70s and 80s. Models are showing a 
disturbance and associated cold front grazing east side areas this
weekend. This could bring a slight uptick in winds Saturday and 
potentially some cooling over there into Sunday, but most other 
areas won't even notice a change. -Spilde 

&&

.AVIATION...For the 10/06Z TAFs...VFR conditions are being observed 
in most places this afternoon, and this should continue through 
early evening. Northerly flow and low level moisture favors the 
Umpqua Basin for MVFR ceilings Wednesday morning. Model consensus 
now shows the coast remaining VFR tonight, so have kept them clear. 
Confidence is medium on this aspect of the forecast because there is 
some chance fog will form in vicinity of KOTH early Wednesday 
morning. MVFR ceilings are also possible east of the Cascades, 
especially in northern Klamath and much of Lake County. Conditions 
should improve to VFR everywhere by late Wednesday morning as a 
drier air mass moves in. Keene

&&

.MARINE...Updated 300 AM PDT Wednesday 10 October 2018...A 
thermal trough near the coast will bring gusty north winds and 
choppy seas to areas south of Cape Blanco through the remainder of
the week. Steep fresh swell will affect areas north of Cape 
Blanco through Wednesday and then subside some. Unusually long 
period southerly swell will develop Wednesday, peak Thursday 
night, then slowly subside Friday, and this may bring rough bar 
conditions at Brookings and elevated surf at Port Orford. 

Keene/Smith

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Frost Advisory from 2 AM to 9 AM PDT Thursday for ORZ024-026. 

CA...None.

Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT Friday 
     for PZZ356-376. 
     Small Craft Advisory until 11 PM PDT this evening for 
     PZZ350-370. 

$$

MAS/CZS/NSK/MSM