276 
fxus66 kmfr 022151 
afdmfr 


Area forecast discussion 
National Weather Service Medford or 
151 PM PST Tuesday Dec 2 2008 


Short term...an upper level trough is moving east of the area. 
Shower activity has diminished with just a few isolated showers this 
afternoon. Moist onshore flow has kept low clouds along the coast 
and into Douglas County and portions of Josephine and Jackson 
counties. A ridge will build into the area tonight and Wednesday. 
Stable conditions with lingering moisture and light winds will 
allow low stratus and fog to develop tonight in inland valleys and 
coastal areas west of the Cascades. Low clouds and fog will 
persist through Wednesday morning with partial clearing in the 
afternoon. Expect some low clouds to linger in the rogue and 
Illinois valleys and into the Umpqua valley during the afternoon. 
The NAM and GFS continue to show a weak trough moving from 
northwest to southeast over the outer waters Wednesday afternoon 
and along the coast of northern California Wednesday evening. This 
trough may weaken the high slightly. However...high pressure is 
expected to persist inland with an inversion continuing. This 
will allow valley fog and low clouds continue into Wednesday night and 
Thursday morning. The 12z NAM and GFS also indicate low level 
moisture moving into the east side with winds out of the north to 
northeast...so expect some low clouds to develop over areas east 
of the Cascades Wednesday night into Thursday morning. 


On Thursday...high pressure over the area strengthens with 
continued stable conditions. This will allow for low clouds and 
fog for inland valleys west of the Cascades. Also a thermal trough 
develops along the coast...bringing drier and warmer offshore flow 
to the ridges...especially from the Cascades west. These conditions 
are forecast to persist into Friday. Dry offshore flow may allow 
for fog and low stratus to clear briefly during the afternoon 
Thursday and again Friday afternoon over some inland valleys. 


Long term...models start in reasonable agreement Saturday 
morning with upper level ridge firmly in place over the region 
over a cutoff low off the Southern California coast. The upper 
level low opens a bit into a full latitude trough over the West 
Coast by Sunday morning with the GFS and European model (ecmwf) in agreement except 
for the timing of a front that the European model (ecmwf) brings to the coast by 
Sunday morning...and the GFS about 12 hours later. Have gone with 
a compromise of the timing and probability of precipitation of these two solutions. By the 
time the next...much stronger system moves into the region on 
Tuesday the European model (ecmwf) and the GFS are in very good agreement with the 
timing and quantitative precipitation forecast on this more seasonal system. 






&& 


Aviation...this afternoon...conditions are mostly VFR with areas 
of MVFR ceilings continuing along the coast into the Umpqua and 
southern Oregon Cascades. Areas of terrain obscurations from the 
Cascades westward in Oregon through this afternoon. 


Inland...late this evening and overnight expect VFR conditions with 
IFR ceilings and visibility developing in fog over valley locations west of 
the Cascades in Oregon and northern California. Along the 
coast...expect MVFR ceilings to become widespread this evening and 
persist through the night with local IFR ceilings and visibility. 


Low ceilings and fog along the coast will gradually improve to VFR in 
the late morning. Inland...Wednesday morning...VFR except IFR in 
fog over inland valleys west of the Cascades continuing during 
the morning ... gradually improving to VFR with areas of MVFR 
in low ceilings and patchy fog for valleys in Douglas...Jackson...and 
Josephine during the afternoon. 




&& 


Mfr watches/warnings/advisories... 
or...air stagnation advisory until 2 PM PST Friday for orz024-orz026- 
orz029. 


California...none. 


Pacific coastal waters...Small Craft Advisory for hazardous seas 
until 10 PM PST this evening for pzz350-pzz356-pzz370- 
pzz376. 
Small Craft Advisory for hazardous seas from 10 am Wednesday to 
10 PM PST Thursday for pzz350-pzz356-pzz370-pzz376. 
Small Craft Advisory for winds from 10 am Wednesday to 10 PM PST 
Thursday for pzz356-pzz376. 


$$ 


Cirrocumulus