930 
fxus66 kmfr 212301 
afdmfr 


Area forecast discussion 
National Weather Service Medford or 
301 PM PST Sat Nov 21 2009 




..updated for High Wind Warning for coastal zones...Wind 
advisories for Shasta Valley and Lake County...and Winter Weather 
Advisory for snow and blowing snow over the Cascades and much of 
Klamath County. 


Discussion...quick-moving developing frontal system will impact 
the County Warning Area tonight through Sunday morning. The main impacts will be 
strong winds and some snow over the Cascades and the east side. 
The fast movement of this system...along with more westerly 
winds...will favor the Cascades receiving more snowfall and The 
Mount Shasta area receiving less than the previous storm. Models 
have settled on a 990mb low centered west of the Washington/or border late 
tonight. The strongest winds will impact coastal waters and 
coastal zones tonight...with winds affecting the Cascades through 
the east side late tonight through Sunday morning. Very strong 800 mb 
flow of 50kt is noted over northwestern portion of the County Warning Area late 
tonight...but stability should keep most of this area from getting 
advisory level winds. This situation may need to be looked at 
during the late afternoon. Significant snow will fall during a 
short period between tonight and tomorrow morning. A foot is 
possible in the higher terrain of the Cascades with several inches 
expected east of the Cascades in Klamath County. On Sunday in the 
postfrontal environment expect snow showers above 3500 feet and 
rain showers in the lower elevations. Ridging will build over the 
region Sunday night...essentially ending the precipitation over 
the County Warning Area. 


Models have been very persistent with upper ridging from Monday 
through Wednesday over northern California and southwestern or...with the 
resultant weather impacts being morning fog Monday through 
Wednesday in the favored low elevation areas like the rogue and 
Illinois valleys...and the Umpqua Basin. A weak warm front brushes 
the coast on Wednesday but will not likely result in any 
significant precipitation. GFS and European model (ecmwf) both put an end to the 
dry weather on Thanksgiving day but their solutions are still 
fairly different. There are still unknowns regarding the forecast 
for Thursday...but at this point it seems reasonable to expect 
light snow in the mountains and light rain in the valleys on late 
Thursday. It still seems there will not be a large storm for 
Thanksgiving day travelers in the region. 


&& 


Aviation...middle clouds are streaming over the region today and 
will gradually lower during the day and evening. Current VFR 
ceilings will be short-lived as another front drops most terminals 
to MVFR and occasional IFR in low clouds and showers by this 
evening. Coastal terminals will likely be impacted by low level 
wind shear with gusty winds to 35kt but even stronger 50-60kt 
winds just above the surface. Strong winds will also impact the 
Cascades and the east side late tonight and Sunday morning. 
Mountains and east side will have snow tonight and Sunday 
morning...reducing visibilities. Mountain obscuration will be 
widespread by tonight through Sunday as deep moisture pushes into 
the region. 




&& 


Mfr watches/warnings/advisories... 
or...Winter Weather Advisory from 7 PM this evening to 7 am PST 
Sunday for orz027-orz028-orz029-orz030. 
Wind Advisory from 10 PM this evening to 7 am PST Sunday for 
orz031. 
High Wind Warning until 4 am PST Sunday for orz021-orz022. 


California...Wind Advisory from 10 PM this evening to 4 am PST Sunday for 
caz081. 


Pacific coastal waters...Storm Warning until 4 am PST Sunday for 
pzz350-pzz370. 
Gale Warning until 4 PM PST this afternoon for pzz350-pzz370. 
Hazardous seas warning until 4 am PST Monday for pzz350-pzz356- 
pzz370-pzz376. 
Gale Warning until 4 am PST Sunday for pzz356-pzz376. 


$$ 


Keene