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Area forecast discussion 
National Weather Service Medford or 
311 am PST Monday Nov 23 2009 


Discussion...there were no dramatic changes in the 00z run of 
model data. High pressure will build over the California offshore 
waters today into Wednesday...pushing the storm track northward. 
The main changes to the forecast were to adjust temperatures to 
more precisely reflect the effects of night and morning valley low 
clouds and fog...which are expected for much of the next week 
under a building high pressure ridge. 


The one very notable exception is a weak to moderate cold 
front...still indicated by both the GFS and European model (ecmwf) models to reach 
the coast in the afternoon on Thanksgiving day and more rather 
slowly east with any inland impacts to travel primarily late 
Thursday evening into Friday morning. Snow levels still look to be 
around 5500 to 6000 feet when precipitation is likely to begin 
then gradually fall to 3500 to 4000 feet by sunrise on Friday. The 
European model (ecmwf) is weaker/less amplified with the trough and would keep the 
bulk of precipitation from southwest Oregon northward. The European model (ecmwf) 
has done better with the last two systems and is favored. But...I 
will still include a hedge toward the GFS solution with likely 
probability of precipitation for Siskiyou County and a chance of precipitation for areas 
east of the Cascades. This scenario would result in snowfall 
amounts generally between 1 and 5 inches with the most in the 
vicinity of Crater Lake. Isolated to scattered showers are 
expected to gradually taper off Friday afternoon into the evening. 


High pressure is expected to return next weekend and persist into 
Monday. 




&& 


Aviation...IFR conditions are widespread in the Umpqua basin and 
patchy elsewhere...including western Siskiyou County and Modoc 
County. IFR is expected to develop shortly in the Rogue Valley. 
Conditions will improve late this morning. Otherwise...VFR 
conditions will prevail. Valley low clouds and fog will develop 
again tonight. 


&& 


Mfr watches/warnings/advisories... 
or...none. 


California...none. 


Pacific coastal waters...Small Craft Advisory for hazardous seas 
until 4 PM PST this afternoon for pzz350-pzz356. 
Hazardous seas warning until 10 am PST this morning for pzz370. 
Small Craft Advisory for hazardous seas until 4 am PST Wednesday 
for pzz376. 


$$ 


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