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Area forecast discussion 
National Weather Service Medford or 
830 PM PST Thursday Nov 20 2008 


Discussion...the fast moving cold front of today has exited our 
area. This evening skies are clearing of middle an upper clouds and 
showers have ended. Some lower clouds are banked up against high 
terrain in westerly flow but as these dissipate fogs will form 
in western valleys. Friday the fogs will burn off about middle day 
under weak high pressure. 


The high pressure will be brief as the next front is forecast to 
reach the coast Friday night and move across our region late Friday 
night through Saturday morning. It should be about as strong and 
about as cold as the front that provided a dusting to a couple 
inches of snow to elevations above 5000 feet this morning. 


High pressure should be the dominant feature early next week with 
cooler temperatures and decreased cloud cover except for night and 
morning valley fog. 


The next trough of interest is now expected to close off and drop 
southward over the offshore waters. This will lead to a split flow 
aloft with the Pacific northwest having the weaker northern branch 
overhead. This should lead to the arrival of a weak front Tuesday 
which will stir up the atmosphere and provide a slight chance to 
chance of precipitation west of the Cascades...mainly north of the 
Umpqua Divide. Both models indicate weak ridging Wednesday and 
another trough in the Gulf of Alaska. 


There is significant uncertainty about conditions beginning 
Thanksgiving day itself. The models have returned to their usual 
biases...which means I would lean with a slower solution than the 
GFS but will be watching for the arrival of a cold front sometime 
toward the end of the week...probably not any earlier than Friday. 
Given the disparity in model solutions...I will include slight chance 
probability of precipitation on Thursday and Thursday night for now as a hedge. 


&& 


Aviation...mountain obscurations will gradually diminish tonight 
with areas of IFR in valley fog and low ceilings are expected to 
develop and persist into Friday morning. Then VFR everywhere. 


&& 


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


California...none. 


Pacific coastal waters...Small Craft Advisory for hazardous seas 
until 10 am PST Sunday for pzz350-pzz356-pzz370-pzz376. 


$$ 


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