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fxus65 krev 211058 
afdrev 


Area forecast discussion 
National Weather Service Reno Nevada 
300 am PST Friday Nov 21 2008 


Short term... 


A shortwave ridge will dominate the area today with relatively light 
low level flow and clearing skies this afternoon. Some patchy 
morning freezing fog can be expected in the vicinity of Truckee 
before quickly burning off after sunrise. Easterly surface flow will 
keep temperatures lower than the past days...but still 5-8 degrees 
above normal. 


A weak shortwave trough will move across the Pacific northwest and brush northern 
areas of the County Warning Area on Saturday. A few very light showers cannot be 
ruled out near the Oregon border...but any measurable precipitation 
should remain just north of the area. Therefore the forecast will 
remain dry...however cloud cover will increase north of Interstate 
80. Winds will pick up somewhat over northern areas on Saturday...but 
gusts should remain below 20 miles per hour as the short wave approaches. 
Further south inversions will remain in place and keep temperatures 
cool and winds fairly light. 


A ridge builds back over the area by Sunday with dry conditions. The 
GFS tries to push moisture and clouds into the area Sunday night 
ahead of a deeper low...however the European is much weaker and 
slower with this feature. Will keep partly cloudy skies in the 
forecast for now for Sunday night. High temperatures will remain 
above normal...in the upper 50s to low 60s across western Nevada and in the 
50s in the Sierra through Sunday. Gmcguire 




Long term...Monday through Thursday... 


Medium range models displaying continued disagreements this forecast 
cycle...mainly in the early portion of the forecast...leading to a 
low degree of confidence in the day 4 and 5 portion of the forecast. 
Namely the GFS and...to some degree...the Canadian remain more 
progressive in the early portions of the medium range forecast 
period while the European model (ecmwf) is slightly less progressive. This all 
revolves around the handling of a closed low that tries to develop 
across Southern California then ejects eastward. Operational GFS and some of its 
ensemble members develop this low by Tuesday evening while the European model (ecmwf) is 24 
hour slower. This results in vastly different precipitation pattern with GFS 
developing precipitation by Tuesday across much of the County Warning Area. The European model (ecmwf) is slower 
to develop this precipitation and keeps most of it across the southern County Warning Area...but 
precipitation does develop in deformation axis across some northern areas. 


Idea of a splitting/close low developing seems reasonable given time 
of year and upstream digging trough along the Aleutian Islands. With 
cut off/closed low would tend to favor the slower European model (ecmwf) solution so 
will hold off mentioning much precipitation before Wednesday. Models now slightly 
cooler for Thursday/Thursday night and coming into some agreement for the 
end of the extended. As stated will keep probability of precipitation in forecast for Wednesday 
and Thursday with best probability of precipitation across the south and in the high 
elevations. Things could begin to get interesting by Thursday night and 
Friday...beyond the forecast range...as models in better agreement and 
fairly cold with next upper low developing more on top of the 
forecast area. Weekend after Thanksgiving could be fairly cold with 
periods of snow showers. More later on this as the weekend becomes 
part of the forecast. Mlf 
&& 


Aviation... 
generally VFR conditions for the County Warning Area today. Still show shallow haze 
possible vicinity of ktvl this morning...but as winds pick up from the 
south this should all mix out. Mlf 
&& 


Rev watches/warnings/advisories... 
Nevada...none. 
California...none. 
&& 


$$ 


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