739 
fxus65 krev 200859 
afdrev 


Area forecast discussion 
National Weather Service Reno Nevada 
159 am PDT Sat Mar 20 2010 


Short term... 
ridge strengthening over the west today will bring temperatures 
about 10 degrees above normal. Most western Nevada valleys will reach 
into the lower 70s with middle 50s to low 60s in the Sierra valleys. 
Cirrus clouds will be increasing across the area today...but that 
will have little effect on the warming potential. 


Light winds today will begin to increase by Sunday...becoming 
gusty by late morning ahead of a shortwave dropping through the 
Pacific northwest. Models are having a difficult time resolving 
this feature...so confidence is only moderate at this time. The 
European model (ecmwf) is still the most aggressive...though the 00z run has backed 
off somewhat on the amount of quantitative precipitation forecast. Have made very few changes to 
probability of precipitation compared to the previous forecast...keeping chance probability of precipitation 
through northern Lassen and extreme northern Washoe counties 
Sunday night into Monday morning. Brought slight chance probability of precipitation 
across Pershing County Monday afternoon as some weak instability 
is present and showers are possible. The main effect of the system 
will be to return temperatures to more seasonal values. 


Currently the shortwave cold pool looks to mainly stay northeast 
of the County Warning Area...but if it ends up being slightly more westward... 
there will be more instability which would result in additional 
showers and possibly afternoon and evening convection on Monday. 
Chances for this are minimal at this time. Df 


Long term...Tuesday through Friday... 
few changes made through the period. Models continue to differ on 
how far west the upper low over southern Idaho Monday will drop into 
Nevada. GFS pushes it into Utah while ec is further west into eastern 
Nevada. Leaning toward the ec as many of these systems come further west 
if the ridge amplifies upstream as is the case here. Most GFS 
ensemble members are west of the operational solution too. 
Still...with the low in an ec position...cold pool aloft remains 
over eastern Nevada so have cut back on probability of precipitation and removed any showers west of 
Highway 95. It will also cool off quite a bit with highs in the 50s for 
Nevada with 40s Sierra in ec solution. 


Ec/GFS then similar for Wednesday/Thursday with short wave ridge Wednesday followed 
by a weak brush by across the north Wednesday night. Temperatures will warm back 
to slightly above normal values these days and with such a weak 
system...will leave forecast dry. 


Friday becomes more problematic as 00z ec continues trend of 12z 
solution with a stronger...colder system for Friday. GFS in contrast 
splits it and has hardly any precipitation. Truth likely lies somewhere in 
between with ensembles showing a good bit of spread. Will add slight 
chance probability of precipitation to eastern California from Tahoe northward for now and cool off temperatures 
slightly to near normal. Wallmann 




&& 


Aviation...VFR through Sunday. Wallmann 




&& 


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


$$ 


Http://weather.Gov/Reno