122 
fxus65 krev 111146 cca 
afdrev 


Area forecast discussion 
National Weather Service Reno Nevada 
320 am PDT Sat Oct 11 2008 


Short term... 
the cold low affecting the area has dropped south with the trough 
axis oriented from SW-NE just south of the County Warning Area. Plenty of wrap 
around moisture and gusty northeast flow remains which is producing 
scattered snow showers over western Nevada south of Pyramid Lake and Interstate 80 
and in the Sierra south of Doyle. Very cold air aloft is 
interacting relatively warm waters in both Lake Tahoe and Pyramid 
Lake to continue to generate lake effect/enhanced snow showers. 
Northeast flow 10-20 kts from the surface to above 500 mb will 
continue to push any lake effect showers to the southwest. The most 
pronounced band is coming off of Pyramid Lake southwest across 
Interstate 80 near Patrick and extending south to Virginia City. 
Showers have increased in this area with some heavy showers likely. 
A lake effect Snow Advisory was issued to cover this band of snow as 
2 to 4 inches of snow is possible before showers decrease later this 
morning. Locally higher amounts are also possible between Palomino 
Valley and Patrick. Motorists on Interstate 80 east of 
Reno...Highway 395 south of Reno and over Geiger grade should be 
careful of wet or slick roads. The best chance for lake effect snow 
around Lake Tahoe is on the southwest to west shores from west of 
South Lake Tahoe to Sugar Pine Point State Park. An inch or two of 
snow is possible in these showers through the morning. Lake effect 
showers should taper later on today and this evening as stability 
increases and warmer air aloft moves over the area. 


The other area of concern this morning is in portions of alpine and 
Mono counties where upslope flow will likely enhance snow showers in 
some areas...especially from Markleeville to June Lake. Current 
radar does not show particularly heavy showers...however showers may 
be heavier than radar indicates due to lack of radar coverage and 
the low topped nature of the showers. A few inches of snow or more 
will still likely accumulate during the morning...therefore the 
warning will be allowed to continue through 5 am. Northeast flow 
becomes more northerly after 5 am which is less favorable for 
upslope...therefore any upslope enhanced snow showers will likely 
decrease during the early morning. However instability and plenty of 
moisture remain to produce scattered showers through the day mainly south 
of Pyramid Lake and Interstate 80. Additional accumulation during 
the day Saturday will be minimal as shower intensity should be less 
than the last 24 hours. 


A tight pressure gradient still across the area will provide another 
day of breezy northeast winds before the low pushes further east. 
Wind gusts up to 30 miles per hour in some areas are expected later this 
morning through this afternoon...especially east of Highway 395. 
This will also make it feel even colder outside. A lake Wind 
Advisory was issued for Pyramid Lake due to the gusty winds. Less 
wind is expected over Lake Tahoe...but the day shift will have to 
monitor in case winds pick up more than expected. 


The low pushes further east by Sunday...however one last short wave 
wrapping around the main low may produce a few snow showers over far 
eastern areas before all precipitation shuts off. No snow accumulation is 
expected. High pressure begins to build into the area on Monday 
bringing drier conditions and warmer temperatures. Northeast surface 
flow will still keep temperatures below guidance for another 
day...but they should at least rebound into the lower 60s in western Nevada 
and northeast California. Until then...temperatures will remain 20-25 
degrees below normal with highs in the 40s and low 50s through 
Sunday. Nighttime temperatures will be cold through Monday morning 
with freezing temperatures expected in all areas and colder valleys 
dropping into the teens. Gmcguire 
&& 




Long term...Tuesday through Friday... 


Flat Ridge with weak zonal flow over northern California and Nevada on Tuesday 
will bring temperatures back above normal for the first time in 
several days. Daytime highs will climb to near 70 degrees at many 
valley locations in western Nevada while mountains will reach the upper 
50s and 60s. A weak short wave moves north of Nevada on Wednesday. Both 
GFS and European model (ecmwf) show little effect on weather in the County Warning Area other than 
local breezes and a degree or two of cooling in the far North. 
Heights fall a bit with the short wave but thickness values change 
little from Tuesday so temperatures should be similar. Warmer 
temperatures for Thursday as heights/thickness increase behind short 
wave. On Friday the GFS brings the next trough near the West Coast 
with increasing southwest flow over the area. Increasing moisture in 
northern California and northwest Nevada could lead to slight chance of precipitation 
in those areas for Friday afternoon and Friday night if the GFS 
verifies. However the European model (ecmwf) has been the better model in the medium 
range lately...and the GFS ensemble members are showing some spread. 
Prefer to follow the European model (ecmwf) here with the trough farther off the 
coast and remaining dry over the Sierra and western Nevada. Rc 
&& 


Aviation... 


Snow showers streaming southwest from Pyramid Lake will remain 
primarily east of krno this morning as the flow aloft turns more 
northerly. There is the potential for MVFR ceilings and visibilities through 
17z. Similar conditions are possible at ktvl. Conditions at klol and 
ktrk should remain VFR although isolated to scattered -shsn are expected 
through the morning. Snow showers will become more isolated after 
17z and end entirely by sunset. VFR conditions all taf sites after 
03z although with clearing skies and lighter winds will bring fog 
into ktrk around 10z. Rc 
&& 




Rev watches/warnings/advisories... 
Nevada...Lake effect Snow Advisory until 11 am PDT this morning for 
nvz003-004. 


Lake Wind Advisory until 7 PM PDT this evening for nvz002-004. 


California...Lake Wind Advisory until 7 PM PDT this evening for caz072. 


&& 


$$ 


Http://weather.Gov/Reno