Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Reno Nevada
250 PM PST Monday Dec 9 2013
very cold air will remain in place over the region with temperatures
below zero in many valleys again tonight. Strong surface inversions
will result in poor mixing and increased haze each day. Although
temperatures will slowly rise through the upcoming week, they will
remain below normal in the lower elevations.
widespread sub-zero temperatures occurred last night across the
region with lows down to around -25 degrees in some of the
elevated valleys of eastern Churchill County. Similar temperatures
are expected again tonight in most valleys as clear skies prevail
with widespread snow cover and strong inversion still in place. In
higher elevations, rising 700 mb temperatures will keep these
locations 25-35 degrees warmer than the adjacent Sierra valleys.
Despite these very cold conditions, record lows will not occur in
Reno, due to an epic cold event in 1972 where lows at the Airport
dropped below -10 degrees each day from December 8-11.
As high pressure remains off the West Coast, a weak shortwave
will move south across the Great Basin on Tuesday, bringing areas
of high clouds through the afternoon and evening. Highs on Tuesday
are likely to remain below freezing again in most valleys. The
main effect of these clouds will be a shorter period of radiational
cooling Tuesday night, so lows will be not quite as cold compared
to tonight. The duration and thickness of the cirrus band is still
uncertain so given the continued snow cover and inversion
strength, the forecast temperatures will be held well below the guidance
The cooling effects of the snow cover in valleys will gradually
become less efficient Wednesday and Thursday, especially on south
facing surfaces where more of the snow will melt or sublimate.
As a result, maximum and min temperatures will be increased by a few degrees
each day and night, but still held below guidance. On Thursday,
trough approaching the Pacific northwest will weaken the inversion
as 700 mb winds become west. Mixing will still be limited in the
valleys, but temperatures may be able to reach 40 degrees in some
Previous model runs produced light precipitation in northeast California-
northwest Nevada by Thursday night, but this potential is looking
less favorable so the slight chance probability of precipitation have been removed. Mjd
Long term...Friday through Monday...
removed showers from northern Washoe/eastern Modoc counties beyond
Friday, otherwise little change to the long term forecast. A quiet
pattern is expected in the long term with afternoon temperatures
near average and no precipitation beyond a low chance of light
showers north of Portola and Lovelock Friday.
Models and ensembles are in good agreement with flat ridging or
northwest flow aloft as a large-scale ridge remains over the
northeast Pacific. This flow should shunt all disturbances well
north and east of California and western Nevada for Little Hope of
precipitation. In fact, friday's showers north of Portola and
Lovelock may need to be removed soon as support is waning for
anything more than a weak brush-by disturbance.
As far as temperatures/mixing, Friday is the best chance for mixing
as the weak disturbance scrapes northern and eastern Nevada and
pushes in a modest reinforcing surface high to scrub out the
stagnant valley air. Saturday through Monday, inversions look to set
up again as low level flow relaxes as the northeast Pacific Ridge
nudges into California and Nevada. This should bring typical middle
December afternoon temperatures in the 40s under clear to partly
cloudy skies. Snyder
valley winds to remain light for most locations of eastern California
and western Nevada through Tuesday as strong surface high pressure
remains in the Great Basin. The light winds will mean inversions and
haze for basin valleys with some reduction in slantwise visibility
especially for the Reno-Carson City-Minden area terminals.
As far as surface visibility and cigs, they will remain VFR for most
locations through Tuesday. The only exceptions will be where patchy
freezing fog or low stratus forms overnight and into the middle morning
hours. This morning that included areas such as the Martis Valley
near ktrk and Stead Airport (fzfg), as well as pyramid and Mono
lakes (stratus). Those areas could certainly see similar
conditions again tonight. Snyder
For more information from the National Weather Service visit...
http://weather.Gov/Reno (all lower case)