Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus65 krev 151128 

Area forecast discussion
National Weather Service Reno Nevada
328 am PST Fri Dec 15 2017


Temperature inversions and reduced air quality in urban valleys
continue through this afternoon, with a weak system tonight
increasing surface winds and bringing improved air quality for the
weekend. Inversions are likely to strengthen again early next
week before a cold front moves through for the middle of next week
and breaks the inversions.


Short term...

A fast moving cold front and band of precipitation will move
through Nevada tonight into Saturday morning. These types of low
precipitation cold fronts (slider storms) can be as challenging,
or more, to forecast than large snow storms. However, this storm
doesn't quite fit the pattern of a classic "inside slider" that
can cause a heavy band of precipitation to move into far western
Nevada. This front is forecast to move through the region quickly
in a southeasterly direction with the highest precipitation
amounts (still less than 0.2") likely in north central Nevada.

Most likely scenario for far western Nevada continues to be
precipitation amounts in 0.01-0.10 range with most of the
precipitation likely falling as snow down to valley floors. Isolated
areas of freezing rain can't be ruled out, but winds ahead of
the front should be enough to mix out trapped cold air in the
lower valleys.

Even though snow amounts from this system are likely going to be
limited to less than 1/2 inch, some impacts to travel should be
planned for. Remember, it only takes a little bit of rain or snow
to create slick roads and hazardous travel conditions.

On the up side, this system should bring enough wind and
increased mixing to push out the pollutants built up under ongoing
temperature inversion. Temperature inversions are expected to
begin to re-develop by Sunday night.

Overall wind isn't expected to be overly strong for this system
with valley gusts in the 15-20 mph range. The exception will be at
the higher elevations along the Sierra crest where a strong
temperature gradient is expected to set up with east winds of
around 70 mph or more possible Saturday into Saturday night as
cold air settles into the Great Basin. -Zach

Long term...Monday Onward...

High pressure returns for early next week resulting in poor mixing
and ventilation Monday and Tuesday. Haze may once again form near
population centers although its shorter duration will preclude
conditions getting as hazy as recent days.

Simulations continue to show a strong cold front moving southward
through the area Wednesday with some much colder air spreading into
the Sierra and western Nevada. Chances for showers remain Wednesday
along this front, especially north of Highway 50 where frontal
forcing will align best with larger scale lift. As the band shifts
south, it is expected to weaken considerably and therefore Mono-
Mineral County will likely see only isolated showers. The storm
doesn't have a significant moisture tap, but it will require
monitoring since it will be so cold. The cold nature of the storm
may result in snow even down to valley floors. Where snow occurs, a
couple of inches are possible across northeast California and northwest Nevada
with lesser accumulation potential farther south.

Temperatures will be seasonal Mon-Tue and then fall to below normal
levels by Thursday. Gusty northeast winds return to the ridges
Wednesday night and Thursday and these winds may persist for a
couple of days, possibly longer depending on the location of the
Main Ridge axis. Some model scenarios keep the ridge axis over the
east Pacific rather than bringing it inland. Valley inversions will
likely return but strength of the inversions will depend on the
ridge axis location as well. At this time, the pattern strongly
favors dry conditions for the Christmas Holiday weekend. Hohmann



Valley inversions will remain strong today, resulting in some
slantwise visibility reductions, especially in the Reno/Sparks,
Carson City, and Minden areas. Increased northerly winds tonight and
Saturday may allow some of the haze to clear out, at least for a day
or two.

A cold front will sweep southeast across the area late tonight and
early Saturday morning and bring a few showers to mainly western Nevada.
Best shower coverage will extend from the basin and range
(knfl/klol) into northeast Nevada with lesser coverage farther west
toward krno-kxcp-ktvl-ktrk. Only brief MVFR conditions are expected
with this fast moving band of showers. While significant snow
accumulations are not expected for area runways, a dusting of snow
is possible, especially on exposed surfaces. For accumulations up to
one inch...there is a 10% chance at krno/kcxp southward to about
kban along the eastern Sierra and about a 20% at klol/knfl. Hohmann


Rev watches/warnings/advisories...

National Weather Service Glossary of Abbreviations