Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 091046

Area Forecast Discussion
National Weather Service Reno NV
246 AM PST Sat Dec 9 2017


High pressure will continue to bring dry conditions along with
valley inversions, cold nights and light winds for the next
several days. Localized air quality issues are possible along the
Sierra Front due to the strong inversions.



Quiet weather days will persist for this weekend into the
start of next week as an amplified ridge of high pressure sits
right over the Sierra and western NV. Overnight lows will continue
to be cold, dipping into the teens and lower 20s, with single
digits for colder valleys near the Sierra and in west central NV.
Inversions will keep temperatures near seasonal average each day
in valleys with highs mainly in the upper 40s and lower 50s. The
warmer, stable air aloft will also inhibit mixing causing hazy
skies and decreased air quality, especially for urbanized areas.
Relatively warmer temperatures with less diurnal fluctuations can
be expected along the mid and upper slopes of the Sierra due to
these inversions.

As for winds, light easterly flow will continue for the next few
days, due to the low level pressure gradient extending from the
surface high across the northern Great Basin. -LaGuardia

.LONG TERM...Tuesday onward...

Little change is expected in the overall weather pattern through
next Thursday as high pressure remains in control of the region.
Inversions will keep afternoon temperatures near average for the
lower valleys, with the Sierra around 5-8 degrees above average.
Nights will remain cold (a bit below average) with the dry air mass,
light winds and little to no cloud cover. Some haze is likely to
continue for the Reno-Sparks-Carson City area, especially below 5000
feet, with periodic degradation of air quality possible.

While winds will generally be light through next week, a period of
moderate east ridge winds may return to the Sierra around midweek as
a weak upper disturbance drops south across the Rockies, nudging the
ridge axis back to the southern Oregon and northern CA coast.

Toward the end of next week, medium range guidance is trending
toward more shortwave energy moving across the Pacific Northwest,
flattening the ridge over CA-NV. This could lead to a weaker
inversion by Friday or next weekend, although for now we will keep a
mention of haze through Friday due to timing differences for this
shortwave. We will only make minor adjustments to the current
forecast, adding some high cloud cover north of I-80 and shifting
ridge wind direction to west by Friday. Temperatures may also edge
upward a couple more degrees Friday, if the flatter ridge scenario
with weaker inversions occurs by that time.

Looking beyond mid-December, there is more spread among the longer
range guidance which may favor a change from the current stagnant
weather pattern. There is a bit more ensemble support for a possible
weather system finally reaching the Sierra and western NV around the
20th-22nd but dry scenarios are also still present, so we will only
be cautiously optimistic at this time for any meaningful
precipitation returning to the region before Christmas. MJD



VFR with light winds into next week with high pressure overhead.
Some haze around KRNO-KCXP is expected, but it should not be a
significant issue other than some minor reductions in slantwise
visibility. MJD


.REV Watches/Warnings/Advisories...


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