Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 180949
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
249 AM PDT Wed Apr 18 2018

.SYNOPSIS...

Chilly weather with periods of brisk winds will continue through
Thursday. A weak storm system will bring light rain and snow
showers later today through Thursday evening. Much warmer
temperatures will quickly return for the upcoming weekend through
early next week, with dry conditions prevailing.

&&

.SHORT TERM...

Two more days of chilly and unsettled weather are expected before
a sharp warming trend begins by Friday. We should finally be able
to string together at least a few consecutive days of warm weather
after dealing with wild temperature swings for much of the month.

Thicker high clouds ahead of a weak elongated upper low will
continue spreading across CA-NV today, with increasing low-mid
level moisture and modest lift producing areas of very light rain
and snow this afternoon and evening. Southwest to west winds will
also increase later today but only to zephyr-type speeds with
gusts mainly around 25 mph (except a bit stronger for Mono and
southern Mineral counties, with Sierra ridge gusts around 50 mph).

For tonight, this area of moisture and lift shifts south and east
to west central NV and Mono County, with shower chances decreasing
outside of these areas. Liquid amounts will generally be 0.10" or
less, except a few areas may receive up to 0.25". A longer
duration of upper divergence over far eastern Churchill/Pershing
counties, and a small deformation zone between Bridgeport and
Hawthorne are currently where these higher precip amounts are most
likely. Snowfall will be sparse (less than 3") and limited to
higher elevations of west central NV and parts of Mono County.

For Thursday, the initial moisture band weakens with only minimal
precip chances south of Hawthorne-Bridgeport and far northern
Pershing County during the morning. However, on Thursday
afternoon, shower coverage will increase across most of the region
with cyclonic flow aloft, shallow instability and moisture
wrapping around the northwest side of the upper low. Snow levels
will generally vary from 5000-5500 feet, and some quick reductions
in visibility are likely in the heavier showers, but accumulations
are unlikely due to April sun angles. Lighter showers will
continue mainly south of US-50 and east of US-95 Thursday evening
with nearly all activity done by midnight. Brisk northwest to
north winds with gusts of 25-35 mph will make Thursday feel even
colder than today, despite similar high temperatures both days.

For Friday, as the upper low departs to the east and ridge axis
moves into northern CA, much warmer temperatures will arrive with
highs jumping about 15-20 degrees from Thursday, along with
minimal cloud cover and light winds. MJD

.LONG TERM...Saturday through Tuesday...

The numerical guidance models continue to struggle with finer scale
details in the extended...but that is to be expected this far out.
Unfortunately...that leads to a relative low confidence forecast of
any precipitation chances in the Sunday to Tuesday time frame.
Confidence is much higher the extended period will see above normal
temperatures. Given the uncertainties in the model forecasts...we
have opted to make few changes to the extended.

The ridge flattens for Saturday...but temperatures remain above
normal. Both the GFS and ECMWF show a trough swinging by to the
north Sunday...but the timing and strength of the feature varies.
The GFS is faster with little hint of precipitation while the ECMWF
is slower...farther south...and produces precipitation Sunday night
into Monday. Given these uncertainties...and the fact the GEFS
ensemble members are all over the place as well...we will leave
the forecast dry for Sunday.

The earlier convective chances that were in the forecast for Monday
have been removed. They appear less likely as the next upper low is
a bit too far west for upper level divergence to aid in convective
development during the day. Monday may see quite a few moderate
cumulus...but little else.

As the next upper low gets closer Tuesday it is more likely we will
see a few showers and possibly thunderstorms by late afternoon in
northeast California and the Sierra...so these were expanded just a
bit. Pinpointing convective development this far out is difficult;
they are more dependent on upper level divergence and low level
convergence that may not be modeled well. The location of any
showers or storms is an approximation and will need to be refined
with time. Again...the confidence in convective precipitation this
far out is low.

&&

.AVIATION...

Isolated to scattered showers will be possible for much of the
Sierra and western Nevada this afternoon into early Thursday
morning. The best chances will be in the Sierra and western NV
south of US-50 and east of US-95. Another round of rain and snow
showers is expected Thursday afternoon and evening. The most
likely effects at the main terminals will be short periods of MVFR
cigs/visibility along with mountain obscurations, but little or
no snow accumulation is expected on paved surfaces.

Winds will increase modestly this afternoon with gusts 15-20 kt,
except KMMH may see some stronger gusts around 25 kt. On Thursday,
a further increase in northwest to north winds is expected, with
gusts 25-30 kts over most areas (except lighter around Tahoe).
MJD

&&

.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&

$$

For more information from the National Weather Service visit...
http://weather.gov/reno



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