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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS65 KREV 242229
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
329 PM PDT Wed Apr 24 2024

.SYNOPSIS...

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Cooler weather along with periods of showers and thunderstorms will
persist through early Saturday. Potential thunderstorm risks include
gusty outflow winds, dangerous lightning, and localized heavy rain
and/or small hail. Please be aware of rapidly changing conditions if
recreating outdoors. Drier weather and a slow warming trend are
expected to return on Sunday and persist into Tuesday.
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&&

.DISCUSSION...

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According to the latest RAP analysis, an upper air low is currently
residing to the west of the southern CA and the northern Baja
Peninsula causing a southerly to southwesterly flow over the CWA
this afternoon. The latest radar imagery along with surface
observations show some isolated to scattered showers and storms
along and east of a line from Sonora Pass, CA to Lovelock, NV as
well as in northern Washoe County that are moving generally north-
northeast. Going through tonight, models depict the upper air low
passing eastward through southern CA and south of the CWA until it
reaches the southern tip of NV by tomorrow morning. At the surface,
models show showers and thunderstorms continuing in eastern and
southern portions of the region through the rest of the day and into
the night with a frontal boundary moving through the area. The most
impressive looking storms in NV currently look to be east of the REV
CWA and in LKN`s CWA at this time which is where the highest 0-6km
bulk shear of around 30 kts is present. Models are showing pockets
of around 500 J/kg of SBCAPE later this afternoon and evening in
Mono and Mineral Counties, so best chances for thunderstorms look to
be in this portion of the region. Storms are not anticipated to be
severe, but they may contain some brief downpours, small hail,
and gusty winds. Portions of Mineral and Lyon counties may see up
to almost an inch of QPF by tomorrow morning with these showers
and storms with southern Mono County and eastern Churchill
counties coming in with about 0.50 inches of QPF. Other counties
that see precipitation such as Pershing and Washoe may see a few
tenths of an inch at most. Will monitor conditions, but not
anticipating any hydro issues with this rainfall.

On Thursday, models show the CWA having a divergent flow aloft in
the morning that becomes west-northwesterly by the evening hours as
a Pacific Northwest upper air trough moves over to control the upper
air flow in the northwestern CONUS. Forecast guidance then has the
axis of the trough passing over the CWA on Friday morning allowing
for the CWA to take a northwesterly flow by the afternoon and
evening hour. By Friday night into Saturday morning, forecast models
have the base of the trough digging down over AZ/southern CA causing
a north-northwesterly upper air flow over the CWA being underneath
the rear portion of the trough. At the surface, temperatures look to
take a cooling trend on Thursday and Friday due to cloud cover
inhibiting daytime heating. Guidance also is still showing a 50-90%
chance for widespread showers beginning in the latter half of
Thursday and going through Friday night with a 15-30% chance of
thunderstorms and/or ice pellet showers. Portions of the Sierra
above 6500-7000 feet may see some accumulating snow with the colder
temperatures. The latest NBM probabilities of 4 inches or more have
come down a bit as they are around 10%. What also came down a bit is
Thursday`s daytime winds though they still look to be on the
breezy side gusting up to around 35-40 mph in northwestern NV. The
latest NBM probabilities of 45+ mph wind gusts look to be around
20-40% with higher elevations having the best potential. QPF
values for late Thursday and going into Friday night are forecast
to range from around a few hundredths to around 0.5 inches in
eastern Pershing county. Severe weather is not anticipated on
Thursday or Friday though we will monitor conditions in case this
changes as small hail and gusty winds cannot be ruled out with
storms particularly on Friday. By Saturday morning, precipitation
chances look to begin to taper off within the region.

Going through the rest of the weekend, ensemble guidance shows a
weak ridge moving over the CWA by late Saturday and continue into
Sunday. A generally zonal flow is then seen on Monday over the CWA with
another trough starting to develop off the coast of southern BC
during the evening hours. Models then start to differ in their
upper air solutions going forward starting on Tuesday as the GFS
has the trough moving southward and turning the CWA`s flow aloft
to southwesterly by late afternoon and evening hours of Tuesday.
The latest run of the ECMWF as an alternative solution delays this
progression of the trough until Wednesday. Will have to wait for
models to come into better agreement in future runs for this far
out to have a better handle on the upper air pattern in the middle
of the week. But at the surface, a warming trend looks to begin
on Saturday and continue into next week at least through Tuesday
and potentially Wednesday. Drier conditions are also expected
going into the midweek after the Saturday morning`s precipitation
chances depart the region. As for winds, some models show winds to
potentially gust up to around 35-45 mph on next Wednesday along
the CA/NV border with a relatively tight surface pressure gradient
in the forecast. Will continue to monitor this going forward as
more forecast details become clearer.

-078
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&&

.AVIATION...

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VFR conditions are expected through the remainder of the today and
going into tomorrow for most of the REV TAF sites. Exceptions
include KTRK which expects some fog to develop between 09-16Z which
will cause IFR visibilities. Also: will be monitoring conditions at
KMMH with showers and thunderstorms expected to continue within
Douglas, Mineral, and Mono counties through most of today though not
expecting precipitation seen at the site to lower visibilities at
this time.

More widespread showers will migrate into the Sierra and western
Nevada by Thursday into the start of the weekend with a bigger
trough. Ahead of the main trough, FL100 winds increase resulting in
enhanced westerly surface winds (25-35 kts) on Thursday afternoon.

-078
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&&

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

$$