High Wind in California, April 21, 2022

Area Forecast Discussion
National Weather Service Las Vegas NV
1024 AM PDT Thu Apr 21 2022

.SYNOPSIS...An active synoptic pattern will continue windy
conditions through Friday for parts of the region. Temperatures
will cool off in response to a storm system today and Friday and
gradually warm up heading into early next week. This next system
is also expected to bring late season, high elevation snowfall
and valley rainfall but accumulations are expected to be minor.

&&

.UPDATE...Breezy to gusty morning so far across the region,
overall gusts have been generally 25-35 mph with some isolated
gusts over 40-45 mph. Winds are expected to increase through the
afternoon, with the strongest winds expected north of the I-15
corridor, specifically across Lincoln, Nye and northwestern Clark
counties. Widespread gusty winds will relax some overnight, but
remain gusty across the higher elevations. The region is expected
to remain mostly dry through this evening with precip chances
increasing tonight and through tomorrow morning from northwest to
southeast across the CWA. Current forecast looks on track and no
updates were needed. &&

.PREV DISCUSSION... /issued at 452 AM PDT Thu Apr 21 2022/

.SHORT TERM...Today through Friday.
In general, expectations have not changed much in regards to this
next low pressure system expected to bring strong gradient winds
to the region, a strong cold front, and even precip to parts of
the CWA.

QPF concerns mentioned in yesterday's discussion are being
realized with the latest 00Z HREF LPMM values. Most hi-res
guidance with their improved spatial resolution are depicting a
much more dry outcome for precip across the CWA due to a lack of
moisture overcoming the Sierra block. The 00Z HRRR especially
blocks almost all precip for even the Owens Valley which synoptic
models were maintaining aggressive QPF for. Latest NBM does follow
suit appropriately, backing off QPF numbers as much as 80% in some
locations. WPC was not as aggressive in backing off desert valley
numbers but either way, values were minor anyway. At this point,
other than the Sierra, the best chance for rain continues to be
where thunderstorms are the most likely, in direct vicinity of the
low center as it swings over and when the cold front pushes
through. 00Z HRRR does depict a broken line of convection moving
southeast Friday afternoon into Clark County as the front arrives,
and that looks like the best shot for any rain. Given the very dry
pre-frontal regime however, this may turn out to be more virga
than actual showers, and if so, could be a secondary area of
strong wind gusts affecting the valley tomorrow evening. Will have
to watch that closely as it could have implications for the
Valley.

Beyond precip, the main story looks to again be gradient winds.
Latest trends in cold front arrival is a bit slower than this time
yesterday, which means pre-frontal gradient winds could persist a
bit longer than originally expected. Also, 00Z HREF means
gradually increase across the board with each run, which is often
the case with the hi-resolution models in this type of gradient
set up. While means are modestly higher, it's enough to push wind
gust potential to near advisory levels for much of the CWA at this
point. Wasn't going to expand the advisory as much as we ended up
doing, but there was some concern with the upper end of the
probabilistic envelope showing much higher winds than advertised
in the deterministic models.

.LONG TERM...Saturday through Thursday.

Dry northwest flow will be over our area Saturday in the wake of
the aforementioned trough as it pulls away over the Four Corners
and Rockies. North-northwest surface winds Saturday still look
light to moderate with sustained speeds 10-15 mph across most of
the area and a little stronger near Laughlin- Bullhead City with
gusts 30-35 mph. High temps will be 3-5 degrees below normal
Saturday with highs in the 70s across the desert zones and in the
80s in the Colorado River Valley and Death Valley.

Model ensembles indicate a large ridge amplifying and migrating over
the western states Sunday and Monday then moving moving away to the
east ahead of a broad Pacific trough approaching the West Coast by
Tuesday. This will lead to a warming trend with temperatures
climbing around 5 degrees each day resulting in highs in the 90s
over the deserts by Tuesday as southwest winds generally 15-25 mph
develop in response to the trough. Model ensembles begin to diverge
with the timing and depth of the inland progression of the trough
Wednesday and Thursday. The NBM indicates a slight decrease in
temperatures those days with breezy to windy conditions each
afternoon.

&&

.FIRE WEATHER...A Red Flag Warning remains in effect today across
much of Clark County, the Colorado River Valley, and northwest
Arizona. The upcoming storm system is still expected to enhance
surface winds out of the southwest this morning and by the time
RH values reach their minimums in the afternoon, about a 6-8 hour
period of critical fire weather conditions looks likely for
desert valleys especially. After 03Z Friday, winds may stay
elevated, but RH values should be increasing and stay above
critical thresholds through Friday. In fact, light wetting rains
are possible for parts of Clark and Mohave counties Friday.

&&

..AVIATION...For Harry Reid...Winds will be on the increase this
morning and continue through the afternoon with gusts around 40kts
possible. Expect the strong winds to continue tonight through
Friday morning before decreasing Friday afternoon. In addition,
there is a chance of seeing a few showers develop on Friday along
with a brief period of CIGS of 6-8kft as a cold front drops south
through the region.

For the rest of southern Nevada, northwest Arizona and southeast
California...At KDAG, west winds increase late this afternoon and
continue through much of Friday with gusts over 40kts possible.
Expect areas of blowing dust and reduced visibility at times. KBIH
will see increasing winds late this morning continuing through early
evening before decreasing. There will be a chance of showers mainly
Friday morning at the KBIH airport. Elsewhere, gusty south-southwest
winds will develop later this afternoon and continue through Friday
with gusts up to 30 kts in the Colorado River Valley and up to 40kts
in the Las Vegas Valley.

&&

.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&

UPDATE...Peters
SHORT TERM...TB3
LONG TERM...Adair
AVIATION...Salmen

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