Area Forecast Discussion
Issued by NWS Las Vegas, NV

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473
FXUS65 KVEF 190934
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
234 AM PDT Thu Apr 19 2018

.SYNOPSIS...A cold Pacific system will move over our region
today and Friday. Winds are not expected to be as strong for most of
the region as recent storms but scattered showers and even a few
thunderstorms will occur today through Friday. The system will
slowly pull away to the east Friday night allowing dry and warmer
weather Saturday through early next week.
&&

.SHORT TERM...through Saturday night.

Compact upper low just off the central California coast early this
morning. Seeing a few showers and isolated thunderstorms developing
along the western foothills of the southern Sierra east of Fresno.
Otherwise, all the radar returns are preceding the low moving into
Santa Barbara and San Luis Obispo Counties.

As cold pool aloft, pocket of H5 temps around -25 deg C, moves
overhead today-Friday mid-level lapse rates steepen. Forecast
soundings and instability progs showing areas of 200-400 J/kg CAPE
and LI`s 0 to -2 across the southern Great Basin today. Instability
wanes overnight while on Friday greatest instability lies within a
small sliver across far northeastern Mohave County.

Due to track of the upper low strongest belt of westerly winds will
skirt across San Bernardino and southern Mohave Counties. Otherwise,
still looking at gusty post-frontal northerly winds developing
across Nye, Esmeralda and Inyo County. Current suite of wind
products looks good.

Dry and warm Saturday under weak area of high pressure.

.LONG TERM...Sunday through Wednesday.

Confidence is still high on dry, breezy and warm conditions as we
head into next week. Operational runs of GFS and ECMWF continue to
show a shortwave trough moving across the Pacific Northwest on
Sunday then across northern Nevada Sunday into Monday. As the wave
passes to the north, breezy winds should develop Sunday and Monday
in response to surface pressure falls north of the region. Any
precip should be north of the forecast area.

During the Tuesday and Wednesday period the GFS and ECMWF solutions
show considerable differences in the synoptic evolution of a
shortwave trough. The GFS supports a progressive wave which quickly
dives south across California Tuesday and shifts to the east into
Arizona Wednesday. Whereas, the ECMWF suggests prolonged ridging
through at least Wednesday before a cutoff low off of the California
coast slowly tracks inland late next week. These patterns would
yield very different weather conditions: windy and cool under the
GFS solution and continued quiet weather and above normal
temperatures under the Euro. The extend forecast is favoring the
Euro due to run-to-run consistency, but forecast confidence after
Monday is very low.
&&

.AVIATION...For McCarran...Southerly wind are forecast to
shift more southwesterly and increase into the 10-20 kt range with
gusts to around 25 kts at times after 14z. These winds are expected
to continue through the afternoon. Most of the shower activity will
remain over the higher terrain, however we could see cigs lower to
around 8-10k feet during the late afternoon and overnight hours.

For the rest of southern Nevada, northwest Arizona and southeast
California...Gusty winds are expected today within a belt of strong
westerly winds across parts of Mohave County, western San Bernardino
County and the Morongo Basin. Otherwise a cold front will move
through the region during the afternoon with northwest winds
developing behind the front. Esmeralda, Inyo and central Nye
Counties will see northwest winds 20-30 kts with gusts to 35kts. The
front gradually shift south during the day. Scattered showers and
isolated thunderstorms will develop in the afternoon mainly north of
Las Vegas with cigs down to 6-8 kft at times.
&&

.FIRE WEATHER...A Pacific system along the central
California Coast will move over the Great Basin and Mojave Desert
today-Friday. The system will produce unsettled weather in the form
of scattered showers along with increasing winds Critical fire
weather conditions will be hampered somewhat by humidity values
generally remaining above 15 percent...especially in the higher
elevations.
&&

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

$$

SHORT TERM/AVIATION/FIRE WEATHER...Pierce
LONG TERM...Boothe

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