Scientific Forecaster Discussion
fxus65 kvef 251034
Area forecast discussion
National Weather Service Las Vegas Nevada
333 am PDT sun Jun 25 2017
Synopsis...the prolonged heat wave over the region will finally
break by Tuesday as a weak weather system moves across the western
states. This system will result in enhanced winds Monday and will
increase the fire danger over portions of southern Nevada and
northwest Arizona. Limited moisture will lead to possible isolated
thunderstorms over the southern Sierra and northwest Arizona today
before drier air moves in by Monday.
Short term...today through Tuesday.
The ridge remains centered over Arizona and Nevada today and the
continued excessive heat warning is a given with similar
temperatures to Saturday. The difference this morning is that there
is a band of considerable mid level moisture extending from Arizona
across southern Nevada and up toward northwest Nevada. This has been
keeping temperatures elevated a few degrees from 24 hours ago. Light
radar returns were noted, but primarily virga is expected. This band
of moisture will continue to lift toward the northeast today as the
eastern Pacific trough begins to nudge inland. This is the feature
that will bring the main weather pattern change Monday and Tuesday,
finally breaking the prolonged heat wave over the region. Increasing
southwest winds will accompany the incoming trough Monday and gusts
around 35 mph can be expected across portions of San Bernardino,
Clark, Lincoln and Mohave counties. Temperatures will lower a few
degrees also, but relief from the excessive heat will be noticeable
by Tuesday as temperatures lower a few more degrees.
Long term...Wednesday through Saturday.
By Wednesday, the ridge over the southwest will continue to be
suppressed a bit as the tail end of a trough drapes over much of the
western Continental U.S. Through the work week. Models are now indicating that
a impulse/shortwave will develop off the coast of northern
California by Friday. The strength and impacts of this feature are
uncertain at this time as model variance is high for Fri and Sat.
Temperatures will be approaching normals by Wed and remaining near
normal through the forecast period. Breezy southwest winds are
expected each afternoon with wind speeds 10 to 15 mph and gusts
around 20 to 25 mph. Wednesday afternoon, both the GFS and European model (ecmwf) are
showing a tight gradient over much of central Mohave County. This
will cause some gusty southwest winds up to 30 mph Wed afternoon.
Otherwise, dry and mostly clear conditions through the rest of the
work week and into the weekend.
Aviation...for McCarran...winds should continue to be light, less
than 6 kts, and could be variable in direction, but should be south
to southwest through the early morning. By around 15-16z winds will
begin to shift north to northeast before settling more easterly
around 060-090 by 18-19z today. Speeds between 15-22z should be less
than 8 kts. By 23z winds should shift to a southwesterly direction
with speeds 10-15 kts. Winds could begin gusting around 04-05z
tonight with speeds up to 20 kts, similar to yesterday's winds. Scattered
to broken conditions between 150-200 kft through 16-18z this morning.
Thereafter, mostly clear and dry conditions.
For the rest of southern Nevada, northwest Arizona and southeast
California...generally, light diurnal winds will continue through
the early morning before a south to southwest push around 22-00z
this afternoon. Gusty southwest winds possible for dag up to 20-25
kts around 23-03z this afternoon. Otherwise, speeds this afternoon
should be 10-15 kts. Some scattered high clouds above 150kft are possible
through much of the morning and into the afternoon. Scattered to
isolated showers and thunderstorms are possible this afternoon along
the eastern Sierra, white mtn, and along eastern Mohave County.
Winds may become variable and gusty near any storms.
Fire weather...the prolonged heat wave over the region will finally
break Monday and Tuesday as a trough moves inland from the eastern
Pacific. This will result in enhanced southwest winds gusting over
35 mph for portions of southern Nevada and northwest Arizona Monday
afternoon and evening leading to critical fire conditions. Isolated
thunderstorms will be possible over the Sierra and northwest Arizona
today then a dry and stable air mass will spread over the region
with the incoming trough.
Climate...near record to record high temperatures will be
possible today and Sunday. The current record of consecutive
days above 110 degrees in Las Vegas is 10 days (1961), and for 115
degrees, 4 days (2005).
Las Vegas, Nevada climate
Forecast high temps (f) daily record Max temps (f)
sun (6/25): 113 115 (1970)
Forecast low temps (f) daily record high min temps (f)
sun (6/25): 89 86 (1974)
Aviation...for McCarran...light southwest to west is expected
this evening with less than 8kts expected. Hot temperatures will
continue through Monday with afternoon highs at or above 110
degrees. Scattered high clouds will be observed today however VFR
conditions will prevail. Typical overnight trends are expected, with
winds coming back up again late Sunday morning out of the northeast,
but remaining below 10kts.
For the rest of southern Nevada, northwest Arizona and southeast
California...isolated thunderstorms will be possible over the
southern Sierra this afternoon with brief gusty winds likely near
any storms. Gusty west winds 25-30 knots will develop across the
western Mojave Desert late this afternoon and evening. Hot
temperatures will continue across the Mojave Desert areas through
the weekend with afternoon highs at or above 110 degrees. Scattered
high clouds and VFR conditions expected.
Hydrology...observed flows on unregulated creeks, specifically
Independence Creek, Big Pine creek and Rock Creek indicated flows
have decreased slightly since their peak flows occurred earlier this
week. Creeks, streams and rivers along the eastern Sierra slopes of
Inyo County as well as the Owens Valley will be flowing high and
fast through into at least early next week. Minor flooding could occur
near creeks as well as a few low water crossings on some roadways.
Remember, never drive through flooded roadways or around barricades.
Also, pastureland or farmland adjacent to creeks, streams or rivers
could experience areas of standing water.
Spotter information statement...spotters are encouraged to report
any significant weather or impacts according to Standard operating
Short term/fire weather...Adair