Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Las Vegas Nevada
959 PM PDT Tuesday Jul 26 2016
Synopsis...hot conditions will continue through the end of the
week. Chances for thunderstorms will gradually increase by this
weekend as a monsoonal push of moisture moves into the Desert
Southwest. Temperatures will cool to around average for this time
of year this weekend into early next week.
Update...showers have nearly dissipated this evening across Mohave
County and most areas are expected to remain dry overnight. There is
an outflow boundary moving south through central Mohave County, but
winds have not been very gusty behind the front. Just a few minor
changes to the pop grids overnight.
316 PM PDT Tuesday Jul 26 2016
Isolated storms have developed this afternoon near Nipton and in
portions of Mohave County, but coverage and intensity have been
quite limited. WV imagery shows a sharp dry intrusion progressing
southward through the area, with at least some convection developing
near this interface. Convection-allowing models (cams) simulate this
limited coverage quite well. Kept slight chance pops through the
evening in Mohave County...but thinking any convection here will
remain quite isolated and brief.
Midlevel temps have warmed slightly in the past 24 hours as the
broad ridge has slid westward into the southern Great Basin. With
the proximity of this ridge to the area, convection will likely be
sparse again tomorrow and Thursday, though at least some cam output
generates isolated convection in Mohave County and the Spring
Mountains on both days and in the southern Sierra on Thursday. Not
too enthused about coverage (or even initiation) given the lack of
upper-level support and the general trend toward large-scale
subsidence. Thus, left inherited low pops alone...or adjusted
slightly downward through this period.
Main story Wednesday and Thursday will be the heat, with
temperatures remaining 5-10 degrees above normal. As previous shift
mentioned, suspect there will be some heat-related impacts across
the area, but expected temps remain a touch below warning criteria.
MOS forecasts have been quite consistent the past several runs, so
modified temperatures very little through the end of the week.
On Friday, the ridge shifts eastward as an upper-level trough
approaches the Pacific northwest. This places the ridge in a more
favorable position for a moisture surge on the western side
advecting into eastern portions of the area. Highest pops are in
Mohave County, the southern Great Basin, and the Spring Mountains,
in closer proximity to the increased moisture. Kept higher chances
in the Sierra as well, but as the upper trough approaches
thereafter, think precip chances in this region will be on the
decrease beginning this weekend. Temperatures should be slightly
cooler owing to somewhat increased cloud cover and the shift of the
ridge to the east.
With the decreasing proximity of the ridge and associated lowering
heights, temperatures look to decrease even more this weekend. The
aforementioned upper trough will deepen, nudging the ridge farther
east. Our area remains on the fringes of the northward push of
moisture west of the ridge and southeast of the trough, making the
extended forecast a bit of a challenge. However, there is decent
model agreement that daily chances of scattered storms will continue
this weekend and early next week as the trough does not shove the
ridge too far to the east. Additionally, as shortwaves embedded
within the longwave trough race eastward across the Pacific
northwest, the moisture surges will likely be enhanced (with
probable increased storm coverage during these periods). Timing of
these features is notoriously unpredictable at the extended range,
but it will be something to keep tabs on as this weekend approaches.
No changes made to the forecast Saturday Onward.
Fire weather...dry and hot conditions will persist across much of
the area through Thursday. However, monsoonal moisture is set to
increase across the area Friday into the weekend along with a
Aviation...for McCarran...mostly diurnal winds with VFR conditions
expected the next 24 hours. Speeds should generally remain below 10
kts. Hot temperatures will lead to high density altitude concerns
through the end of the week.
For the rest of southern Nevada...northwest Arizona...and southeast
California...generally light, mostly diurnally-driven winds are
expected through the period. VFR conditions are expected through the
period, although an isolated storm may occur in Mohave County
early this evening and again tomorrow afternoon.
Spotter information statement...
spotters are encouraged to report any significant weather
conditions according to Standard operating procedures.
Short term/long term/fire weather: Shafer
For more forecast information...see US on our webpage:
http://weather.Gov/lasvegas or follow US on facebook and twitter