Heat in Nevada, August 6 to 10, 2017

Area Forecast Discussion
National Weather Service Las Vegas NV
830 PM PDT Sat Aug 5 2017

.SYNOPSIS...A decreasing trend in thunderstorm coverage is still
expected through next week with dry conditions returning by mid week
in most areas. Storms remain possible from Las Vegas north to
the southern Great Basin on Sunday and then limited to the far
northern reaches of the forecast area on Monday and Tuesday. Normal
temperatures will return under mostly clear skies Tuesday and
beyond.
&&

.UPDATE...Convection continued to die off this evening over southern
Inyo County and in and around the Spring Mountains. The latest HRRR
keeps any new development north and east of these areas. I updated
to remove mention of thunderstorms for the rest of tonight in those
areas. Convection in Lincoln County had been weakening considerably
for a bit but appeared to be pulsing back up at this time. HRRR
continues to spread activity south through Lincoln and central Nye
Counties into northeast Clark and northern Mohave Counties.
Therefore I left thunderstorms in the forecast there. -Harrison-
&&

.PREV DISCUSSION...
201 PM PDT Sat Aug 5 2017

.DISCUSSION...

It has been a rather slow start for thunderstorm development today.
Storm activity through 1 PM has been limited to central and northern
Mohave County and the Sierra and White Mountains. Except for the far
northern reaches of the forecast area, 1-1.5 inch PWATS point to
plenty of available moisture around the region. Thus far, the
thermodynamic profile suggests a down day for San Bernardino County,
the southern portions of Inyo County and the southwestern portion of
Mohave County. SPC mesoanalysis shows weak to moderate instability
in the Sierra, northern Inyo and the southern Great Basin, with
the most unstable conditions over southern Lincoln, Clark and the
northern half of Mohave County. Strong capping aloft has limited
development to this point but with mostly clear skies and plenty of
sunshine to heat the surface, this is expected to erode by mid
afternoon.

Later this afternoon into the evening hours, a decent early August
jet of 50-60 kts noses into the northwest forecast area, providing
support for enhanced storm development in that region and across the
southern Great Basin. The airmass in this region is somewhat drier
and the risk for strong, potentially damaging winds is enhanced.

Expect less shower/thunderstorm coverage heading into Sunday and
Monday. Weak to moderate instability is forecast on Sunday over
Inyo, Esmeralda, Nye, Clark and Lincoln counties...shifting
northward on Monday as the airmass stabilizes over southern Inyo,
southern Nye and Clark counties and a weak disturbance aloft keeps
chances going in northern Inyo, Esmeralda, central Nye and northern
Lincoln counties. Other than a storm or two brushing northern
Lincoln County mid-late in the week, conditions should be dry and
stable.

Temperatures remain below normal Sunday and Monday but then warm to
near or slightly above normal Tuesday-Saturday.

.LONG TERM...Sunday through Friday

Precipitation chances become more limited by the second half of
the weekend as drier air works into the area. In addition, by
Sunday night that vort max finally lifts away from the area and
weakens. The previously mentioned trough on the West Coast does
push toward the area sunday night and Monday, so kept in some
chances for showers and thunderstorms. Instability will be
limited and PWATs will be decreasing however, so precipitation
should be isolated to scattered at best, mainly over the higher
terrain.

By Tuesday, better ridging and much drier air arrive, and we
should go dry everywhere. Think this dry and warm pattern should
continue through the rest of the week.
&&

.AVIATION...For McCarran...Thunderstorms later this afternoon are
expected to be confined to the mountains, with an outside chance of
erratic shifting winds at the terminal due to outflow. Otherwise,
expect fairly typical diurnal winds, with light easterly winds
shifting to southerly in the afternoon and southwesterly in the
evening. Drier and hotter weather can be expected for much of the
upcoming week.

For the rest of southern Nevada, northwest Arizona and southeast
California...Storms are expected roughly north of a line from
Pearsonville to Las Vegas to Wikieup. The main threats will be heavy
rain with mountain obscuration and erratic gusty winds. There is
some potential for strong winds across the southern Great Basin
later this afternoon into the evening. A gradual drying trend is
expected to continue into the upcoming week, with thunderstorm
chances being pushed a bit farther north.
&&

.FIRE WEATHER...A gradual drying trend will continue through next
week. A chance for thunderstorms through this evening over the
southern Great Basin, with heavy rain, strong winds and lightning
possible. Storm activity will begin to favor the higher terrain
beyond Sunday. Even drier conditions are expected to push in next
week, with only isolated thunderstorms expected across the southern
Great Basin and higher elevations of Mohave County. Temperatures
will be warming to near normal by Monday and continuing through the
period.
&&

.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures. This afternoon's primary focus area for thunderstorms
will include the Spring Mountains, the Sierra, Inyo County and the
southern Great Basin where wind damage and/or flooding reports may
be needed. The focus area shifts to Lincoln County and northern
Mohave County this evening.
&&

DISCUSSION/AVIATION...Salmen

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