Area Forecast Discussion
Issued by NWS Reno, NV
FXUS65 KREV 261002
Area Forecast Discussion
National Weather Service Reno NV
302 AM PDT TUE JUL 26 2016
Hot and dry conditions with light winds are expected under strong
high pressure this week. Some increase in moisture will lead to a
few afternoon and evening thunderstorms from Thursday through the
weekend, with temperatures easing down for the weekend as high
pressure weakens and clouds increase.
Strong high pressure builds over eastern California and western
Nevada in earnest today as a weak trough exits into the northern
Rockies. This will push high temperatures to 7-12 degrees above
average for the short term, with mid 80s to mid 90s for Sierra
valleys and upper 90s to around 105 for the lower valleys. With
very dry air in place over the region and mainly clear skies
through as least Wednesday night, overnight temperatures will
still manage to drop into the mid 50s to mid 60s for lower valleys
for some reprieve from the daytime heat.
As far as thunderstorms, there are model hints at some cumulus
buildups over the Sierra south of Highway 50 Wednesday. However,
isolated thunderstorms are still not expected there until Thursday
as several days of hot temperatures and a slight increase in mid-
level moisture combine to allow for a few cumulus to build into
deep convection/thunderstorms. The main concern with any storms
Thursday will be strong outflow winds (very dry lower layers with
"inverted-V" profiles) and isolated lightning strikes.
Finally, there remains a minor concern for additional rounds of
light smoke and haze from the Soberanes Fire (south of Monterey)
and, less so, the Sand Fire (southern CA) for this afternoon and
evening. However, Wednesday and Thursday the potential should wane
somewhat as flow aloft turns more southerly and weakens...although
some light haze cannot be ruled out. Snyder
.LONG TERM...Friday through Monday...
Very few changes were made to the extended forecast this cycle even
though some of the model guidance is starting to trend toward a
little less convective coverage by Saturday.
In a broad sense the model guidance is in fair agreement but due to
resolution issues and the way the models handle explicit convective
development...the GFS remains more aggressive with coverage both
Friday and Saturday than the ECMWF. The very warm temperatures
continue into Friday with triple digits in the lower valleys...but
by Saturday there are changes to the pattern that would support a
This pattern change for Saturday also affects where and how much
convection could be expected. The GFS and...to a lesser extent...the
ECMWF are starting to develop more southwest flow aloft over the
northern half of the forecast area by late Saturday. This would
support less coverage north of I-80 than we currently show in the
forecast. This is true for Sunday as well. The models were already
showing this for Sunday...it is the Saturday appearance that is new.
That makes us a bit reluctant to start reducing coverage Saturday.
Monday originally looked dry and breezy and the ECMWF still looks
that way. Now the GFS has backed off a bit on the strength of the
southwest flow Monday and is producing convection over southern
Bottom line: intense heating and mid level convergence should
produce convection Friday and this may continue into Saturday into
the northern areas if southwest flow does not develop. Less coverage
Sunday mainly confined to areas south of Highway 50. Pops just below
the threshold for showing convection Monday...but this could increase
as we move closer to that day. Fire weather concerns increase with
increased thunderstorm coverage...but will also linger once the
thunderstorms decrease and winds get breezy again. 20
Limited cloud cover again with afternoon wind gusts approaching 20
knots east of the Sierra. A few more cumulus are possible...but no
deep convection today or Wednesday.
Smoke/Haze from the Soberanes Fire in California could reduce
visibility a bit at flight level below 15,000 feet...but should not
cause significant impacts for landing operations.
By Thursday we are likely to see the development of thunderstorms
along the Sierra south of Highway 50. This activity is likely to
spread north and east Friday and Saturday. 20
NV...Heat Advisory from 11 AM Wednesday to 11 PM PDT Friday
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