Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 220054 CCA
AFDREV

Area Forecast Discussion...corrected
National Weather Service Reno NV
554 PM PDT Fri Jul 21 2017

.SYNOPSIS...

Areas of haze from the Detwiler Fire will continue this weekend with
the most dense smoke in the Mammoth area. After one more day of dry
conditions Saturday, low pressure off the coast will bring increased
moisture for early next week. Thunderstorms will begin Sunday with
some on the drier side before more moisture arrives Monday and
Tuesday with wetting rains and localized flash flooding possible.

&&

.DISCUSSION...
The forecast has been adjusted with a much better potential for
thunderstorms Sunday through Tuesday. Low pressure off the coast
is expected to sit there for a couple days with more southerly
flow bringing up monsoon moisture.

In the meantime, haze and localized smoke from the Detwiler Fire will
continue into the weekend. Most areas will see haze with high
level smoke as the lower level winds are more southeast to west.
The exception will be the Mammoth area where upslope winds on the
west slope may bring enough low level smoke to make air quality
poor to hazardous at times.

Saturday still looks hot, and Sunday as well, but the upper low
moves into a favorable position off the Bay Area by Sunday
afternoon. Moisture will increase modestly, with the greatest
increase over Mono/Mineral Counties. Forcing will improve with
diffluence aloft in the NE quadrant of the low even though any
upper waves moving through are weak. Thunderstorms are much more
likely near and east of the Sierra Sunday afternoon and evening.

The greatest coverage and moisture will be over Mono-Mineral
Counties with scattered wet thunderstorms. Further north, lower
levels will still be quite dry with a wet/dry hybrid and not quite
as much coverage. Fire starts will be a concern especially north
of Highway 50. Since the models have really just jumped on this,
we are only highlighting it in the fire forecast for now in case
they change tonight. Otherwise, a decent dry lightning event could
be in the offing Sunday.

By Monday, models continue to increase the moisture with PW
increasing to 1 inch or more. The forcing also remains favorable
so wetting rains are likely from the storms. Localized flash
flooding is also possible if this much moisture is present (and
there is enough solar heating).

Tuesday, the low slowly lifts out with more southwest flow.
Thunderstorms will begin to trend downward Tuesday and Wednesday
with dry conditions expected by Thursday with typical afternoon
winds. Temperatures will also cool and be closer to average during
the work week. Wallmann

&&

.AVIATION...
VFR with areas of haze and afternoon west winds gusting to 20 kts
22-03Z into Saturday. Smoke may present localized MVFR VIS around
KMMH after 01Z this evening if enough smoke arrives from the
Detwiler fire, chances 40%.

Thunderstorm potential increases Sunday through Tuesday with
scattered showers and storms possible each day. The usual threats
of gusty winds, small hail and locally heavy rains will apply.
Wallmann

.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&

$$

For more information from the National Weather Service visit...
http://weather.gov/reno


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