Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 232109

Area Forecast Discussion
National Weather Service Reno NV
209 PM PDT Wed May 23 2018


Wet pattern will continue through Saturday with periods of showers
and thunderstorms. Strong storms with hail and frequent lightning
are likely Thursday, with more widespread rain showers Friday
into Saturday along with high elevation snow impacts. A drying
trend is expected Sunday into next week with temperatures warming
to well above normal.



Rain, rain, and more rain. I could probably end the discussion
right there but that wouldn`t be terribly satisfying now would
it? We`re already at our 5th wettest spring on record at Reno (at
least through May 21) and top-3 is not out of the question by this
weekend. Here`s the key points:

* Numerous showers and storms ongoing this afternoon. Fairly weak
  flow aloft and no big forcing mechanism have kept things
  somewhat disheveled. Anomalously high precipitable water values
  and slow motions have resulted in high short-duration rainfall
  rates, 1-3"/hour. This is a concern for burn areas and steep
  terrain for flash flooding the next couple hours. Storms should
  push north and east of the region late afternoon through the
  evening. Maybe an MCS type deal this evening up into far NW
  Nevada and far NE California. With clearing skies overnight,
  areas of fog likely Thurs morning especially where rain fell

* Thursday is probably our most active day in terms of storm
  intensity as upper low approaches and increases the flow aloft.
  With sufficient instability, parameters are there for heavy rain
  and flash flooding (training type cells anchored to terrain),
  but increased shear could also yield strong or severe storms
  with hail, unusual amounts of lightning, and strong outflow
  winds. Risk of debris flow type flash flooding remains elevated
  tomorrow since strong storms will have high precip intensities
  in moist airmass. Like today, tomorrow morning we may issue
  another "SPC style" 6-hour heads up flood watch for the Slinkard
  Burn area to indicate enhanced risk of storms impacting the fire

* Thursday night, Friday, and into Saturday morning as the upper
  low gets close, things transition to widespread rain showers
  with embedded thunder. Forcing becomes more broad but persistent
  so we could end up with some notable rainfall amounts during
  this period. High intensity rains less likely but we could still
  see minor flooding in urban areas and other prone spots. Cooler
  airmass will help drop snow levels to 7000-8000` Thursday night
  into Friday and Friday night - so we could see some impacts on
  the higher passes for Memorial Day travelers and people
  outdoors. Not a big snow but it`s late season.

* For those like me looking for summer to finally show up, well
  next week you`ll be in luck. Confidence is increasing in a
  pattern shift, at least for 3-5 days, to one of a ridge over the
  west coast. Guidance showing temperatures warming well into 80s
  for W Nevada by Monday and Tuesday. May return to the more
  traditional heat and terrain driven PM storms over the mountains
  by mid-week.




Thunderstorm activity today has been most widespread north of
Highway 50 in far western NV and the Sierra, and north of Interstate
80 out in the Basin and Range. The highest coverage of storms should
continue to shift north this afternoon and early evening, affecting
northeast CA and northwest NV. Thunderstorms have been rather weak,
producing heavy rainfall but only weak outflow to around 20-25 kts.
Reports and radar indicate very small hail so far (0.25" or less). A
few storms could get a bit stronger north of I-80 this afternoon but
are expected to remain mostly weak with sub-35 kt winds and hail of
0.5" or less.

It will be mostly quiet late tonight into Thursday morning except
for fog in the Martis Valley at/around KTRK. A stronger area of low
pressure approaching the California coast is expected to bring
STRONGER THUNDERSTORMS THURSDAY afternoon and evening, most
widespread in the Sierra, northeast California, and out into far
western Nevada. Many storms could contain hail to 0.5" in diameter,
brief torrential rain, and wind gusts to 35 kts; however, a few of
the strongest storms could bring hail to 1-1.25" in diameter and
wind gusts to 45 kts. Also, unusual amounts of lightning will be
possible with stronger storms on Thursday.

Overnight into early Friday morning, the potential for rain with
embedded thunderstorms will continue for northeast CA and far
northwest NV. Frequent lightning and moderate to heavy rainfall with
terrain obscuration will be the main threats below 10 kft MSL,
although small hail will also be possible. -Snyder


.REV Watches/Warnings/Advisories...
NV...Flash Flood Watch until 5 PM PDT this afternoon NVZ003.

CA...Flash Flood Watch until 5 PM PDT this afternoon CAZ073.



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