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956
FXUS65 KREV 251014
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
314 AM PDT Tue Jun 25 2024

.SYNOPSIS...

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* There is a 15-40% chance of showers and thunderstorms today,
  most likely to occur in the afternoon and early evening, and
  across areas as far north as I-80. A few showers may persist
  overnight into early Wednesday morning.

* Strong gusty winds will bring choppy lakes and heightened fire
  weather concerns Wednesday.

* The warmth will continue through the weekend with only a brief
  dip to near normal Thursday behind a frontal system.
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.DISCUSSION...

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* Main change overnight was to add the northern Sierra Front to
  the Fire Weather Watch Wednesday. Also, post frontal winds do
  not look as strong Thursday although it is still going to be
  breezy and very dry.

* Moisture continues to increase with PWATs already exceeding
  1.00" over southern NV. Model ensembles show PWATs near this
  level across much of the eastern Sierra and western NV today,
  and locally as high as 1.20" south of Hwy 50. Normally, we
  convect early and cloud over, resulting in more showers and less
  lightning potential as the day goes on with these values.
  Blended guidance continues to show decent thunder potential
  (30-40%) this afternoon and the HREF Composite Reflectivity
  ensemble indicates storms firing as early as 11 am to noon along
  the eastern Sierra with storms lifting north and east through
  the afternoon before decreasing after 00Z as skies cloud over
  and heating support wanes. If we can get enough heating early,
  then a few stronger storms will be capable of very heavy
  rainfall this afternoon. While storms will diminish in the
  evening, there are indications that additional showers will
  continue overnight across western NV and far northeast CA.

* Winds will be the next problem as a trough advances inland over
  the PacNW and pushes a front through the northern Great Basin
  late Wednesday into Thursday. Winds aloft increase late tonight
  and early Wednesday morning then peak late Wednesday (700 MB
  winds 30-35 kts). Tightening gradients/strong mixing will allow
  for sustained winds to reach 20-25 mph across areas near and
  north of I-80 with gusts approaching 40 mph in the windiest
  spots. This will bring rough lake waters and heightened fire
  weather concerns as drier air works back into these areas. Winds
  will stay up across the ridges Wednesday night/early Thursday
  morning as the front makes its way through the area.

* LONG TERM(Thursday and beyond): The frontal passage will arrive
  Thursday, bringing in dry northwest winds. Although wind speeds
  will have dwindled from Wednesday, we will still see valley
  gusts of 30 mph and Sierra ridge gusts of 45+ mph. With the
  drier air come concerns for lower relative humidity values
  across the region. Any fires that may have started from early
  week convection may carry on the gusty breezes and further the
  drying of fuels. Friday we will settle into a more zonal upper
  level pattern, with a ridge starting to build into the
  Intermountain West for Saturday with afternoon breezes. Then for
  Sunday yet another dry trough will swing through the Pacific
  Northwest, reintroducing breezy winds and knocking a couple
  degrees off of daytime highs. Looking into the first week of
  July, things look to heat up again while a dry trough along the
  PacNW coast will keep shower activity out of our area. HRICH
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.AVIATION...

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* Storm chances increase and expand northward today with a 25-40%
  chance along the eastern Sierra from KMEV-KMMH and generally a
  10-20% elsewhere. Storms will start as early as 18-20Z along the
  eastern Sierra, then advance north and east across western NV
  during the afternoon and early evening. Erratic outflows to 35
  kts and very heavy rainfall will accompany stronger cells.

* Typical SW-W afternoon breezes will be confined to mainly far
  northeast CA and northwest NV today with lighter winds elsewhere
  outside of storm outflows.

* A trough will bring drier conditions Wednesday, but much
  stronger winds as FL100 winds increase to 25-35 kts. Strongest
  winds will north of Hwy 50 where sustained winds will reach
  15-20 kts with gusts as high as 35 kt. Moderate turbulence
  Wednesday may continue overnight as winds aloft remain elevated
  ahead of the main cold front that is expected to drop through
  the region Thursday.

Hohmann
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&&

.FIRE WEATHER...

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* Main change was to add the Northern Sierra Front (NVZ420) to the
  fire weather watch Wednesday.

* For today, storms will fire early (possibly late morning) along
  the Eastern Sierra of Mono Co and far western Mineral/southern
  Lyon counties (30-40% chance), then lifting north and east for a
  10-25% chance of storms as far north as I-80 in the afternoon.
  Moisture has increased considerably and we expect stronger
  storms to be capable of very heavy rainfall. As storms push
  farther north and east, heating may wane a bit as cloud cover
  thickens and we lose our primary lift from daytime heating. This
  could result in a decrease in storms as we make it toward late
  afternoon or early evening. How fast this occurs will dictate
  the lightning coverage too.

* Drier air and stronger winds arrive Wednesday as a trough moves
  through the PacNW. Sustained winds of 20-25 mph with gusts 30-40
  mph will combine with RH below 15% to bring critical fire
  weather to much of NW NV and northeast CA. Latest guidance
  indicates RH levels will fall very close to 15% along the Sierra
  Front where strong winds are expected. So we have added Fire
  Zone 420 to the watch. Winds will be more marginal farther south
  although localized critical conditions may occur across
  Churchill County in the northern part of Fire Zone 429. Also,
  while winds will not quite reach criteria in these southern
  areas, drier air and breezy conditions may be an issue for any
  holdovers from lightning that occurs today.

* Winds will be breezy out of the northwest Thursday, generally
  10-20 mph with gusts 25-30 mph. These forecast speeds are down a
  bit from what we were seeing Monday. It still looks much drier
  Thursday afternoon with RH dropping to 8-15% across much of
  western NV.

Hohmann
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&&

.REV Watches/Warnings/Advisories...
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NV...Fire Weather Watch from Wednesday afternoon through Wednesday
     evening NVZ420-423-458.

CA...Fire Weather Watch from Wednesday afternoon through Wednesday
     evening CAZ270-278.
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&&

$$