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Area Forecast Discussion (AFD)

Issued by Reno, NV (REV)

FXUS65 KREV 182048

Area Forecast Discussion
National Weather Service Reno NV
148 PM PDT Tue Jun 18 2019


Another day of hot temperatures Wednesday then a cold front will 
bring widespread breezy conditions Thursday. Noticeably cooler 
temperatures forecast for Friday and Saturday before warming Sunday. 
Another low pressure area, centered off the west coast, will keep 
summer temperatures in check next week but also bring several 
days of breezy winds.



* Changes: Minor upward adjustment to winds for Wednesday,
  Thursday, and again Monday into Tuesday next week. Increased
  POPs slightly for E Sierra high terrain Friday. Factored in an 
  upward trend in temps Sunday, Monday with models now showing a 
  bit more ridging building in.

* Pretty big pattern shift coming up with a pair of anomalous 
  troughs digging into the west over the next 7-10 days. After a 
  couple more days of heat, this will lead to (refreshing) near to
  below normal temperatures along with periods of breezy 
  conditions. Buildups or isolated storms possible E Sierra south 
  of Tioga today and Wednesday.

* First trough has a track right over the Great Basin leading to a
  notable cooldown Friday-Saturday with some frosts and freezes
  possible for mountain valley communities. This trough will 
  yield gusty winds Wednesday-Thursday due mainly to the strong 
  thermal gradient. Some localized fire weather concerns are 
  possible in lower elevation areas with already cured grasses. 
  GFS now painting more appreciable shower possibility behind the 
  front Friday over the E Sierra. Nice upper wave in the 
  simulations providing lift. Pretty quick recovery in temps 
  Sunday-Monday with some ridging building in, albeit briefly.

* Second trough in the ensemble guidance has a much further west
  position compared to the first, just off the west coast. As such
  temps will fall only to near normal next week. This is more of a
  classic (mainly) dry southwest flow aloft scenario that would
  bring us daily breezy conditions Monday through much of next
  week. If lower elevation vegetation dries out enough by then, we
  could be looking at more of a fire weather concern next week. A
  few buildups or t-storms possible downwind of Lassen and in the
  Mono-Mineral convergence zones.

* Further out starting the last weekend in June into early July,
  GEFS and ECMWF ensembles do really build the Four Corners ridge
  which would heat us up, but also lessen the wind to more of a
  typical zephyr. T-storm chances initially low could increase if
  that pattern held long enough.




* No significant aviation weather concerns through Wednesday morning 
  with just a few buildups over the higher terrain and light north 
  to northeast winds. Can't rule out an isolated t-storm over the 
  mountains S and SW of MMH through early evening.

* Increased gusty winds will become a factor Wednesday afternoon
  and again Thursday as an unseasonably strong cold front drops
  into the Great Basin. Likely to be some moderately rough air
  around due to low level wind shear (mornings) and vigorous
  mixing (afternoons). Mountain wave turbulence is possible
  Thursday due to slightly stronger ~35 kt W/SW flow aloft
  forecast in GFS. No meaningful precipitation is simulated with 
  this front for the Sierra and Western Nevada but some localized 
  blowing dust is possible over Central Nevada with MVFR 
  visibility at times.




* Walker River, Eastern Sierra: Walker River forecasts have been 
  dialed down some due to anticipated cooler weather late week 
  plus decreasing snow contributing area coupled with reservoir 
  management. With mainstem no longer in flood stage, the flood 
  warning was cancelled earlier today. But have expanded the flood
  advisory to cover all Walker Basin plus Eastern Sierra streams 
  to discuss potential for high flows and minor spot flooding 
  through Friday. Peak flows along the Walker headwaters and 
  streams are likely Thursday morning, about a day after the 
  hottest temps. Peak flows will occur at night or pre-dawn and 
  that's always tricky to see so we're encouraging extra vigilance
  from campers, hikers, and travelers.

* Humboldt River: no changes here as the long march upward 
  through minor to moderate flood stages continues. As usual this 
  river responds slowly so it will be a while, probably into July,
  before things start to ramp back down.



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