textproduct: Reno

KEY MESSAGES

* Showers and thunderstorms widespread today and tomorrow with risk of heavy rains and flash flooding. Possible showers overnight tonight.

* Temperatures cooling to near or below normal levels through the weekend along with typical afternoon breezes.

* No significant heat or strong wind events indicated into next week.

DISCUSSION

* Showers and t-storms are a good bet (30-80% chances) this afternoon through early evening, mainly along and east of Hwy 395 per the latest HREF/NBM guidance. Main concern is locally heavy rain with rates 1-1.5"/hour along with erratic outflows and lightning. Thursday appears to be the highest risk of heavy rains with another round of showers/storms forecast. If the stars align and we don't cloud over, storms could produce rainfall amounts of 1.5-2.5"/hour, as such WPC has placed much of the region in a rare slight risk for excessive rainfall Thursday. Flood Watches in effect today and tomorrow.

* Impacts wise the major concern is recent and ongoing wildfire burn areas being more susceptible to flash flooding, mud slides, and debris flows - so we will be quick to warn on these spots. The Stallion Fire is notable with steep terrain and a history of debris flows from fires in the vicinity in the last 5-10 years. New fire starts from lightning outside storm cores are certainly possible with very dry vegetation, and outflow winds of 30-40 MPH could drive fire in random directions rather suddenly. HREF suggesting outflows nearing 60 MPH over the dry lake beds between Fallon-Winnemucca today and tomorrow, so blowing dust will be a concern.

* Sufficient moisture and instability is present for overnight and early morning showers and isolated storms. HREF is showing this nicely over Western Nevada, Tahoe, and the eastern Sierra tonight, roughly 20-40% odds. Either way, storm initiation Thursday will be earlier than normal, early-mid morning most likely. If we do cloud over quickly tomorrow, on the other hand, then that could reduce the intensity of storms/rainfall rates.

* Going into Friday, a bit drier airmass works in but instability remains and with upper trough to our west, chances for storms continue but at a lower confidence level. Roughly 10-20% along Hwy 395 up to 30-40% out along Hwy 95.

* For the weekend into early next week, airmass continues to dry but not too excessively and temperatures remain near to just below seasonal normals, coupled with daily zephyr breezes. Guidance is not showing anything too strong on the winds, 10-15 MPH gusting to 20 MPH in the afternoons, so that is good news for any continuing fire suppression efforts.

-Chris

AVIATION

* Showers and t-storms are a good bet (30-80% odds) near and east of RNO-CXP-MEV-MMH today, with more widespread activity forecast for Thursday (50-90% most areas, with 30-40% in the Sierra around TRK/TVL). MVFR-IFR conditions possible in heavy rains, lightning, and erratic outflow winds of 25-35 knots. Blowing dust also possible around HTH/NFL/LOL both days.

* Airmass is moist and unstable enough to allow for showers and isolated storms overnight tonight into Thursday morning, 10-30% chances. But the most favored times for storms remain the afternoon and early evening.

* Wildfires, specifically the large Bug/Stallion Fires N of RNO, will continue to produce haze and smoke restrictions to visibility (5-10 SM) through at least Thursday depending on fire activity. Winds are more variable today/tomorrow so smoke forecasts are low confidence. New fire starts from lightning also could add to smoke/haze levels.

-Chris

FIRE WEATHER

* Obvious concerns are with thunderstorms today and tomorrow producing heavy rains, strong outflow winds, and new lightning starts outside the cores.

* Flood Watch in effect today and tomorrow for increased potential of flash flooding, mud slides, and debris flows on current and recent burn areas, including the Bug and Stallion Fires just north of Reno. Stallion Fire probably slightly higher risk with steeper terrain involved, but any rainfall can create hazardous conditions for movement of fire personnel. Rainfall rates over 1"/hour are expected from any storms both days.

* Outflow winds producing sudden shifts in fire behavior and direction are also a concern both days. Latest high resolution models indicating potential for gusts of 30-40 MPH close to active fires, with potential for gusts over 50 MPH out east toward the Highway 95 corridor.

* New lightning starts given the very dry fuels are a definite possibility. While heavy rains are favored from storms, lightning outside storm cores can still produce new starts or holdovers that simmer for several days or longer. Fire Weather Watch in effect for the Tahoe Basin Thursday as that has the nexus of slightly drier storms and quicker storm motions, but admittedly confidence is low.

* Also of note is potential for overnight showers and storms tonight into Thursday morning - roughly 20-40% chances. So the risk of lightning and outflows and brief heavy rains doesn't necessarily die off when the sun goes down.

-Chris

REV Watches/Warnings/Advisories

NV...Flood Watch through Thursday evening NVZ001-003.

Flood Watch from Thursday afternoon through Thursday evening NVZ004.

CA...Fire Weather Watch from late tonight through Thursday evening CAZ272.

Flood Watch through Thursday evening CAZ073.