textproduct: Reno

KEY MESSAGES

* Shower and isolated thunderstorm chances continue this afternoon for the E.Sierra from Mono County to the Tahoe Basin.

* Near 100 degree highs for W.Nevada valleys Tue-Wed. Moderate to localized major HeatRisk concerns.

* A pattern change Thurday-Friday may increase fire weather concerns due to increased T-Storm chances along with gusty winds and low humidity. Cooling expected by next weekend.

DISCUSSION

Afternoon showers and thunderstorms are expected across the eastern Sierra today, with a 30-40% chance of showers in Mono County and a 15-20% chance of thunderstorms. The strongest instability will focus over Mono County, where surface CAPE may reach 600 J/kg and mid-level lapse rates range from 8.5-9.0 C/km. Instability weakens northward into the Tahoe Basin with a lesser, 10-15% chance of an isolated thunderstorm. Storms are expected to develop after 1pm and dissipate after around 8 PM as daytime heating fades. Any storms that form may produce brief heavy rainfall, small hail, cloud-to-ground lightning, and outflow wind gusts up to 50 mph.

Shower and storm chances decrease Monday and Tuesday, with only a 10-15% chance of isolated showers along the Sierra crest. Any activity that forms may drift onto the west slopes due to an easterly steering flow. Otherwise, expect light afternoon winds through Monday. Westerly Zephyr winds return Tuesday afternoon, with gusts of 20 to 25 mph and isolated gusts up to 30 mph by early evening.

Afternoon temperatures will remain 10-15 degrees above mid-June averages, with highs in the mid 90s across W.Nevada and low to mid 80s in Sierra valleys. Additional warming persists into early next week when some of the hottest days of the year thus far are expected. W.Nevada valleys have a 10-30% chance of reaching 100 degrees for the first time this year by Tuesday-Wednesday (30-60% chances for hotter rural valleys). Typically the first 100 degree day occurs around mid-July. Overnight lows will offer little relief, staying in the mid-60s, and moderate HeatRisk will be widespread with isolated major HeatRisk in hotter rural valleys. Plan ahead by staying hydrated and limiting outdoor activity during peak afternoon heat.

Heat will persist through midweek, with highs in the upper 90s across much of W.Nevada and mid to upper 80s in Sierra valleys. A pattern change around Thursday to Friday may bring 5-10 degrees of cooling, along with higher chances of thunderstorms and increased winds, increasing fire concerns late next week. See the fire weather section below for details. Fuentes

AVIATION

Plan on another day of warm temperatures with showers and isolated thunderstorms, especially for the Sierra terminals. For KMMH, there is a 20% chance thunderstorm within 10 miles, while chances for KTRK/KTVL will be around 15%. Expect gusty/erratic winds, brief downpours, and occasional lightning with any storm. Otherwise, widespread VFR conditions and typical afternoon breezes prevail.

Above average temperatures Monday through Thursday will result in density altitude concerns. Nevada terminals will be the most vulnerable to the density altitude concerns as temperatures approach the triple digits. Edan/Fuentes

FIRE WEATHER

An extended stretch of hot, dry weather is expected through next Thursday, with the hottest temperatures expected on Tuesday and Wednesday as highs rise 10-20 degrees above normal as afternoon RH drops into the teens and single digits. Overnight RH recovery will remain poor across W.Nevada, especially in the Basin and Range, where some stations across Pershing and Churchill counties only recovered to 15-18% this morning.

Winds will stay light through Monday, then increase Tuesday as westerly zephyr breezes return, bringing gusts of 20 to 25 mph, then up to 30 mph by late afternoon and early evening. These dry and gusty conditions could produce brief periods of critical fire weather conditions, particularly across the northern Sierra Front and far northern Washoe County.

Looking ahead, a potential ridge breakdown around the Thursday- Friday timeframe may increase the chances for thunderstorms, lightning ignitions, stronger outflow winds, and higher afternoon winds. After several days of hot, dry conditions, vegetation will be more susceptible to burning, raising the overall fire threat. Fuentes

REV Watches/Warnings/Advisories

NV...None. CA...None.