textproduct: Reno

KEY MESSAGES

* Near 100 degree highs for W.Nevada valleys through at least Wednesday with Moderate to localized Major HeatRisk concerns.

* Shower and thunderstorm chances confined to the Sierra crest of Mono county today and Wednesday, though chances less than 15%.

* A pattern change Thursday-Friday increases fire weather concerns due to increased thunderstorm chances along with gusty winds and low humidity. Cooling expected by next weekend.

DISCUSSION

There is a 10-15% chance for showers and thunderstorms today along the Sierra crest. However, the most likely scenario will be increased cumulus buildups along the higher terrain due to strong surface heating.

Speaking of heating, afternoon highs reach near 100 across much of western Nevada and northeast California, with near 90s for lower Sierra communities. Overnight lows will provide little heat relief as lows stay in the mid to upper 60s for western Nevada. These trends will continue through Thursday. As such, the Heat Advisory for Churchill and Pershing counties has been extended. Limit outdoor activities, take plenty of breaks in the shade, and remember to drink water this week.

Thunderstorm chances return in earnest Thursday, mainly along the Sierra crest, per latest hi-res guidance. The current forecast highlights Mono county for Thursday (15-30% chance), though hi-res models hint at showers creeping into the Tahoe Basin and even northward along the Sierra of northeast California. Storms that develop Thursday will be capable of brief, heavy rainfall and outflow gusts up to 50 mph.

Friday looks to be the day of greatest concern, with increased chances for elevated to locally critical fire weather conditions. For further details, please see the fire weather section below. Chances for showers and thunderstorms becomes more widespread Friday, with a 15-25% chance for lightning extending from central Mono county up through the OR border, and east to the Churchill/Pershing and Lander county borders. Model sounding DCAPE values range up to 1400 J/kg, coinciding with outflow gusts up to 60 mph. Planning to be outdoors Friday? Keep an eye and ear to the skies; when thunder roars, go indoors!

-Giralte

AVIATION

VFR conditions for all terminals today. The only exception may be KMMH today where there is a less than 10% chance of showers and thunderstorms. Impacts from these storms include gusty and erratic outflow winds, brief downpours, and lightning. Additionally, mountain obscurations may develop along the highest peaks of the Sierra.

Above average temperatures through mid-week will result in density altitude concerns. Nevada terminals will be the most vulnerable to these concerns as temperatures approach the triple digits.

-Giralte/Fuentes

FIRE WEATHER

Near triple digit heat will continue through Thursday, peaking today and tomorrow. With the heat, a very dry air mass will continue to drive afternoon humidity levels into the single digits and cause poor overnight recoveries in the teens and low 20% vicinity across the W.Nevada Basin and Range.

Typical afternoon zephyr breezes return on this afternoon, bringing gusts of 20 to 25 mph. These hot, dry, and breezy conditions will combine to create brief, localized areas of elevated fire weather where vegetation is already dry, primarily in Washoe county and parts of northeast California.

A pattern chance Thursday into Friday will open the door for fast-moving, high-based dry thunderstorms. A few storms could develop Thursday afternoon in Mono County before drifting north into the Tahoe Basin overnight and Friday morning. Friday afternoon will bring the greatest threat, with widespread scattered thunderstorms chances.

Due to the low chance of wetting rains (<10%) associated with the fast-moving storms, new lightning ignitions will elevate fire weather concerns. In addition, the dry low-level airmass will favor stronger thunderstorm outflows with wind gusts of 50-60 mph. These strong outflows could rapidly spread any new ignitions, especially in areas of dry fuels. After several days of hot and dry conditions, vegetation will be more susceptible to burning, increasing the overall fire threat.

-Giralte/Fuentes

REV Watches/Warnings/Advisories

NV...Heat Advisory from 11 AM this morning to 5 AM PDT Friday NVZ004.

CA...None.