textproduct: Reno

KEY MESSAGES

* Isolated thunderstorms today may produce lightning, brief heavy rain, small hail, and outflow gusts of 45 to 55 mph.

* Hotter and drier weather arrives Thursday, with only isolated storm chances remaining across the southern Basin and Range through Friday.

* A Fire Weather Watch is in effect Friday afternoon through Saturday evening for critical fire weather conditions across northeast California and far northwest Nevada.

DISCUSSION

Isolated Thunderstorms Through Friday:

* Early-afternoon radar and satellite imagery show the forecast area largely dry, with cumulus developing across northeast California, northern Washoe County, and portions of the western Nevada Basin and Range. The 12Z REV sounding measured 1.03 inches of precipitable water, near the 80th percentile for late July. Forecast soundings around the region contain 600-1600 J/kg of MUCAPE, DCAPE of 1200-1600 J/kg, and midlevel lapse rates of 7-8 C/km. This environment favors high-based, poorly organized storms capable of small hail and erratic outflow gusts of 45-55 mph.

* Thunderstorm chances of 15-25% will favor northeast California and northern Washoe County, as well as Mono and Mineral counties, before shifting into the western Nevada Basin and Range this evening. Forecast soundings indicate west to northwest storm motions (265-300 degrees) at 15-25 kt, supporting east to southeast movement around 20-25 mph. This should limit the threat for prolonged heavy rainfall, although brief heavy rain remains possible beneath stronger cells. Southwest flow pushes the deeper moisture east Thursday, leaving 10-20% storm chances mainly across Mono, Mineral, and eastern Churchill counties through Friday.

Hot, Dry and Windy Into the Weekend:

* An approaching eastern Pacific trough will flatten the western side of the Four Corners ridge and strengthen southwest flow across the region. Temperatures rise Thursday and peak Friday, with upper 90s to lower 100s across western Nevada valleys and 80s in Sierra communities. Moderate HeatRisk is expected Friday, with pockets of Major HeatRisk across the western Nevada Basin and Range.

* Afternoon west to southwest gusts of 25-35 mph will overlap minimum RH of 5-10% Friday and Saturday. The strongest overlap will occur across northeast California and far northwest Nevada, where 3-8 hours of critical conditions are possible each afternoon. Winds may activate holdover fires from this week's lightning. Dry and breezy conditions linger Sunday before winds ease early next week, with typical late-July warmth and mostly dry weather continuing through Wednesday.

-Johnston

AVIATION

* VFR conditions prevail through this evening, with haze possible at KRNO through 22/21Z. Isolated thunderstorms should remain outside the main terminal areas, but may produce lightning, brief mountain obscuration, and outflow gusts of 35-45 kt. Afternoon west winds will gust 15-22 kt before easing between 23/03-07Z. KTRK is expected to develop LIFR fog and low stratus after 23/04Z, with 1/2SM visibility and ceilings near 200 feet possible into Thursday morning.

* RNO: VFR conditions prevail, with south-southwest winds shifting west-northwest and increasing to 14 kt with gusts near 22 kt between 23/01-05Z before becoming light overnight. Dry and VFR conditions continue Thursday, followed by stronger afternoon winds Friday and Saturday. Hotter temperatures will increase density- altitude concerns.

-Johnston

FIRE WEATHER

* Isolated thunderstorms are expected this afternoon across northeast California, northern Washoe County, the eastern Sierra, and portions of the western Nevada Basin and Range. Dry lightning potentially causing new fire starts will be the main concern today, as storm motions are fairly fast around 20-25 mph. Gusty outflow winds of 45-55 mph are also possible around these storms.

* A drying and warming trend begins Thursday, although a 15-20% chance of storms in Mineral and Mono counties continues Thursday and Friday. Friday and Saturday will be the two main days of concern this weekend. Increased winds gusting to 35 mph and afternoon minimum RHs ranging from 5-10% will overlap each afternoon across northeast California and far northwest Nevada, yielding 3-8 hours of critical fire-weather conditions. For this reason, and due to the proximity of these conditions to the Biscar Fire, we have issued a Fire Weather Watch from 1 PM Friday through 9 PM Saturday.

-Justin

REV Watches/Warnings/Advisories

NV...Fire Weather Watch from Friday afternoon through Saturday evening NVZ458.

CA...Fire Weather Watch from Friday afternoon through Saturday evening CAZ270-278.