textproduct: Reno

KEY MESSAGES

* Shower and isolated thunderstorm chances again this afternoon, mainly for Mono county.

* 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

Shower and thunderstorm chances renew for the Sierra crest of Mono county again this afternoon. CAPE values range from 250-500 J/kg with DCAPE values over 1200 J/kg, resulting in max outflow wind gusts up to 50 mph. As the upper level high tracks further inland, we will experience more of a NE flow, which will help push showers and storms that develop over the west side of the crest.

Temperatures will continue to rise through at least Tuesday, where afternoon highs for the Sierra Front and W NV will reach into the triple digits for the first time this year. Overnight lows will be quite warm for these areas, into the mid 60s, providing limited overnight heat relief. As for our Sierra counterparts, highs may break 90, most notably Truckee and the lower valleys of Alpine and Mono counties, as well as NE CA (Susanville, near Honey Lake, etc.). As of now, the record high for South Lake Tahoe on Tuesday is 88. The current forecast has South Lake topping out at 89 that same day. Could we have a record breaker on our hands? Overall, this early season heatwave will bring widespread Moderate HeatRisk concerns, with isolated areas of Major HeatRisk. For more information on HeatRisk, visit wpc.ncep.noaa.gov/heatrisk.

Winds will return to our typical afternoon zephyr breezes Tuesday, bringing a handful of localized critical fire weather concerns for northern Washoe county. The larger fire weather concern, though, comes with an emerging ridge breakdown pattern by Thursday of this week. With said pattern, the chances for thunderstorms increases. However, the areas of highest instability range from I-80 and northward Thursday and Friday. CAPE values nudge a bit higher, from 300-600 J/kg. For more details on the associated fire weather impacts of this pattern shift, please see the fire weather discussion below.

-Giralte

AVIATION

VFR conditions for all terminals through the majority of the forecast period. The exception may be KMMH today where isolated showers and thunderstorms have a 10-15% chance of developing. 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

A stretch of hot, dry weather is expected through Thursday, with the hottest temperatures Tuesday and Wednesday as highs rise 10-20 degrees above normal. Additionally, afternoon RH drops into the teens and single digits with poor overnight recoveries over W NV, especially in the Basin and Range.

Winds stay light today, then increase Tuesday as westerly zephyr breezes return, with gusts of 20 to 25 mph, increasing 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 Thursday through Friday will increase the chances for thunderstorms, lightning ignitions, stronger thunderstorm outflow winds, and increased afternoon gusts. Storm motions will be faster, as well, increasing the risk for dry lightning starts. After several days of hot and dry conditions, vegetation will be more susceptible to burning, raising the overall fire threat.

-Giralte/Fuentes

REV Watches/Warnings/Advisories

NV...Heat Advisory from 11 AM Tuesday to 5 AM PDT Wednesday NVZ004.

CA...None.