textproduct: Reno

KEY MESSAGES

* Summer-like heat will maintain widespread moderate to areas of major HeatRisk through Thursday.

* Thunderstorm activity increase through Friday, raising concerns for impacts to fire, recreation, and aviation.

* Cooler and drier weather is favored to return over the weekend.

DISCUSSION

Our ongoing stretch of hot weather peaks today and Wednesday as daytime highs reach the mid/upper 80s and 90s regionwide. Lower valleys of NE California and W Nevada -- including Reno -- may even breach the triple digits the next two afternoons. Moreover, temperatures will only fall to the mid/upper 60s the next few nights, providing minimal relief from the heat for those in lowest valleys. Such conditions will maintain widespread moderate (2 out of 4) HeatRisk through Thursday with major (3 out of 4) HeatRisk seeping into lower W NV valleys. A cooling trend begins in earnest after Thursday, returning temperatures closer to seasonal averages by the weekend.

A ridge breakdown sequence takes place during the second half of the week, allowing thunderstorm activity to increase after today as the pattern becomes less subsident. Showers and storms will be initially confined to the Sierra south of Tahoe Wednesday afternoon (10-20% chances) before expanding north and east Thursday afternoon towards the Tahoe Basin and into the Sierra Front.

Large scale ascent ahead of an approaching low will maintain shower and thunderstorm potential Thursday night into Friday morning -- mainly across the Sierra into NE CA/far NW NV. Thunderstorm chances/coverage peaks Friday afternoon as strong daytime heating overlaps with synoptic lift and residual moisture aloft. A few thunderstorms may even become strong to marginally severe given the presence of modest deep-layer shear. While storms will likely lean on the wetter side (PWATs of 0.6-0.8"), faster storm motions suggest that new fire starts will be possible with any lightning strikes outside of the main rain cores. Best shower and storm chances shift eastward on Saturday before dry weather prevails early next week.

-Salas

AVIATION

Well above normal temperatures and density altitude impacts will be the primary concern today -- especially at KRNO and other western Nevada terminals where triple digit heat is possible this afternoon. W/NW breezes will be slightly stronger this afternoon with surface gusts of 15-25 mph.

Similar heat will maintain density altitude concerns Wednesday, but a cooling trend should mitigate any impacts late this week. Shower and thunderstorm activity begins to trend upward after today before peaking on Friday.

-Salas

FIRE WEATHER

Strong eastern Pacific ridging will sustain hot and very dry conditions through Thursday, allowing fuels to dry further over the next few days. A critical ridge breakdown pattern will increase the potential for elevated thunderstorms and new lightning ignitions/strong outflow winds during the second half of the week. Friday afternoon is of particular concern as it is when thunderstorm coverage will be greatest, focusing across areas north of I-80. A Fire Weather Watch has been issued for these areas, going into effect Friday. While storm coverage will be less widespread, thunderstorms will pose new ignitions during the Thursday afternoon through Friday morning timeframe.

-Salas

REV Watches/Warnings/Advisories

NV...Fire Weather Watch from Friday morning through Friday evening NVZ458.

Heat Advisory until 5 AM PDT Friday NVZ004.

Fire Weather Watch from Friday morning through Friday evening NVZ423.

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