textproduct: Reno

KEY MESSAGES

* Warmer than average temperatures persist through Monday, but area waterways continue to run dangerously cold and swift.

* Showers and thunderstorms expected each afternoon through the holiday weekend, posing impacts to outdoor activities.

* Gusty winds will pose aviation, recreation, and fire impacts Monday and Tuesday with cooler, showery weather from mid to late week.

DISCUSSION

Maturing showers and isolated thunderstorms are noted from Lassen County to the Oregon border, the W NV Basin and Range, and S Mono County where better moisture quality aloft resides. These areas will continue to be the focus for additional shower/t-storm development through the afternoon as continued surface heating increases instability (albeit still weak). Unlike yesterday, there does seem to be slightly better upper support as a subtle shortwave to the west and marginal speed divergence aloft promote weak synoptic ascent. While these features won't be the main driver of showers/t- storms today, they at least won't hinder its development. Expect the usual hazards (strong outflow winds/blowing dust, lightning, brief heavy rain) from any thunderstorms.

Warm weather prevails this holiday weekend as daytime highs reach the 70s and 80s through Memorial Day. Keep in mind, mountain lakes, rivers, and creeks are still running cold and swift (water temps in the 40s and 50s) so be sure to exercise caution if near waterways. Showers and thunderstorms return to the W NV Basin and Range, and southern Mono County Sunday afternoon as a weak low pivots into southern California. Steering flow becomes more southerly on Sunday, which may direct storms northward into areas of W NV south of I-80 -- including the Greater Reno-Carson-Minden area -- as the afternoon progresses. Be prepared for additional thunderstorm impacts Sunday if planning any outdoor activities.

A strong, compact Pacific low and attendant cold front will approach and pass through the region during the first half of the upcoming week. Wind impacts will be the primary concern Monday and Tuesday ahead of the cold frontal passage. Blended guidance indicates that there is a moderate to high probability (50% or greater) of 35+ mph wind gusts across NE California and far NW Nevada Monday afternoon. As such, be prepared for hazardous lake recreation due to choppy waters, bumpy flights, and blowing dust/reduced visibilities near sinks and playas in W Nevada. elevated to critical fire weather conditions are also likely Monday (more details below). Similar odds exist on Tuesday, but shift farther south and east.

The core of the low moves overhead by the middle of the week, which when combined with daytime heating, will increase the potential for showers and thunderstorms/pellet showers Wednesday and Thursday afternoons. Falling snow levels will also allow for light snow along Sierra passes Wednesday and Thursday with a low chance (10-20%) of 1+" along Tahoe passes, and 30-60% chance of 2+" along mountain passes south of Tahoe. Temperatures will also sharply cool around midweek with daytime highs falling from the 70s and 80s on Monday to the 50s and low 60s by Wednesday. The upper low is slow to depart the region, so the end of next week is trending on the cool and wet side.

-Salas

AVIATION

VFR conditions expected for most E.Sierra and W.Nevada terminals this afternoon. KMMH and KHTH could see isolated showers this afternoon with brief light to moderate rainfall and gusty outflows. Thunderstorm chances (15-20%) will increase on Sunday at KMMH which could yield MVFR conditions from brief heavy rain, small hail, sudden/strong wind shifts, and lightning. Fuentes/Salas

FIRE WEATHER

UPDATE: A Fire Weather Watch was issued for eastern Lassen County, the Surprise Valley, N Washoe County, and the western Humboldt Basin in anticipation of gusty winds and low RH Monday afternoon. Otherwise, the forecast below remains on track.

A critical fire weather environment remains on track to unfold Monday afternoon across eastern Lassen Co, the Surprise Valley, and much of NW Nevada where gusty winds overlap low humidities. Duration of critical wind/RH is trending towards 4-8 hours in Lassen and far N Washoe County with 2-4 hours in Pershing County.

Fuels are the limiting factor in this case as there is uncertainty in the continuity of receptive fuel beds, but local intel from dispatch centers/GACC suggests the cured grasses and sagebrush will be capable of carrying fire in valleys/midslopes of far NW Nevada. Farther south, elevated fire weather conditions will be possible, but fuel conditions aren't as dry per local units.

Winds remain elevated on Tuesday and will shift from southwesterly to north/northwesterly as a cold front sweeps through the region. Temperatures cool and humidity rises behind the front, with increasing chances of showers Wednesday and Thursday.

-Salas

REV Watches/Warnings/Advisories

NV...Fire Weather Watch from Monday afternoon through Monday evening NVZ423-458.

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