textproduct: Reno

KEY MESSAGES

* Light showers and embedded thunderstorms will increase in coverage today, posing a risk of new lightning fire starts. * Typical July heat continues through midweek with breezy afternoon winds posing minor fire and recreation impacts.

* Hotter temperatures and increasing heat risk probable by late week into next weekend.

DISCUSSION

Early morning satellite imagery reveals a weak shortwave pivoting into California with attendant synoptic ascent/upper cloud deck overspreading the western states. As this feature lifts northward, so will a band of light showers--first across areas south of US-50 in the morning, then moving towards/north of I-80 in the afternoon and evening. Thunderstorms embedded within this band will be possible in the afternoon, but there are still some questions on if synoptic ascent will compensate for abundant cloud cover and limited surface heating. However, ample moisture and lift from the trough is enough to warrant a low 15% chance of isolated afternoon storms in portions of the Sierra and western Nevada--including the Tahoe Basin and Greater Reno-Carson-Minden area.

Farther north, lesser cloud cover will allow for better surface heating and greater instability across Lassen County, the Surprise Valley, and N Washoe County, supporting a 15-30% chance of thunderstorms this afternoon. While new lightning fires will be possible wherever storms develop today, areas near the Oregon border are favored for new lightning ignitions given it's where storm chances/coverage is greatest.

Dry, southwesterly flow will begin to scour out moisture after today, but there will be enough residual moisture to yield a couple distinct areas of 10-15% shower/storm chances Monday afternoon: 1) near the Oregon border and 2) the broader Mono-Mineral-Lyon county vicinity. Further drying will largely preclude shower and thunderstorm formation from Tuesday onward. Otherwise, seasonably warm temperatures (80s in the Sierra; 90s in lower valleys) with typical afternoon breezes prevail through Wednesday.

High pressure expands across the southwestern states later in the week before settling near the Four Corners area next weekend. This pattern will likely result in a heat wave from Thursday into the weekend when daytime highs will flirt 90F in the Sierra and triple digits across lower elevation valleys. Looking further ahead, there continues to be hints of monsoonal thunderstorm activity along with more heat during the week of July 13th, which is consistent with the advertised weather pattern.

-Salas

AVIATION

An upper level disturbance will increase cloud cover today and provide increased chances of a light band of showers in the morning with 10-20% odds of an isolated thunderstorm across Tahoe and Sierra Front terminals between 21Z and 02Z this afternoon. Otherwise, expect light morning winds to become breezy each afternoon with typical west gusts of 20-25 kts. Fuentes/Salas

FIRE WEATHER

* No significant changes to the fire weather forecast. Refer to the discussion below for more details. -Salas

A shortwave trough will track across the E Sierra today and could trigger isolated areas of elevated, fast moving thunderstorms. These storms will be capable of producing isolated cloud-to-ground dry lightning strikes and gusty outflow winds.

Areas across the Tahoe Basin and Sierra Front could see areas of banded light showers with a 10-15% chance of afternoon thunderstorms. However, the best potential for dry strikes today are expected across portions of E Lassen County into the Surprise Valley, and far N Washoe county near the Oregon border (15-20% chance). A few of these storms could be better organized with isolated stronger cells, which could be capable of producing hail and strong outflow winds up to 50 mph. Any new ignitions could rapidly spread with these gusty outflow winds.

In addition, this passing wave could produce localized critical conditions due to a wind increase late this afternoon and evening across NE California/NW Nevada, mainly across Fire Weather Zones 278 and 458. Wind gusts could reach 25-35 mph with minimum RH dipping to 10-15%. Fuentes

REV Watches/Warnings/Advisories

NV...None. CA...None.