textproduct: Reno

KEY MESSAGES

* Showers this afternoon, with anticipated increases in coverage and intensity into this evening. Concerns for fast-moving storms producing dry lightning, heavy rainfall, and gusty outflow winds.

* Tuesday, widespread storm activity brings more concerns for heavy rainfall leading to localized flooding potential.

* Storm activity continues midweek with storm chances persisting for Mono and Mineral, while winds increase for areas near the OR border. Monsoonal moisture may return this weekend and next week.

DISCUSSION

Hazy skies across the region this morning from nearby fires, with clouds and rain above, keeping the skies dark and gloomy. There was noticeable residue from rain containing ash and smoke particles covering vehicles across the Reno/Sparks area this morning. Luckily the morning showers so far have been concentrated near the Elephant Fire, which should help efforts. Recent HRRR near-surface smoke modeling suggests the smoke tapers after these showers, so let's hope the moisture continues to abate the smoke.

In the past 12 hours, rainfall at South Lake Tahoe has accumulated to 0.10 inches, and the radar shows more on the way. However, nailing down exact amounts and where they will fall tends to be more difficult with the convection expected to develop this afternoon. There could be storms that produce heavy rainfall, but with fast-moving storm motions, it is hard to say just how much measurable precipitation any given point may realize. PWATs at NWS Reno were already measuring 0.99 inches at 12z this morning, which is a tad higher than guidance suggested would be available at that hour. So, we are thinking storms could produce localized rainfall amounts of 0.1-0.5 inches across the general area, but if training storms develop, amounts could be much higher. This leads us to considering a localized flooding threat under wet storms, especially if occurs. This afternoon is a great opportunity to make sure your storm drains are cleared and ready to handle any heavy rains that may fall. Another issue for the afternoon convection is the potential for dry lightning, especially over northeastern California and northwestern Nevada, from the I-80 corridor north to the Oregon border. From I-80 to the south, the existing moisture field suggests this is the highlighted area for flooding potential, although any storm today is primed to create flooding concerns. Widespread showers are modeled to continue into the overnight hours, tapering before sunrise on Tuesday.

For Tuesday, we expect the showery nature of the system to convert to a more convective look than even today, with even more emphasis on a widespread heavy rainfall threat as moisture continues to stream in. Blended guidance suggests the PWATs nudge over 1.00 inch, although the 12z sounding from last night exceeded the predicted amounts, so we think this might be a tad underdone. At any rate, there will be moisture. As for instability, there is an appreciable increase Tuesday afternoon, suggesting some clouds clearing Tuesday morning to allow for the heating to build at the surface. If clouds hang out longer than expected from the overnight showers, this could work to limit the overall instability values, but any clearing will help the numbers. The best clearing looks to occur over the Sierra Front, the Basin and Range and along the Sierra crest to the west, although there also appears to be a few pockets where clouds linger over Mono County and the Tahoe Basin. For that reason, nailing down where the best CAPE values will be found will boil down to where the sun shines the longest before convective initiation. The expectation is to see CAPE values ranging 100-800 J/kg, but the aforementioned caveats will dictate the locations of these fields. Another kicker is an inbound trough from the northwest that could provide a bit more lift, but tbd on exactly where and when this may influence storm development.

Wednesday, the influence from the northerly trough will be more pronounced as the ridge to our east advances, bringing a drier airmass to the northern Sierra. The shower and storm chances follow, with far southern Mono County, far southeastern Mineral County and out to eastern Churchill and Pershing counties, with chances ranging 5-15%. The position of the ridge's center of circulation is forecast to build over the Four Corners area Thursday, which will retrograde the shower and storm threat. For Thursday the focus is along and south of I-80 with chances ranging 10-20%. While this reestablishment of ridging over the Four Corners is a favorable position to reintroduce widespread showers and storms, signals become more murky into the weekend. What we can say for now, there will be showers and storms in the vicinity. Whether or not they will still remain to the east or continue to retrograde as the high pressure builds remains the question. We will be monitoring this as the week progresses. HRICH

AVIATION

* Light SHRA today with a 15-50% chance of TSRA this afternoon, especially for TAF sites south of US-50 including KMEV, KHTH, KBAN and KMMH. Gusty winds up to 35 kts are possible near SHRA/TSRA. Otherwise, winds will be south to southwest 7-12 kts with gusts to 20 kts.

* Shower and storm coverage increases Tuesday with similar TSRA potential to Monday on most sites after 18Z. Gusty outflow winds, heavier rain showers, small hail and terrain obscuration continue to be the main concerns. HRICH/HC

FIRE WEATHER

* Storms trend wetter today and Tuesday, increasing the potential for wetting rainfall. However, storm motions will remain on the faster side today, so new lightning ignitions are possible away from main rain cores. Storms will be slower and wetter on Tuesday limiting the fire risk.

* Gusty and erratic outflow winds up to 45 mph could also accompany thunderstorms. Moreover, an increasingly unstable environment this afternoon and again Tuesday will be more favorable for deeper vertical plume growth/more active plume behavior on any new/existing fires that become intense.

* Winds also appear to increase midweek with the approach of an upper trough leading to brief periods of elevated to critical conditions over portions of NE CA, especially over mountain ridges due to gusts to 30-35 mph, and a 20-50% chance of exceeding 35 mph. HRICH/Salas/HC

REV Watches/Warnings/Advisories

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