textproduct: Reno

KEY MESSAGES

* Afternoon shower and thunderstorm chances each day this week, becoming wider in areal coverage through midweek.

* Abundant moisture and slower storm motions will introduce flash flooding from heavy rain as the main concern.

* Uncertainty later this week into next weekend on whether the monsoonal pattern will persist or if drier conditions emerge.

DISCUSSION

Light showers earlier this morning have progressed out of the area, leaving clearing skies behind, providing ample daytime heating to get storms firing today. Southerly flow will allow for a south to north propagation of storms with showers and thunderstorms initially developing along the Sierra of Mono county today (30-50% chance). Storms are expected to track northward into the Sierra Front (chances diminish to ~25%). The 12Z sounding out of NWS Reno this morning recorded a PWAT of 0.9", which is well above the 90th percentile for today's sounding climatology. The mean wind in the bulk of the profile topped out at about 30 kts, which hints at faster storm motions. So, to get any flooding right now, we would need training storms. However, the decent wind speeds at the LCL/LFC layer indicate that storms today may become tilted (reduces the potential for hail development), resulting in a similar setup to last Monday/Tuesday, which produced localized flooding concerns.

Showers are expected to continue into NE CA and northern Washoe county after sunset. Thunder chances for this area decrease to about 15% for the overnight period. CAM guidance places some light showers around the Tahoe Basin tonight, too, though confidence on that materializing remains low.

Monday, CAM guidance starts convection once again in Mono county but with a more southwesterly flow, storms are to push into Mineral/S Lyon counties before continuing into the Basin and Range south of I-80. Model PWATs range from 0.8-1.1" and with slower storm motions forecast, flash flooding quickly becomes the concern. As such, a Flash Flood Watch is in effect for the aforementioned counties Monday afternoon through Monday evening. Also, some of the CAM/higher resolution guidance introduces a lower-end chance for narrow shower bands with embedded lighting in parts of northeast CA Monday afternoon-evening.

Tuesday, we see larger areas of diffluence aloft associated with typical convection initiation time. CAPE values are pushing 1000 J/kg with PWATs topping out at 1-1.2". Widespread convection will be the name of the game with storms once again developing in Mono county before pushing northward. Storm motions remain slow and with the abundance in monsoonal moisture, flooding is once again a concern. Make sure you have multiple ways to receive weather warnings and never drive through flooded roadways!

Model guidance is a bit mixed for later this week and next weekend with the Four Corners high propagating closer to Texas, which would reduce storm chances past Wednesday. However, some models have the high retrograding back towards the Four Corners by the end of the week, which in turn increases storm chances. As of now, the forecast remains on track with daily chances for showers and thunderstorms mainly in west central NV along and east of US-95 and southward to Mono County, though uncertainty in the intensity and areal coverage of storms remains.

-Giralte

AVIATION

VFR conditions will prevail for most of the period today. The exception will be this afternoon from roughly 22-03Z when showers and thunderstorms are expected to impact first KMMH and then KRNO/KCXP/KMEV. Brief periods of MVFR conditions likely due to lower CIGS/VIS from heavy rain. Vicinity showers likely for KTRK/KTVL for a similar time frame, which will allow for mountain obscurations at all terminals. Light showers may develop over KTRK/KTVL late tonight, though confidence remains low. If these showers do develop, the main terminal impact would be light rain and lower CIGS.

Another round of showers/t-storms is expected Monday afternoon- early evening, with best chances (up to 50%) at KMMH and lesser chances (10-20%) for the western NV sites (KRNO/KCXP/KMEV).

-Giralte

REV Watches/Warnings/Advisories

NV...Flood Watch from Monday afternoon through Monday evening NVZ001.

CA...Flood Watch from Monday afternoon through Monday evening CAZ073.