textproduct: Reno

KEY MESSAGES

* Dry weather with unseasonably warm temperatures continues today with enhanced afternoon breezes.

* The weather pattern shifts to cooler and wetter conditions starting tomorrow with valley rain and high elevation snow chances during the latter half of the week.

* Isolated to scattered thunderstorms are possible Thursday and Friday, though confidence remains low on the extent of the impacts.

DISCUSSION

The latest RAP analysis of the upper air pattern displays a weak upper ridge over the CWA with an upper low off to the west over the Pacific and another low over SW Canada this morning. Models have the ridge residing over the CWA pretty much all day allowing for high temperatures around 10-15 degrees above seasonal averages to continue today. NE CA and W NV valley will have daytime highs in the lower to middle 70s today with Sierra communities being in the middle 60s. Areawide dry conditions persist today with breezy afternoon winds gusting up to around 20-25 mph. For tonight, low temperatures are forecast to be in the upper 30s to middle 40s for NE CA and W NV valleys and in the upper 20s to middle 30s for the Sierra communities.

On Wednesday, forecast guidance projects the Pacific upper low starting to open into a trough and moving towards N CA, which will push the resident ridge to the east. Even with this pattern change aloft, the latest forecast has area temperatures still well above normal by 10-15 degrees. Some portions of the region though could see daytime highs a degree or two cooler though compared to Tuesday's highs. Light precipitation chances (15-35%) return to the region during afternoon for NE CA, the Tahoe region, and N Washoe County. While the higher end chances look to be closer to the OR border, rain looks to be the primary precipitation type with snow levels above 8500-9000 ft. Any rain would have to overcome the lower dry layer to reach the surface, so do not be too surprised if virga occurs. CAMs still are projecting pockets of ~100-500 J/kg in the aforementioned areas so an isolated thunderstorm or two may be possible during the afternoon though not anticipating severe weather.

On Thursday and Friday, forecast guidance has the CWA underneath the front part of the trough yielding a southerly flow aloft. At the surface, area temperatures continue to cool being ~5-10 degrees above normal on Thursday and then generally around normal on Friday. Precipitation chances become more widespread on these days being around 20-60% on Thursday and increasing to around 40-90% on Friday. Chances for thunderstorms within these showers currently look to be around 10-20% on Thursday and 15-30% on Friday. There still is uncertainty on timing, location, and intensity of the thunderstorms so please watch for forecast updates especially if you have outdoor activities planned through the tail end of the week. With temperatures cooling, snow levels look to drop down to around 7500-8000 ft late Friday allowing precipitation type to turn to snow in higher portions of the Sierra.

For the weekend, a larger PacNW trough absorbs the smaller trough in the region as it makes its way through the Western CONUS. This will cause temperatures to drop below normal with area highs forecast in the 40s and 50s by Sunday. Precipitation chances (40-80%) continue for the weekend as does the thunderstorm chances (10-20%). With temperatures cooling, snow levels will drop a bit more over the weekend with the latest NBM forecast showing levels around 6.5-7 kft by Saturday night. Will continue to monitor this as measurable snowfall for more portions of Sierra looks to be possible at this time. -078

AVIATION

VFR conditions are expected once again for all area TAF sites today. Dry conditions persist today with KRNO/KCXP/KMEV/KMMH seeing afternoon gusts up to around 15-20 kts. An approaching Pacific low changes the weather pattern on Wednesday causing rain and isolated thunderstorm chances (15-35%) in NE CA and far NW NV. The precipitation chances then increase and become more widespread through the remainder of the week. Isolated to scattered thunderstorms are possible Thursday and Friday along with potential Sierra snow showers going into the weekend. -078

REV Watches/Warnings/Advisories

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