textproduct: Reno

KEY MESSAGES

* Lingering shower and isolated thunderstorm chances will continue each afternoon through Wednesday mainly near the eastern Sierra.

* Expect drier weather with temperatures warming to around 10 degrees above average by Friday and Saturday.

* Shower and thunder chances may return for the upcoming weekend, mainly on Sunday and continue through early next week.

DISCUSSION

While the low pressure trough that triggered Monday's shower activity has exited to the east, a secondary wave dropping southward along the CA coast is tracking a bit closer to the Sierra. Upper level forcing and divergence associated with this wave is projected to line up along the Sierra crest and adjacent portions of northeast CA, combined with terrain-driven convergence and a bit more daytime heating, resulting in another round of showers with isolated thunder. Most unstable CAPE values on high resolution guidance increase to between 200-600 J/kg in close proximity to the crest this afternoon, increasing the potential for lightning (15-25% chance) compared to yesterday. While most activity will remain in the higher terrain or push west of the crest where instability is greater, a few showers could develop closer to US-395 in far western NV and southward near the CA-NV border in Lyon/Mineral counties, and near favored convergence zones in northern parts of Lassen/Washoe counties. The most favored hours for showers/thunder are between 2-6 PM, with most activity winding down by 9 PM. Although snow levels will climb to near 8000 ft, a well-placed slow moving cell could still produce slick Sierra travel with minor accumulation of pellets or small hail.

For Wednesday, a similar setup is again projected for afternoon showers near the Sierra crest, although decreased forcing and instability will limit cell development, with thunder chances dropping below 10%. Even on Thursday some cumulus buildups are again projected near the Sierra crest, but shower chances drop below 10%.

Although a prevailing north-northeast flow is expected for much of this week, temperatures will warm up each day, climbing to near seasonal averages today (mid-upper 60s lower elevations and mid 50s for Sierra communities) and peak near 80 and 70 degrees in these respective areas by Friday-Saturday, about 10-15 degrees above early May averages. A modest back door front passage across central NV is still projected to bring increased north wind gusts 25-35 mph Thursday afternoon along the US-95 and US-6 corridors of Mineral/southeast Mono counties.

For the upcoming weekend through early next week, a closed low approaching the west coast brings increased south to southwest winds by Saturday. Showers may begin late Saturday in far northeast California and near the Sierra crest. Then shower and isolated thunder chances increase and expand to the eastern Sierra-western NV Sunday, potentially extending through next Monday-Tuesday, along with daytime highs dipping to near early May averages. Confidence remains low regarding the systems timing and track, which is typical for slow-moving spring cut-off lows. MJD

AVIATION

For this afternoon, isolated showers with about 20% chance for thunder will be capable of producing short periods of MVFR conditions for the Sierra/Tahoe area terminals, mainly between 21-02Z. For western NV terminals, shower chances decrease to around 15% with VFR conditions prevailing. For Wednesday, shower chances decrease to 10-15% at KTVL/KMMH and below 10% elsewhere with VFR conditions prevailing at all terminals.

Overall winds will be light today and Wednesday with gusts below 20 kt, but brief gusts to 30 kt could occur near shower/t-storm activity.

Decreasing cloud cover each night will set up favorable chances (50-70%) for FZFG at KTRK with LIFR conditions this morning and again early Wednesday, mainly between 08-15Z. An east flow over the Sierra may make the fog more patchy or intermittent each morning, but fog potential increases late tonight if precip occurs at KTRK today. MJD

REV Watches/Warnings/Advisories

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