textproduct: Reno

KEY MESSAGES

* Shower and isolated thunder chances return this afternoon with temperatures remaining below average.

* Shower and thunder chances decrease and shift to areas near the Sierra Tuesday-Wednesday, with a gradual warming trend.

* Expect drier weather and further warming for late this week, then shower chances may return for the upcoming weekend.

DISCUSSION

Light showers are lingering across parts of eastern CA-western NV CA early this morning as an upper level trough remains overhead through today. Another shortwave will drop southward along the CA coast Tuesday and continue its southward track through Wednesday, although a small area of upper divergence and terrain-focused convergence sets up near the Sierra. With these weak meandering weather systems slow to clear our area, shower chances will linger through midweek, although coverage is likely to decrease each day through Wednesday.

Today will see a near-repeat of Sunday's activity, with isolated to scattered showers popping up around midday and peaking between 2-5 PM. Lightning has been sparse the past few days and today looks to be similar, with only low end 15-20% chances east of US-95 in west central NV and clipping southern Mono County, with 5-15% chances elsewhere. Spotty short-lived rain with a few pellets are again expected as today's highs remain on the cool side (near 60 degrees for lower elevations and upper 40s near the Sierra), although a majority of the region won't receive notable rainfall amounts. For the Sierra, snow levels edge upward to near 7000 feet this afternoon and isolated mountain sites could see an inch or two of snow, but for main passes there's only a minimal (less than 20%) chance for any accumulating snow on roads. Overall, winds today will be lighter (gusts 20 mph or less) compared to Sunday, although brief stronger gusts of 30+ mph may occur near shower activity.

For Tuesday, the focus area for PM showers shifts to areas near the Sierra, based on the track of the next shortwave closer to the CA coast, while for western NV drier air with limited instability reduces the shower risk. The potential for lightning is sparse, generally around 10% near the Sierra crest northward to western Lassen County. Temperatures edge upward by about 5-8 degrees compared to today, near late April averages of mid-upper 60s in lower elevations and mid 50s for Sierra communities.

The warming trend continues Wednesday-Friday, and while we can't rule out a few PM showers near the Sierra crest of Alpine-Mono counties Wednesday and Thursday, the overall outlook for mid-late week will favor a dry pattern. Highs climb to near 80 degrees for lower elevations while Sierra valleys rebound to near 70 by Friday. While lighter winds are projected for most areas, a shallow back-door front passage may bring increased north winds Thursday afternoon for the US-95 and US-6 corridors of Mineral/southeast Mono counties.

However, this warm and dry pattern isn't expected to be long- lasting, as medium range guidance continues to advertise another trough of low pressure dropping into the western US for the first weekend of May. Showers may begin by late Saturday in far northeast CA, with increased shower/isolated thunder chances expanding to the Sierra/western NV and several degrees of cooling currently on tap for Sunday. With this trough projected to evolve to a slow-moving closed low relatively typical for spring, shower chances could carry on through the first few days of next week. Given the varied locations/tracks of this potential low among the ensemble members this far in advance, confidence remains on the lower side for precip amounts and favored locations. MJD

AVIATION

A persistent upper trough overhead will lead to another round of shower activity starting around 19-20Z for the Sierra/Tahoe area terminals and after 21Z for the western NV terminals. Coverage will be isolated, with brief MVFR conditions in -SHRA for KTRK/KTVL/KMMH and short periods of terrain obscuration for KRNO/KCXP/KMEV. This shower activity winds down between 02-04Z. For Tuesday, isolated showers again bring similar brief MVFR potential for the Sierra/Tahoe area terminals, but western NV should remain dry with VFR conditions prevailing. Overall winds will be lighter today and Tuesday with gusts 20 kt or less, but brief gusts to 30 kt could occur near shower activity.

While cloud cover should limit FZFG formation around KTRK this morning, more clearing tonight sets up a greater potential (50-70%) chance for FZFG with LIFR early Tuesday mainly between 08-15Z, especially if precip occurs at the airport today. MJD

REV Watches/Warnings/Advisories

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