Marine Weather and Tide Forecast for Carnelian Bay, CA

DISCUSSION

All heat-related advisories and warnings remain in place through this weekend as strong high pressure ridge prevails across the southwest US and much of the Great Basin. The highest daytime temperatures are expected across Pershing and Churchill counties where warmer desert valleys could reach or surpass 105 degrees Friday through Sunday afternoon. An increase in mid-high level moisture brings increased cloud cover from the eastern Sierra into Mineral-Lyon counties this afternoon, then more of this cloud cover expands northward to the Reno-Tahoe region at times Friday afternoon through Saturday. While these clouds may shave off a couple degrees from afternoon highs in the Heat Advisory areas, it would also lead to less cooling for Friday and Saturday nights, with more areas remaining above 65 degrees and warmer valley sites holding above 70 degrees. For those heading to the Sierra communities to escape the valley heat, highs near or above 90 degrees will still feel summer-like, although nights will be notably cooler.

This moisture push brings an increase in PW values to 0.6"-0.7" this afternoon into Mono-Mineral-Lyon counties, then climbs to 0.65"-0.85" Friday and Saturday afternoons in these areas and also expands northward to more of western NV. Lack of adequate forcing and warm air aloft should prevent anything more than cumulus buildups, and perhaps a few raindrops reaching the ground this afternoon in southern Mono-Mineral counties. For Friday afternoon, a bit more instability and upper level forcing bring increased shower/isolated thunder chances (25-40%) to the eastern Sierra, with lower chances (10-20%) extending northward into far western NV. Rainfall looks to be sparse unless a cell is able to redevelop over the same area or anchor to a terrain feature, but with downdraft CAPE approaching 1500 J/kg, stronger outflow gusts of 40-50 mph are within reason.

A similar scenario sets up each afternoon this weekend, although the majority of the shower/t-storm chances remain limited to Mono, Mineral and southern Lyon counties, with chances dropping to less than 10% north of US-50.

Areas of haze and smoke mainly from the Gann Fire in central CA linger through this morning and should lift and disperse this afternoon. Wind patterns near the fire indicate less spread of smoke into the Tahoe-Reno regions tonight, although lighter haze may linger across the Sierra and western NV through Friday.
However, the latest smoke trajectory guidance hints at a return of smoke from the larger Oregon fires late tonight along the OR border, then expanding into northwest NV and northeast CA late Friday night into Saturday. Overall winds from today through Saturday resemble a typical zephyr-type pattern with SW-W gusts near 25 mph each afternoon.

Looking to next week from Monday onward, the heat will gradually ease with a few 100 degree highs lingering early in the week for parts of west central NV, but by mid-late week highs settle into near seasonal averages of lower-mid 90s for lower elevations and lower 80s near the Sierra. This cooling is likely to be accompanied by increased SW-W winds especially Mon-Tues which would lead to elevated-locally critical fire weather concerns. Dry air spread across most of the region, but lingering moisture and instability in Mono-Mineral-southern Lyon counties could lead to afternoon showers/t-storms in these areas each day through midweek. Later next week, blended guidance favors a northward expansion of these shower and thunder chances, but confidence is lower on this scenario. MJD

AVIATION

* SW-W wind gusts mainly 20-25 kt prevail at the main terminals each afternoon through at Saturday, generally ramping up between 20-22Z and diminishing by 03-05Z.

* VFR conditions continue this week. Lingering areas of haze around the main terminals may produce minor reductions in slantwise visibility, with this haze expected to thin out later today through Friday.

* Prolonged daytime heat will result in density altitude concerns through this weekend. MJD

REV Watches/Warnings/Advisories
NV...Heat Advisory until 8 AM PDT Monday NVZ001-003-005.

Heat Advisory until 8 AM PDT Friday NVZ004.

Extreme Heat Warning from 8 AM Friday to 8 AM PDT Monday NVZ004.

CA...Heat Advisory until 8 AM PDT Monday CAZ070-071.