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KEY MESSAGES

* Warmer than average temperatures persist today, then much cooler conditions are expected from Tuesday through late week. * Gusty winds will bring aviation, recreation, and fire weather concerns today and Tuesday.

* Shower and isolated thunderstorm chances decrease today, but return on Tuesday with the highest overall chances Wednesday through Thursday.

DISCUSSION

We'll see one more warm day across eastern CA/western NV today to close out the Memorial Day weekend, with highs again in the 80s for lower elevations and lower-mid 70s for Sierra communities. However, as a spring storm approaches the Pacific NW coast, southwest to west winds will ramp up with gusts 35-45 mph this afternoon-evening especially in areas from US-50 northward, where Lake Wind Advisories and/or Red Flag Warnings (see the Fire Weather section below) are in effect. Be aware of these winds if planning lake recreation today, as relatively calm conditions this morning will become much more hazardous as the day progresses. Patchy blowing dust could reduce visibility downwind of desert sinks and playas in parts of northwest NV. For the Sierra, the strongest ridge winds (peak gusts 75-85 mph) are expected to arrive tonight into Tuesday morning as a cold front associated with the incoming storm edges closer. While a few showers and brief thunderstorms may pop up this afternoon in parts of Mono and southern Mineral/Lyon counties, this potential is lower (10-20% chance) compared to recent days.

For Tuesday, high temperatures will be 15-25 degrees cooler from US-50 northward and 5-15 degrees cooler south of US-50 as the cold front pushes southward. The most likely timing for the cold front passage is Tuesday morning for northeast CA-northwest NV, then clearing the I-80/US-50 corridors by midday/early afternoon and exiting southern Mono-Mineral counties later in the afternoon. West winds will shift to northwest and produce gusts 30-40 mph across much of the region mainly from I-80 southward, leading to another day of choppy lake conditions, with patchy blowing dust potential shifting to parts of west central NV.

As the main storm center/upper low drops southward, shower chances will increase by Tuesday morning across northeast CA- northwest NV, and slowly advance southward to the Tahoe basin/far western NV by late Tuesday, and into west central NV Tuesday night. Increased instability and forcing near the low keeps a risk for isolated lightning Tuesday afternoon. The best overall precip chances (40-70%) favor northeast CA/northwest NV with a few locations potentially receiving 0.25-0.50" of rainfall. Otherwise, precip amounts are likely to be light and spotty, while snow levels around Tahoe dip to near 6500-7000 feet by late Tuesday afternoon.

For Wednesday and Thursday, the upper low is projected to meander over CA/NV, leading to increased precip/isolated thunder chances regionwide and the coolest temperatures of the week (highs in the 50s-lower 60s). The locations receiving the most rain/higher elevation snow will be dependent on the eventual track of this low, but current blended guidance favors the eastern Sierra Wednesday afternoon-evening, then shifting to western NV/northeast CA Thursday. Snow levels are forecast to bottom out around 6000-6500 ft Wednesday morning, then gradually rise to around 7000-7500 ft Wednesday afternoon-night and climb further on Thursday as the low starts to weaken and/or lift out of western NV. Higher passes across Mono/Alpine counties (Ebbetts, Sonora, Tioga) are at the most risk for light (up to 4") but impactful snow accumulations, and an inch or two over Mt. Rose Summit can't be ruled out. The main Tahoe area passes including Donner/Echo summits are less likely to see snow accumulate on roads, but a well placed precip band could produce brief slushy conditions especially in the morning or night hours on Wednesday.

Showers could linger into Friday, otherwise temperatures look to warm up closer to late May averages (upper 70s-near 80 for lower elevations/near 70 for Sierra communities) for the final weekend of May. Overall precip chances decrease, although a weaker shortwave brushing across northern CA/NV could produce low-end shower chances again next weekend. MJD

AVIATION

Winds will be the main aviation impact today and Tuesday. SW-W winds increase this afternoon with gusts near 30 kt for western NV terminals and near 25 kt for the Sierra/Tahoe area terminals. As FL100 winds increase tonight with gusts 60-70 kt, turbulence and periods of LLWS are likely, while gusts of 25-30+ kt could mix down to the surface at times, especially for KTVL/KTRK. Windy conditions with turbulence and periods of LLWS continue on Tuesday with gusts again 25-30 kt, shifting to a W-NW direction for most terminals (except remaining SSW at KTVL).

Otherwise, VFR conditions will prevail through Tuesday, followed by increased chances for rain showers Wednesday-Thursday that could bring MVFR conditions at times with terrain obscurations, although wind speeds will decrease. MJD

FIRE WEATHER

* Red Flag Warnings remain in effect this afternoon and evening for northeast CA and northwest NV, including Pershing County where the Quartz Fire continues to burn in the northeast part of that county. Southwest to west winds become gusty in advance of a cold front, while minimum humidity levels drop to 10-20%.

* Uncertainty remains on the extent of vegetation that has dried out sufficiently, but information from local fire partners and the growth of the Quartz Fire suggests that areas of cured grasses and sagebrush will be capable of carrying fire in valleys/midslopes of far northwest NV. Farther south, elevated fire weather conditions will be present, but the latest fuel moisture data from local fire partners isn't showing widespread coverage of dry vegetation.

* Gusty winds return on Tuesday and shift to a more northwest direction, as a cold front sweeps through the region. Areas near and south of US-50 in west central NV, and the US-6 corridor in southeast Mono County could see a short duration of near- critical wind and humidity conditions Tuesday afternoon. Otherwise, temperatures cool and humidity rises behind the front on Tuesday, with increasing chances of showers and wetting rainfall Wednesday and Thursday. MJD

REV Watches/Warnings/Advisories

NV...Red Flag Warning from noon to 11 PM PDT Monday NVZ458.

Lake Wind Advisory from 5 PM Monday to 2 PM PDT Tuesday NVZ002.

Lake Wind Advisory from 2 PM Monday to 5 AM PDT Tuesday NVZ003.

Lake Wind Advisory from 2 PM to 11 PM PDT Monday NVZ004.

Red Flag Warning from 2 PM to 11 PM PDT Monday NVZ423.

CA...Red Flag Warning from noon to 11 PM PDT Monday CAZ270-278.

Lake Wind Advisory from 5 PM Monday to 2 PM PDT Tuesday CAZ072.