Las Vegas, NV 89104 Weather

Key Messages

* An incoming trough brings widespread rain and mountain snow chances, gusty winds, and cooling temperatures this week.

* Increasing confidence for a dry conditions and seasonable temperatures this weekend.

Discussion

Today through Monday.

Our next system begins to encroach on the region today in the form of a closed low spinning off the California coast. Over the remainder of the work week, it will slowly move through the forecast area, eventually transitioning to an open wave as it phases with a PacNW shortwave. Northward moisture advection and upper-level divergence in the left exit region of a jet streak will spur isolated to scattered showers and storms today. Best chances (25- 50%) are generally northwest of Interstate 15 and in Mohave County. The slow-moving nature of the system results in a similar setup on Wednesday. Precipitation chances are higher across the board (+25%) on Wednesday due to additional moisture and colder air aloft, but the same places will be favored. Finally, the main vort max associated with the low swings through on Thursday, bringing the best potential for widespread precipitation (60-90% in most locations). However, the phasing with the PacNW shortwave sends a secondary vort max down the backside and keeps the trough overhead through the end of the work week. As a result, isolated to scattered shower chances linger on Friday.

Overall, best odds of precipitation impacts are in the southern Great Basin, Inyo County, and northern Mohave County where chances of 1.00"+ range from 25-50%. Thunderstorm development will aid this potential, but training convection is going to be required given the flow aloft. The biggest "bust" potential is in the southern Mojave Desert (think of the area bounded between Twentynine Palms, Barstow, Las Vegas, Kingman, and Lake Havasu), where models have this zone kind of caught in a dry slot between the two main precipitation regimes. This area has a 40-70% chance of 0.10" or less. There is a minor wintry component of this system as snow levels bottom out around 8kft in the Sierra. However, as they do, precipitation will largely be done, so any impacts are expected to be confined to elevations above 9kft where forecast snow totals range from 3-10" (the higher amounts near the crest). Lastly, gusty south-southwest winds (20-40 mph) will accompany this system as well, but any impacts should be confined to the local lakes.

By Saturday, ensemble guidance has our area firmly on the backside of the trough. We will see a dry northerly flow that quickly scours out moisture and precipitation chances, and produces some gusty north winds. On Sunday and Monday, the flow weakens and becomes more zonal/southwesterly, keeping us dry with light winds and slightly below-normal temperatures.

Aviation

For Harry Reid...For the 18Z Forecast Package...Winds will be generally light and diurnal through the day today, with light easterly winds this morning, light-to-breezy southeasterly winds this afternoon around 8 kts, and light southwesterly winds overnight. Gusty south-southeasterly winds pick up Wednesday afternoon with gust speeds topping out between 25 and 30 kts. FEW- SCT aoa 10 kft through the TAF period.

For the rest of southern Nevada, northwest Arizona and southeast California...For the 18Z Forecast Package...Light and diurnal winds in the Las Vegas Valley and Colorado River Valley through the day today, with gusty south-southeasterly winds Wednesday afternoon to 30 kts. KBIH will gust from the south-southeast this afternoon to 30 kts with the potential for gusts from variable directions due to vicinity thunderstorms. 30 percent chance of showers and thunderstorms over the KBIH terminal, with best chances between 01 and 05Z. Gusty east winds at KDAG to 25 kts, with potential direction changes due to vicinity showers between 21 and 02Z. FEW- SCT aoa 10 kft, though expect BKN aoa 8 kft with thunderstorm activity overhead.

Spotter Information Statement

Spotters are encouraged to report any significant weather or impacts according to standard operating procedures.