Las Vegas, NV 89107 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

through Monday.

Our next system begins to encroach on the region today in the form of a closed low spinning off the CA 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 storm today. Best chances (25-50%) are generally northwest of I- 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"+ 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 06Z Forecast Package... Favorable conditions are expected through Tuesday, with winds following typical diurnal directional trends and speeds generally remaining less than 8 knots. Northeast winds Tuesday morning will turn more southeasterly by 21Z. There is a 15 percent chance of seeing an isolated gust to 12 knots once winds turn southeast, but any gusts should be short-lived. Isolated convection is possible during the afternoon and early evening over the higher terrain surrounding the valley, but no precipitation is expected near the field. VFR conditions will prevail through Tuesday night, with SCT clouds and bases generally remaining AOA 10kft AGL.

For the rest of southern Nevada, northwest Arizona and southeast California...For the 06Z Forecast Package...Light winds following typical diurnal directional trends are expected at area TAF sites overnight into Tuesday morning. Most sites will see light winds continue into Tuesday afternoon. One exception will be across the northern Owens Valley, including KBIH, where southerly winds gusting 30 to 35 knots are expected during the afternoon and early evening. Gusty easterly winds are also expected across the western Mojave Desert, including KDAG. Isolated areas of convection will be seen over higher terrain during the afternoon and early evening, but no direct impacts are expected at area terminals.

Spotter Information Statement

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