Las Vegas, NV 89140 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 12Z Forecast Package...Winds will continue following typical daily directional patterns with some variability, remaining light except during this afternoon when southeasterly winds increase to around 8KT. FEW-SCT clouds around 10kft are expected through the period, with isolated afternoon and early evening convection over the higher terrain that is not expected to impact the terminal. VFR conditions will continue.

For the rest of southern Nevada, northwest Arizona and southeast California...For the 12Z Forecast Package...Across the region, winds will continue following typical daily directional patterns, with speeds around 5-10KT. One exception to this is across the western Mojave Desert/KDAG where easterly winds this afternoon are expected to increase to 12-15KT with gusts to 20-25KT through sunset. Additionally, KBIH in the northern Owens Valley will experience gusty up-valley southeasterly winds late morning into tonight, with gusts peaking at around 25-30KT this afternoon through late evening. Isolated to scattered thunderstorms are expected across the region this afternoon and evening, especially over higher terrain. Have included VCTS mention for KBIH this evening for thunderstorms expected to develop over surrounding mountains, however, confidence is too low at this time to include TS elsewhere. VFR conditions prevail outside of thunderstorm activity with ceilings expected to remain at or above 10kft.

Spotter Information Statement

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