183 FXUS65 KVEF 161122 AFDVEFArea Forecast Discussion National Weather Service Las Vegas NV 422 AM PDT Tue Sep 16 2025
.KEY MESSAGES...
* Warm and dry weather will continue through Wednesday.
* Chances for showers and thunderstorms will spread over the region from south to north Wednesday night through Friday, with slight chances lingering through the weekend. Thursday and Friday will be the most likely period for widespread rainfall and impacts. &&
.DISCUSSION...through Monday. Clear skies and light winds again early this morning. The main concern for this forecast is still the remnants of Mario and how much rain could fall. Satellite imagery from Monday evening showed the tropical storm looking very poor, although a new burst of convection overnight suggests Mario is not quite dead yet. Regardless of whether it is a TS, TD, or remnant low, tropical moisture will be surging north across our area from Wednesday evening through Thursday night. Precipitable water should reach one inch over nearly all of our CWA, with up to an inch and a half in the lower elevations of the Colorado River Valley and possibly Death Valley. Models have honed in a little on rainfall timing since yesterday, and amounts have generally risen. The best chances for heavy rain seem to be focused on Thursday and Friday. 25th percentile rain amounts now show about one tenth of an inch over most of the Mojave Desert and two to four tenths in the mountains (these numbers were nearly zero yesterday), and 75th percentile amounts show half an inch to one inch for most of the Mojave Desert and up to two and a half inches in the mountains, both of which are up roughly 30 percent since yesterday. Not enough confidence in the details to issue a Flash Flood Watch yet, although if model trends continue, one may be needed later today or early tomorrow morning. The most likely "failure mode" for flash flood potential will be overcast skies inhibiting instability and causing rain to be more stratiform than convective. Once we get past Friday, there is a lot of model disagreement on how much instability and forcing will be available, so low confidence in PoPs over the weekend and into early next week. The forecast will reflect slight chances for showers and thunderstorms, mainly in the afternoons, which is a good middle ground assuming moisture does not get scoured out (moderate to high confidence) and there is no synoptic forcing (low to moderate confidence). &&
.AVIATION...For Harry Reid...For the 12Z Forecast Package...Winds will take on typical diurnal trends for both speed and direction today, with sustained speeds generally below 8 kts. However, expect a repeat of the last couple of days with intermittent gusts around 15 kts this afternoon and early evening from the southeast. High clouds expected early Wednesday morning, continuing to increase through the day. Temperatures will remain below 100 degrees.
For the rest of southern Nevada, northwestern Arizona and southeastern California...For the 12Z Forecast Package...Winds will take on typical diurnal trends for both speed and direction today, with sustained winds generally below 8 kts for the Las Vegas Valley and Colorado River Valley TAF sites, gusty south-southeast winds between 15 and 20 kts at KBIH this afternoon, and gusty west winds to 20 kts at KDAG after sunset. Expect intermittent gusts from the southeast at Las Vegas Valley TAF sites around 15 kts - will not be persistent enough for the prevailing TAF. High clouds expected around sunset tonight at KDAG and KEED, spreading and increasing northward through Wednesday. &&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. &&
$$
DISCUSSION...Morgan AVIATION...Soulat
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NWS VEF Office Area Forecast Discussion