502 FXUS65 KVEF 171724 AFDVEFArea Forecast Discussion National Weather Service Las Vegas NV 1024 AM PDT Wed Sep 17 2025
.KEY MESSAGES...
* Seasonably warm and dry conditions will persist today.
* Increasing moisture associated with the remnants of Mario will move into the region Thursday through Friday, bringing chances for showers and thunderstorms. Locally heavy rain and high rainfall rates will lead to an increased risk of flash flooding. &&
.DISCUSSION...through Tuesday. The tropical moisture is knocking on our southern door. Satellite loop showed cirrus outflow from the remnants of Mario nearing our southern CWA border, and surface obs showed dewpoints up 10-20F in the past 24 hours at sites including KDAG, KNXP, and KBLH. On a positive note, recent model runs show very little change from 24 hours ago with respect to precipitation timing as well as the most probable amounts (25th to 75th percentile range), which increases forecast confidence. That said, there is still significant uncertainty in one very important regard - will there be enough sunshine in between the clouds Thursday and/or Friday to allow for destabilization and intense rainfall rates, or will solidly overcast skies prevent instability from being realized, resulting in less-hazardous stratiform rain? Because of that uncertainty, will not issue a Flash Flood Watch at this time. Best guess is that the best heavy rain potential will be along and west of Highway 95 Thursday and Thursday night. Best forcing exits by Friday night, leaving more of a low-grade monsoon pattern in place for Saturday and possibly Sunday. Not much confidence in Monday or Tuesday, but the overall pattern favors mostly dry weather with temperatures climbing back above normal for late September.
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.AVIATION...For Harry Reid...For the 18Z Forecast Package...Light and diurnal winds with speeds of less than 10 knots are expected through the rest of the day. Cannot rule out a stray gust to 15 kts this afternoon from the east. Winds will become southwesterly overnight, returning to the east-northeast Thursday morning. FEW-SCT aoa 25 kft through the day today, increasing to BKN-OVC overnight. SCT-BKN aoa 12 kft push into southern Nevada after sunset and persist through the remainder of the TAF period. Best chances of 98- 100 degrees this afternoon exist between 23 and 01Z.
For the rest of southern Nevada, northwest Arizona and southeast California...For the 18Z Forecast Package...Light and diurnal winds are expected today, with speeds generally less than 10 knots. The exception will be KDAG, where gusty west winds between 20 and 25 kts will pick up after sunset and last through the night. BKN- OVC high clouds will increase south-to-north across the region today, with SCT-BKN mid-level clouds reaching KDAG, KBIH, KEED, and KIFP this afternoon and KLAS, KVGT, KHND this evening. Precipitation chances increase areawide on Thursday with convection beginning as early as 15Z. Heavy downpours and strong outflow winds are the main concerns.
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.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures.
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DISCUSSION...Morgan AVIATION...Meltzer
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NWS VEF Office Area Forecast Discussion