Las Vegas, Nevada

• Isolated showers and thunderstorms continue through the day today before becoming widespread overnight into Sunday.
• Conditions dry out on Monday as gusty north winds pick up across the region. Temperatures remain slightly below normal next week.

Today through Friday.

Showers and thunderstorms have largely waned, though light shower activity continues in northeastern Clark County as of 1 AM. Moisture will continue to surge northward into the Mojave Desert today as longwave troughing across the western CONUS helps to usher anomalous subtropical moisture into the region. Expect isolated showers and thunderstorms across the forecast area this afternoon, with best chances across southeastern Nevada and northwestern Arizona. Forecast instability is not as high as it was yesterday, likely due to the potential for persistent cloud cover through the morning and afternoon hours. As a result, convection will initially favor the higher terrain before pushing north-northwestward over adjacent desert valleys. Cannot rule out isolated instances of flash flooding beneath stronger storms and/or beneath training storms (forming and moving over the same location repeatedly). A shortwave trough embedded within the aforementioned longwave trough will attempt to close off over the southeastern Pacific Ocean as it pushes into the southern California Coast this evening. Meanwhile, the center of the longwave trough will sag southward, ultimately phasing with the shortwave as they pass through the Desert Southwest tonight into Sunday morning. The associated moisture surge coupled with the approach of the longwave trough axis will result in widespread showers and isolated thunderstorms across southeastern California, southern Nevada, and northwestern Arizona this evening through Sunday. Forecast precipitation amounts remain least certain across southern Nye, Clark, and Lincoln counties, as the trajectory of the moisture plume will depend on how rain-shadowed we get / far north moisture advects into our region. Drier model runs for the next 48 hours insinuate an additional 0.10 to 0.25 inches across southern Nye and Clark counties and 0.50 to 0.75 inches across eastern Lincoln County... while wetter runs favor 0.50 to 0.75 inches for southern Nye/Clark counties and 1.00 to 1.50 inches for eastern Lincoln County through Sunday night. Meanwhile, confidence is best over Mohave County, where there continues to be an 80% chance of over an inch of rainfall, with higher amounts in the higher terrain and underneath embedded thunderstorms. As a result, the Flash Flood Watch for Mohave County remains in good shape and will go into effect at 5 PM MST tonight. Will continue to assess the need to expand the areal extent of this watch as we move through the day today. Since the 0.03 inches picked up at KLAS yesterday, Harry Reid Airport now needs 0.23 inches of rainfall today to tie the Wettest October on record (currently 1.45 inches set in 2005).

Precipitation is expected to clear out Sunday night into Monday morning for the start of the work week as the longwave trough pushes eastward. Expect gusty north-northwesterly winds in the wake of the trough axis Sunday night into Monday, with gust speeds between 20 and 30 mph. Topographic enhancement may result in greater gust speeds along the Colorado River Valley, which could allow wave heights on Lake Mohave and Lake Havasu to exceed 2 feet. Afternoon highs will range 3 to 5 degrees below-normal through the work week.

For Harry Reid...For the 18Z Forecast Package...Sky conditions gradually deteriorate throughout the day as ceilings lower and precipitation chances increase. Isolated showers (and a 10% chance of thunder) are possible as early as mid-afternoon, but the more widespread precipitation arrives tonight. Latest guidance has a 50% chance of CIGs getting down to 2kft between 09z and 13z Sunday. Some visibility reductions due to rain are possible, but precipitation intensity should mostly be on the light side. Some improvement in sky conditions is anticipated Sunday afternoon, but timing and extent are still uncertain. South-southwest winds will be on the increase as this occurs.

For the rest of southern Nevada, northwest Arizona and southeast California...For the 18Z Forecast Package...Moisture and cloud cover continue to increase, with the best precipitation chances along and north of I-15 through the afternoon. This evening and overnight, rain chances spread to areas south and east. Precipitation intensity will largely be on the lighter side, but periods of increased rain rates and reduced visibility are possible. Expecting CIGs to drop down to 2-4kft across most of the area tonight and Sunday morning, resulting in MVFR conditions and significant terrain obscuration. Gusty south winds expected across our northwestern zones today, with lighter breezes elsewhere.

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