Area Forecast Discussion

KEY MESSAGES

* Precipitation chances and cooler temperatures continue through the weekend. Heavy rain and thunderstorms may result in flash flooding at times.

* Cool and dry conditions for early next week.

DISCUSSION

through Thursday

An unsettled weather pattern continues through the weekend as an upper level trough interacts with anomalous moisture associated with the remnants of Tropical Storm Vance. This afternoon, scattered showers and thunderstorms have been very efficient in the moist environment, dropping a quick 0.50 inches or more as they move over and flash flooding has been reported. Instability has also been impressive early this afternoon which has allowed for strong to severe thunderstorms with hail to develop in portions of Clark County. Scattered showers and thunderstorms will continue in southern Nevada and Mohave County which could lead to additional impacts such as heavy rain, flash flooding, and hail. By early tonight, this round will have waned as showers become more isolated in eastern Lincoln, northeast Clark, and northern Mohave County tonight through much of Saturday. This lull in activity will end Saturday evening though as the trough approaches. Forcing and moisture will increase with the incoming trough, however there continues to be uncertainty in how much moisture will advent northward into the area. The difference between the HRRR and RRFS/REFS is vast, especially on Sunday. Favored the RRFS/REFS solution as anomalous moisture is expected to be in place for most areas, but low confidence in how much will fall. The highest confidence for rainfall that could be moderate to heavy at times is in Mohave County where NBM has a 70%-80% probability for over 1 inch of rainfall from Saturday night through Sunday night. This is also where there is some agreement for at least 200% of normal PWATs (with higher anomalies possible). Given this signal for heavy rain along with saturated soils from recent rainfall today- issued a Flash Flood Watch for Saturday night through Sunday night in Mohave County outside the Colorado River Valley. Heavy rain and flash flooding is possible outside of this area, and if the ECMWF solution with higher PWATs further north and west verifies- later shifts may need to expand this flood watch. Precipitation will be possible areawide. , snow levels will remain high (generally above 9,0009,500 feet). The peaks of the Sierra and Spring Mountains could pick up several inches of snow, but recreational areas like Lee Canyon should see little to no accumulation.

As the trough exits early next week, a tightening surface gradient along its western flank will drive breezy to gusty winds Monday, particularly across the southern Great Basin. Most gusts will subside Monday evening, though terrain-channeled winds through the Colorado River Valley could linger into Tuesday. Cooler air will settle in behind the system despite shortwave ridging building overhead, keeping highs roughly 5 degrees below seasonal normals through Tuesday under dry conditions.

AVIATION...For Harry Reid...For the 00Z Forecast Package

The breezier prevailing winds have reduced but shower activity continues around the area. Chances for storms will be possible in the lines of showers, and could result in gustier winds and cloud bases as low as 6000 ft AGL along with chances for lightning. Storm chances decrease into the evening and winds ease into night, becoming light and variable while chances for showers linger through the night and much of Saturday morning. Showers exit late that morning with winds turning easterly. Breezy southeast winds arrive into Saturday afternoon, but reduce into that night.

For the rest of southern Nevada, northwest Arizona and southeast California...For the 00Z Forecast Package...Showers continue to move across the Las Vegas Valley and the Colorado River Valley with some isolated thunderstorms. Storm chances ease into the evening, but shower chances look to linger into the night. Winds reduce into the evening and overnight, becoming light across much of the region. Lingering shower chances exit the region into Saturday morning with winds beginning to build in the late morning.

SPOTTER INFORMATION STATEMENT

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