Area Forecast Discussion
Issued by NWS Las Vegas, NV
Issued by NWS Las Vegas, NV
677 FXUS65 KVEF 151942 AFDVEF Area Forecast Discussion National Weather Service Las Vegas NV 1242 PM PDT Mon Jul 15 2024 .SYNOPSIS...Scattered monsoon activity today, with rain chances largely confined to our eastern areas tomorrow through Wednesday. Later in the week, temperatures rise and precipitation chances expand westward as high pressure builds in from the east. && .SHORT TERM...through Wednesday. Shower and thunderstorm development is anticipated once again this afternoon as monsoonal moisture lingers. Best chances (40-70%) are along and south of I-15 where the better moisture is, but 25-40% PoPs exist from northwestern Inyo County over to northern Lincoln County. The I-15 corridor and points south also have the best odds of seeing localized flash flooding, with the WPC giving this area at least a 5% chance of excessive rainfall. Based on mean flow within the cloud layer, most concerned with the Twentynine Palms area, the Mojave Preserve up into the southern McCullough Range, and the northern Hualapai Mtns up towards Hackberry and Valentine. Yesterday, we saw rain rates of 1-3" per hour, and I wouldn`t discount the potential to see similar rates today. By 7-8PM this evening, convective activity is expected to cease as daytime heat is lost. For Tuesday and Wednesday, the development of a westerly component in the flow will shunt some of the low-level moisture off to the east. As a result, the best rain/storm chances move into northwestern Arizona and eastern Lincoln County. Elsewhere, PoPs remain below 20% due to the drier air. This also allows temperatures to climb a few degrees, placing much of the Mojave Desert in the 100- 115 range and the southern Great Basin in the 90-105 range. Despite the slight increase in temps, HeatRisk remains in the Moderate category. .LONG TERM...Thursday through the weekend. Later in the week, the Four Corners high strengths and slowly retrogrades. SSE flow due to the anticyclonic circulation brings moisture westward while the rising 500mb heights induce additional warming. Because the moisture never truly leaves the region earlier in the week, it gets trapped underneath the high. The end result is the return of Major HeatRisk to most of our Mojave Desert valleys by Friday and the weekend, all while PoPs gradually expand west and increase. This creates a fair amount of uncertainty in the forecast, particularly the temperature forecast, as any afternoon convection or convective cloud debris will limit afternoon heating. However, if temperatures aloft suppress, or mostly suppress, shower/storm activity, it`ll likely be hot with more humidity than usual. && .AVIATION...For Harry Reid...Generally light winds favoring an easterly direction this afternoon, outside of outflow from convection, with some variability in the easterly wind direction. Scattered storms initially developing over the higher terrain surrounding the valley. There is a 30% to 40% chance of storms moving off the terrain and directly impacting the field. Outside of direct impacts from storms in the valley, outflow winds from nearby storms could bring periods of gusty, erratic winds to the terminal area. Storms should end by early evening with light westerly winds expected after sunset. Isolated storms are possible again late morning and afternoon on Tuesday, but the majority of the activity should be confined to northwest Arizona. For the rest of southern Nevada, northwest Arizona and southeast California...Scattered thunderstorms will continue to develop across much of the region this afternoon and persist through sunset before decreasing. Storms will be capable of producing lightning, brief periods of heavy rainfall, CIGs less than 10kft that could obscure areas of higher terrain, and sudden gusty outflow winds. Away from areas of convection, south-to-west winds at 10kts to 15kts with occasional gusts to 20kts are expected. The thunderstorm activity should diminish after sunset, with winds falling below 10kts in most areas overnight. Additional thunderstorms are possible on Tuesday, but coverage is expected to be more limited, with the majority of the activity remaining over northwest Arizona and the higher terrain north and west of the Las Vegas Valley. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ DISCUSSION...Woods AVIATION...Salmen For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter