Area Forecast Discussion
Issued by NWS Las Vegas, NV
Issued by NWS Las Vegas, NV
006 FXUS65 KVEF 140906 AFDVEF Area Forecast Discussion National Weather Service Las Vegas NV 206 AM PDT Sun Jul 14 2024 .SYNOPSIS...Another round of widespread thunderstorms is expected today, bringing the threat for strong outflow winds, frequent lightning, and isolated heavy rainfall. Drier air gradually moves in during the workweek, limiting thunderstorm activity. Temperatures remain several degrees above normal for this time of year. && .SHORT TERM...Today and Monday. High pressure over the Four Corners and low pressure off the Pacific Coast continue to draw southeasterly monsoonal flow into the Desert Southwest. Today`s thunderstorms should be similar to yesterday`s, featuring strong outflow winds, frequent lightning, and localized heavy rainfall. Convection begins in the late morning and early afternoon, lasting into the evening. Storms have 1.2 to 1.5 inches of PWAT and 800-1800 J/kg of CAPE to work with south of I-15, and .7 to 1 inch of PWAT and 500-800 J/kg of CAPE north of I-15. Orographic lift will help enhance storms over high terrain across the board. Surface humidity values may be a little higher today due to yesterday`s precipitation, but air at the surface is still fairly dry and forecast soundings display an inverted V pattern. This is a sign of high based storms that can produce strong outflow winds, especially given DCAPE values between 1500 and 2000 J/kg. Similar to yesterday, peak gusts over 50 mph may occur with the strongest storms. Little or no precipitation may reach the surface with some storms. This is especially noteworthy in the Sierra, Owens Valley, and southern Great Basin where there are increased fire weather concerns due to dry lightning. A Red Flag Warning is in place through the evening for this reason. However, locally heavy rainfall is still a possibility as there is decent moisture for storms to work with at higher levels of the atmosphere. Forecast soundings in northwest Arizona display a long and skinny CAPE profile above storm bases. Any storms that produce enough rainfall to overcome dry air near the surface may bring a few tenths of an inch of rain. The highest totals may also be found in areas where training storms occur. The WPC gives a Marginal (5 percent) risk of excessive rainfall and flash flooding for northwest Arizona today. One factor that may inhibit heavy rainfall is dry air entrainment at the mid levels, but storms could still produce strong outflows and frequent lightning. On Monday the flow around the high will take a more southwesterly direction, drawing dry air into the region and reducing PWAT values, particularly in Inyo County and the southern Great Basin. POPs are confined to high terrain around the forecast area with the greatest potential in northwest Arizona. The greatest concern remains gusty outflow winds and frequent lightning with these storms. .LONG TERM...Tuesday through Sunday. Relatively drier flow continues through Tuesday, limiting precipitation chances to high terrain over northwest Arizona. Afterwards, ensembles seem to show moisture creep back into the area as flow becomes more favorable again later in the week. As of now the greatest precipitation potential later this week is in northwest Arizona and southern Nevada over high terrain. Temperatures remain above normal and increase by several degrees through the week. Pockets of Major (Level 3) HeatRisk appear again on Wednesday in low elevations along the Colorado River. && .AVIATION...For Harry Reid...Light winds this morning will turn to the east by late morning and then to the southeast by early afternoon. Scattered areas of convection are once again expected today, with the storms initially developing over the higher terrain surrounding the valley around 20Z. After 21Z, there is a 50% to 60% chance of storms moving off the terrain and directly impacting the field. Even if a storm does not directly affect the field, gusty outflow winds from nearby storms have a high (greater than 70%) probability of causing impacts to the terminal area. The convection is expected to end earlier today than Saturday, with most storms dissipating by 02Z. Southwest winds will develop tomorrow evening and become light and variable overnight. Northeast winds will redevelop by late morning on Monday. Isolated convection is also possible again on Monday, but coverage will be less than this weekend and should remain confined to the higher terrain. For the rest of southern Nevada, northwest Arizona and southeast California...Scattered thunderstorms are expected to occur again across most of the region today. Storms should begin to develop after 18Z and persist through sunset before diminishing. Any storms will be capable of producing lightning, brief periods of heavy rainfall, CIGs less than 10kts that could obscure areas of higher terrain, and sudden gusty outflow winds. Away from areas of convection, south-to-west winds 10kts to 15kts with occasional gusts to 20kts can be expected. The thunderstorm activity should diminish after sunset, with winds falling below 10kts across the region overnight. Additional thunderstorms are possible on Monday, but coverage is expected to be more limited, with most storms remaining over northwest Arizona or the higher terrain of southern Nevada. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ DISCUSSION...Meltzer AVIATION...Planz For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter