Area Forecast Discussion
Issued by NWS Las Vegas, NV
Issued by NWS Las Vegas, NV
288 FXUS65 KVEF 192007 AFDVEF Area Forecast Discussion National Weather Service Las Vegas NV 107 PM PDT Thu Sep 19 2024 .SYNOPSIS...An area of low pressure will slowly move south along the California coast today before turning inland and moving across the southern Great Basin tomorrow. This will keep temperatures several degrees below normal through Friday as well as bringing the threat of precipitation to the region. Drier and warmer conditions will return over the weekend and continue into next week as a high-pressure ridge builds over the western US. && .SHORT TERM...through Saturday. Current infrared and water vapor satellite imagery show a cut-off low pressure system churning off the coast of central California. This system will continue to dig south and east, moving through our forecast area tomorrow. Showers and thunderstorms will be possible in the crest of the Eastern Sierra this afternoon and evening as this system continues to push south. While the Sierra-Nevada are expected to intercept the majority of the moisture, there is around a 25% chance the White Mountains and the northern portion of the Owens Valley will see showers and thunderstorms from the meager moisture that manages to spill over the Sierra. Snow levels in the Eastern Sierra will be around 9,500 feet or higher with 1 to 3 inches of snow accumulation possible along the ridgeline. Precipitation chances will increase across the Mojave Desert and southern Great Basin tomorrow as this low pressure system tracks inland and through our forecast area. The better dynamics and instability associated with this trough will result in increased convective potential, meaning that thunderstorms will be possible tomorrow. Heavy rain and lightning will be the primary threats with any thunderstorms that develop. Small hail and graupel will also be possible with thunderstorms tomorrow, but will not pose the same threat as the heavy rain and lightning. Unlike typical monsoonal convection, convection tomorrow will continue into the evening and the overnight hours as the low continues to track east. The far eastern portions of our forecast area will see a 20 to 30% chance of precipitation early on Saturday morning as this low exits the region. Outside of these morning precipitation chances in the eastern portions of our forecast area, weather on Saturday will be dry and mild as we find ourselves under dry northerly flow aloft with rising 500 mb heights. These rising heights will allow for temperatures to warm up a few degrees from Friday into Saturday. However, temperatures will still be slightly below normal. .LONG TERM...Sunday through next Thursday. Dry weather and warming temperatures will continue into early next week as an upper-level ridge establishes itself over the Western US. Forecast uncertainty increases around Tuesday/Wednesday as a cut-off low is forecast to drop down the leeward side of this ridge. The uncertainty arises from interensemble discrepancies regarding where the leeward side of the ridge will be located relative to our forecast area and how far southwest this low will dig into the southwestern US. Should this system slide down the leeward side of the ridge and eject right into the Central Plains as some models indicate, we will see the early week warming trend continue. If this low ends up in the Four Corners region as a few models show, we would be looking at temperatures cooling a few degrees during this time. However, it is worth noting that the latter solution is in the minority with only 23 of the 100 ensemble members that make up the Canadian, GFS, and ECMWF ensembles showing a solution similar to it. && .AVIATION...For Harry Reid...East to southeast wind direction this afternoon into the early evening hours. Sustained speeds 8-12 knots, there is about a 50% probability for an occasional gust to between 14-17 kts. Winds will shift back to a westerly direction overnight with speeds 8 kts or less. East to southeast wind direction will be favored again Friday afternoon into early evening. However, there will be isolated showers and thunderstorms developing over the higher terrain tomorrow afternoon and evening. Any impacts in the valley may hold off until late tomorrow afternoon and evening when there is about a 30% probability for wind gusts greater than 30 kts. There will be some periods Friday with ceilings down to 8 kts in the valley. For the rest of southern Nevada, northwest Arizona and southeast California...An area of low pressure will slowly move east across southern California tomorrow, and through northwest Arizona Friday night. Highest probability for showers and thunderstorms will be under the low center in San Bernardino County Friday afternoon and early evening, then southern Nevada and northwest Arizona Friday night. Ceilings will range between 6-8 kft AGL at times with localized mountain obscurations. Aside from the gusty wind potential associated with any showers and thunderstorms Friday, surface winds will generally be from an east to southeast direction in northwest Arizona and southern Nevada. While, surface winds at KBIH will be from the north. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ DISCUSSION...Stessman AVIATION...Pierce For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter