Area Forecast Discussion
Issued by NWS Las Vegas, NV
Issued by NWS Las Vegas, NV
875 FXUS65 KVEF 191623 AFDVEF Area Forecast Discussion National Weather Service Las Vegas NV 923 AM 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. && .UPDATE...The latest infrared and water vapor satellite imagery show the low pressure system spinning off the coast of central California. This system will continue to dig south before moving inland and through our forecast area on Friday. Precipitation today will be limited to the Sierra crest, with the mountains expected to block most of the moisture from spilling over into our forecast area. The northern portion of the Owens Valley and White Mountains of Inyo County have around a 25% chance of seeing light precipitation from the little moisture that manages to get past the Sierra. As the low pressure system moves through our forecast area tomorrow, we will see more widespread precipitation chances across the southern Great Basin and Mojave Desert. Precipitation chances will linger into Saturday morning for the far eastern portions of our forecast area as the low pressure system exits the region. The biggest change to the short term forecast is the introduction of a Marginal Excessive Rainfall Outlook (ERO) to San Bernardino and Mohave Counties on Friday due to the convective potential as the center of the cut-off low moves overhead. Essentially, pockets of heavier precipitation will be possible with isolated thunderstorms embedded within scattered showers. Outside of the addition of this Marginal ERO, the current forecast remains on track with no major changes necessary at this time. && .SHORT TERM...Today through Saturday. A deepening upper-level low-pressure center off the central California coast this morning will drift southward towards SoCal today before turning east and moving inland across our area on Friday. Precipitation will remain limited to northern Inyo and Esmeralda counties today as the Sierra will block most of the moisture. Any moisture that is able to make it over the crest will be light, and less than .15" of rain is expected around Bishop through this evening. Snow is likely in the higher elevations of the Sierra, where up to 4 inches may fall. However, snow levels will generally be 9500 feet or higher, so significant impacts are not expected. As the low turns inland tonight and Friday, showers will spread across the southern half of the region. Given the cold-core nature of this system, there is the potential for weak convection to develop as the center of the low passes across San Bernardino, southern Clark, and Mohave counties, where CAPE values of 200-400 J/kg are forecast. However, moisture associated with this system will continue to be limited, and the probability of any area seeing .25" or more of rain is less than 30%. The chance of seeing .50" of rain is nearly zero in all areas except for far eastern Mohave County where there is a 10% chance of that occurring. It is still not out of the question that the Spring Mountains could see their first dusting of snow with this system Friday, although snow levels will be around 10,000 feet, so any that does fall will be limited to the highest peaks. The low will also deliver a reinforcing shot of cooler air, keeping temperatures 10 to 15 degrees below normal through Friday. Winds are not expected to be impactful with this system. By Saturday, the low will shift east of the area, and only a few isolated showers are expected across far eastern Mohave County early in the day. As high pressure builds in the wake of the low, most areas will see temperatures rebound back to near-normal levels. .LONG TERM...Sunday through Wednesday. By Sunday morning, the low should be long gone, with rising heights as high pressure noses in from the Pacific. There are differences in the details as usual, but there is strong consensus among the models that ridging will set up residence over the West through (and beyond) the long term period. Thus, we can expect dry weather and above normal temperatures areawide. The 01Z/19 run of the NBM gives Las Vegas a 13% chance of reaching 100F on Wednesday, with slightly higher chances later in the week. && .AVIATION...For Harry Reid...Light winds expected overnight with mostly clear skies. Winds will remain light through the morning hours before trending easterly after noon, then more southeasterly in the mid-afternoon and evening hours with speeds of 8-12 knots. Winds will shift back to the southwest after dark. Skies will remain mostly clear through the period. For the rest of southern Nevada, northwest Arizona and southeast California...Generally light winds are favored through midday across the regional TAF sites across the Mojave Desert and Colorado River Valley, with more southeasterly winds of 8 to 12 knots filling in during the afternoon and evening hours. Further north, SCT-BKN cloud cover between 6-8kft AGL along with periodic shower activity is expected near KBIH with localized mountain obscuration possible through the period. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ UPDATE...Stessman SHORT TERM...Planz LONG TERM...Morgan AVIATION...Outler For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter