Area Forecast Discussion
Issued by NWS Las Vegas, NV
Issued by NWS Las Vegas, NV
949 FXUS65 KVEF 160230 AFDVEF Area Forecast Discussion National Weather Service Las Vegas NV 730 PM PDT Sun Sep 15 2024 .SYNOPSIS...A large low pressure system dropping down from the northwest into California and Nevada will bring widespread gusty south to southwest winds to the region today through Monday along with a significant cooling trend. A second trough of low pressure will move across the area midweek bringing a reinforcing shot of cool air along with scattered showers. && .UPDATE...Gusty southerly to southwesterly winds are increasing across the forecast area this evening. The strongest winds overnight will be in sections of southern Nevada and southeast California including Death Valley, and a Wind Advisory is now in effect for these areas until 8 PM PDT Monday. Gusts of 40 to 50 mph still appear possible. The upper level trough is currently centered over the Pacific Coast of Northern California and Oregon. As it moves inland overnight, precipitation chances increase in the southern Great Basin, particularly Esmeralda County. Faint radar returns are already appearing over Mineral County and the best precipitation chances for Esmeralda and southern Nye counties should begin early tomorrow morning. && .SHORT TERM...Through Tuesday night. A potent upper level system is expected to drop into the region tonight and Monday. Not much changes overall synoptically with this system with strength and timing well collaborated across models. Widespread gusty winds will be the main impact with this system that most people will see. No changes were made to the wind headlines as the timing and impact levels remain on track from previous forecasts. The strongest winds are expected tonight in Inyo County and Esmeralda County, then Monday afternoon for areas further east. South to southwest winds will gust 40-50 MPH with the strongest winds starting tonight in western portions then spreading east by Monday late morning. Areas of blowing dust could also impact areas as the winds ramp up. WInds will diminish Monday night as the upper level system pushes east away from the area. With height falls and a cooler airmass moving in with the approaching low, temperatures will drop. High temperatures on Monday will be about 10-15 degrees cooler than today. Also watching the potential for precipitation impacts as the upper level trough pivots into a neutral position and briefly sits over northern California Monday. Strong forcing will develop around the center of the low which will allow for precipitation to develop in parts of northern Inyo County into Esmeralda and central Nye County. With little movement of the low and its associated area of strongest lift, continuous rainfall is expected Monday morning through the early afternoon. Modest moisture will be available as the trough moves in as PWATs around 0.50-0.75 inch set up across the region. HREF continues to highlight Esmeralda County with the highest risk for rainfall impacts with a 10%-30% probability for 3 hour rainfall amounts over 1 inch, mainly Monday morning. This would be the area closest to the trough axis and thus will see the strongest and longest duration of forcing. WPC has that area in a slight risk for excessive rainfall with isolated flash flooding possible, which is reasonable given the amount of forcing, available moisture, and the flashy nature of that area. Rainfall with be heaviest 5AM through about 11AM before the center of the low shifts eastward. About 0.50 inch of rainfall totals are likely in Esmeralda County, with the wettest solutions across the ensembles suggesting high end potential amounts of 0.75-1.00 inch rainfall totals. While the forcing will spread east as the low shifts, the available moisture and duration will limit precipitation impacts further east. Ensembles show little to no probabilities for impactful precipitation across the Southern Great Basin where scattered showers could develop Monday afternoon. Further south, it will remain dry as better forcing will remain to the north. The trough axis will pass the region Monday night, with dry anticyclonic flow setting up behind it. Precipitation will diminish as the trough shifts east and by Tuesday morning, it will be dry across the region. With northwest winds aloft pushing cooler air into the region, it will be cool Tuesday with high temperatures remaining about 10 degrees below normal. Winds near the surface will be lighter on Tuesday as the upper level system moves away from the area and the pressure gradient decreases. Impactful winds are not likely (below 20% probability) for Tuesday. .LONG TERM...Wednesday through Saturday Lighter winds are expected Wednesday through the end of the week as the tight pressure gradient and low level jet moves east along with the trough. However, the system will leave cold air over the region in its wake. Morning lows will be 10 to 15 degrees below normal for mid September. Another deep low will drop down from the Pacific Northwest into the Great Basin midweek. It should provide some reenforcement for cool temperatures, keeping highs around 10 degrees below normal through the end of the workweek. Some guidance is not showing a strong wind signal with this system, but others highlight the potential for elevated winds. This will depend on the placement of the trough and where the tightest pressure gradient will form. Lastly, moisture advection with the system will bring increased precipitation chances midweek, particularly in the southern Great Basin. As this system exits towards the end of the week, Pacific high pressure moves in behind it and should boost temperatures for next weekend. && .AVIATION...For Harry Reid...Gusty southerly winds can be expected at the terminal through Monday afternoon. While winds should settle around 220 to 240 degrees by 22Z, some variability is likely before then, with winds possibly backing to the east as far as 160 degrees. Sustained winds of 15 to 20 knots are likely, and there is a 60 percent chance of seeing an occasional gust to 30 knots after 22Z. Winds will diminish overnight, but occasional gusts to 15 knots will still be possible. The elevated southwest winds will continue Monday with gusts over 30 knots likely through the afternoon. VFR conditions will continue through Monday with only a few clouds with bases AOA 10kft expected. For the rest of southern Nevada, northwest Arizona and southeast California...Breezy south-to-west winds will continue across the area into this evening, with gusts of 20 to 30 knots likely at area TAF sites. Some decrease in winds is expected after sunset, but occasional gusts to 20 knots will continue overnight. Winds will increase again on Monday with gusts as high as 40 knots possible over the western Mojave Desert, including KDAG. Gusts of 30 to 25 knots are likely elsewhere. Hazy skies due to the wildfires over southern California can still be expected over the western Mohave desert today, possibly spreading into the lower Colorado River Valley overnight. However, visibilities should remain greater than 6NM in all areas. Otherwise, no significant cloud cover is expected, except at KBIH, where SCT-BKN clouds with bases AOA 10kft are possible. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ UPDATE...Meltzer SHORT TERM...Nickerson LONG TERM...Meltzer AVIATION...Planz For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter