Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000 FXUS65 KVEF 251710 AFDVEF Area Forecast Discussion National Weather Service Las Vegas NV 1010 AM PDT Sun Jun 25 2017 .SYNOPSIS...The prolonged heat wave over the region will finally break by Tuesday as a weak weather system moves across the western states. This system will result in enhanced winds Monday and will increase the fire danger over portions of southern Nevada and northwest Arizona. Limited moisture will lead to possible isolated thunderstorms over the southern Sierra and northwest Arizona today before drier air moves in by Monday. && .UPDATE...Quick update this morning account for the latest trends and short term guidance. Clouds and light virga showers continue to drift north across southern Nevada and northwest Arizona. These are associated with an axis of higher moisture that could result in very isolated showers over the higher elevations of Lincoln, Clark, and Mohave county this afternoon. Showers/isolated thunderstorms will also be possible across the Sierra again this afternoon. The main threat with any storms will be outflow winds. The forecast focus for today will be the increasing winds across the region and any areas of critical fire conditions associated with them. && .AVIATION...For McCarran...Light winds generally out of the east will veer southwest and increase this afternoon. Winds over 10kts are anticipated by 23Z today. Expect gusty west-southwest winds to continue through much of the night, with gusts over 20kts possible after 03Z. There with a chance that winds will drop off for a brief time between 10Z and 15Z and go light, however confidence is too low at this time and did not include it in the current TAF forecast. Gusty southwest winds will continue tomorrow, with stronger winds anticipated after 18Z Monday than what we should see today. Otherwise, virga concerns in the McCarran airspace will be minimal through the afternoon, and VFR scattered clouds should move away by tonight. For the rest of southern Nevada, northwest Arizona and southeast California...Winds will increase out of the west or southwest this evening and overnight, with the strongest winds expected in San Bernardino county on the downslope side of the Spring Mountains. After a brief lull Monday morning, west winds will pick back up Monday late morning, and will be stronger than today. Otherwise, isolated showers or virga are possible in the higher terrain this afternoon, but widespread ceiling/precip issues are not anticipated. && .PREV DISCUSSION... 333 AM PDT Sun Jun 25 2017 .SHORT TERM...Today through Tuesday. The ridge remains centered over Arizona and Nevada today and the continued Excessive Heat Warning is a given with similar temperatures to Saturday. The difference this morning is that there is a band of considerable mid level moisture extending from Arizona across southern Nevada and up toward northwest Nevada. This has been keeping temperatures elevated a few degrees from 24 hours ago. Light radar returns were noted, but primarily virga is expected. This band of moisture will continue to lift toward the northeast today as the eastern Pacific trough begins to nudge inland. This is the feature that will bring the main weather pattern change Monday and Tuesday, finally breaking the prolonged heat wave over the region. Increasing southwest winds will accompany the incoming trough Monday and gusts around 35 mph can be expected across portions of San Bernardino, Clark, Lincoln and Mohave counties. Temperatures will lower a few degrees also, but relief from the excessive heat will be noticeable by Tuesday as temperatures lower a few more degrees. .LONG TERM...Wednesday through Saturday. By Wednesday, the ridge over the southwest will continue to be suppressed a bit as the tail end of a trough drapes over much of the western CONUS through the work week. Models are now indicating that a impulse/shortwave will develop off the coast of northern California by Friday. The strength and impacts of this feature are uncertain at this time as model variance is high for Fri and Sat. Temperatures will be approaching normals by Wed and remaining near normal through the forecast period. Breezy southwest winds are expected each afternoon with wind speeds 10 to 15 mph and gusts around 20 to 25 mph. Wednesday afternoon, both the GFS and ECMWF are showing a tight gradient over much of central Mohave County. This will cause some gusty southwest winds up to 30 mph Wed afternoon. Otherwise, dry and mostly clear conditions through the rest of the work week and into the weekend. && .FIRE WEATHER...The prolonged heat wave over the region will finally break Monday and Tuesday as a trough moves inland from the eastern Pacific. This will result in enhanced southwest winds gusting over 35 mph for portions of southern Nevada and northwest Arizona Monday afternoon and evening leading to critical fire conditions. Isolated thunderstorms will be possible over the Sierra and northwest Arizona today then a dry and stable air mass will spread over the region with the incoming trough. && .CLIMATE...Near record to record high temperatures will be possible today and Sunday. The current record of consecutive days above 110 degrees in Las Vegas is 10 days (1961), and for 115 degrees, 4 days (2005). Las Vegas, NV Climate Forecast High Temps (F) Daily Record Max Temps (F) SUN (6/25): 113 115 (1970) Forecast low Temps (F) Daily Record High Min Temps (F) SUN (6/25): 89 86 (1974) && .HYDROLOGY...Observed flows on unregulated creeks, specifically Independence Creek, Big Pine Creek and Rock Creek indicated flows have decreased slightly since their peak flows occurred earlier this week. Creeks, streams and rivers along the eastern Sierra slopes of Inyo County as well as the Owens Valley will be flowing high and fast through into at least early next week. Minor flooding could occur near creeks as well as a few low water crossings on some roadways. Remember, never drive through flooded roadways or around barricades. Also, pastureland or farmland adjacent to creeks, streams or rivers could experience areas of standing water. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ UPDATE...WOLCOTT AVIATION...ALLEN SHORT TERM/FIRE WEATHER...Adair LONG TERM....Kryston HYDROLOGY...Pierce For more forecast information...see us on our webpage: http://weather.gov/lasvegas or follow us on Facebook and Twitter

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