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FXUS65 KVEF 180428 AFDVEF

Area Forecast Discussion National Weather Service Las Vegas NV 928 PM PDT Mon Jun 17 2024

SYNOPSIS
A transient weather system will bring gusty conditions and cooling temperatures to the region today and Tuesday, with afternoon highs dropping below 100 for all but the lowest elevations Tuesday afternoon. Thereafter, high pressure will gradually rebuild with increasing potential for major heat impacts by next weekend for much of the region.


UPDATE
Strong northerly winds associated with the passing of a "cool" front this evening. Observed gusts across southern Nevada have ranged from 30 to 40 mph, with isolated cases of gusts exceeding 50 mph. Gust speeds will continue to wane through the night, but are not expected to fully diminish until mid-Tuesday- morning. Temperatures tomorrow (Tuesday) will be the coolest of the forecast period at around 6 degrees below seasonal averages. No changes made to the forecast this evening as it looks to be in good shape.


PREVIOUS DISCUSSION
132 PM PDT Mon Jun 17 2024/

DISCUSSION
Through next Monday.

Mostly clear skies over southern Nevada and the Mojave Desert as an upper trough/shortwave moves through northern Nevada. Associated cold front running from near Ely-Beatty-Lone Pine with gusty northwest winds filling in behind the cold front. Meanwhile, pre- frontal gusty southwest-west winds are continuing throughout far southern Nevada, eastern California deserts and northwest Arizona.
Still expecting FROPA in the Las Vegas Valley between 8 pm and 10 pm this evening.

Those gusty northerly winds will linger through at least Tuesday morning before they begin to subside during the afternoon hours.
Cooler air filtering in behind the front will give the area a brief reprieve from the hottest start to a June since 2013. Temperatures quickly rebound back to normal Wednesday.

Finally, we have been monitoring smoke from the Post and Hesperia Wildfires in southern California. Latest HRRR Smoke output suggests much of the smoke/haze will affect southern San Bernardino and Mohave counties the rest of this afternoon and tonight. If both fires remain active the HRRR suggests more favorable trajectory for smoke/haze to work back toward southern Arizona Tuesday.

For the long term we are monitoring the influx of 'monsoon' moisture into at least Arizona by weeks end and the return of 'hot' temperatures areawide. An inverted trough over the western Gulf of Mexico, in the Bay of Campeche is progged to move west across mainland Mexico reaching the eastern Pacific/Sea of Cortez Friday.
Lower level moisture progged to reach eastern Arizona Thursday and continue west toward Mohave County Friday. Some guidance suggests potential for a secondary influx from a gulf surge advecting moisture up the lower Colorado River over the weekend. This will need to be closely watched this week but for now NBM does have a slight chance of thunderstorms over the higher terrain of eastern Mohave County each day Friday-Monday.

Building heights under the subtropical ridge will lead to another period of well above normal temperatures with highs approaching 110 degrees on Saturday. Highs at or greater than 110 degrees are in the forecast Sunday through Tuesday. Las Vegas probabilities of 110 degrees or higher are at 50% or greater Saturday through next Thursday. As such, expect widespread 'Moderate' HeatRisk, while some desert valleys return to 'Major' HeatRisk on Saturday and beyond.
Excessive Heat products may be needed.


AVIATION
For Harry Reid...Gusty southwesterly winds will continue through the afternoon hours with gusts to around 25 knots.
A cold front will move through the area this evening, causing winds to shift to the northwest with gusts over 20 knots possible after about 03Z. Wind will begin to diminish during the early morning hours and become lighter around 10kt from the northeast Tuesday afternoon periods of FEW to SCT high clouds will pass over the area through the TAF period.

For the rest of southern Nevada, northwest Arizona and southeast California... Gusty southerly to southwesterly winds continue this afternoon in the Las Vegas Valley and Colorado River Valley. Winds at these locations will shift to the north to northwest this evening with the passage of a weak front. Gusts accompany the frontal passage but should subside later in the night. At KDAG, winds remain gusty out of the west through the evening. Elevated smoke from wildfires in southern California may spread over KDAG but should have minimal impact on aviation. In the Owens Valley including KBIH, winds maintain a northerly direction with an increase in gusts in through the evening then decreasing overnight. FEW-SCT high clouds will pass over much of the forecast area through Tuesday morning.


FIRE WEATHER
Very dry conditions will persist today with minimum relative humidity dropping below 15% for most areas this afternoon and evening. A Red Flag Warning remains in effect for AZZ101-102 today due to the very dry conditions and persistent gusty winds resulting in high fire start and spread risk. Sustained winds in northwest Arizona will likely exceed 20 mph for much of the day.
Elsewhere, it will be dry but winds will struggle to jump to impactful levels for an extended period of time and fuels remain marginal. NVZ460 could reach Red Flag Warning criteria briefly this evening and early overnight; however, due to the short-lived threat held off on the issuance.

SPOTTER INFORMATION STATEMENT
Spotters are encouraged to report any significant weather or impacts according to standard operating procedures.

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