Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000 FXUS65 KVEF 181148 AFDVEF Area Forecast Discussion National Weather Service Las Vegas NV 348 AM PST Wed Jan 18 2017 .SYNOPSIS...
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Our brief stretch of dry weather will end this evening and Thursday as the first in a series of wet storm systems pushes across the region. This will be quickly followed by a second system Friday into Saturday and yet another Sunday into Monday. These storms will bring significant snowfall to the mountains and rain to the deserts.
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&& .SHORT TERM...
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Today through Thursday Night. Shortwave ridging that has brought us clear and dry conditions for the past couple days will exit to the east today as a sharp trough pushes in from the west. This will result is rapidly deteriorating conditions this evening and overnight. Precipitation will begin to spread across the Sierra late this afternoon and into the desert regions this evening. This timing is 3-6 hours faster than what was shown 24 hours ago and this is now reflected in the forecast. This means the precipitation is expected to reach Clark County sometime this evening and the Colorado River Valley around midnight. Gave a slight boost to precipitation amounts due to the prolonged nature of this system. This resulted in slightly higher snowfall estimates for the Sierra and Spring Mountains which has prompted an upgrade to Winter Storm Warnings for both those zones. * A note about the Winter Storm Warnings/Winter Weather Advisories: In an attempt to limit confusion we opted to issue products that cover both the first and second system despite a short break between systems. We did this instead of having a mix of Advisories, Warnings, and Watches for the same zones. For the desert areas, expect most locations to receive 0.20-0.50 inches of rain, with locally higher amounts possible under heavier showers and across Mohave County. Please see the winter weather products for more details about snowfall, snow levels, and timing. Precipitation is expected to taper off from west to east during the day Thursday, but again, this will be followed quickly by a second system Friday. .LONG TERM...Friday through Tuesday night. The second storm will begin to impact the area Friday by afternoon. This trough is progged to have a much better moisture tap, with the bulk of moisture transport in a southwest to northeast trajectory, which should help avoid interception by the Sierra for most the area. The storm has evolved a bit in the models with a perhaps slightly longer precipitation duration than previously thought, as the wave widens over the area. With the moisture tap and moisture trajectory, along with consistent model signals, the heaviest precipitation will likely occur from the Spring Mountains and Sheep Range in Clark County eastward into Mohave county. Liquid/equivalent amounts in these areas are favored to be around either side of a half-inch for valleys/deserts, with amounts just above an inch for the mountains and southeast Mohave county. This would yield significant snows above 5000 ft. The heaviest precipitation will likely occur over a shorter period Friday evening with perhaps some embedded convection helping precipitation rates a bit. Snow levels look to start around 4000 feet in the Southern Great Basin, and around 5000 feet in southern portions of the area. Breezy to gusty southerly winds are expected with this system on Friday with speeds around 20 mph and gusts in the 30s mph; locally higher gusts are possible. Very windy conditions are expected across western San Bernardino county early Saturday as the system exits with gusts on the plus side of 40 mph. After a brief break on Saturday, the third trough takes aim at the region for later Sunday through Monday. Quite a few of the details have yet to be worked out by models, but there is general agreement it will be a potent and cold system, with a healthy moisture tap, yielding more chances of decent precipitation along with gusty winds.
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&& .AVIATION...
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For McCarran...VFR conditions along with light winds favoring typical diurnal trends are expected through Wednesday. East winds at 5-10 kts with occasional gusts cannot be ruled out this afternoon. The next series of storm begins to impact the area tonight bringing precipitation and CIGs rapidly lowering to around 5k feet between 03z-09z. Precipitation and low CIGs are expected to persist through much of Thursday before improving. Additional storm system will impact the region into early next week. For the rest of southern Nevada...northwest Arizona...and southeast California...VFR conditions are expected across most of the region through the day. Precipitation and rapidly lowering CIGs to 5-10k feet are expected to push west across the region this evening. Winds of 8-15 kts and gusts 20-25 kts favoring a southerly direction are expected at most terminals by this afternoon. Precipitation and low CIGs are expected to persist through much of Thursday before improving. Additional storm system will impact the region into early next week.
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&& .SPOTTER INFORMATION STATEMENT...
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Spotter activation is not expected today. A series of storm systems will impact the region tonight through early next week. Spotters are encouraged to report rain and snow amounts as well as any weather-related impacts/damage.
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&& $$ Short Term/Aviation...Wolcott Long Term.............Steele For more forecast information...see us on our webpage: http://weather.gov/lasvegas or follow us on Facebook and Twitter

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