831 
FXUS65 KVEF 070534
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
1033 PM PDT Wed May 6 2020

.SYNOPSIS...Above average temperatures expected to continue through 
the weekend. A weak disturbance may result in some isolated 
thunderstorms Sunday, but chances are very low at this point. Drying 
fuels and a chance of breezy to windy conditions across parts of the 
region early next week may result in elevated fire weather concerns.
&&

.EVENING UPDATE...
Very little change in the forecast details this evening. In the near 
term, the focus was on winds for the Colorado River Valley tomorrow. 
Latest hi-res guidance continues to indicate the elevate winds down 
the river channel which may warrant a Lake Wind Advisory but this 
looks borderline at the moment. Beyond that, above average 
temperatures through the weekend and the low end possibility for low 
or no precipitation thunderstorms across northwest Arizona Sunday. 

.DISCUSSION...Through Tuesday.

Little changes from previous forecasts. Heat still mainly on track
as ridge of high pressure remains in control. The Excessive Heat
Watch still looks marginal outside of Death Valley, but still
waiting for a clear trend in the temperatures to either trim it
back or upgrade to a warning. Left it as-is for now.

The wind forecast through tomorrow gets a little tricky. A
shortwave passing by through Oregon, Idaho, and into Montana will
be the straw that breaks the camel's back and sets in motion an
interaction between the thermals of the higher Great Basin and
lower Mojave Desert. With continued baking during the day, low-
level thermal low continues to build into the Mojave Desert, at
the same time surface high pressure strengthens in the Great
Basin. Drainage flow from the higher terrain of the Great Basin
will align to cross gradients and help push potentially stout
north to northeasterly winds into Lincoln county, and also down
the Colorado River valley by tomorrow morning. Everything looks
sub-advisory now, but quite an interesting mesoscale and synoptic
scale interaction that will likely cause a few hours of gusty
winds in the morning; stronger than they would otherwise be if
either the mesoscale or synoptic scale were isolated from one
another.

Things still look interesting for the weekend. A little bit of 
low and mid-level moisture seeps into the region underneath the 
ridge ahead of a pattern change taking shape by Sunday (aided by
the low-level thermal low mentioned earlier). A deep upper-level 
low off the Pacific Northwest coast will start to knock the ridge 
down and to the east. A leading shortwave will eject over the 
region Sunday afternoon and evening, should should provide some 
forcing for ascent as well as helping to nudge lapse rates to be 
on the more unstable side. Indeed, forecast soundings for areas 
like northern Mohave county show some rather classic inverted-v 
profile. This would be conducive of dry thunderstorms and gusty 
winds Sunday afternoon and night. As the low strengthens off the 
coast and the area transitions to dry southwest flow, expect 
decreasing temperatures but increasing winds for Monday and 
Tuesday to start off next week. Given the potential dry lightning 
follow by dry gusty winds, went ahead and added some dry 
thunderstorms to the forecast grids to start raising some flags in
advance of the weekend. 
&&

.FIRE WEATHER...Hot and dry weather expected through the end of
the week. A pattern change will bring elevated fire danger over
the weekend - first with a chance of dry thunderstorms Sunday and
Sunday evening, followed by cooler but dry and breezy conditions 
for Monday and Tuesday. 
&&

.AVIATION...For McCarran...A southwesterly push will move in between 
21z-00z with winds picking up to around 10 knots through sunset. 
Lighter southwest winds will persist for much of the overnight 
before a shift to the north is expected as a weak cold front passes 
through the valley. Confidence in timing of this shift is low and 
could occur as early as 09z or as late as 14z. Luckily, it doesn't 
look to be stronger than 10 knots once the shift does occur. Winds 
slowly shift to the east northeast throughout the day with speeds 
expected to remain at 10 knots or less. BKN high cloud cover will be 
prevalent for much of the period.

For the rest of southern Nevada, northwest Arizona and southeast 
California...West to southwest winds will continue for the remainder 
of the afternoon at speeds around 10 knots for much of the area. A 
cold front will work its way southward this evening across the 
southern Great Basin and through the remainder of the area by mid-
morning tomorrow. Winds will shift to the north behind this boundary 
and increase to 10-15 knots tomorrow morning across much of southern 
Nevada. Winds will be a tad stronger down the Co. River Valley; up 
to 15-20 knots gusting 25-30 knots through around 21z. BKN high 
clouds will be prevalent for much of the period. 
&&

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

$$

DISCUSSION...Steele
AVIATION...Guillet

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