FXUS65 KVEF 202107

Area Forecast Discussion
National Weather Service Las Vegas NV
206 PM PDT Fri Oct 20 2017

A cold front will move through the region this evening with
northerly winds diminishing behind the front, except down the
Colorado River Valley where northerly winds will continue to gust
through portions of Saturday. Cooler conditions will be seen
Saturday before high pressure builds over the region next week
bringing dry conditions and above normal temperatures.

.SHORT TERM...Tonight through Sunday.

Strong westerly winds have been ongoing this morning and early
afternoon over most areas of the CWA. Strong downslope winds were
seen over the eastern Sierra slopes, the Owens Valley and western
Esmeralda County where some wind damage was noted earlier this
morning. These southwest to west winds will diminish behind a cold
front that is currently moving through the area. Northerly winds
behind the front will remain fairly gusty, but most areas will
remain below any advisory levels. The cold front is forecast to move
through southern Nevada right around sunset this evening with winds
generally 15 to 25 mph with some gusts up to 30 mph possible. By
Saturday, the front will have exited the area to the south with the
entire area in a northerly flow. Surface pressure gradients will
increase along the Colorado River where gusty north winds will
occur. Although gusty winds are likely, it looks like they will
remain below criteria needed for a wind advisory, but will be strong
enough for a Lake Wind Advisory which has slightly lower criteria.
Along with the gusty north winds, we will also see very dry
condition along the Colorado River with humidity values dropping
below 10 percent. These dry conditions combined with the gusty winds
and critical fuel levels will increase the fire danger. Have gone
ahead and issued a Red Flag Warning for the afternoon hours on
Saturday for those river zones.

Cooler temperatures will be seen area wide Saturday with readings
generally 7-10 degrees below normal. High pressure will start to
build over the area Sunday leading to lighter winds, warming
temperatures and continued dry conditions.

.LONG TERM...Monday through Friday.

Dry and warm fall weather is expected to begin the work week with
high pressure forecast over the area Monday and Tuesday sending high
temperatures back to 6-8 degrees above normal.

A few degrees of cooling is forecast by midweek with high pressure
breaking down and the upper flow flattening as an upper level trough
and associated cold front move into the Pacific NW. While this
system if forecast to move east across the northern Rockies and
Northern Plains on Thursday, models bring a shortwave south through
the Great Basin, bringing a cold front and gusty north winds through
the region. There are model differences in how strong the front will
be when it passes through the forecast area and whether additional
energy late Friday reinforces the northerly flow.

.AVIATION...For McCarran...Gusty, southwest to west continue into
early this evening ahead of a cold front that is forecast to move
through the valley around 02z. Winds behind the front will generally
be northwest 15-25 kts through the overnight hours. Winds will
decrease after sunrise with speeds around 10 kts through much of

For the rest of southern Nevada, northwest Arizona and southeast
California...Strong, southwest winds will increase in a band from
San Bernardino County to Mohave County ahead of an approaching cold
front that will move through the area late this afternoon and early
evening. Winds will shift north and become gusty. Lighter winds
expected across much of the area Saturday. Exception will be down
the Colorado River Valley where gusty, north winds will continue.

.FIRE WEATHER...A cold front will move through the region this
afternoon and overnight bringing gusty north winds down the Colorado
River Valley. Humidity values will drop below 15 percent by late
morning with minimum values falling into the mid to upper single
digits by late afternoon. The gusty north winds, low humidity
values, combined with critical fuel levels will lead to the issuance
of a Red Flag Warning from noon until 6pm for the Colorado River

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


LONG TERM....Salmen

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