Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 251615

Area Forecast Discussion
National Weather Service Las Vegas NV
914 AM PDT SUN SEP 25 2016

.SYNOPSIS...Mostly clear skies and a warming trend can be expected
through Monday. Northerly winds will be strong and gusty at
times...especially down the Colorado River Valley today. An upper
level low moving up from the south will provide a slight chance of
showers across northwest Arizona and southern Nevada Tuesday
through Friday.

.UPDATE...Wind has increased along the Colorado River Valley this
morning.  The Wind Advisory looks good. No changes made to going
forecast this morning. -Berc-

.SHORT TERM...Through Tuesday night.

Strong high pressure off the California coast will continue to build
over California and northern Nevada while an area of low pressure
over northern Mexico tracks slowly west. This will provide a dry
northeast to east flow over the region into Monday. This pattern
will lead to an increasing surface pressure gradient which will
bring increasing northeast to east winds over the southern portions
of the forecast area. The strongest winds are expected to be down the
Colorado River Valley today where gusts up to 45 mph are likely at
times through the day...especially in the vicinity of
Laughlin/Bullhead City. The previous shift issued a wind advisory
for this area and that still looks good. Temperatures over the area
will continue to rise with readings about 3-5 degrees warmer than
yesterday. Surface gradients on Monday are expected to be more
relaxed and although there could be some locally breezy areas down
the Colorado River, wind advisories are not expected at this time.

By Tuesday, the upper low over northwest Mexico is expected to start
tracking north. As this happens, moisture is expected to start
working north as well. We will start to see a few clouds develop
over the southern areas of the forecast area Monday afternoon with
deeper moisture and thicker cloud cover arriving Tuesday.
Precipitation chances are expected to increase during the day
Tuesday over mainly Mohave County, but will spread north and west
into Clark and western San Bernardino Counties by Tuesday afternoon
and evening. Instability isn`t great, forcing from the upper low
could help generate a few isolated thunderstorms. With PW values
between 1"-1.25" any heavier storms could produce isolated areas of
flash flooding with lesser chances west. With the close proximity of
the upper low and increased vorticity showers and thunderstorms
could also persist through Tuesday night.

.LONG TERM...Wednesday through Sunday.

The beginnings of the system that will bring unsettled weather to
the forecast area by the middle of the week could be seen on
satellite loops with an elongated trough digging over eastern
Arizona with substantial nearby moisture over northern Mexico. The
medium range models continue to indicate that the resulting cutoff
low will pull moisture our way and eventually lift up directly over
southern Nevada by Wednesday. now looks like its
effects may linger through Friday as the upper low shears and holds
back energy and moisture over southern California . Both the GFS and
ECMWF solutions indicate this scenario and it will lead to
sufficient moisture and instability holding over the Mojave Desert
and southern Great Basin for potential isolated to scattered showers
and thunderstorms to develop Thursday and Friday before a broad
Pacific Northwest trough can muster a dry southwest flow to scour
all the moisture out by next weekend. PoP and weather grids were
modified Thursday and Friday to reflect this trend. This will keep
temperatures near or slightly below normal for the second half of
the week into the weekend.

.AVIATION...For McCarran...Northeast winds will persist through much
of the day with speeds generally between 10-15 kts with gusts
approaching 20 kts at times in the afternoon. Skies will remain
mostly clear. Winds will diminish this evening, but are expected to
remain northeast through much of the night.

For the rest of southern Nevada...northwest Arizona...and southeast
California...North to northeast winds expected over much of the area
today with winds generally in the 10-20 kt range. The strongest
winds are expected down the Colorado River Valley where winds up to
35 kts are possible this afternoon. Winds will diminish somewhat
overnight, but expected to remain north to northeast.
Mostly clear skies through the period.

.SPOTTER INFORMATION STATEMENT...No significant weather is expected
today. Gusty north winds are expected down the Colorado River Valley
today. Spotters are encouraged to report according to
standard operating procedures.


Short Term/Aviation...Gorelow
Long Term...Adair

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