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Area forecast discussion
National Weather Service Las Vegas Nevada
436 am PDT sun Jul 23 2017

Synopsis...
wet weather pattern is expected to begin developing tonight as a
significant push of monsoon moisture spreads northward across the
area. Periods of showers and storms can be expected across much
of the area tonight through Tuesday night, especially across northwest
Arizona and southern Nevada, before a drying trend begins mid to
late this week.

&&

Short term...today through Tuesday

Today will be the last relatively dry day before unsettled weather
moves in tonight and into the beginning of the work week. Showers
and storms are expected to develop this afternoon in areas
similar to yesterday including Mohave, Lincoln, and the higher
elevations of Clark County in addition to a slight uptick in rain
chances over the southern Sierra. A good push of high-grade
monsoon moisture is expected overnight tonight into Monday
morning which could continue showers and storms overnight across
Mohave and Lincoln counties. Hi-res models are beginning to hint
at a vort Max pushing across southern Mohave County into southern
Nevada and southeast cali tonight which could facilitate stronger
overnight convection and put a damper on monday's activity for
the affected areas. With copious amounts of available moisture on
Monday across much of the area widespread activity will be
possible with potential for stronger storms in areas that can get
the addition of diurnal heating and increasing instability into
the equation. These storms will be where the concern for flash
flooding and strong, gusty winds are present. Tuesday will be
highly dependent on the events that occur on Monday and Monday
night as to whether or not we have an active day or are left with
overcast skies and less intense shower and storm activity.

All in all, the short term forecast period still has many moving
parts which could greatly effect specific impacts and locations of
convection and severity so checking back for updates is
recommend!

Long term...Wednesday through Saturday.

Gradual drying and warming is expected for the Wednesday and
Thursday as weak southwest flow returns to the region. Enough
moisture is likely to remain in place for afternoon showers/storms
over favored high terrain.

By Friday, high pressure once again pushes back to a favorable
location near The Four Corners, allowing for a moist southeasterly
flow into the region. However, this is where guidance begins to
diverge, with the GFS keeping the high and favorable flow well into
the weekend while the European model (ecmwf) is significantly different, pushing the
high to near Reno and keeping much of the moisture to the south of
Las Vegas. For now i've split the difference, increasing dew points,
and pops over the area, but with a emphasis on areas south of Las
Vegas.

&&

Fire weather...activity this afternoon will be focused in areas
similar to yesterday with the addition of the southern Sierra as
moisture levels begin to creep upward. Storm chances and
increasing cloud cover spread westward Sunday night and continue
across a majority of the area for Monday and Tuesday as monsoon
moisture spreads northward. Potential for strong storms will be
present Sunday night through Tuesday with details on timing and location
still unclear. Southerly winds between 10-15 mph are expected
each day with gusts of around 20 mph possible, especially across
the Colorado River valley.

&&

Hydrology...
creeks, streams and rivers in northern Inyo County have shown
decreasing flows over the last couple of days. However, some Road
closures continue in the area. Bishop creek bypass and Big Pine
creek bypass continue to be utilized to minimize flows through
Bishop and Big Pine. Remember, never drive through flooded
roadways or around barricades. Also, pastureland or farmland
adjacent to creeks, streams or rivers could experience areas of
standing water.

&&

Aviation...for McCarran...light and variable winds this morning
follow a similar trend to yesterday shifting to the southeast this
afternoon and evening remaining around 10 knots or less. Chances for
storms across the higher elevations will be present this afternoon
which could push storm outflow boundaries down through the valley
creating brief, erratic wind shifts and gusts. Isolated
showers/storms could work their way down across the valley
overnight tonight into early Monday but confidence in timing of
these details is low so have not included in current taf.

For the rest of southern Nevada, northwest Arizona and southeast
California...typical diurnal winds are expected this morning before
south to southeasterly flow initiates at most sites this
afternoon. Most areas will see winds around 10 knots or less
except for along the Colorado River valley which could see
sustained winds of 10-15 knots through tonight. Showers and
storms are expected across Mohave and Lincoln counties once again
along with the higher elevations of Clark County and the southern
Sierra this afternoon. Overnight storms will be possible tonight
into early Monday across southern Mohave, Clark, and southeast San
Bernardino counties.

&&

Spotter information statement...spotters are encouraged to report
any significant weather or impacts according to Standard operating
procedures.

&&

$$

Short term/aviation/fire weather...guillet

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