Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Las Vegas Nevada
317 am PDT Thursday Sep 18 2014
Synopsis...southwest flow ahead of a low pressure system will
continue to push drier air into the area. Enough moisture will still
be in place for a chance of thunderstorms over mainly Lincoln and
Mohave counties today. Most of the area will be dry Friday as a
southwest flow persists. Southeast flow will pull moisture back into
the area over the weekend leading to a chance of thunderstorms.
Short term...through Friday night...an upper trough will move into
northern California today with southwest flow continuing to push
drier air into our forecast area. The models...especially the
nam12...continue to indicate a tongue of pretty moist and unstable
air ahead of this dry air which will keep a chance of thunderstorms
today over mainly Lincoln and Mohave counties. The upper trough is
then forecast to become a closed low just off the central California
coast by Friday while southwest flow brings further drying to our
forecast area. There may still be just enough lingering moisture for
a slight chance of thunderstorms Friday over eastern portions of
Lincoln and Mohave counties. Cannot rule out isolated thunderstorms
over the Sierra Friday afternoon due to the proximity of the upper
low. Temperatures will cool to near normal by Friday as heights fall
due to the approaching upper low.
Long term...models in good agreement that an upper level low will
be situated near the Southern California coast Saturday morning. As
the slow starts to track slowly northeast its forecast to start
pulling moisture into the forecast area from Southeast Arizona by
Saturday afternoon. How much moisture will be pulled into the area
is still in question...but have generally included slight chance
probability of precipitation over the entire region with the better chances over the south
and east. Chances of showers and thunderstorms will continue
Saturday night and Sunday as the low and associated dynamics tracks
through the area. Have upped probability of precipitation a bit as the models have trended
wetter over the couple of runs. Temperatures will be close to normal
with readings below normal in areas of thicker cloud cover.
The low will continue to track northeast Sunday night and Monday
with precipitation chances ending across the area with drier
conditions moving in from the west. The southwest flow will increase
by Monday and Tuesday as a trough develops off the coast and in turn
will bring above normal temperatures back into the region.
Aviation...for McCarran...thunderstorms are possible this afternoon
in the Peach Springs corridor with dry air moving in from the west.
Significant cloud cover is not expected at the terminal today. South
winds up to 10 kts early this morning will transition to
east/southeast under 8 kts after 14z before becoming southwest near
15 kts with gusts around 20 kts after 21z.
For the rest of southern Nevada...northwest Arizona...and southeast
California...light winds will become south/southwest 10-20 kts by
late morning or early afternoon. Gusts around 25 kts possible in
portions of southeast California and in Nye County. Dry air will
continue to push in from the west today but scattered thunderstorms
are expected in Lincoln and Mohave counties.
Spotter information statement...
spotters are encouraged to report any significant weather conditions
according to Standard operating procedures.
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