Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Las Vegas Nevada
239 am PDT Sat Oct 25 2014
Synopsis...today will bring one more day of unseasonably warm
conditions to the region with winds increasing as a trough
approaches the area. A cooling trend will begin Sunday and continue
into early next week with temperatures then rebounding to slightly
above normal by the middle of next week.
Short term...through Monday night...satellite imagery clearly shows
an upper level circulation about 300 miles off the northern
California coast. Over the next 12 to 18 hours, it is forecast to
open up, weaken and lift off to the northeast. Moisture associated
with this system stretches from British Columbia down through
Washington, Oregon, the northern half of California and well out
into the Pacific Ocean north of the Hawaiian islands. But sadly, we
are not expected anything other than some enhance cloud cover. Also
there is a weak area of low pressure off the central Baja California coast this
morning moving northeast towards the area and it has been generating
some thin cloud cover that could bring scattered high clouds to
parts of the area today. Warm conditions will continue today with
winds becoming gusty by the afternoon.
As the Pacific trough moves into the West Coast today, shortwave
energy at the base of the trough is forecast to swing across the
Great Basin resulting in gusty winds this afternoon and evening. A
Wind Advisory GOES into effect for much of the northern zones later
this morning and based on 00z hires model data, there is no need to
expand the advisory to other areas. The strongest winds are still
expected over the higher elevations of the Sierra with downslope
winds pushing down the eastern Sierra slopes and possibly into the
Owens Valley later this afternoon into tonight. Precipitation chances look
minimal with this system and only a few light showers are expected
over the southern Sierra.
The trough axis shifts east across the area Sunday and a surface
cold front pushes south through the region. Although the front is
expected to be dry, cooler air will filter into the region behind it
and drop saturdays well above normal temperatures down several
degrees Sunday and then to normal or below on Monday. There could be
some enhanced flow in north wind prone areas like the Colorado River
valley behind the front but models show nothing significant at this
Long term...Tuesday through Friday...ridging is expected over the
area Tuesday through Wednesday with warming temperatures and mostly
clear skies with some high clouds at times. Still seeing model
differences beginning Thursday with the GFS more progressive with a
Pacific trough while the European model (ecmwf) keeps the ridge over the area longer.
However...not really much difference in the sensible weather either
way with dry conditions continuing and high temperatures several
degrees above normal. If the more progressive GFS verifies winds on
Friday could be stronger than forecast with temperatures a touch
cooler than forecast.
Aviation...for McCarran...southwest winds up to 8 kts to continue
through the morning hours followed by stronger southwest winds
across the terminal this afternoon. Wind gusts will generally be
between 20 to 30 miles per hour.
For the rest of southern Nevada...northwest Arizona...and southeast
California...stiff winds up to 15 kts continue in the Owens Valley
this morning but should begin to subside towards daybreak before
increasing again later this morning and continuing into the evening.
South winds gusting to 40 kts are possible north and west of Las
Vegas today with gusts generally between 25-30 kts elsewhere.
Mechanical turbulence may develop near and just east of the Sierra
crest today through Sunday morning along with some mountain
obscurations due to cloud cover.
Spotter information statement...spotter activation is not expected
but strong wind and damage reports will be needed from spotters
today into Sunday morning.
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