Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Las Vegas Nevada
921 PM PDT Thursday Oct 30 2014
Synopsis...warm southwest flow can be expected Friday before a
cold Pacific storm moves into the southern Sierra Halloween evening
then across the rest of the region Saturday and Sunday. This system
will produce gusty winds and much cooler temperatures along with
rain showers and mountain snow showers. Dry conditions with a slow
warming trend are expected Monday through the middle of next week.
Update...scattered clouds continue to drift across the region this
evening. Short range forecast remains on track and no update planned
issued 315 PM PDT Thursday Oct 30 2014
Short term...today through Sunday night.
A significant change in the weather is still on track this weekend
and it now appears energy will dig a little deeper into the base of
the eastern Pacific trough...bringing it across southern Nevada and
the Mojave Desert Sunday.
Our region was under the back side of a highly amplified ridge over
the northern intermountain region and our focus is now on the deep
eastern Pacific trough working its way toward the West Coast. A weak
disturbance will lift form Southern California across southern
Nevada overnight accompanied by high clouds which should thin out a
little after sunset. The leading edge of the incoming Pacific system
will move into the southern Sierra late Friday afternoon with
increasing developing south winds across the entire region. The
latest high res models indicate gusts will generally remain below 35
miles per hour...except for the high peaks...and no wind advisories are planned
Friday. The first shortwave rounding the base of the trough will
eject across the Sierra around 12z Saturday and snow should taper
off to showers behind it. The Winter Storm Watch was replaced by a
Winter Weather Advisory for snow and blowing snow from 5 PM Friday
through 11 am Saturday. The ejecting shortwave will produce a brief
shot of scattered to numerous showers across the southern Great
Basin and the Spring Mountains Saturday. Also...this will produce
stronger winds across central and southern Nevada Saturday and gusts
over 40 miles per hour will be possible.
Another upstream shortwave is now forecast to drop into system and
slide down through western Nevada into southeast California Saturday
night and Sunday morning which will drag a substantial cold pool
down over southern Nevada. There is quite good agreement among the
operations models with this scenario and this would favor additional
snow showers over the southern Nevada mountains. Probability of precipitation were increased
Sunday to indicate this trend and will need to be bumped up if this
scenario holds up in the next few model runs. This setup could favor
at least a few inches or more of snow in the Spring Mountains.
Temperatures were lowered slightly Sunday and Sunday night with this
deeper and slower progression of the closed upper low.
Long term...Monday through Thursday...
The weekend system finally moves east of the area Monday and high
pressure then settles over the southwest. This will result in dry
conditions and relatively light winds across most of the region
through the long term. The exception will be along the Colorado
River valley where gusty north wind conditions are possible through
middle week. Cooler conditions will linger Monday and Tuesday in wake
of the system but then a warming trend should return temperatures
back to above normal for early November.
Aviation...for McCarran...winds should mainly be 8 kts or less and
favor typical diurnal directional trends through tonight. Scattered-broken
clouds at or above 25k feet. A storm system will approach the area Friday
resulting in gusty south to southwest winds over 20 kts Friday
evening into early Saturday evening. As the storm moves across the
area on Saturday there will be the potential for cloud bases as low
as 7k-10k feet as well as few rain showers in and around the Las Vegas
Valley mainly in the morning hours.
For the rest of southern Nevada...northwest Arizona...and southeast
California...VFR conditions with winds 10 kts or less favoring
typical diurnal trends are expected through Friday morning. Gusty
winds over 20 kts are expected Friday afternoon into Saturday as a
storm system passes across the area. Cloud bases as low as 5k-10k
feet along with possible showers can be expected especially north of
kdag-klas-kigm line with the greatest chances in and around kbih.
Visibility in valleys may briefly lower to MVFR in any rain Showers. Mountain
obscurations and mechanical turbulence will be possible across much
of the area in that time frame.
Spotter information statement...spotters are encouraged to report
any significant weather conditions according to Standard operating
procedures Friday through Sunday.
For more forecast information...see US on our webpage:
Http://weather.Gov/lasvegas or follow US on facebook and twitter