Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 09/26/19

Area Forecast Discussion

National Weather Service Reno NV

 325 PM PDT Wed Sep 25 2019

.SYNOPSIS...

Above average temperatures and benign weather conditions are
expected for today and Thursday before the pattern begins to shift
on Friday. A stronger weather system is expected to move into the
region Friday through the weekend bringing gusty winds, much
colder temperatures and shower chances to the region. These
conditions are likely to continue into early October.

&&

.Discussion...

Main Forecast Messages up Front:

*Warm and dry conditions through Thursday.
*Gusty winds are expected Friday and Saturday.
*Turning MUCH colder Saturday into next week, 20+ degrees below
 average; hard freezes for Sierra valleys and light freezes for
 western Nevada.
*Mixed rain and snow possible for Reno early Monday morning.

.Short Term...

Mainly modest adjustments were made to the short term forecast
through Friday night. Temperatures were cooled a little north of
Interstate 80 while winds were marginally increased for Friday.
Otherwise, expect relatively benign weather through early Friday
as ridging keeps temperatures above seasonal averages.

As the front drops out of the Pacific Northwest, the upper winds
begin to swift more westerly tonight into Thursday. We will see
the return of light breezes for Thursday afternoon with gusts to
around 20 mph as western Nevada temperatures reach the mid 80s
allowing for better mixing of the surface layer and for faster
winds aloft to reach mix down. Gradients tighten further for
Friday with gusts increasing to around 30 mph along the Sierra
Front of Nevada and 30-35 mph for the Basin in Range. Else will
likely see gusts generally in the 25-30 mph range.

Some low precipitation chances will begin to move into the region
north of Interstate 80 with snow levels starting above 10000 ft.
Snow levels begin to rapidly fall to around 7000 feet north of a
Susanville to Gerlach line by late Friday evening into early
Saturday morning as temperatures begin to drop. Boyd

.Long Term...Saturday through Wednesday...

There were several changes made to the inherited forecast, mainly
due to better model agreement with cooler temperatures and slightly
higher chances of precipitation for the weather systems Saturday and
Sunday through Monday. The details of the forecast will be expanded
upon in the following sections.

Precipitation: The biggest changes were to speed up the progression
of the cold front Saturday morning. POPs and QPF were increased
along and ahead of this front due to the increased chance for the
formation of a band of showers. Showery weather will then be
possible Sunday and Monday as a secondary cold front passes across
the region. With the chance for colder temperatures Sunday and
Monday behind the secondary front, snow levels could lower down to
the valley floors in far northern Washoe and Lassen counties. Mixed
precipitation could also occur down to the valley floors in the Reno-
Sparks metro area. However, forecaster confidence is low due to the
significant run-to-run variance in the deterministic model snow
levels.

Winds: Behind the cold front Saturday morning, winds look to be
sustained out of the north-northwest between 10-15 mph, before
calming overnight Saturday. Winds will then increase ahead of the
secondary cold front Sunday before decreasing Tuesday as transient
ridging takes place over the western US.

Temperatures: High temperatures this weekend are expected to be 20-
25 degrees below normal. Highs will likely struggle to get out the
50s in western NV valleys and the valleys of northeast CA, while
highs in Sierra valleys will most likely stay in the 40s to low 50s
through Wednesday. Overnight lows below freezing are possible for
Sierra locations starting as early as Saturday night, with colder
temperatures possible Sunday and Monday nights. -Johnston

&&

.AVIATION...

With continued easterly flow and warming/drying over the last day
or so, the threat of patchy fog on the KTRK airfield is much lower
for tonight. Still, be aware that some could form closer to the
airfield along Martis Creek. VFR conditions are expected
elsewhere. Winds remain light through Thursday morning with an
increase out of the west expected for Thursday afternoon as
heating increases and winds aloft mix to valley surfaces. Gusts
will generally be around 20kts, so no significant impacts are
expected at area terminals.

Conditions begin to change in earnest Friday as a strong cold
front approaches the region. Winds increase further with gusts
around 30kts. Gusty winds can be expected again Saturday just
ahead and along the frontal boundary with a pronounced wind shift
to northerly flow. LLWS can be expected with FROPA. Expect areas
of Mtn Wave turbulence Friday through the weekend.

Considering the weekend: we will see aircraft icing potential
increase as precipitation spreads across the region. Snow levels
will be falling below KTVL/KTRK elevations by Saturday night and
could approach some valleys floors along the Sierra Front, like
KRTS, while precipitation could be mixed at KRNO. More convective
elements along the frontal boundary could bring periods of
graupel as well. Expect widespread mountain obscurations as well.
Boyd

&&

.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&

$$

For more information from the National Weather Service visit...
http://weather.gov/reno