292
FXUS65 KREV 170939
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
239 AM PDT Tue Sep 17 2024

.SYNOPSIS...

* Well-below average temperatures continue through most of the
  week.

* Another storm system brings additional precipitation chances and
  keeps temperatures below average through the rest of the week.

* A warming and drying trend starts on Friday and into the weekend
  as the storm leaves the area.

&&

.DISCUSSION...

An upper low level system is evident in this morning`s water
vapor satellite imagery. It will be slowly moving to the east-
northeast as it leaves the region later today. In the meantime,
expect intermittent rain showers and a few embedded isolated
thunderstorms. Storm chances through this morning are low,
generally less than 15%. Rainfall accumulations are expected to
be light with amounts up to 0.1 inches in most areas, and up to
0.25 inches in Pershing and northern Washoe (north of Pyramid
Lake) county. Some light snow showers are possible, around 10%
chance, early this morning in the Sierra above 8000 ft, but any
accumulations will be light if any at all.

Hi-res models continue to show a break in precipitation late this
morning and afternoon until the next upper low approaches the
region this evening and overnight. Currently, this system is just
offshore of the West Coast. That`s why we are getting such a short
break between systems. Chances for showers increase to 50-90%
Wednesday morning, once the low is right over us with the higher
chances along the Sierra and the Sierra Front. At the moment, NBM
guidance shows a 40-70% chance of liquid precipitation greater
than 0.5 inches over a 24 hour period across both aforementioned
areas including Reno, Lake Tahoe and the Davis Fire. Snow levels
remain above 8000 to 9000 feet, with possible snow amounts in the
Eastern Sierra crest over Mono County between 2-4 inches with
isolated higher amounts of 6-8 inches in the highest peaks. NBM
shows a 40-80% chance of seeing amounts greater than 4 inches, and
10-40% chance of amounts greater than 6 inches above 9000 ft.
Sierra passes including Ebbetts, Sonora and Tioga have a 10-40%
chance of receiving 4 inches of snow per the latest guidance by
Thursday morning. Snow chances in the Tahoe Basin are very dismal
with only the highest peaks only getting an inch or two at most,
which makes sense as the ECMWF EFI is highlighting the Eastern
Sierra for this event, because the low takes a more southerly
approach. This system also has better dynamics and very marginal
instability that will result in better chances for thunderstorms
with a 10-30% chance on Wednesday afternoon along the Sierra.

The back to back systems in the area are also why we continue to
have a couple more days of well below normal temperatures.
Afternoon highs will remain 10-25 degrees below normal through
Thursday, once the system slowly leaves the area. The subsequent
northerly to northwesterly flow will result a slow warming trend.
Temperatures finally reach seasonal values over the weekend, but
generally a degree or two below normal. We should continue warming
up early next week to slightly above normal as an upper ridge develops
in the Eastern Pacific.

-Crespo

&&

.AVIATION...

Generally VFR to MVFR conditions are expected through Wednesday
morning. MVFR conditions are due to low CIGS near SHRA and -TSRA.
Although, -TSRA chances are less than 15% through Wed AM. Chances
increase on Wed PM. There will be VIS reductions with the strongest
showers/storms down to 4-5 SM for brief periods of time. This
activity will be intermittent through this morning, then we get a
break between 18Z Tue to 00Z Wed. Intermittent showers resume
afterwards. Snow levels remain above 8-9 kft. Therefore, expect
snow in the higher elevations of the Sierra. Better chances for
snow are expected after 6Z Wed, especially for the Eastern Sierra.
Icing concerns are possible with snow. Furthermore, mountain
obscurations are likely through Thursday.

Winds will be generally from the west and northwest between 5-12
kts today with gusts up to 25 kts between 20Z Tue to 3Z Wed. Then
light and VRB winds are expected tonight.

-Crespo

&&

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

$$