Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 140258
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
758 PM PDT Fri Oct 13 2017

.UPDATE...

The latest HRRR guidance has a few showers over far northern
Washoe County and the Surprise Valley through the evening...then
clouds begin to decrease. The latest NAM guidance agrees with this
scenario. Based on the current trends in satellite imagery and
the lack of radar returns...we have opted to decrease shower
coverage over the far northern parts of the forecast area late
this evening and decrease cloud cover as well. The forecast past
tonight remains on track with low level winds shifting to the
north then east over the ridges late tonight. Updates out soon.

&&

.PREVIOUS DISCUSSION... /Issued 244 PM PDT Fri Oct 13 2017/

SYNOPSIS...

Below average temperatures are on tap through Saturday as a trough
moves over the West. Strong easterly winds are likely at the
northern Sierra crest late tonight and Saturday morning as strong
surface high pressure builds into the Great Basin. Warmer
temperatures and dry conditions are expected early next week, with
the potential for cooler, wetter, and windier weather late week.

DISCUSSION...

A weak cold front will drop south through the region tonight turning
the flow northerly, then easterly. The depth of the colder air is
fairly shallow, but it will be enough to bring a bit of cooling for
temperatures into Saturday. It will also limit mixing potential
Saturday with stronger inversions in place. As a strong surface high
sets up over the Great Basin tonight into Saturday, it will
strengthen the gradient, especially across the Sierra. This will
bring gusty easterly winds of 60 to 80 mph across the Sierra crest,
with western Sierra slopes likely to see breezy winds tonight into
Saturday as well. While this is only a middle of the road type of
event for strength of wind speeds, it will be enough to generate
choppy conditions on Lake Tahoe and a Lake Wind Advisory has been
issued for tonight into midday Saturday.

Upper level ridge builds across the west for the early part of next
week with warming temperatures and mostly clear skies. Winds will be
light until midweek when an approaching system will begin to
increase wind speeds. It currently looks like Thursday will be the
windiest day next week, with southwest winds gusting in valleys
possibly as strong as 40 to 50 mph and ridges gusting over 100 mph.

These winds are in response to a strong jet ushering in a plume of
Pacific moisture and a trough into the west. The Sierra and western
Nevada are on the edge of the deeper moisture, which looks to move
into the northwest. An interesting development in the most recent
GFS run is that the main low coming into the west coast absorbs a
weaker secondary low off the southern California coast. This
enhances the precipitation chances across much of Nevada and has
ensemble support from about 50% of the perturbations. The EC keeps
this piece of energy off the coast, never merging it with the main
trough, and limits precipitation chances to areas mainly north of
Highway 50. While the finer details of this system aren`t clear at
this time, what we can say is this is the best shot at precipitation
the region has seen in some time. Anyone with plans the end of next
week should anticipate the potential for windy, cooler, and wetter
conditions. -Dawn

AVIATION...

Breezy northwesterly surface winds this afternoon due to a cold
frontal passage. The strongest winds will be north of I-80 where
surface gusts are likely to reach 20-25 kts. There may also be a
brief period of low level wind shear this evening as post-frontal
surface winds trend to northerly while winds aloft remain westerly
25-35 kts. By Saturday, easterly flow returns with gusts across
Sierra ridges possibly reaching 50-65 kts. JCM/Dawn

&&

.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory from 2 AM to 1 PM PDT Saturday for Lake Tahoe
     in NVZ002.

CA...Lake Wind Advisory from 2 AM to 1 PM PDT Saturday for Lake Tahoe
     in CAZ072.

&&

$$

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



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