River Flood Warning 10, NWS Reno, NV

Area Forecast Discussion
National Weather Service Reno NV
208 PM PDT Sun Jun 18 2023

.SYNOPSIS...

A cold front will bring strong gusty winds through Monday and
unseasonably cool temperatures through Tuesday. The strong winds
will bring choppy lake waters, bumpy air for aviation, and strong
cross winds to high-profiled vehicles. Look out for a return of
freezing morning temperatures to Sierra valleys Tuesday and
Wednesday mornings. By midweek onward more typical late day winds
return along with a rebound to milder temperatures.

&&

.DISCUSSION...

Well, if you wanted dry and sunny weather, then here you go! This
upcoming week will be dry for the most part, with just some gusty
winds today and Monday. Currently, we have a trough swinging by
to the north that will start to lift and move further east as we
get into mid-week. Towards the end of this week, a couple smaller
shortwave troughs look to pass through, bringing slight chances
for precip mainly near the Oregon border.

700 mb flow will increase out of the SW today and peak overnight
tonight around 55 kts. As a result, Sierra ridgetops are expected to
reach gusts of 75+ mph and lower valleys up to 45 mph this
afternoon/overnight. These winds will bring choppy lakes, impacts to
aviation, and possible blowing dust down across the Basin and Range.
As the stronger winds aloft shift east Monday, ridge winds will
begin to decrease late Monday morning into the afternoon. The
rest of the week and through this weekend we'll return to our
usual afternoon zephyr breezes.

As this trough swings south, a dry cold front will bring much cooler
air into the region overnight tonight, starting this week off well
below average for this time of year. You may notice that Monday
morning will be a little cooler than previous days, with temps
slightly below average. High temperatures Monday will drop all
the way to the upper 60's across western NV and mid-50's in the
Sierra, roughly 15-20 degrees below normal. Tuesday morning will
be by far the coolest morning we've had in a while as cooler air
continues to settle in and winds lighten. The EC EFI has a really
strong signal of this cooler air for Monday's high and Tuesday's
low. After Tuesday, we'll be generally warming each day through
the weekend. The only exception being this Friday, when a
shortwave could drive temps down again but not to the extent of
what we're about to see.

There will also be two main days of increased chances for precip.
One being Monday afternoon through early Tuesday morning for
northwest NV and northeast CA, the other day being Friday. The
current upper-level jet/low pressure will supply large scale
ascent and additional instability, which is what will help produce
scattered showers for Monday-Monday night. There's a low risk of
lightning, but it's still worth noting and can't be ruled out due
to the convective nature of the storm. I hate to say the S-word
this far into the year, but if you're in far NE CA/NW NV and
above 5000-5500 ft, you may see an occasional snowflake falling
but no accumulation. I know, it's not the most pleasant thing to
read in mid-June, but we hope this will be the last we use the
S-word until at least October... but we'll see how that goes.

Looking ahead to Friday, long range ensembles are hinting at
possible light precip in the afternoon for areas near the Oregon
border. A shortwave passing through creating enhanced divergence
aloft be the main cause of the showers. Otherwise, it'll be warm
and sunny with light breezes through the weekend!

-Justin

&&

.AVIATION...

* Wind will continue to bring turbulence and nighttime LLWS
  through Monday evening as a cold front swings through the
  region. Ridge level wind gusts to 80 kts have already been
  reported early this afternoon and with the upper jet sagging
  south tonight, we will continue to see ridge winds peaking
  through tonight into Monday morning. Ridge winds will then
  slowly back off Monday afternoon and especially Monday night.
  Surface winds will remain strong across all areas through this
  evening and then shift to areas along and south of I-80 by
  Monday. SW-W winds today will shift more W-NW on Monday, gusts
  generally around 35 kts at area terminals.

* Scattered rain and snow showers will be possible Monday and
  Monday night generally north of KSVE-KWMC. There is even a
  15-20% chance of thunder Monday afternoon-early evening for
  these areas. Elsewhere, expect VFR conditions.

* Good flying weather will prevail Tuesday-onward as a weak large
  scale trough remains near the west coast. Typical afternoon
  breezes with gusts 20-25 kts and most of the precipitation
  remaining north of the region, maybe skirting far northeast CA
  and northwest NV.

&&

.HYDROLOGY...

All flood warnings and advisories for Mono County, the Walker River
system, and the Humboldt River at Imlay remain in effect until
further notice.

* Creeks and streams area-wide will continue to run high, cold,
  and fast with some potentially out of their banks. Cooler
  temperatures are expected early this week, so we may see that
  reflected in a slight decrease in snowmelt flows by mid week.
  Streams draining from the eastern Sierra in Mono County where
  abundant snowpack remains to be melted, will see a leveling off
  and subsequent height falls. Stream banks may still be unstable
  and any debris can send flows into unexpected areas, so take
  caution near waterway edges.

* The latest forecast for the West Walker at Coleville (WWBC1)
  keeps the flows around minor flood stage each night through
  Monday night, so a River Flood Advisory will remain in effect
  there for now. Recent adjustments to reservoir management will
  help mitigate high flows into the Mason Valley, where flows are
  expected to remain below the recent peak crests from June 7th.

-Justin

&&

.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory until 8 PM PDT Monday for Lake Tahoe in
     NVZ002.

     Lake Wind Advisory until 8 PM PDT Monday NVZ001.

     Lake Wind Advisory until 8 PM PDT Monday for Washoe Lake in
     NVZ003.

     Lake Wind Advisory until 8 PM PDT Monday NVZ004.

CA...Lake Wind Advisory until 8 PM PDT Monday CAZ071.

     Lake Wind Advisory until 8 PM PDT Monday for Lake Tahoe in
     CAZ072.

     Lake Wind Advisory until 8 PM PDT Monday CAZ073.

&&