Area Forecast Discussion
Issued by NWS Reno, NV

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589
FXUS65 KREV 260928
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
228 AM PDT Fri Apr 26 2019

.SYNOPSIS...

Well above average temperatures into early this weekend will
continue increased mountain snowmelt with cold and swift flows for
area streams. Minor flooding is possible for agricultural areas
in the Carson Valley late each evening into the early morning
through Sunday. Cooler weather with a chance for showers returns
next week.

&&

.SHORT TERM...

No major changes were made to the current short term forecast. A
mainly dry surface boundary and upper level shortwave will drop
south late today into tonight. Moisture is fairly limited with
this feature but there may be just enough forcing to produce a few
showers and possibly even a thunderstorm over parts of Lassen
County late this afternoon or early this evening.

Saturday looks to be the last well above normal day in terms of
temperatures as we will be between the system for Friday and a
closed low moving toward the area Sunday.

As this closed low approaches Sunday...cloud cover will increase
while heights decrease as a longwave trough drops down from the
north. The combination will lower high temperatures 8-10 degrees
from Saturday...but we will still be mainly above normal. The two
features try to phase Sunday afternoon into Sunday night with the
GFS is a little quicker than the NAM. The potential phasing of
the features should help to create showers over the southern part
of the forecast area where upper level diffluence will be
enhanced. Moisture is deepest over the southern CWA as well.

While we do not explicitly mention thunderstorms Sunday
evening...it is not completely out of the question.

.LONG TERM...Monday through next weekend...

A few adjustments were made to Tuesday to drag the threat of
showers southward and to lower temperatures a bit more. The
forecast ideas remain the same with ensembles showing the similar
general ideas. However, there are still showing many solutions to
potential sensible weather, especially for the Tuesday- Wednesday
period.

Monday the weak upper low will continue tracking south of the
region, but a few showers remain possible for Mono and Mineral
Counties. The speed of the system varies from exiting by Sunday
night to Monday night. Right now, ensemble means support Monday
afternoon as it passes through, maximizing potential instability
for Mono/Mineral. With modest instability we added a slight chance
of thunderstorms too.

Tuesday, all ensemble runs show a slider system moving through,
but the trajectory varies. Some drop it south to Highway 50 before
moving east with showers for much of the area. Others keep it
north of the Oregon border and few if any showers. We will keep in
the slight chance of showers for Tuesday, with a little increase
for Tuesday morning with the main surface front. Temperatures will
also be cooler, closer to if not below average for late April.
With a brisk north wind, it will feel cooler.

Low amplitude ridging is expected behind this system with
temperatures warming up toward late week, but not nearly as warm
as they are currently. Models hint at the possibility of a weak
upper low for Friday into next weekend, but timing with that one
varies by as much as 2-3 days between ensemble members. X


&&

.AVIATION...
VFR today with some afternoon buildups, but no thunderstorms
today. Afternoon west breezes again gusting to 20 kts. A similar
day is expected Saturday. A couple weak systems are expected to
move through Sunday through Tuesday with a few showers and
thunderstorms possible. At this time, it appears most
Sunday/Monday will be south of Highway 50, and north of there for
Tuesday.

&&

.HYDROLOGY...

Most rivers and streams are expected to stay significantly below
flood stages this week. The primary exception is the West Carson
River. The flood watch for the West Carson River was upgraded
Thursday to a Flood Advisory through Monday morning. The most
recent RFC forecast for the West Carson river has levels reaching
flood stage each night through Sunday Night. The West Fork Carson
River is expected to BARELY reach flood stage and would only
affect small parts of the southern end of the Carson Valley.
However, periodic road closures for Mottsville and Centerville
Lanes will be possible during the overnight hours when it will be
difficult to see flooding conditions. The only other impact
expected would be minor flooding of agricultural areas adjacent to
the West Fork of the Carson River.

High flows are expected to continue into the weekend. Still, the
highest flows are still beyond the forecast window for most rivers
and streams draining high elevation terrain, especially from the
Lake Tahoe area south through Mono County. Remember: snowmelt
peaks typically occur in the evening and overnight hours in the
higher portions of the basin while peaks are more likely in the
early morning hours in the lower portions of the basin.
-Boyd/Bardsley

&&

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

$$

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



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