Area Forecast Discussion
Issued by NWS Reno, NV
FXUS65 KREV 300950
Area Forecast Discussion
National Weather Service Reno NV
250 AM PDT Sun Apr 30 2017
Warmer and drier conditions will continue today. High pressure
over the area will weaken slightly allowing breezy winds this
afternoon and evening. A weak surface boundary passes through by
late Monday. The ridge rebuilds by the middle of next week with
light winds and above normal temperatures. By late next week
cooler and wetter weather may return.
Very few changes were made to the short term forecast this cycle.
A ridge of high pressure positioned off the west coast should
bring mainly benign weather to the region the next few days. High
temperatures are likely to be 4-7 degrees above normal. Overnight
lows will be near seasonal averages with the exception of
the higher elevations of the Sierra. Here the lows will be above
average as warming increases aloft. Some areas above 7500 feet may
not fall below freezing overnight.
Northwest flow aloft over the eastern half of the forecast area
today and Monday will usher a weak wave through much of the CWA
tonight and early Monday. Ahead of this wave northwest winds are
likely to increase late this afternoon with gusts in the 35-40
mph for a brief period of time from roughly Gerlach southeast to
Lovelock...Fallon and Hawthorne. These gusty winds will occur
mainly after 5 pm today. If the winds were to develop earlier we
would need a Lake Wind Advisory for Pyramid Lake...but the late
start and short duration means we will not issue at this time. The
lake closes at sunset...about when the peak winds will occur.
Winds will be a bit lighter Monday behind the wave. Earlier we
thought temperatures might cool down a bit for Monday and
Tuesday...especially as Tuesday will see north to northeast low
level flow. But the low level temperature advection is minimal and
what little cool air advection there is is likely to be overcome
by the increased hours of daylight and higher sun angle of early
Ridge top winds over the Sierra were increased for Tuesday night
as east flow is normally a favored direction for gusty winds
.LONG TERM...Wednesday through the weekend...
By Wednesday the ridge axis will move over the southwest U.S.
with well above average temperatures expected through the end of
the week. Temperatures will be 6 to 12 degrees above normal
through the second half of the week peaking around Thursday when
areas in western Nevada could reach 80 degrees, which for Reno,
would be the first this year. Along with above freezing overnight
low temperatures in the Sierra, snowmelt runoff is expected to
increase significantly. For more details see the Hydrology section
By Thursday the ridge of high pressure already begins to break
down as a sharp trough approaches the west coast. Models are in
relatively good agreement that over the weekend a fairly large
scale cutoff low pressure will settle into the southwest U.S. This
will bring cooler temperatures and increasing chances for
precipitation, and possibly thunderstorms, for the end of the week
and into the weekend.
Cutoff lows are dynamic and the weather they produce is highly
dependent on exactly where you are relative to the low pressure,
especially when it comes to thunderstorm potential. Have held off
any mention of thunderstorms at this time for that reason. The
details of which day will be the coldest, windiest, rainiest, or
most thunderstormy will be difficult to sort out until we have a
better idea of the exact trajectory of the low pressure. However,
what can be said is that a return to cooler and wetter weather is
expected by the weekend, so if you can, enjoy the nice weather
this week. -Zach
VFR conditions with light winds will be the norm through the early
afternoon hours today. Later this afternoon into the evening
gusty northwest winds will develop for areas east of the Sierra.
There will also be an increase in winds aloft so some turbulence
over the ridges is possible later today and tonight.
Winds decrease a little for Monday and light east to northeast
flow develops for Tuesday. VFR continues through the middle of the
week. By late Tuesday night there could be stronger winds over
the Sierra ridge tops as easterly flow strengthens. This would
lead to increased turbulence over and west of the Sierra.
By later this week the pattern begins to change with showers
returning to the area.
Above normal temperatures into the middle part of the coming week
will lead to increased snowmelt and higher flows on many area
streams and rivers. Flows are already significantly above normal
for this time of year and this increase in temperature will only
exacerbate those conditions. Overnight lows are likely to remain
just above freezing in the higher elevations through much of the
week. This could mean some minor melting in the higher elevations
even at night. There is also a good chance for showers to return
late next week and next weekend. Any additional rainfall could
create more runoff and even higher flows.
Record to near record snow pack in the Sierra will mean a
prolonged period of high flows through the spring and possibly
into early this summer. Peak flow forecasts vary across the region
with the Truckee and Carson peak forecasts falling in the middle
of May while the Walker and Lower Humboldt are forecast to peak
in June. These are peaks for the main river systems...not the
feeder streams. And even after these peaks occur...flows will
remain elevated for an extended period.
A Flood Warning remains in effect above Rye Patch Reservoir on
the Humboldt River. Flood Advisories are in place on portions of
the Truckee River due to high flows from reservoir releases and
snowmelt and in the lower part of the Carson River due to releases
from Lahontan Reservoir.
Remember that these elevated river flows are moving fast and that
water temperatures are cold. The cold waters make hypothermia a
distinct possibility for anyone in the water and the swiftness of
the water can carry someone away rather quickly. In any areas
where flows are high...even areas without warnings or advisories...
bank erosion is possible.
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