Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Reno Nevada
314 am PST Wednesday Jan 28 2015
Moist flow will keep cloud cover over the region through late
Thursday. A few showers are possible south of Highway 50 Thursday
into Friday before drier conditions return for the weekend.
Some breaks in cloud cover are allowing for the early formation of
freezing fog in the Martis Valley. It is likely that other Sierra
locations will also see some fog as these breaks move across the
Sierra. It does look like there will be intermittent periods of
increasing/decreasing sky coverage so expect some fluctuations in
fog thickness through the morning. The potential for more
widespread freezing fog will increase over the next couple of
nights for typical locations like the martis and Sierra valleys as
skies clear across the northern Sierra.
A very low amplitude ridge will be in place today with upper level
moist flow keeping ample cloud cover over the region. While an
extremely isolated high elevation shower cannot be ruled out, the
overall conditions will be dry today. Area high temperatures will
not vary widely from Sierra valleys to western Nevada valleys for
the next couple of days. Temperatures will reach the low/middle 50s.
Slightly cooler conditions will occur Friday as flow responds to a
deepening low near the California/NV/AZ border, shifting more northerly.
Still, highs will be above seasonal averages hanging around 50
degrees in the Sierra and western Nevada. Some light
precipitation will be possible as the low meanders a bit before
dropping south into southern Arizona. These low chances will
remain south of Highway 50 in Mono and Mineral counties. Drier
flow returns for the weekend with a moderately amplified ridge off
the California coast. Boyd
Long term...Saturday through Tuesday...
No significant changes were made to the current forecast. Ridge axis
is expected to move over western Nevada Saturday, keeping the region dry
with light northeast winds in lower elevations and stronger ridge
gusts over the Sierra. This northeast flow with inversion in place
will limit daytime heating despite little to no cloud cover, keeping
highs generally in the lower to middle 50s for western Nevada and Sierra
For Sunday and Monday, the ridge is expected to flatten as moisture
spreads into the Pacific northwest. Weak shortwave energy moving
through this moist flow is tracking a little farther south on the
latest guidance, which would increase middle and high level cloud cover
across most of the region Sunday through Monday. Precipitation
potential is still limited due to marginal forcing, but some light
showers are possible over northeast California-northwest Nevada Sunday night,
and extending south to near Interstate 80 by Monday. The southern
extent of shower potential is quite uncertain at this time, so
current confidence level for any measurable precipitation spreading south
of a Susanville-Gerlach line is low.
Temperatures on Sunday are likely to increase by a few degrees as
inversion weakens and flow becomes west, although cloud cover will
prevent further heating especially north of Susanville and Gerlach.
Monday will be a little cooler although the amount of cooling will
depend on the eventual track of the shortwave moving across the
By Monday night, overall precipitation chances should diminish as shortwave
departs the region. There is a small possibility for this wave to
dig a bit south with a narrow band of showers forming in west
central NV, but the majority of the guidance data pushes this system
and precipitation chances farther to the east.
By Tuesday, ridge returns to the West Coast with dry conditions
prevailing. The amplitude of the ridge axis varies which would
affect daytime temperatures. The latest GFS shows a sharper axis off the
coast which would lead to cooler highs for the region with
increasing northeast flow especially for ridges. The European model (ecmwf) and most
of the ensemble data favored a lower amplitude ridge, which was
indicated by the inherited forecast. We will keep this forecast
intact for now which would keep highs in the 50s for most of the
Clearing skies and leftover moisture from tuesday's rain allowed
fzfg to roll into ktrk between 200 and 230 am. This fog dispersed
momentarily around 3 am as a band of clouds moved overhead, but
with few significant clouds upstream we will keep mention of fzfg
through later this morning. Conditions appear favorable for
redevelopment of fzfg around ktrk eastern Sierra/Plumas counties
for early Thursday morning mainly from 09-17z.
Otherwise VFR conditions with light east winds are expected today
through Thursday. At kcxp where east flow is typically enhanced,
speeds will be a little higher in the 10-15 knots range mainly between
21-03z both days. Mjd
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