NATIONAL WEATHER SERVICE FORECAST DISCUSSION
Area Forecast Discussion
Issued by The National Weather Service
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000
FXUS66 KSTO 181146
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
346 AM PST Mon Feb 18 2019

.SYNOPSIS...
Dry Today and Tuesday with cold morning lows. Minimum temperatures
near freezing in the central valley today and Tuesday. A weak,
cold system moves through Wednesday and Thursday with light
mountain and foothill snow. Dry Friday with more light
precipitation possible over the weekend.

&&

.DISCUSSION...
Dry northerly flow between high pressure over the eastern Pacific
and a trough over the Great Basin bringing fair skies to the CWA
this morning. Clearer skies allowing for a little cooler
temperatures this morning but breezy north winds keeping morning
temperatures a little warmer than anticipated. Gradient from MFR-
SAC is about 7 mb at this time and is expected to weaken slightly
through the day bringing a little less wind. More sun and a
slightly warmer airmass should bring a little warming most areas
today. For tonight...northerly surface gradient forecast to be
slightly weaker for a little lighter winds. This should allow for
a little cooler temperatures in the valley but warmer airmass may
offset this cooling a bit. Overall, went for slightly cooler
minimums tonight per much of the guidance. Therefore, frost
concerns return and may need another frost advisory now that we
are entering blooming period for some crops. Should see a little
warming on Tuesday as high pressure slides across the region.

Cold upper trough dropping out of the Gulf of Alaska and through
the Pacific Northwest will bring clouds to most of the CWA Tuesday
night which should bring up overnight lows a few degrees. Light
precipitation from this fairly dry system is forecast to spread
southward over the forecast area on Wednesday. Snow levels with
this system will start out around 2000 feet then lower to below
1000 feet northern zones on Thursday as the upper low drops
southeast of the region and cooler air filters in. The highest
elevations of the Sierra may see a half of foot of snow with this
system with most areas only seeing an inch or two of snow.
Therefore...impacts with this system should be fairly minimal.
Skies clear Thursday night as high pressure pushes back over the
west coast with another round of breezy north winds.

.EXTENDED DISCUSSION (Friday THROUGH Monday)

Upper level ridging builds in on Friday in the wake of a departing
cold upper level low. Northerly upper level flow develops, with
dry weather across the area. Breezy northerly winds are expected
as surface pressure gradient increases. This wind should keep
overnight lows from getting as low as they might otherwise for
much of the Valley, though the mountains and sheltered areas will
be quite cold.

Upper ridge breaks down quickly as yet another cold upper low
pressure system drops out of the Gulf of Alaska and moves into the
Pacific Northwest Friday night and Saturday. Models continue to
differ on just how far south precipitation will reach with the GFS
digging precipitation somewhat farther south than ECMWF. Have
continued the trend of spreading bring precipitation further
south, with the potential for some precipitation across the area
for Sunday and Monday. The current track should limit moisture, so
snow and rain amounts are not expected to be large. Confidence is
still low on this system, though. Snow levels with this system
will are currently estimated at around 3000-4000 feet, but this
may change as model confidence increases. EK

&&

.AVIATION...


VFR conditions expected over the next 24 hours. Northerly winds
10 to 15 kt with isolated gusts to 20 to 25 kt by afternoon.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 9 AM PST this morning for Central
Sacramento Valley-Motherlode-Northeast Foothills/Sacramento
Valley-Northern Sacramento Valley-Southern Sacramento Valley.

&&

$$
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