Area Forecast Discussion
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FXUS66 KSTO 191141

Area Forecast Discussion
National Weather Service Sacramento CA
341 AM PST Tue Feb 19 2019

Dry today with cold morning lows. Minimum temperatures near
freezing in the Valley. 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.


Dry northerly flow aloft again this morning between high pressure
ridge over the eastern Pacific and a low pressure trough over the
Great Basin. Therefore, the CWA is under fair skies this morning
with light northerly winds most areas. Early morning temperatures
are running similar to 24 hours ago except in areas where winds
are lighter such as the northern Sacramento valley where
temperatures are running several degrees lower than yesterday
morning. Still expecting temperatures close to freezing in the
central valley this morning so will leave frost advisory in place
although winds are breezy enough that a hard freeze is unlikely.
High pressure over the state will bring fair skies and a little
warming today but cold airmass will keep daytime highs several
degrees below normal. A shortwave trough dropping out of the Gulf
of Alaska and into the Pacific Northwest will bring a threat of
light showers to the northern forecast area by Wednesday morning.
This precipitation threat will spread southward across the
forecast area during the day on Wednesday. Cool northerly flow
will keep snow levels between 1500 and 2500 with snow levels
dropping even more overnight Wednesday into Thursday.
Precipitation chances shift to the Sierra Cascade range on
Thursday as the upper low moves into the Great Basin. Orographics
will bring the greatest amount of precipitation over the Northern
Sierra but even here, snowfall totals should mainly fall short of
snow advisory criteria most areas. Upper level and surface
gradients will bring breezy north winds again Thursday with
clearing and decreasing winds expected Friday as high pressure
slips over the state.


Upper level ridging breaks down Saturday as a cold upper low
pressure system drops out of the Gulf of Alaska/British Columbia
and spreads into NorCal Saturday. The latest ECMWF is now
trending towards bringing precipitation further south, spreading
across the area by Saturday evening. Additional disturbances
dropping down will continue precipitation through Sunday into
early next week, mainly over the mountains. The current mainly
overland track should limit moisture, so snow and rain amounts are
not expected to be large. Snow levels with this cool system will
are currently estimated at around 2000-3000 feet over the Sierra
and as low as 1500 feet over Shasta County. EK



VFR conditions expected to continue over the next 24 hours.
Northerly winds 5 to 12 kt. EK


Frost Advisory until 9 AM PST this morning for Carquinez Strait
and Delta-Central Sacramento Valley-Motherlode-Northeast
Foothills/Sacramento Valley-Northern Sacramento Valley-Northern
San Joaquin Valley-Southern Sacramento Valley.


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