Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 202242

Area Forecast Discussion
National Weather Service Sacramento CA
342 PM PDT Tue Mar 20 2018

Wet weather returns today and continues into the weekend. Snow
will remain above pass level through Wednesday. Snow will be
possible at pass level Wednesday night through Saturday.


Showers continue to spread over NorCal this afternoon in a warm
air advection environment. Snow levels are already running above
pass levels with freezing level currently around 8000 feet. Little
if any snow is expected over the Sierra roadways through
Wednesday afternoon. Periods of Showers are expected through
early Wednesday morning with a brief break mid-morning to early
afternoon. Rainfall amounts through Wednesday afternoon will be
0.25-0.75 for valleys and 1-3 inches over the mountains. Breezy
south winds will develop Wednesday afternoon lasting into early
Thursday with a few gusts to 40 mph.

Strong cold front will sweep southeast Thursday with heavy
precipitation and rapidly dropping snow levels. Confidence in
the exact timing of frontal passage and lowering snow levels is
not high at this time and some changes to details are likely over
the next day. However, it is likely rain will change to snow by
Thursday afternoon at the latest with several inches over the
passes. Travel is likely to deteriorate rapidly as this change
over occurs. Stay tuned to the latest forecasts updates, as
confidence should improve by Wednesday afternoon.

Thunderstorms with small hail will also be possible Thursday, as
a very unstable airmass moves over NorCal. Additional valley
rainfall amounts up to 1.50 inches are possible with mountain
values 2.00-5.00 inches. This will increase the threat for minor
small stream and poor drainage area flooding. A brief break in the
wet weather looks possible Late Thursday night and Friday
morning, before a colder system brings potential heavier and lower
snow Friday night.

Upper low/trough along the West Coast with cyclonic flow will
keep showers in the forecast over Interior NorCal Saturday. Snow
levels Saturday will be low, 1500-2500 feet. Precipitation for the
most part looks light and focused more over the foothills and
mountains. Sunday is trending dry and warmer, as upper ridging
develops with dry northwest flow. Dry weather continues early next
week, with a warming trend as heights increase over Interior



Dtrtg conds ovr Intr NorCal this aftn into eve as pcpn sprds ovr
fcst area. Areas MVFR/IFR conds aft 00z in rain. Sn lvls AOA 080.
Lcl S-SW sfc wnd gsts to 25 kts ovr hyr trrn tngt into Wed mrng.


Winter Storm Watch from Wednesday evening through Thursday
evening for West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.


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