textproduct: Sacramento

KEY MESSAGES

- A prolonged pattern of wet and unsettled weather is expected into next week.

- Minor impacts tonight and Saturday.

- Moderate to heavy rain starting Saturday night off an on through Christmas.

- Though exact details remain uncertain this far out, there is the potential for major impacts to mountain travel due to heavy snow by mid-week (Christmas Eve and Christmas Day).

..Late Saturday/Sunday - Christmas Day

A moderately strong atmospheric river is still on track to push several waves of rain over the area. AR landfall tools showing a nice east west tail of IVT values that lines up to impact the forecast area. Confidence is high with some uncertainity only in the southern line of it which at this time looks to be right around Sacramento. South of that line precipitation amounts could be notably lower. Ensemble systems have been consistent with the area and lines up well with WPC Excessive rain outlooks right over Central California.

Main impacts from this storm still look to be the heavy rain which when it is all over has the heaviest amounts in the higher terrain of Butte County where probabilities of 10 inches is around 90%. Elsewhere from 3 to 8 inches looks likely. The rain will have heavier periods off an on during this stretch. At this time, we believe main stem river flooding is not at risk but we will have to keep an eye on that is the AR happens to hit one area longer then expected. We have issued a Areal Flood Watch for the entire area to cover for urban, small streams and creeks flooding that is likely.

Holiday traffice impacts also seem likely. We have issued a winter storm watch for the tail end of the storm as snow levels eventually fall to around 5500 to 6000 feet starting Tuesday evening through Friday. Current probabilities showing a high (great then 80%) chance of 30" above 5500 feet. Once it gets closer we will get more exact amounts in the forecast as snow level flucuations often occur with these systems but several feet of snow seems likely.

Last impact would be wind with this system. It will be gusty at time throughout, but Wednesday is standing out as the strongest day. EFI values in the moderate range on Wednesday and NBM probabilities suggest a greater then 50% chance of wind gust from 35 to 45 mph on Wednesday.

WR

AVIATION

Ceilings primarily remain IFR/MVFR through the TAF period. Visibilities may lower to MVFR periodically due to rain. Heaviest rain rates are expected after 00z Sunday. Southerly to southwesterly winds with sustained speeds generally 12 kts or less throughout the TAF period, with lingering gusts up to 25 kts through 06z Saturday.

STO WATCHES/WARNINGS/ADVISORIES

Flood Watch from Saturday afternoon through Friday afternoon for Burney Basin / Eastern Shasta County-Carquinez Strait and Delta- Central Sacramento Valley-Motherlode-Mountains Southwestern Shasta County to Western Colusa County-Northeast Foothills/Sacramento Valley-Northern Sacramento Valley-Northern San Joaquin Valley-Shasta Lake Area / Northern Shasta County- Southern Sacramento Valley-West Slope Northern Sierra Nevada- Western Plumas County/Lassen Park.

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