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Atmospheric River Brings Flooding Threat

Here’s a look at your forecast for Santa Cruz, Monterey, San Benito, and southern Santa Clara Counties!

After a few weeks of cold, unsettled weather, the pattern shifts to something more hazardous. A strong storm system combined with a moderate atmospheric river will lead to gusty winds, heavy rain, and a high risk of flooding Thursday & Friday. A storm like this would be serious by itself, but compounded with saturated soils from our wet winter, it will likely reach the next level. Streams in the coastal mountains area likely to flood with possible flooding for inland streams. Strong winds may cause power outages, road closures and/or property damage. Occasional rain will continue this weekend, though it won’t be as intense. Two additional atmospheric river events are possible, however. One on Tuesday and another by the end of the week. These would likely exacerbate existing flooding. Another thing worth mentioning will be the warmer weather brought on by this sub-tropical air mass.

AIR QUALITY: Good

Overnight: Increasing clouds. Chilly initially with lows reaching into the upper 30s to low 40s, then leveling off with the increase in clouds.

Thursday: Overcast throughout the day. Rain will be light at first, starting in the coastal mountains and eventually spreading inland. Moderate to heavy rainfall rates expected in the coastal mountains by afternoon and will continue into the overnight. Occasionally heavy rainfall  can be expected elsewhere. The flooding threat will increase late as rainfall accumulates. As for winds, they will slowly increase throughout the day as well, becoming strong and gusty later in the day. Wind speeds in the 30-40mph range will knock down tree branches, gusts up to 50 could take down whole trees. The strongest gusts will be on the outer coast and coastal ridges with some funneling for inland valleys. Highs mainly in the 50s.

***GALE WARNING***
… for the near coastal waters along Santa Cruz and Monterey Counties including Monterey Bay in effect from 9AM Thursday until 9AM Friday.  

*Southeast winds 25 to 35 kt with gusts up to 45 kt. (slightly lesser in the bay)

*Strong winds will cause hazardous seas which could capsize or damage vessels and reduce visibility.

Mariners should alter plans to avoid these hazardous conditions. Remain in port, seek safe harbor, alter course, and/or secure the vessel for severe conditions.

**WIND ADVISORY**
…for the entire KION viewing area in Monterey, Santa Cruz, San Benito, and Santa Clara Counties in effect from 1pm Thursday until 4pm Friday.

*South winds 20 to 30 mph with gusts up to 50 mph expected.

*Gusty winds could blow around unsecured objects. Tree limbs could be blown down and a few power outages may result.

Use extra caution when driving, especially if operating a high profile vehicle. Secure outdoor objects.


*FLOOD WATCH*
… for the entire KION coverage area in Monterey, Santa Cruz, San Benito, and Santa Clara Counties in effect from Thursday afternoon through Sunday morning.

A strong winter storm will impact the region Thursday into Friday with showers lingering into Saturday. This system is tapping into very moist subtropical moisture which will allow for moderate to periods of heavy precipitation. Latest model guidance suggests the coastal slopes of the Santa Cruz Mountains and Santa Lucia Mountains will receive the greatest accumulation of precipitation.

*Flooding caused by excessive rainfall is possible.

*Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations. Creeks and streams will see rapid rises. Flooding may occur in poor drainage and urban areas. Low-water crossings may be flooded. Storm drains and ditches may become clogged with debris.

*Rainfall totals will range from 1.5 to 4 inches. Locally up to 6-8 inches over favored peaks and higher terrain of the Santa Lucia Mountains where prolonged moderate to heavy precipitation and higher rain rates are currently forecast. Pre-existing saturated soils will not be able to absorb
excess rainfall. Urban and small stream flooding is expected along with a 25% exceedance probability that some main stem rivers may rise above flood stage.

Continue to monitor the latest forecasts and be alert for possible Flood Warnings. Those living in areas prone to flooding should be prepared to take action should flooding develop.


Friday: Heavy rain and gusty winds persist overnight, especially in the coastal mountains. Temperatures will remain mild overnight with most areas in the 50s, rising into the 60s during the day. Rain & wind will slowly taper off during the day but additional heavier bursts will be possible. The flooding threat will be highest early in the day on small streams.

Extended: Additional rounds will be possible into Saturday and maybe even Sunday. Highs return to normal (if not above) and lows will finally be back above normal. Another wet & heavy storm possible early next week roughly around Tuesday and perhaps another late in the week.


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This week's normal temperatures:

--COASTAL CITIES--
LOW: 45ºF
HIGH: 63ºF

--INLAND CITIES--
LOW: 41ºF
HIGH: 67ºF

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-The outlook from the Climate Prediction Center for March 16th – 22nd calls for the likelihood of BELOW normal temperatures and ABOVE normal precipitation.

- El Niño/La Niña STATUS: La Niña Advisory

- Forecast: Transition to neutral with possible El Niño developing this summer
-Area drought status: 
Moderate Drought (D1) for the northern Santa Cruz Mountains, San Benito County, southeastern Monterey County and southern Santa Clara County Abnormally dry (D0) for the rest of Monterey & Santa Cruz Counties.

Article Topic Follows: Weather Authority
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Dann Cianca

Dann Cianca is the chief meteorologist at KION News Channel 5/46.

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