textproduct: Eureka

SYNOPSIS

Scattered thunderstorms are possible this afternoon and evening. Some of these storms may be strong and bring strong winds and hail. Lingering showers and isolated thunderstorms are expected Monday. Warmer and drier conditions are likely for the remainder of the week.

KEY MESSAGES

-Scattered and some isolated strong thunderstorms (15-25% chance) over the the interior Sunday afternoon with some storms pushing closer to the coast.

-Lingering showers, clouds, and cooler conditions are likely Monday followed by warmer and generally calm conditions by midweek.

DISCUSSION

An upper low off the coast of California continues to bring moisture and unsettled conditions. Thunderstorm activity is expected to peak today as the low pulls tropical moisture up the Sacramento Valley. Precipitable water of around an inch or higher along with high instability (CAPE of up to 1000 J/kg) will bring scattered thunderstorms. The highest thunder chances are in interior Humboldt, interior Del Norte, and Trinity Counties. The Yolla Bolly's, eastern Mendocino, and northern Lake are likely to see some activity as well. Storm potential will peak late this afternoon and into the early evening. The strongest storms could bring locally heavy downpours, strong winds up to 50 mph, and damaging hail. Rainfall totals range from a few hundredths to over a half inch in areas of Del Norte. There are low, but nonzero chances, for some areas to see over an inch, especially in northern Humboldt, Del Norte, and northern Trinity, should stronger storms develop. Should training cells develop, especially over a burn scar, flash flooding may be possible.

Easterly steering flow will help push any storms closer to shore, though any storms will weaken as they move to the west off the high terrain. The deep and persistent marine layer near the coast is likely to continue through the day. Some disruption might be possible with east flow and remnant thunderstorms, but any erosion is likely to rebuild by the evening.

Showers continue into Monday. The track of the low, which will be over the central CA coast, has moved south somewhat. Shower activity will also drift south into Trinity, Mendocino, and Lake County. Isolated afternoon thunderstorms are possible in the interior, mainly in northern Trinity County. Afternoon thunderstorm chances are much lower than today at only around a 10-15% chance. Colder air being pulled from the northeast aided by lingering clouds will briefly cool interior temperatures into the 60s Tuesday. Clouds and valley moisture will limit any overnight frost concerns. The east wind will likely help erode and shallow the marine layer, but most models show stratus persisting through the early week. Benign and weak high pressure will build late in the week, bringing slightly warmer than average temperatures but otherwise dry, seasonable, and calm weather.

AVIATION

A return of coastal stratus overnight into Sunday stretching the length of the west coast. Dissipation started at Del Norte and consequently KCEC by Saturday late afternoon while KACV remained overcast into Saturday late night into Sunday. With the marine layer lifting for a short spell at KCEC late Saturday evening, MVFR/VFR will continueS until the early morning hours Sunday with a high probability (87%) of cloud base less than 500ft which will put flight categories in LIFR. Similar conditions for KACV with almost 50% probability of less than 500ft cloud base and near 75% probability of less than 1000ft. Stratus could bring visibility down as well with NBM suggesting less than a mile of visibility through the late morning at KACV and much longer at KCEC, possibly into the late afternoon. KUKI could get a southerly push of stratus up through Cloverdale and Hopland early Sunday morning, lowering flight categories to LIFR for a few hours as it did in the previous morning. /EYS

MARINE

Overnight into Sunday morning, a cold air mass will approach the western seaboard, this cold air will disrupt the surface pressure gradient allowing the northerly winds to weaken down to gentle breezy conditions. This will begin an extended period of lighter winds and smaller seas through next week as relatively light winds flow over the coastal waters. From Sunday through the week, the GFS wave model shows two main swells impacting the coastal waters, the first is a long period, westerly swell building up to 6ft@15s and another is a NW swell of 4ft@8s. Minimal impact is expected next week from fresh, short period waves.

BEACH HAZARDS

This morning, a long period northwest swell with periods between 17-20 seconds will arrive. This swell continues to be monitored as it may pose a moderate risk of sneaker waves for coastal areas. A Beach Hazards Statement has been issued for the coast Sunday. Sneaker waves are anomalously large, unexpected waves that sweep across beaches without warning. There can be up to 30 minutes of smaller waves before a sneaker wave arrives to the shoreline. Choose your recreation wisely by avoiding steep beaches and jetties as well as staying much farther back from the ocean than normal. Never turn your back on the ocean!

EKA WATCHES/WARNINGS/ADVISORIES

CA... Beach Hazards Statement through this evening for CAZ101-103- 104-109.

NORTHWEST CALIFORNIA COASTAL WATERS... None.