textproduct: Eureka

SYNOPSIS

More widespread rain and mountain snow is expected today into Sunday. Thunderstorms with gusty winds and small hail are possible in Mendocino & Lake this evening and overnight. A chilly start to the week is expected with near-freezing temperatures possible in the colder valleys. Additional rain is possible again Wednesday.

DISCUSSION

An area of low pressure is quickly approaching California early this afternoon. Widespread moderate to locally heavy rain is expected, along with gusty south winds this afternoon. Generally, the strongest winds will be in southern Humboldt, Mendocino, and Lake Counties. Gusts could reach 35 to 40 mph, with locally higher gusts of up to 50 mph possible over ridges and coastal headlands. A few thunderstorms are possible within the strongest rain bands. Stratiform rain turns showery this evening and overnight. The strongest of these showers, especially in Mendocino & Lake Counties, may have thunder, gusty winds up to 40 to 50 mph, and small hail. Rainfall totals range from as little as a 0.25" to over 3". The highest rain amounts are concentrated in Mendocino, Lake, and Trinity Counties where heavier showers are likely to continue overnight. Snow levels will quickly fall this evening from around 6000 ft to 3500 to 4000 ft. 6 to 8 inches of snow are possible on Highway 3 at Scott Mountain Pass. Over 3 feet of snow are possible in the highest elevations in Trinity County.

Sunday, showers continue but begin to taper off as the low begins to exit the area. A few afternoon thunderstorms may still develop with lingering moisture and instability, mostly over the interior. Cloud cover may be too abundant to allow for much warming, which will limit instability. Temperatures Sunday night to Monday morning will be chilly, with 30s to low 40s expected for many areas. Some valley fog may keep temperatures high enough to prevent a widespread freeze or frost, but some of the coldest valleys could still dip near or below freezing. Temperatures will remain chilly Monday and Monday night, with highs in the 50s across the area, and lows in the 30s. Frost may be possible in more valleys with fewer valleys experiencing fog. High temperatures begin to rebound Tuesday with 60s likely in most interior valleys. This will be temporary however, as confidence is increasing on another area of low pressure approaching the area Wednesday. This system has been trending wetter and farther south in recent models runs. The NBM is showing around a 70-90% chance for wetting rain (>0.1") for Del Norte and Humboldt Wednesday, with much smaller chances inland and south into Mendocino & Lake. The chance for over 1" is low, around 30% in the mountains of Del Norte, and near zero elsewhere. JB

AVIATION...(11/18Z TAFs)

SHRA continue moving across the region as a surface low approaches. Mainly MVFR conditions, dropping to IFR/LIFR with the heaviest rain is expected to continue through the period across the TAF sites and other terminals. Chance of thunderstorms increase across the interior after 20Z. A period of VCTS in UKI is expected for this afternoon (11/20Z-12/00Z), and again tonight (12/07Z) through at least Sunday morning (12/18Z). Expect gusty and erratic winds and possible hail with any TSRA (thunderstorm). S-SE winds at 5-10 kts increasing to with occasional higher gusts this afternoon. S-SE winds at 5-10 kts with occasional higher gusts. However, a rapid and brief increase in south winds is expected with the frontal boundary pushing onshore mid/late afternoon, especially for areas south of Cape Mendocino. Expect a period of gusts between 20-30 kts in UKI. /ZVS

MARINE

Hazardous marine conditions for small crafts have developed across the water with a rapid increase of south winds as a frontal boundary moves through. Fresh to strong south breezes is already observed over the southern waters this afternoon, and quickly spreading to portions of the northern waters. A period of isolated gale force gusts is expected in the southern inner waters and around Cape Mendocino. The frontal boundary is also leading a line band of moderate to heavy rain south of Cape Mendocino.

Winds should gradually ease and become gentle to moderate breezes south of Cape Mendocino tonight, while light and variable over the northern waters as the surface low passes overhead. Thereafter, breezy W-NW winds will develop early Sunday. A period of steep seas around 6-7 feet at 6-7 seconds is expected tonight. A west-nortwest seas around 5-7 feet at 9-10 seconds and some small swells will dominated the waters on Sunday.

Monday, northerly winds returns as high pressure starts to build into the area. This will promote moderate to fresh northerly breezes across the waters Monday through Tuesday, with the strongest winds south of Cape Mendocino. Wednesday, a brief wind shift to south is expected over the northern waters as a frontal system moves through, followed by strengthening northerly winds Wednesday night through Friday as the pressure gradient tighten. There is a potential (75- 95% chances) of gale force guts late next week. /ZVS

EKA WATCHES/WARNINGS/ADVISORIES

CA... Winter Weather Advisory until 11 PM PDT Sunday for CAZ107.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until midnight PDT tonight for PZZ450- 455-470-475.