textproduct: Eureka

SYNOPSIS

An approaching cold front introduces more extensive cloud cover and light rain to Del Norte and northern Humboldt counties this evening into Friday. Colder temperatures will follow through the weekend.

DISCUSSION

A trough with a compact and deepening surface low will near the region, clipping NW CA late this evening. The best shot of light rain will be from Del Norte to Northern Humboldt. Areas of Del Norte could see periods of moderate rain with around a 50% chance for over 1 inch of total rainfall. Chances for anything over 0.1 inches quickly lowers to zero south of Cape Mendocino.

The interior ridges will see some gusty winds from the stronger winds aloft with the trough. There is a high chance (70%) for gusts to exceed 30 mph coastal and interior ridges of Del Norte late Thursday into Friday morning. Chances for gusts over 25 mph and locally up to 30 mph are also high for south Mendocino and Lake counties this afternoon. This will create some fire weather concerns for those areas due to the drier conditions.

A colder air mass will arrive overnight Friday. This will bring the potential for frost for some of the coldest interior valleys (particularly Hayfork). Chances for chilly temperatures and frost will continue into at least early next week. A trough will pass through Sunday. This storm system and a shortwave disturbance preceding it Saturday will be mostly dry, but could bring an afternoon shower or two for the interior. The extended outlook looks to remain dry with no chance for wetting rainfall.

AVIATION...(18Z TAFs)

VFR conditions are now being observed at all TAF sites with a few lingering low clouds off the Del Norte County coast. High and mid level clouds are streaming over the region as a cold front approaches. Ceilings will descend this evening as a cold front approaches, particularly in Humboldt and Del Norte counties. Rain will begin at CEC a little after 00Z with several hours of light to moderate rain expected. The rain will likely reach ACV after 03Z with only a brief period of 2-3 hours of light rain likely. Southerly winds will increase ahead of the front with a few gusts into the teens or even low 20 kt range possible at CEC before the frontal passage. Ceilings will fall overnight into the morning hours. Conditions will be much more favorable in Mendocino and Lake counties overnight into Friday with VFR prevailing and some gusty northwesterly winds this afternoon and again Friday afternoon.

MARINE

A trough approaching from the west will weaken the northerlies today. Though the W to SW winds will remain relatively light, there is a strong westerly wind fetch around the low which will drive in a quick pulse of steep west northwesterly seas around 9-12 ft at 10-11 seconds for most of the waters. Seas may reach hazardous levels at 12 ft for the far NW waters out around 30 to 60 NM. These seas will increase rapidly tonight through Friday morning and will bring dangerous conditions to small crafts. The northerlies will restrengthen Friday afternoon, and will be near gale to gale strength in at least the outer waters by Saturday and are likely to continue into early next week.

FIRE WEATHER

A trough and surface low will clip the region today. Light precipitation is expected from around Cape Mendocino and northward through northern Humboldt and Del Norte, with no precipitation expected south and east of the cape. This storm system will increase westerly winds this afternoon and into Friday. RH will be on the rise with the moist flow, but there will be a period of near to locally critical fire weather conditions this afternoon (Thursday) in Trinity, eastern Mendocino, and Lake Counties. Recoveries will be good overnight tonight, even in areas without rain. Northerly to westerly winds will remain gusty Friday, although RH trends higher. A pronounced offshore wind surge will then develop Friday night, drying out the interior somewhat Saturday with min RH dropping to the low 20 to upper teens. The extended forecast does not include any more chances for wetting rain.

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 2 AM to 5 PM PDT Friday for PZZ450.

Small Craft Advisory from 11 PM this evening to 5 PM PDT Friday for PZZ470.

Small Craft Advisory from 5 AM to 5 PM PDT Friday for PZZ475.