textproduct: Eureka

SYNOPSIS

Strong high pressure over the area brings dry conditions and high temperatures to interior valleys through Thursday. A cold front will bring rain to Del Norte and mainly northern portions of Humboldt county Friday. The coolest day is expected to be Saturday before temperatures start warming on Sunday and into next week.

DISCUSSION

High pressure remains strong across the area this afternoon with continued hot temperatures and shallow marine layer at the coast. Thursday an upper level trough starts to approach the area and will start to cool temperatures off across the interior in the afternoon. Most inland areas will continue to see highs in the mid to upper 80s with low 90s in the Trinity River Canyon. The marine layer is expected to remain fairly shallow. This will also increase the afternoon winds across the interior areas with gusts to 15 to 20 mph.

Friday morning as the trough moves onshore some clouds are expected to move in and the marine layer is expected to deepen and expand. In the morning this may bring drizzle to the north coast. Friday afternoon and evening the front associated with this trough is expected to bring some rain, mainly to Del Norte county, and to a lesser extent, Humboldt county. The probability of a wetting rain (0.10 inches) in Del Norte county is 50 to 60 percent in the mountains, but only around 10 percent at the coast. Farther south in northern and central Humboldt counties there is a 20 to 40 percent chance of a wetting rain. Some of this light rain may make it into the Trinity Alps. Elsewhere across the area a few sprinkles are possible, but notable rain is not expected. Breezy north winds are expected across the area, especially the interior with gusts to 30 mph.

Saturday behind the front things are expected to start to dry out, but generally it is expected to be fairly chilly and breezy day across the interior and especially the higher elevations. Highs are expected to be in the low 70s north of Lake county with mid to upper 70s in Lake county. Sunday and into early next week high temperatures are expected to climb back into the upper 80s to around 90.

AVIATION

The shallow marine layer persists along the coast this afternoon. The cigs have lifted slightly this and may clear out for a short period of time at KACV and KCEC late this afternoon or early this evening. The RRFS indicates the potential for some clearing for KACV shortly after 00Z. It is possible some stratus will work its way north into Ukiah tonight, but confidence is low on that as well. Thursday late in the day the probabilities increase for the coast to see some clearing. Thursday night the approaching trough is expected to lift CIGS to MVFR. MKK

MARINE

Northerly winds continue across the waters this afternoon. This continues to bring short period wind driven waves. In addition to this there is southerly winds around 3 to 4 feet around 19 seconds. The northerly winds are expected to diminish in the northern waters on Thursday as an upper level trough moves approaches the area. Thursday night and Friday the lighter winds continue to push farther south. A fresh northwest swell may keep these waves slightly elevated even as the winds diminish. Saturday the northerly winds are expected to return in the afternoon and evening. These are expected to increase to strong to near gale force on Sunday. Next week some gale force gusts are expected in the outer waters as high pressure returns. MKK

FIRE WEATHER

An upper-level ridge remains firmly established over northwest California, keeping hot and dry conditions intact across interior valleys through Thursday. Daytime highs on interior valley floors will reach the 90s both today and Thursday. High-resolution guidance continues to indicate a 10% probability of localized triple-digit heat up to 105 degrees, strictly confined to the lowest elevations of the Klamath and Trinity river corridors. Minimum relative humidities will drop into the teens across these interior zones during the afternoon hours. Along the coast, a compressed marine layer will keep low clouds, cool temperatures, and patchy dense fog entrenched.

A significant pattern change occurs Friday into Saturday as a deeper upper-level trough and cold front move onto the west coast. This front will bring a high probability of wetting rain to the northern coastal areas, with a 50% to 60% chance of exceeding 0.10 inches in coastal Del Norte County and a 30% to 40% chance in northern Humboldt County. Otherwise interior areas will remain dry outside of isolated sprinkles, but will experience a temperature drop of 15 to 20 degrees, dropping Saturday highs into the 70s. As the core of the cold trough moves overhead on Saturday afternoon, localized destabilization will support around a 10% chance of thunderstorms across the higher terrain of northeastern Trinity County.

Winds will remain light with standard afternoon breezes inland again Thursday. Behind the front on Friday afternoon, strong westerly winds will develop across Lake and southern Mendocino counties. There is a 70% chance that wind gusts will exceed 30 mph in low elevations, with a high probability of gusts over 40 mph across exposed ridges. Breezy conditions continue Saturday afternoon, with a 50% chance for lower elevations to see gusts over 30 mph. Winds are forecast to shift to the northeast at least briefly across Lake County by Sunday afternoon.

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 3 PM this afternoon to 3 AM PDT Friday for PZZ455.

Small Craft Advisory until 9 AM PDT Thursday for PZZ470.

Small Craft Advisory until 3 AM PDT Friday for PZZ475.