textproduct: Eureka

SYNOPSIS

Dry weather and above-seasonable temperatures are expected to continue with widespread Minor HeatRisk for the interior through Friday. Temperatures will cool gradually this weekend and into early next week, yet remain above normal. The chance of precipitation increases early to mid next week.

DISCUSSION

A massive 500mb ridge centered over southern California resulted in another unseasonably warm day in the interior of Northwest California today (Wednesday). Max temperatures on Tuesday, soared well into the lower 90's across mostly Mendocino and Lake Counties. The hot spot on Tuesday was at an AirNow station in Ukiah with a peak temperature of 95F. This is +20F above late March 30-year averages. Elsewhere across the interior highs on Tuesday were mostly in the 80's. 24-hour temperature trend so far has been around -2F to -5F as of 2 PM and should start to reverse or approach zero this aftneroon. The above normal warmth and minor heat risk is forecast to continue through the end of the week in the interior with only small day-to-day changes. Greatest downward trend so far today has been along the coast due to an influx of cool-damp ocean air. A shallow, yet extensive marine air mass offshore has been banked up against the coastline today. Visible satellite imagery clearly showed extensive low cloud cover or stratus hugging the coastline today. Surface stations have reported low ceilings with periodic fog and vsby around 1/4SM or less. There was still considerable spatial and temporal variability of the stratus. Some immediate coastal areas have been socked in under low clouds while just a few miles inland places like Fortuna and Blue Lake were basking under bright sunshine. The shallow marine layer and low clouds and fog will hang around through the end of the week. Greater coverage and duration will possible as the layer deepens on Friday in response to a transient shortwave trough. Gusty coastal northerlies are forecast to follow for the weekend in the wake of this trough.

High temperatures in the interior are forecast to moderate more substantially over the weekend and the heat risk will generally diminish. It will still remain above late March normals for portions of the interior and some of the hotter interior valleys will continue to have minor heat risk. Greater cooling will be possible early to mid next week with the passage of a synoptic scale trough and eventual frontal passage. Some precipitation is possible as well Tue into Wed. The greatest chance for rain is forecast across Del Norte and northern Humboldt Counties (40-60%). Chance for measurable rain falls off sharply for southern Mendocino and Lake Counties (20% or less). The front could end up stalling offshore and provide light rain or drizzle to only interior Del Norte as well as coastal areas north of Cape Mendo.

AVIATION

High pressure will continue over the area keeping conditions dry and winds weak. A shallow layer of coastal stratus kept lower ceilings and visibilities for coastal terminals into early afternoon. The stratus continues to burn away and will continue to retreat toward the ocean this afternoon. Stratus has a high probability of remaining just offshore and oscillating in and out of coastal terminals today. A short period of VFR may be possible for coastal terminals before the coastal stratus moves back inland this evening. IFR to LIFR conditions are expected overnight tonight. VFR conditions are expected for inland terminals, like KUKI. /JLW

MARINE

As high pressure gradually pushes east, the pressure gradient over the area has continued to weaken. This will allow for gentle to mostly calm north winds through Thursday with only locally enhanced winds to around 15 kts in the lee of Cape Mendocino. Calmer winds will remain as long as high pressure covers the area. As high pressure finally breaks down, stronger winds will begin to return first to the southern waters Friday. Stronger winds will return this weekend, with gale conditions very likely (80% chance) in the outer waters by Sunday.

Calm winds will generally limit any meaningful short period seas through the week. That said a minor, long period southerly swell and modest mid period westerly swell will combine to create at least some seas up to 6 feet through mid week. Steeper short period seas will return this weekend with the wind. /JHW

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... None.