textproduct: Eureka

KEY MESSAGES

* A frontal system brought thunderstorms, hail, and showers Wednesday and could return Thursday.

* There is a slight chance for thunderstorms in mainly in Trinity, Humboldt and Del Norte counties on Thursday.

* Warmer temperatures and dry conditions return end of the week.

SYNOPSIS

An upper level low brought instability and channeled flow up the interior valley and through terrain, using orographic lift to dynamically charge the atmosphere with lightning and hail embedded thunderstorms causing a slight outbreak Wednesday evening. cooler temperatures and a chance for showers and Thursday are possible. Warmer and drier conditions are expected Friday and into the weekend.

DISCUSSION

An upper level low that has moved south over the PACNW is expected to continue impacting the area Thursday. This is expected to bring some showers and possible thunderstorms to the area Thursday afternoon and evening. Low pressure will continue to meander eastward on Thursday. This will pull some more marine influence near shore with weak southerly wind. Southerly wind may also help pull in some marine fog and clouds closer to the Lost Coast and into the upper Russian River. The chance (10%) of thunderstorms will continue, but the core of instability and thunderstorm chances will shift further east, more focused around the Trinity Alps. The potential near the coast will reduce.

A high pressure ridge will gradually rebuild Friday and into the weekend. This pattern will allow for interior temperatures to dry back out and warm back into the 90s. Moderate north winds will return near shore, helping form a shallow but persistent marine layer especially north of Cape Mendocino. High pressure will most likely persist through next week. Most models show weak to moderate high pressure, but about 20% of ensemble members show unusually strong high pressure around next Tuesday that could push interior highs closer to 100. Aside from isolated showers today and tomorrow There is near 0% chance of wetting rain for the next 10 days. /JHW /EYS

AVIATION

With variable wind patterns and localized formation of stratus, the terminals will differ overnight into Thursday morning. KCEC will stay clear longer than KACV tonight but expect stratus to fill in by 13z with ceilings below 500ft and possibly 300-400ft a few hours before dawn. Southerlies are likely to dominate the from groups at KCEC into Thursday morning. KACV will likely have southerly winds veering to easterly/offshore by 11-13z with IFR conditions, ceilings around 300-400ft. Northwest and westerly winds prevail by Thursday afternoon at KACV with a return of LIFR flight conditions Thursday night.

MARINE

Low pressure moving inland has weakened northerly wind and pushed strong winds further offshore. Seas have fallen in the inner waters along with the wind and will continue to fall in the outer waters overnight with seas generally below 6 feet by mid Thursday morning. Southerly winds will form along shore in the inner waters early Thursday with gentle gusts staying below 15 kts. Moderate to strong northerly winds will gradually return to the southern waters by Friday and gradually spread north through the weekend, though winds will most likely remain much calmer closer to shore. Short period wind waves will dominate the marine environment with only a very minor southwest mid period swell up to 2 feet to speak of. /JHW

FIRE WEATHER

Storm potential will remain Thursday, but shift focus towards the Trinity Alps area. Any storms will be weak with light rain. Aside from storms, winds are mostly gentle and terrain driven with generally high RH over 30 percent and good overnight recoveries. Any new starts are not expected to spread rapidly. Conditions will significantly dry and warm over the weekend with thermal belts contributing to much worse RH recovery. There is little to no chance of wetting rain for the next 10 days. /JHW

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 AM PDT Thursday for PZZ470-475.