Marine Weather and Tide Forecast for Ukiah, CA

KEY MESSAGES

- Temperatures ease through the end of the week with only minor HeatRisk

- Very slight chance of dry thunderstorms over high terrain thursday with greater changes on Friday.

- A lifting but persistent marine layer forming along shore.

DISCUSSION
Conditions started to cool much more rapidly today with most interior valleys struggling to reach even 90. Cooling will continue Thursday as a broad trough approaches the area. The trough will help generate some upper level clouds and pull in more marine influence, helping to drop interior temperatures into the 80s and creating a more lifted marine layer along the coast.

The trough will also help increase upper level instability. Combined with a moisture surge up the Sacramento Valley, there is a chance (10) of isolated, mostly dry thunderstorms over eastern Trinity and as soon as Thursday evening. Thunderstorm potential will increase Friday with a 20% chance of isolated dry storms Friday afternoon over northern Humboldt and Trinity Counties and a lesser chance extending as far south as the Yolla Bollys. Otherwise, temperatures will bottom out Friday with slight warming into the weekend.
Seasonably warm and dry but otherwise unimpactful conditions will build into the weekend. Long range models indicate potential for a moderate heatwave next week. /JHW

AVIATION
A shallow, LIFR marine layer once again blanketed the coast this morning. Most of the coast has cleared to VFR this afternoon though a shallow marine layer still lurks just offshore.
Most models indicate the layer quickly resurging to create LIFR coastal conditions, though marine layer lifting may push ceilings closer to IFR. A lifted marine layer will also increase the potential impact the Russian RIver valley and KUKI with IFR conditions likely there by Thursday morning. /JHW

&

MARINE
Strong north winds persisted all through the day int he far outer waters, helping to generate steep short period seas.
Moderately steep seas over 10 feet filled in throughout the inner waters, despite calmer winds near shore. Winds in the outer waters w ill gradually weaken and push further offshore overnight into Thursday with short period seas slowly falling mostly below 6 feet by Friday. Winds will be mostly calm Friday with moderate north winds rebuilding and pushing close to shore Saturday and Sunday.
/JHW



FIRE WEATHER
A now receding heatwave has left fuels much drier than they were just one week ago with ERC broadly near the 90th percentile across the interior. ERC is forecast to remain high despite increasing RH over the coming days. Overall weather conditions will greatly moderate through Friday with highs mostly in the 80s, increasing marine influence, and RH closer to 30 percent.
Winds will remain gentle and terrain driven.

That said, the approaching trough that is helping cooling conditions will also pull up some tropical moisture combined with increasing instability. In combination, these two factors could create some very isolated, mostly dry, thunderstorms Thursday afternoon in far NE Trinity County (10% chance). Small waves rotating around the trough may trigger convection overnight. Some high resolution models hint at weak storm activity in the early morning hours (also 10% chance Friday. Much more robust activity is likely (25% chance)
across northern Humboldt and Trinity Counties by Friday evening with lower chances as far south as the Yolla Bollys. Storm motion appears slow and isolated overall, but ignitions are still very likely given the current ERC values. Any storms could also produce some rain and gusty erratic outflow winds. /JHW



EKA WATCHES/WARNINGS/ADVISORIES
CA...
Fire Weather Watch from late Thursday night through Friday evening for CAZ403-406-409-410.

NORTHWEST CALIFORNIA COASTAL WATERS...
Small Craft Advisory until 3 AM PDT Thursday for PZZ450-475.

Gale Warning until 9 PM PDT this evening for PZZ470.