textproduct: Eureka

KEY MESSAGES

* Dry and unseasonably warm weather forecast through midday on Thursday.

* Moderate to heavy rain and gusty south winds across much of the area throughout Friday.

* Potential for Coastal Flooding, especially around Humboldt Bay, due to high astronomical tides paired with persistent and strong southerly winds Friday and through the weekend.

* Additional rain and wind possible over the weekend and into early next week.

SYNOPSIS

Dry weather is forecast through Thursday along with above normal temperatures. By Friday, a strong storm is forecast to bring moderate to heavy rain across the area and strong southerly winds. Additional rounds of wind and rain are possible over the weekend and into early next week.

DISCUSSION

A brief period of high pressure will continue to take hold of Northwest California through mid Thursday. Dry air and warmer than average conditions will continue as a result. There is over an 80% chance of high temperatures over 65 degrees along the Mendocino Coast today through Thursday with over a 70% chance of high temperatures over 65 degrees along the Humboldt and Del Norte Coast. Interior valley temperatures will range from the low 70s to high 70s. Also, early morning low clouds/fog can be anticipated through this time period for moist interior valleys, as well as a general marine layer along the coast overnight/early morning that will clear and scatter by the afternoon.

By late Thursday, a cutoff low pressure system will approach the Pacific Northwest. Models also depict a troughing pattern lasting through early next week with a potential for multiple rounds of rainfall and strong southerly winds. Widespread rainfall and gusty winds are expected for Northwest California, as a result.

With the first front, southerly winds are anticipated to ramp up by late Thursday evening with ensemble models indicating rain beginning very early Friday morning. Moderate to heavy precipitation is expected through the day Friday, with showers likely through Saturday and the potential for another bought of moderate rainfall on Sunday. The National Blend of Models (NBM) indicates over an 80% chance of 24-hour rainfall totals of an inch or more for Del Norte, Humboldt, northern and western Trinity, and northern Mendocino from 4am Friday (11/13) to 4am Saturday (11/14) and a 65 to 85 percent chance for half an inch or greater during the same time period for southeastern Trinity, southern Mendocino, and Lake counties.

NBM also indicates at least an 80% chance of 24-hour max wind gusts of 45 mph or greater for the coastal headlands and higher terrain areas of Humboldt and Del Norte counties on Friday. The need for wind advisories will need to be assessed for these areas. Otherwise, also on Friday, there is a 65% chance of 24-hour max wind gusts of 35 mph or greater for more populated areas of Humboldt and Del Norte (including communities along the Del Norte Coast and the greater Humboldt Bay region) along with higher terrain areas of Trinity, Mendocino and Lake counties.

The ECMWF Extreme Forecast Index (EFI) is highlighting the rainfall this weekend for Northwest California with it being the first time precip has been highlighted this season. One unusual thing is how much instability models indicate with this system, as well, on Friday. NBM is showing up to a 30 percent chance of thunderstorms. This is not something typical from a pattern like this, so this will need to be closely monitored. The impacts of this rain may be more limited than they would be later in the season. Creeks and streams are very low and the soil is very dry limiting the potential for flooding, at least with this first system. /JLW

AVIATION

Coastal terminals can expect southerly winds and VFR conditions through mid-afternoon. The new REFS data shows that MVFR to IFR ceilings are more likely than not to develop over North Coast terminals through the evening. Offshore winds developing late overnight are likely to evaporate the weak marine layer with areas of surface fog possible through the morning. Inland terminals are likely to have westerly winds building this afternoon after the surface inversion breaks. Calm winds and VFR conditions are expected overnight. Terminals in coastal river valleys are likely to have morning fog, especially in the Trinity, Klamath, and Eel river valleys. DS

MARINE

A mid-period swell dominates the waters Tuesday morning with southerly winds building through the evening. A marginal small craft advisory has been issued for all waters through 10am Wednesday as buoys continue to record steep seas and increasing southerly short period waves. Southerly winds will continue through the week, peaking Friday morning with periods of strong gales through the morning. The sea state this week will continue to be a mix of W swells and southerly short period seas. Small craft advisories are likely through the week as a generally stormy pattern continues. This weekend, seas are expected to grow as high as 25-30feet as another large WNW swell of 25ft @ 18s is forecasted to enter the coastal waters late Friday night. Large waves are expected to last through early Sunday morning. DS

COASTAL FLOODING

Water levels inside Humboldt Bay continue to run 1.2 to 1.5 feet over the astronomical tides. Winds will continue to be southerly which tends to increase water levels slightly. The max high tide is expected to drop each day through the weekend, yet increasingly stronger southerly winds are likely to offset this decrease in max tide height. The water levels are expected to be slightly below 8.8 feet the next couple of days around high tide (11/10 @11:45am, 11/11 @12:06pm, 11/12 @12:55pm).

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 AM PST Thursday for PZZ450-470- 475.

Small Craft Advisory until 10 AM PST Wednesday for PZZ455.