textproduct: Eureka

KEY MESSAGES

* Coastal warmup for early Next Week with offshore flow.

* Hot temperatures return early next week with widespread Moderate to locally Major HeatRisk through mid week.

* Elevated fire danger returns this weekend with breezy northwest afternoon winds, although this will diminished some by slightly cooler temperatures and higher afternoon RH.

* Sunday night into Monday morning northeasterly winds and poor RH recovery will increase fire danger mainly in Del Norte, Humboldt and Trinity counties.

SYNOPSIS

Slightly cooler temperatures inland are expected for the weekend with breezy afternoon winds. Temperatures will be trending higher Monday and Tuesday with moderate to major HeatRisk expected early next week. Temperatures will diminish slightly mid to late in the week, but remain hot.

DISCUSSION

An upper level low pressure system will continue its path east into British Columbia today. This upper level low has generally cooled temperatures and increased RH today with interior temperatures around 5 degrees cooler than yesterday. Lake County will barely be affected by the upper level low, maintaining hot temperatures today and tomorrow in the mid 90s to low 100s.

The rest of the weekend and into mid week will be defined by an upper level high pressure system centered over the Southwestern US building west into Northwest California. This will aid in warming and drying out the region, especially interior regions of Northwest California. There is potential for moderate to major HeatRisk by Monday and Tuesday, mostly for interior Mendocino, Trinity and Lake counties (specifically: the Klamath River Valley up river from Weitchpec, the Trinity River Valley, the hottest valleys of southern Trinity and southern Humboldt, the Eel River Valley in NE Mendocino, the Round Valley, Potter Valley, Russian River Valley in southern Mendocino and the hottest valleys of Lake County). On Monday (in the areas previously mentioned), ensemble models indicate a 65 to 80 percent chance for high temperatures over 100 degrees with Tuesday looking at a 75 to 90 percent chance. Relative Humidities will also be very low (10 to 20%) Monday through Thursday. With the warming and drying and breezier winds, there is an elevated Fire Danger for next week (more details in the Fire Weather Section).

Additionally, a surface ridge in the NE Pacific is migrating east bringing strong northerly winds to the area along with general offshore and downslope flow. This offshore flow will begin overnight tonight and continue to some degree through Tuesday morning. Offshore flow will be most pronounced over Del Norte County, but will be prominent over high elevation regions throughout Northwest California and also affecting coastal locations. This pattern will aid in warming and drying coastal and near coastal areas. Ensemble Models indicate a 60 to 90 percent chance for temperatures over 70 degrees for coastal southwestern Humboldt and the Mendocino Coast through the next couple of days. Also, on Monday, there is a 55 to 75 percent chance for over 70 degree highs at the Eel River Delta, around Humboldt Bay and along the Humboldt Coast up through the Del Norte Coast with a slightly higher chance on Tuesday. By Monday, there is about a 65 to 75 percent chance for high temperatures above 75 degrees along the Del Norte Coast.

One thing to note with these higher than average temperatures along the coast is that the gradient for the warmest temperatures will be very steep and very dependent on the presence and persistence of offshore and downslope flow. Where there is little downsloping occurring, temperatures will not be as warm.

Monday night and into Tuesday offshore winds are expected to be lighter with some stratus potentially forming in localized areas along the Humboldt coast. Tuesday, winds are expected to be lighter at the coast. This may allow a southerly surge of clouds and south winds to start moving north. The models show this starting Tuesday night, but sometimes this happens earlier than expected. Tuesday afternoon may be the warmest along the Humboldt coast with the lighter winds if the marine layer doesn't return. Wednesday and Thursday temperatures are expected to start cooling by a few degrees in some locations, but overall it looks to remain hot. /JLW

AVIATION

VFR conditions prevail for most terminals in Northwest California this afternoon and evening. There is a band of clouds which could affect coastal terminals with lower ceilings this evening, but the clouds have thinned as they reached the coast. The main story is the stronger generally northerly winds across the region. Gusts from 20 to 25 knots are possible for most terminals in the region through late this evening. Coastal Del Norte and higher elevation coastal areas could see gusts up to 35 knots. General offshore flow aloft could hinder stratus development at the coast tonight, but some MVFR to IFR ceilings could develop overnight. /JLW

MARINE

Northerly winds continue to be strong south of Cape Mendocino with stronger winds continuing to push north. Later in the afternoon and evening, the winds are expected to get closer to the coast and increase in the northern outer waters. In addition to the wind driven waves there is a small southerly wave lingering around 2 feet at 14 seconds. This is expected to continue to diminish over the next several days.

Winds are expected to peak and push closest to shore Sunday afternoon and evening across much of the area. A Gale Warning has been added for the northern inner waters (PZZ450), mostly due to the stronger winds from about Orick north to Pt St George. Late Sunday evening and overnight, the stronger winds are expected to push farther off shore. The winds are expected to turn more to the northeast, as well, so even if the winds near the coast remain slightly elevated, the fetch will be limited. The winds are expected to drop below gale in the outer waters on Tuesday, but winds are generally expected to remain around 20 to 25 in the outer waters. Closer to the coast we may see a flow reversal with localized southerly winds. This may be Tuesday or Tuesday night. MKK

FIRE WEATHER

As the trough moves through the region today, the pressure gradient will tighten resulting in stronger afternoon westerly winds with gusts over 25 mph for a good portion of the interior this afternoon. However, the west- northwesterly winds will also bring slightly increased relative humidity with minimums in the 20s instead of teens. This will keep the fire threat from becoming critical. Sunday afternoon breezy winds are expected again, although they will be slightly more limited to the areas closer to the coast. RH is expected to be slightly lower as well for the Trinity and Lake counties with the warmer valleys dropping into the high teens in the afternoon.

Sunday night into Monday morning is starting to look like a more critical time period, especially on the ridges of Del Norte county. Gusts of 30 to 40 mph are are possible at the ridges and possibly the northeast aligned drainages. It is also expected to be fairly dry. The challenge at this point is determining where the inversion will be with dry and breezy conditions above and much calmer and higher RHs below it. The current forecast is now showing a fairly big area of eastern Del Norte county with recoveries of only 30 to 40 percent. This will also impact the interior ridges of Humboldt, and Trinity counties to a lesser extent. This will need to be monitored as it gets closer.

Afternoon RH will trend much lower across the interior to the low teens and likely some single digits by Monday and then remaining dry into mid next week. Afternoon west-northwesterly gusty winds can be expected each afternoon. These winds are expected to be more typical for the summer afternoons only lasting a few hours and not as strong as over the weekend. MKK

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 11 AM PDT Sunday for PZZ450.

Gale Warning from 11 AM to 9 PM PDT Sunday for PZZ450.

Gale Warning until 9 PM PDT Sunday for PZZ455.

Small Craft Advisory until 9 PM PDT this evening for PZZ470.

Gale Warning from 9 PM this evening to 3 AM PDT Tuesday for PZZ470.

Gale Warning until 3 AM PDT Tuesday for PZZ475.