textproduct: Eureka

KEY MESSAGES

* Coastal warmup through Tuesday with offshore flow.

* Hot temperatures for the interior through the week with widespread Moderate to locally Major HeatRisk through mid week.

* Elevated fire danger continues Today with breezy northwest afternoon winds.

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

SYNOPSIS

Breezy northerly winds continue today with gusty offshore flow overnight and general offshore flow aloft. This is expected to keep coastal areas mostly clear and above normal. High pressure continues to build in Monday bringing hot temperatures to the inland valleys (warming to near 105). Slight cooling is expected late in the week.

DISCUSSION

Today and through this week Northwest California will be defined by an upper level high pressure system centered over the Southwestern US. This will aid in warming and drying out the region, especially interior regions of Northwest California. There is high probabilities 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). Currently, a Heat Advisory has been issued for Monday and Tuesday for interior Mendocino (excluding the Southwestern Mendocino Interior) and Lake. Heat Advisories could be extended for the middle of the week.

Additionally, a surface ridge in the NE Pacific continues to migrate 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 70 to 90 percent chance for temperatures over 70 degrees for coastal southwestern Humboldt and the Mendocino Coast through the week. Also, on Monday, there is a 60 to 80 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 more of a 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 /MKK

AVIATION

VFR conditions prevail at terminals in Northwest California this afternoon. Gusty north to northwesterly winds will continue at most terminals into this evening. Most exposed coastal areas and higher terrain areas nearshore can expect gusts from 20 to 30 knots, with gusts for Pt St George possibly up to 40 knots. The highest gusts will mostly move offshore late this evening with winds at most terminals diminishing; however, winds could remain elevated along the Del Norte Coast through the night, especially around Pt St George. Strong offshore flow aloft will most likely keep conditions clear across the region, with potential for some patchy coastal stratus formation, but not very likely. /JLW

MARINE

Winds and waves continue to increase with gales throughout all marine zones. This afternoon/evening, the gales have moved closer to the coast with gale warnings remaining on track. Monday the winds in the southern waters will start to gradually move farther off the coast. The gale in the southern outer waters may end sooner than the warning indicates, but for now will leave it the same. Winds are expected to gradually diminish through the week before increasing again over the weekend. MKK

FIRE WEATHER

This 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.

Tonight and into Monday morning could be 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... Heat Advisory from 11 AM Monday to 11 PM PDT Tuesday for CAZ110-111-113-114-118>120.

NORTHWEST CALIFORNIA COASTAL WATERS... Gale Warning until 3 AM PDT Monday for PZZ450.

Gale Warning until 9 PM PDT this evening for PZZ455.

Gale Warning until 3 AM PDT Tuesday for PZZ470-475.