textproduct: Eureka

KEY MESSAGES

* Hot temperatures will bring a moderate to major heat risk for portions of the area Today through Mid Week. Moderate heat risk continues through the week.

* Overnight northeasterly winds and poor RH recovery will increase fire danger mainly in Del Norte, Humboldt and Trinity counties tonight and to a lesser extent Tuesday.

* Coastal warmup through Tuesday with offshore flow.

SYNOPSIS

Breezy northeast winds are keeping coastal areas mostly clear and will help warm temperatures above normal today and tomorrow. High pressure continues to build, bringing hot temperatures to inland valleys (warming between 95 to 105 or more in the hottest valleys). Some coastal clouds are expected to return starting Tuesday and expanding Wednesday through late in the week.

DISCUSSION

Throughout the week, fluctuations of an upper level high pressure system, centered over the Southwestern US, will affect Northwest California. Due to this high pressure system, warming and drying will continue for the region, especially for inland areas.

There is still high probabilities for moderate to major HeatRisk throughout the work week with different areas peaking on different days. Currently, there are Heat Advisories in effect for interior regions of Mendocino County and Lake County which will remain in effect through tomorrow. Tomorrow, interior Del Norte County has a Heat Advisory in effect. Interior Humboldt and Trinity counties have Heat Advisories in effect tomorrow and Wednesday with Trinity County's Heat Advisory lasting into Thursday. With the warming and drying and breezier winds, there is an elevated Fire Danger this week (more details in the Fire Weather Section).

General offshore flow aloft peaked last night, but will continue at least through mid week. Warmer than average high temperatures will peak today for the Del Norte, Southwest Humboldt, and Mendocino coasts with highs peaking in the upper 60s to low 70s right along shore and highs peaking into the 80s only a few miles inland. Warmer coastal temperatures are anticipated to cool slightly for the previously mentioned areas tomorrow, while coastal temperatures along the Humboldt Coast, north of Cape Mendocino, are expected to peak. On Tuesday, for the northern Humboldt Coast, areas within a couple miles of the ocean have a 65 to 80 percent chance for highs over 70 degrees tomorrow, with higher probabilities for coastal areas further than a couple miles from the ocean. 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.

Tuesday, the upper level ridge starts to move overhead bringing a few subtle changes to the region, such as lighter winds. This may allow a southerly wind reversal along the coast which could bring stratus north to the Mendocino coast. This may also bring some southerly winds to Ukiah keeping temperatures a few degrees cooler for some areas of Mendocino County. The lighter winds may be a factor in allowing areas of the Humboldt Coast, north of Cape Mendocino, to warm up due to the combination of the lighter winds at the surface and the offshore flow aloft. This has the potential to bring high temperatures in the mid to upper 70s. Farther south it looks like the southerly winds may start to bring stratus northward.

Wednesday through Friday, the upper level ridge in forecast to very slowly move off to the east. This will likely bring a return of stratus to much of the coast, although afternoon clearing is likely most afternoons. Hot temperatures are expected to continue with most valleys continuing to see highs around 100. Some cooling is finally expected for the weekend. /JLW /MKK

AVIATION

This afternoon, breezy winds are expected to continue for the terminals of Northwest California, although they have been lighter than they were yesterday afternoon. Tonight and into Tuesday morning, the offshore flow is weaker which may allow some stratus to develop along the Humboldt Coast. Ground fog may also develop. The Mendocino coast is anticipated to begin seeing a southerly surge of stratus at some point early Tuesday morning.

MARINE

The strongest winds have migrated away from shore with gale conditions continuing for the outer waters today. Tomorrow, gale conditions will continue for the northern outer waters while dropping off in the southern outer waters. Larger swell from the previous days constant strong northerly winds will continue for all marine zones into this evening.

Tonight and Tuesday the winds and seas continue to diminish as the high pressure gradually pushes the winds farther off the coast. Tuesday morning, the weakening northerly winds could allow a southerly surge of winds and clouds or fog to move north. This southerly surge may increase to around 10 to 15 kt along the Mendocino Coast Tuesday afternoon. Tuesday night and Wednesday the northerly winds continue to weaken and allow some light southerly winds to spread across more of the area. These light winds and seas are generally expected to continue through Thursday morning. Thursday afternoon through Friday and into the weekend are expected to see increasing northerly winds, once again. There is the potential for gales again over the weekend, but confidence is low on this at this point. MKK

FIRE WEATHER

General northeasterly flow aloft will continue while gradually weakening over the next couple of days. Gusts of 20 to 30 mph are still possible over ridges and favorably aligned drainages. 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.

Afternoon RH will trend much lower across the interior with values in the low teens to some single digits by this afternoon. Interior areas are anticipated to remain this dry through much of the week. Afternoon west- northwesterly gusty winds can be expected each afternoon, as well. These winds are expected to be more typical for summer afternoons, only lasting a few hours and not as strong as this past weekend.

Smoke discussion. This afternoon the HRRR smoke model is showing some smoke moving into eastern Trinity County, although this is expected to be fairly shortlived. In Del Norte County, the northeasterly winds are expected to return tonight into Tuesday, but not as strong. However, due to the more persistent northeasterly winds aloft this may bring some smoke out to the coast. The HRRR and RRFS models both show some smoke make its way out to coastal Del Norte and then south into Humboldt County. Confidence is low on this, but it will need to be watched. MKK

EKA WATCHES/WARNINGS/ADVISORIES

CA... Heat Advisory from 11 AM to 11 PM PDT Tuesday for CAZ102.

Heat Advisory from 11 AM Tuesday to 9 PM PDT Wednesday for CAZ105-106.

Heat Advisory from 11 AM Tuesday to 11 PM PDT Thursday for CAZ108-116-117.

Heat Advisory until 11 PM PDT Tuesday for CAZ110-111-113- 114-118>120.

NORTHWEST CALIFORNIA COASTAL WATERS... Hazardous Seas Warning until 9 PM PDT this evening for PZZ450.

Small Craft Advisory until 9 PM PDT this evening for PZZ455.

Gale Warning until 3 AM PDT Tuesday for PZZ470.

Gale Warning until 9 PM PDT this evening for PZZ475.