textproduct: Eureka

KEY MESSAGES

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

* Elevated fire danger returns Saturday and into next week with periods of breezy winds and increasingly hot, dry conditions.

* Westerly to northeasterly winds through the weekend and into Monday will bring the greatest fire weather risk.

SYNOPSIS

Temperatures will be trending higher over the next week with moderate to major HeatRisk possible early next week. Hot interior temperatures in combination with periods of breezy winds this weekend through Monday with increase the fire weather risk.

DISCUSSION

A tight upper low is currently moving over Northwest California bringing a shield of high clouds to the northern half of the area. Model guidance indicates there is a small 5k ft layer of elevated instability associated with this low around 15k feet above the surface. However, moisture is very limited and any convective growth today/this evening is expected to quickly be squashed before any thunderstorm threat can develop. Thus the forecast remains dry today.

Beginning on Friday ridging will begin to build toward the west coast while at the same time a sharp trough moves through the Pacific Northwest. This will leave our region right in between these two features through Saturday with warming temperatures across the interior and a stronger onshore stratus push closer to the coast. The trough will move inland on Saturday into Pacific Northwest and a trailing dry front will move through Northwest California. Northerlies will increase over the coastal waters behind the front and then push inland from the west-northwest resulting in gusts in excess of 20 mph across much of the region, with much higher gusts in the King Range and other favored terrain. Enhanced fire weather risk will develop as a result and more details are included below in the fire weather discussion.

As the trough departs, the ridge will finally win out and build directly over the west coast. Temperatures are forecast to warm significant into the lower 100s across many interior valley locations. Widespread moderate to major HeatRisk is expected with a potential for heat advisory level heat Monday through Wednesday next week. /RPA

AVIATION

Coastal stratus has been persistent around Humboldt Bay but has otherwise cleared across the region. No precipitation is expected as an upper low bring some high clouds to the region today and this evening. As the low departs, northerly winds over the coastal waters will persist resulting in onshore flow into areas north of Cape Mendocino. This should support redevelopment of stratus overnight with a push into the coastal river valleys. IFR to LIFR conditions are expected at CEC and ACV overnight through Friday morning. Farther inland VFR is expected to persist through the forecast period at UKI and most other interior terminals. /RPA

MARINE

Northerly winds will persist over the coastal waters for the next week with a building ridge of the western US and a strengthening thermal trough. A quick passing dry frontal boundary will strengthen the pressure gradient on Saturday resulting in an expansion and strengthening of the northerly winds over all waters. Gales will be possible in all of the waters over the weekend into early next week, with gales very likely over the outer water zones. Steep waves in excess of 10 feet will likely develop in response to the strengthening winds. /RPA

FIRE WEATHER

Lighter winds and gradually increasing overnight relative humidity recoveries are expected through Saturday morning as a trough approaches the Pacific Northwest. Stronger marine layer pushes into the near-coast valleys and along coastal ridges are likely Friday and Saturday mornings. Farther inland dry air will remain in place with afternoon relative humidity values falling into the teens on Friday.

As the trough moves through the region on Saturday the pressure gradient will tighten resulting in stronger afternoon westerly winds with chances for gusts over 25 mph increasing to 50 to 70% for a good portion of the interior Saturday afternoon. Thankfully 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. A robust burst of dry NE winds will likely follow the departing trough later Sunday through Monday over the interior ridges of Trinity, Humboldt, and Del Norte counties.

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 not expected to be more typical for the summer only lasting a few hours and not as strong as Saturday. /RPA

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 5 AM PDT Saturday for PZZ455-475.