textproduct: Eureka

SYNOPSIS

Hot temperatures continue this afternoon and there is a slight chance for thunderstorms this afternoon in northern Trinity county. Temperatures are expected to start cooling on Tuesday and Wednesday, especially closer to the coast. Highs are expected to generally in the 90s through the end of the week and into the weekend.

DISCUSSION

An upper level trough is moving into the Pacific Northwest. The southern extent of it is lowering heights aloft. This generating some instability over Trinity and Siskiyou counties this afternoons. Lapse rates aloft are steep, but it still looks like there will be some inhibition around 500 mb. So have left the slight chance of thunderstorms in the forecast, but confidence is low on anything developing. Tonight the marine layer is expected to bring clouds back to the coastal areas. This may reach slightly farther inland and gradually deepen with the approaching trough. A shortwave is expected to move through overnight and this may bring some drizzle to portions of the coast. The pattern looks similar on Tuesday and as heights continue to gradually fall this will bring lower temperatures across the area. This will be enhanced in the near coastal areas that see influence from the deeper marine layer. With this the surface temperatures expected to be cooler and lapse rates aloft are not as steep so this makes it less likely we will see thunderstorms, although there is still a small potential.

The pattern remains fairly similar through much of the week. Most of the ensemble clusters keep the ridge axis just east of the area. This is generally expected to keep high temperatures in the 90s and the marine layer moderately deep with marine clouds around. The probability of exceeding 100 degrees for much of the rest of the week is only around 5 to 10 percent for most of the warmer areas. Some areas along the Trinity river, especially near Big Bar have higher probabilities of exceeding 100 degrees. For now there are no days with an obvious through for thunder, although that will continue to monitored. MKK

AVIATION

Stratus is being scoured out from the coastal terminals as northerly winds increase just offshore. A persistent southerly reversal has kept LIFR ceilings over CEC, but NW wind gusts exceeding 30 knots are expected this afternoon as a tight pressure gradient drives the strongest winds towards the coastline. ACV will be slightly more sheltered with gusts 10 to 15 knots. Afternoon terrain driven winds will once again bring gusty southerlies to UKI this afternoon. IFR ceilings are expected to return to ACV late this evening after 06Z (HREF 50 to 70%). Models show potential for drizzle in and around Humboldt Bay by Tuesday morning with the return of the marine stratus layer. Northerly winds will likely remain gusty at CEC overnight - combined with interior offshore flow, stratus will struggle to redevelop until after sunrise when winds turn southerly and diminish. Winds expected to remain lighter and southerly on Tuesday, allowing the resurgence of a widespread marine layer Tuesday evening.

MARINE

Gale force winds in the northern outer waters will expand southward in coverage today, with gusts exceeding 40 to 45 knots likely in NW PZZ470. As these winds push towards the coast, near- gale to gale gusts are possible nearshore of Point Saint George and Cape Mendocino this afternoon. Seas 9 to 11 feet are already being observed on buoys as waves propagate into the inner waters. Steep wind driven seas 12 to 17 feet are expected through Tuesday afternoon, with the strongest winds and waves expected late this afternoon and overnight in the outer waters. High pressure will begin to break down Tuesday afternoon, diminishing hazardous conditions by midweek.

FIRE WEATHER

Overnight offshore winds remain breezy in Del Norte and northern Humboldt counties. This is keeping RH recoveries poor to moderate in the high elevations, while recoveries are moderate to good in the lower elevations. High pressure moves eastward Tuesday and Wednesday. The marine layer will gradually deepen, improving RH in the near-coastal areas and lowering high temperatures 5-10 degrees. Offshore flow will begin to weaken, as well.

Upper-level moisture from the east along with elevated instability does bring a 10-15% chance for isolated dry thunderstorms in northern Trinity County. Today looks like it has the higher potential, but it is possible Tuesday as well. There is also a small chance for nocturnal lightning tonight. There is some elevated instability overnight, but the shortwave doesn't look strong enough to spark any thing off. Moisture and instability decreases by Wednesday into later in the week, along with thunderstorm chances. JB

EKA WATCHES/WARNINGS/ADVISORIES

CA... Extreme Heat Warning until 11 PM PDT this evening for CAZ102-105-107-108.

Heat Advisory until 11 PM PDT this evening for CAZ106-110- 111-113>115.

NORTHWEST CALIFORNIA COASTAL WATERS... Hazardous Seas Warning until 11 AM PDT Tuesday for PZZ450.

Small Craft Advisory from 5 PM this afternoon to 11 AM PDT Tuesday for PZZ455.

Gale Warning until 11 AM PDT Tuesday for PZZ470.

Small Craft Advisory until 9 PM PDT this evening for PZZ475.

Gale Warning from 9 PM this evening to 9 AM PDT Tuesday for PZZ475.