Point St. George to Point Arena between 150 and 250 NM Offshore Forecast
|Tonight...N Winds 15 To 25 Kt. Seas 7 To 10 Ft.|
|Tue...N Winds 10 To 20 Kt. Seas 7 To 10 Ft.|
|Tue Night...N Winds 10 To 20 Kt. Seas 7 To 9 Ft.|
|Wed...N Winds 10 To 15 Kt. Seas 7 To 8 Ft.|
|Wed Night...N Winds 10 To 15 Kt. Seas 6 To 7 Ft.|
|Thu...N Winds 15 To 20 Kt. Seas 6 To 7 Ft.|
|Thu Night...N Winds 15 To 20 Kt. Seas 6 To 9 Ft.|
|Fri...N Winds 15 To 20 Kt. Seas 7 To 10 Ft.|
|Fri Night...N To Nw Winds 15 To 25 Kt. Seas 8 To 10 Ft.|
|Sat...N To Nw Winds 15 To 20 Kt. Seas 8 To 9 Ft.|
|Sat Night...N To Nw Winds 15 To 20 Kt. Seas 7 To 9 Ft.|
| Area Forecast Discussion|
National Weather Service Eureka CA
302pm PDT Monday Jun 21 2021
Cooler temperatures are forecast for the interior through mid week as an upper level low meanders around offshore. In addition to the cooling, this upper low will also bring a slight chance of thunderstorms in the interior Tuesday and Wednesday. A warming trend is forecast for the interior toward the end of the week.
A southeasterly speed max with higher mid layer moisture has been moving across the Trinity County this afternoon. Terrain induced wave clouds were apparent on visible imagery indicative of the stable nature of the atmosphere. Another speed max will develop later tonight aimed at NE Trinity County. The atmosphere appears too stable with elevated CAPE generally under 100J/kg. SREF calibrated thunderstorm probabilities are around 10% this evening and 5% overnight, while HREF neighborhood probabilities of 20% or more stay just north of the area through the night. Convective allowing models, such as the HRRR (High-Resolution Rapid Refresh) and NAM- nest has the convection firing up well north and northeast of the area tonight, however a few isolated lightning strikes near the tip of NE Trinity County is not completely out of the question, though unlikely to occur.
Convective parameters look slightly better for storms on Tuesday, however once again soundings indicate a fair amount of CINH to overcome. SREF and HREF neighborhood probabilities do increase near the Siskiyou County border, and a few lightning strikes appear possible for NE Del Norte and the mountains of northern Trinity Counties. Less probable is storms over South Fork Mountain and Yolla Bolly Mountains where soundings are more stable.
The offshore low will slowly edge closer to the coast from the southwest on Wednesday. This seems to be the best day for thunderstorms across the area. The soundings still do not look all that great, but the GFS soundings has higher surface based CAPE with equilibrium levels colder than -20C. The southeasterly flow aloft is a favorable pattern for storms to form farther west out toward eastern portions of Humboldt and Mendocino County, in addition to the mountains of Del Norte and Trinity Counties. NAM soundings do indicate elevated CAPE of 150-250J/kg by Wednesday evening over the coast and coastal waters as mid level moisture of debris clouds spread northwestward over the coast. The lower level marine environment will likely make storm prorogation out over the coast unlikely. This will need to be watched closely. Convective allowing models should shed more light on this once within range, about 24-48 hours out.
The cut-off low should start to meander southward on Thursday. Southeasterly-easterly flow aloft and wrap around moisture may bring another threat of storms on Thu, primary for SE Trinity and NE Mendocino Counties.
ENS and GFS ensemble means clearly show a massive 500mb height anomaly extending into the Pacific NW toward the latter portion of the week and over the weekend. All WPC 500mb clusters show this pattern to one extent or another, with a cut-off low somewhere, either offshore to our southwest, over northern California or south offshore Central/Southern California. Bottom line, if the low lingers over or in the vicinity of northern California during the latter portion of the week, temperatures will not warm up as much or as quickly as the GFS indicates. We may even see multiple days of interior storms through Friday.
ENS and GEFS probabilities for 850mb temperatures of 25C or more increase Sunday and Monday. Widespread triple digit heat is probable for many of the interior valleys once again. Looking at the National Blend of Models, the strongest warming appears to occur in the northern most portion of the forecast area, at least initially, the ridge extends southward into the forecast from the north. There is still about 10F degrees of mid spread, 95-105F, for places like Hoopa and Weaverville. A few hotter valley spots could hit 108 to 112F again. High heat risk is expected for the valleys both Sunday and Monday.
Winds and seas continue to diminish as an upper low approaches. Winds have shifted to light, southerly breezes this afternoon. Relatively light winds will persist across all waters, allowing short period waves to diminish through Tuesday. Winds will then pick up again to a moderate northerly breeze early on Wednesday, with winds continuing to increase and move closer to shore later in the week.
A southerly swell of 3 ft at 18 seconds is currently impacting the area. A northwesterly swell of 2 to 4 ft will build in on Tuesday and sporadically persist for the rest of the week.
Thunderstorm activity is expected to occur north of the area tonight, though isolated lightning strikes will be possible over far NE Trinity County near the Siskiyou County border. The potential for storms will increase slightly on Tuesday, once again mainly near Siskiyou County, though a few late day strikes will be possible over South Fork Mountain and the Yolla Bolly Mountains. The threat for isolated interior storms will increase Wednesday afternoon and early evening. Lightning activity is expected to be isolated at this time, so will continue to use headlines in the fire weather planning forecast.
.EKA WATCHES/WARNINGS/ADVISORIES... CA...None. NORTHWEST CALIFORNIA COASTAL WATERS...None.