Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
939 FXUS66 KEKA 212218 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 318 PM PDT Fri Jun 21 2024 .SYNOPSIS...Hot weather in the interior expected this weekend. Dry weather and above normal temperatures in the interior expected to continue early to mid next week. Cooler temperatures possible late next week. && .DISCUSSION...Visible satellite imagery showed extensive coastal stratus north of Cape Mendocino again this afternoon. Stratus has been persistent along the Mendocino coast too, south of Fort Bragg. A couple of clear areas have been opening up in the lee of Cape Blanco and in the lee of Cape Mendocino this afternoon again. These clear slots may spread southward this evening and provide clearer/sunnier skies, however confidence that will occur is not high. Extensive low clouds offshore over the coastal waters and a steady northerly influx of cool-damp marine air underneath a solid inversion will result in more stratus generation this afternoon and evening. Inland areas away from the shoreline have been clearing out, but coastal areas have been socked in. Coastal forecast has been based largely on observations, climatology and persistence. It may take another day or two for the coastally trapped shallow moisture to finally release after weak frontal passage on Sunday. Interior temperatures are forecast to peak on Saturday; upper 90`s to around 103F. Moderate heat risk is forecast for Trinity, Lake and interior Mendocino counties on Saturday. This level of heat affects most individuals sensitive to heat, especially those without effective cooling and/or adequate hydration. The heat risk is forecast to diminish on Sunday but it will still be quite hot and toasty in the Trinty, Lake and interior of Mendocino; upper 90s to around 100F. Above normal temperatures are forecast to continue into early to mid next week. NBM has been trending warmer, though the coverage of moderate heat risk diminishes. Late week, NBM remains consistent with temperatures trending down as another trough digs offshore over the NE Pacific and approaches the west coast. Potential for rain or showers with this trough is not zero, generally less than 10% for a few hundredths. NBM probabilities for more meaningful rain, a tenth or more, is minuscule; 5% or less near the Oregon border late in the week. Potential for stronger west-northwest winds across the interior will be a greater concern for fire weather with low min RH`s <30%. NBM 24-hour probabilities for peak gusts >35 mph increase to 60% or more mid to late next week. DB && .AVIATION...Persistent coastal stratus has continued to engulf the North Coast through this afternoon resulting in mostly IFR conditions. However, afternoon Vis satellite verified several minor eddys and breaks-in overcast (BINOVC) streaks parallel to the immediate coast. Thus, small areas of partial clearing were in affect by 2PM...especially over Humboldt Bay. Now the eddys near CEC were the catalyst for several wind direction reversals...which resulted in CEC maintaining IFR Cigs. Coastal stratus also continued to pile up along the coast at ACV. Some breaks into late afternoon and evening expected, otherwise continued stratus overnight/morning. Inland areas will remain VFR or mostly SKC except for a few CU that popped up over extreme SE Trinity county and the Trinity Alps. /TA && .MARINE...A summer-time northerly wind regime will persist across the waters through the weekend into early next week. Strongest winds are forecast to occur over the outer waters and nearshore downwind of Cape Mendocino and perhaps near Pt St George. Most notable expansion fan will initially develop south of Cape Mendocino this evening and overnight. A low end gale warning is in effect for gusts up to 40kt. Moreover, very steep waves are projected to build to around 10 feet with periods from 7-9 seconds across the southern waters - mostly outside 10NM. Surface pressure gradient will be disrupted on Saturday, mostly north of Cape Mendo, and north winds may lay down slightly. Hazardous seas are still expected with waves around 6-7 feet at 6-7 on Saturday north of Cape Mendocino across the outer waters. Northerlies will then spike up again with low end gales in the realm of possibilities for the remainder of the weekend (Saturday night into Sunday night) mostly downwind of Cape Mendocino. A gale warning for gust >33kt for southern outer waters may need to be extended into Saturday night, based on the HREF probabilities of 80-100%. As mentioned above the dry front will through a wrench in the gears as far as forecast confidence goes; the coverage for gale gusts does not appear to be sufficient based on a gust factor of 25%. The duration is much more difficult to pin down, but all it takes is 2 hours. After frontal, passage gradients should tighten with longer duration and greater coverage for gale gusts for the later portion of the weekend downwind of Cape Mendocino. National Blend of Models (NBM) indicates northerly winds remaining sufficiently elevated to support at least small craft advisory early next week, followed by steady decrease into mid week. Granted winds around 20-25kt are forecast to persist in the lee of Cape Mendocino. DB && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 9 AM PDT Saturday for PZZ450. Small Craft Advisory until 10 AM PDT Sunday for PZZ455. Small Craft Advisory until 6 PM PDT Saturday for PZZ470. Small Craft Advisory until 3 PM PDT this afternoon for PZZ475. Gale Warning until 9 AM PDT Saturday for PZZ475. && $$ Visit us at https://www.weather.gov/eureka Follow us on Facebook and Twitter at: https://www.facebook.com/NWSEureka https://www.twitter.com/NWSEureka For forecast zone information see the forecast zone map online: https://www.weather.gov/images/eka/zonemap.png