Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
612 FXUS66 KEKA 231248 AAA AFDEKA AREA FORECAST DISCUSSION...UPDATED National Weather Service Eureka CA 548 AM PDT Mon Sep 23 2024 Updated Aviation Discussion .SYNOPSIS...Warm and dry conditions will continue to gradually settle in today with weakening north winds along the coast. Heat will peak early this week with above average temperatures pushing out even along the coast. /MH && .DISCUSSION...Overall synoptic pattern continues with an anomalously amplified upper ridge dominating the area, with the axis crossing the area by tonight, allowing for a bit cooler temps for Tuesday, and considerably cooler Wednesday as an upper trough moves in, combining with a closed low off of southern California. Ensemble data reveals that the biggest climatological anomaly for surface temperatures will be over the coast (although some interior valleys could hit toasty temps above 100 degrees). Along the coast in Crescent City, there is a 50 percent chance of high temperatures between 70 and 74 degrees, with the NBM deterministic solution coming in at 68 degrees (average high is 64 degrees). With a calibrated probability of 90% chance of 68 degrees or more at KCEC, it would be a safe bet to bump this up to lower 70s, with a 75% chance of 70 or more. At Arcata, there is a 60% chance of at least 74 degrees for a high temperature. However, we are not anticipating a record breaking event (record is 82), as we stand a 0% chance of 77 degrees or more, according to NBM, as NBM also indicates that offshore flow will generally be not particularly strong and onshore breezes are advertised to kick in by late morning or early afternoon. Also wind speeds toward Del Norte County will be relatively strong, thanks mostly to an increased surface pressure gradient. Little spread in solutions reveal that confidence is high for wind gusts. Mean max wind speeds and gusts are 17 and 30 mph respectively. To get closer to the wind/wind gust solutions suggested by calibrated probabilities in the short term, HiRESWarw was used in conjunction with the mean NBM solution for period 1 afternoon winds/wind gusts over the land with wind gust multipliers near 1.55 this afternoon, giving Crescent City wind gusts pushing 30 mph from the northwest this afternoon. With the incoming upper trough, NBM indicates coastal stratus/drizzle returning Wednesday (mainly Del Norte and Humboldt Counties), with a near 100% chance of sky cover over Crescent City by around 2PM Wednesday, with a 50 percent chance of accumulating drizzle at some point in the afternoon or evening. There will also be a near 100% chance of cloudy conditions occurring with about a 20 percent chance of accumulating drizzle in Arcata (ACV), but this drops off to the south. /MH && .AVIATION...The biggest problem off the bat will be the potential for low-level wind shear this morning for KCEC. KCEC stands at least a 50 percent chance of reaching a 30 mph wind gust this afternoon, since probabilities would suggest at least a 50 Also, determining lower visibility this morning is a challenge as well this morning, as well as Tuesday morning. Probability of visibility at 5 miles or less this morning is generally topping out at 30% chance for ACV and 60% chance for CEC , with NBM deterministic visibility plummeting to near 1/2 mile at KACV at 13Z. Also, higher probabilities of lower ceilings occur for Tuesday morning. Probs for lowest visibility peak out between 12Z and 14Z this morning. Will monitor observations closely as we are entering the time period of greatest potential of plummeting visibility, according the the NBM. Visibility will be something to watch for conditions near 12Z Tuesday. KCEC stands a 50% chance of getting visibility from for less than 2 miles, for example. This forecast could get challenging for ceilings as KCEC stands a 40 percent chance of stratus at less than 500 feet. && .MARINE...Near gale conditions with occasional gusts to around 35 kt and large steep northerly wind waves near 10 feet are forecast to continue in the outer waters through today. Steep wind waves will also propagate into the inner waters today, primarily in the northern inners. Northerly conditions will ease tonight and then lay down more substantially on Tuesday and Wednesday as the thermal trough weakens and shifts inland. A series of mid period NW swell will build early next week, peaking around to around 8 ft on Wed. Potential for gale force northerlies and large steep waves over 10 feet will increase Fri-Sat. DB && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 9 AM PDT this morning for PZZ450- 455. Small Craft Advisory until 9 AM PDT Tuesday for PZZ470. Small Craft Advisory until 3 AM PDT Tuesday 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