Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
856 FXUS66 KEKA 201446 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 512 AM PDT Fri Sep 20 2024 .SYNOPSIS...Key messages include stronger north/northwest wind over the waters today and breezy conditions along the coast. Gradual warming over the weekend and into early next work week, then turning cooler Wednesday. && .DISCUSSION... Ensembles reveal an upper trough being edged out by an approaching ridge from the west northwest. NBM forecasts a most likely scenario of maximum wind gusts of 25 to 35 mph from the northwest along much of the coast. Calibrated NBM probabilities give about a 50 percent chance of wind gusts topping 25 mph at Arcata and 100 percent chance at Crescent City, with strongest peak gusts more likely centered around 3-5 PM PDT this afternoon. May want to keep an eye on Crescent City as the chance of the peak wind gusts over 35 mph there are 75%, dropping to about 5% chance of reaching gusts of 40 mph at Crescent City. Overall high confidence with these peak wind gust forecasts as ensemble solutions are relatively close to each other.. Looks rather warm Monday and Tuesday, especially along the coast, relatively and climatologically speaking. Comparing ensembles to climatology, Monday and Tuesday look rather warm, and especially for the coast (relatively speaking, considering climatology), and Tuesday in particular stands out between the two days. At Arcata, we stand a 60% chance of reaching 70 degrees or more and 80% chance of hitting 75 or more for Tuesday (mean ensemble solutions give a stronger indication of offshore flow for Tuesday. Look for a noticeable cooling for Wednesday with highs on the coast closer to normal in the 60s and interior valley topping out in the 80s to around 90. The cooler weather will keep going for the work week. /MH && .AVIATION...A thin layer of low ceiling, foggy marine stratus has established itself right along the NW California coast and within the coastal river valleys. Degraded visibilities and low ceilings are showing LIFR conditions at the coastal terminals and should remain as such for most of the morning. NBM model guidance is currently showing a drop in the probability of stratus through the day with a 12% chance of ceilings <500ft AGL and 30% chance of any cloud coverage at all sticking around by 2200Z at KACV. These probabilities tell that the coastal clouds will most likely dissipate entirely from the terminal spaces during the day. HREF low cloud coverage probabilities also supports this scenario. This evening, elevated winds will flow offshore, possibly keeping the coastal terminals clear of stratus. However, there is a 45% chance that low clouds will return to KACV by the early morning hours of tomorrow. In addition, notable wind shear at the marine layer/free atmosphere boundary is forecasted due to both directional and speed differences between layers at KACV and KCEC. KUKI shows its similar pattern of daytime winds from the W/NW before dying off at or around sunset (0200Z). Some extremely high- resolution models suggest breezy winds (10-15kts) along the mountain ridges inland, which could possibly mix down into the terminal space creating the increasing in the forecast for daytime winds our of the NW. No cloud layers are forecast to develop over the inland areas, leading to VFR conditions inland. && .MARINE...Strong northerly winds (>20kts) are forecast to remain in the outer waters today. These winds are creating steep wind waves and conditions that warrant a small craft advisory in all the coastal waters before upgrading to a Gale Warning at 9am this morning. This Gale warning is a response to substantially model guidance agreement of a low-level jet (winds at 925mb 40-50kts) building over our waters from this morning through Saturday afternoon. These LLJ winds have a good chance to mix down to the ocean surface with high-resolution models showing sustained northerly winds speeds reaching just under 35kts & gusts possible up to 40kts. Wind waves in the outer waters for this time period are forecast to ramp up as well due to surface winds with certain areas currently forecasted to max out around 14ft@10s. These windy and wavy conditions could warrant an extended marine hazard statement for Saturday morning into the weekend. More confidence on these details will be available within the next 12-24hrs as observations verify the true strength of the winds allowing more high resolution models to initialize and extend through this time period of interest. && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 9 PM PDT this evening for PZZ450- 475. Hazardous Seas Watch from this evening through Saturday morning for PZZ450. Small Craft Advisory until 9 AM PDT Saturday for PZZ455. Small Craft Advisory until 9 AM PDT this morning for PZZ470. Gale Warning from 9 AM this morning to 9 AM PDT Saturday for PZZ470. Gale Watch from this evening through Saturday morning 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