Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
576 FXUS66 KEKA 181138 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 438 AM PDT Wed Sep 18 2024 .SYNOPSIS...There is a chance for showers today with the highest chance across the interior areas in the afternoon. There is also a slight chance of thunderstorms. Thursday through early next week high pressure is expected to bring a warming and drying trend. Above normal temperatures are expected by the weekend. && .DISCUSSION...The upper level low is dropping south along the coast with the low center currently around 100 miles offshore. This is well defined on Water Vapor satellite. The current radar shows a line of rain showers beyond 40 miles or so from the coast this morning. The CAMS show these showers generally staying off the coast as the low continues to drop south. This afternoon the models are showing some instability developing as the low moves by the area and coincides with peak heating. There is also a slight chance for thunderstorms mainly in Mendocino and Lake counties, but also up into Trinity county and southern Humboldt. The HREF shows a 60 to 80 percent chance of CAPE exceeding 200 j/kg. The NBM prob thunder shows a 15 to 20 percent chance of thunder in Mendocino and Lake counties. The NAM soundings show the CAPE as fairly skinny. So overall not a great setup for thunderstorms, but the 15 to 20 percent from the NBM looks reasonable. Tonight may be the coldest night for many areas with temperatures dropping into the low to mid 40s. High pressure building in is warming temperatures aloft and on the higher terrain. The valleys may see some fog again, although that will be impacted by how much rain falls today. With the warming temperatures aloft and the possibility of valley fog it looks like frost will be unlikely. High pressure is expected to continue to build over the area on Thursday and strengthen through the weekend and into early next week. Highs may reach 100 in the warmer valleys by Monday and this brings areas of moderate heat risk in Mendocino and Lake counties. This is well above the normal high temperatures of the upper 80s in Ukiah for this time of year. Much of this period of time the models are showing east to northeast winds overnight and the ensemble clusters are in good agreement on this. This combined with breezy winds in the afternoon along the coast should keep coastal clouds to a minimum. The surface winds in the afternoon looks to start diminishing late in the weekend or early next week. This may allow coastal temperatures to warm into 70s. MKK && .AVIATION...MVFR conditions have been holding strong along the coast through the night and early this morning due to multiple cloud layers forming as a response to a passing cold front. These elevated ceilings should mix out quickly due to some gusty coast winds arriving around noon creating VFR conditions of the rest of the day light hours. Sunset tomorrow is showing a resurgence of marine clouds with probabilities at 25% for ceilings <500ft AGL and 50% at <2000ft AGL at KACV. KCEC shows slightly less of a chance of these conditions forming. Inland at KUKI, models are quite honestly all over the place as to how daytime heating will impact the flow of wind at the terminal. However, general consensus at this point is pointing towards westerlies <10kts building during the day with VFR conditions through the forecast period. && .MARINE...Mostly gentle, northerly winds are being observed this morning with seas at 4ft@9s. Northerly winds will increase this evening into Thursday with gusts possible above 35 kts in the outer waters by early Thursday evening. Short period seas will build in response with heights up to 9ft@7s in the far outer waters. Most models keep the steepest waves out of the inner waters except right around Cape Mendocino. Besides short period waves, the sea state will be modified through Thursday by a minor northwest, mid-period swell up to 5 feet. This complex sea state will create conditions that are hazardous for smaller crafts. With high pressure generally building over the northeastern Pacific, moderate to strong northerlies will continue for the outer waters through the week and likely into the weekend. The maximum wind speeds are currently forecasted downwind of Cape Blanco off the coast of Crescent City for the later part of this work week. The chances of steep seas pushing into the inner waters will increase Friday into Saturday as passing shortwave pushes strong winds closer to shore. /JHW && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 3 PM this afternoon to 3 PM PDT Friday for PZZ470. Small Craft Advisory from 9 PM this evening to 3 PM PDT Friday 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