Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
950 FXUS66 KEKA 012205 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 305 PM PDT Sat Jun 1 2024 .SYNOPSIS...A very late season atmospheric river will bring light rain to the North Coast Sunday afternoon through Monday morning. Heat will quickly build back in by mid next week with interior highs over 100 degrees. && .DISCUSSION...Largely seasonable weather has persisted today under the influence of weakening high pressure. Skies have been mostly clear allowing the interior to warm into the 80s. Meanwhile a gentle sea breeze has kept the coast cool mostly below 60. All that said, high clouds are apparent on satellite spreading across the area, the first sign of an approaching upper level trough. More high clouds and moisture will continue to stream into the area tomorrow as a late season atmospheric river travels south down along the coast. This stream of moisture will bring light rain all along the coast tomorrow afternoon through Monday morning. Rain will be strongest in the terrain of Del Norte where south facing slopes will bear the highest rain rates. Most likely rainfall over the 24 hour period ranges from 0.7 to 1.7 inches along the highest terrain. Even Around Humboldt Bay, 0.2 to 0.5 inches is most likely. More minor wetting rain of 0.1 to 0.2 inches is most likely in Trinity and along the Mendocino coast through early Monday afternoon with only trace amounts for the more southern interior. Despite the time of year, the system has a very winter time profile with very little surface instability, so any thunderstorms even over high terrain is very unlikely (< 5% chance). ECMWF EFI highlights how unusual such rain is for June, even for Del Norte County where it is highlighted above the 90th percentile for climatology. That said, impacts will generally be minor with debris on roadways and slipperiness from oil buildup will be the main concerns. Rain and clouds will help cool interior temperatures into the 70s for Monday, but such cool conditions will be very short lived. There is very high confidence that high pressure will rapidly build across northern California mid next week, brining the hottest temperatures of the year so far. For the valleys of Mendocino and especially Lake Counties, NBM is already showing a 60 to 80% chance of highs above 100 next Wednesday and Thursday. Though not quite record breaking, such conditions will bring the first high heat risk of the year, especially across Lake County where influence from the central valley could help keep even overnight temperatures as high as 70. /JHW && .AVIATION...18Z TAF ACV/CEC...VFR conditions prevail this afternoon with dissolved stratus. A weak shortwave trough will move through tonight to increase low clouds and some coastal drizzle. Ceilings will generally lower tonight to MVFR levels. CEC will have the best shot of light drizzle, and these conditions would lead to lower VIS and perhaps dips into LIFR (25%) earlier. A deepening marine layer should lead to higher CIGS. Rainfall chances will increase throughout the day Sunday as a late season Pacific low pressure system nears the region. UKI....Firmly VFR with NW wind gusts to ease this evening. A jet of NW winds aloft of up to 35 kts will create low level wind shear through 10Z Sunday. Stratus will build in from the west into the high terrain with deepening from a weak shortwave trough, but soundings indicate the depth will not be enough to near the valley. /JJW && .MARINE...Northerly winds and seas have eased in the northern waters, and are also quickly subsiding in the souther zones. On Sunday, seas will drop range from 3 to 5 feet with the arrival of a small, period NW swell at around 3-4 ft at 10 seconds. Winds will be light, up to 12 kts and split in flow. Southerly winds will increase Sunday night through Monday morning ahead of a trough. On Monday, a slightly larger, mid period NW swell will move in, building to around 8 ft at 10 seconds early Tuesday morning. Light, split wind flow will transition to light northerly winds Monday. These winds will slowly increase in the southerly zones, initially south of the cape. Tuesday, the NW swell will hold in size, then slowly lowering late in the day. A larger reinforcing swell then move in. Northerly winds in the southern waters will further increase, exceeding 22 kts south of the cape in the afternoon. On Wednesday, a seasonably large, longer period WNW swell (300 degrees) will build in, currently forecast up to around 12 ft at 14 seconds. Northerly winds will be on the increase throughout the day, with gale conditions probable by late Wednesday. /JJW && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Excessive Heat Watch from Tuesday morning through Thursday evening for CAZ114-115. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 11 PM PDT this evening for PZZ455-475. && $$ 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