Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
924 FXUS66 KEKA 302222 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 322 PM PDT Tue Apr 30 2024 .SYNOPSIS...Clearing skies inland will encourage more cold temperatures in interior valleys overnight. Strong northerly winds, especially along the Humboldt/Mendocino coast, will continue tonight into Wednesday. NE flow will develop mid-week to encourage warming and drying through Friday before potential returns for measurable rainfall this weekend. && .DISCUSSION...Broken altocumulus remains offshore this afternoon as a surface low weakens over the PNW, leaving the CWA mostly clear. Moist NW flow continues to moderate coastal and interior temperatures, with current observations reading in the 50`s and 60`s following cold interior morning temperatures in the upper 20`s and 30`s. As the Pacific High builds into the PNW, the pressure gradient will continue tightening along the coast and enhancing northerly winds. HREF indicates that 25-35 mph winds will stay confined to the coastal headlands of Cape Mendocino south to Point Arena, and exposed ridges in southern Humboldt, Mendocino and Lake counties through early Wednesday. A cold upper trough digging into the PNW is trending east, further minimizing precipitation impacts for NorCal. Building high pressure subsidence will continue to usher mid to upper-level dry air into the CWA, encouraging temperatures to drop in interior valleys beneath clearing skies again tonight and early Wednesday morning. A frost advisory has been issued for lower elevations in Trinity, northern Humboldt and interior Del Norte counties, with 50-75% NBM probabilities of <36 degrees. HREF anticipating scattered cloud deck north of the Cape, potentially enhancing the probability for coastal temperatures to hover around 40. Widespread and increasingly breezy offshore (NE) flow Wednesday will promote widespread warming and drying across the region, especially in the interior as an inverted trough develops in the Sac Valley. Winds are forecast to mix down and extend inland, with 25-35 mph gusts likely across Del Norte, Humboldt, Mendocino and Lake counties and exposed ridges. RH values are currently forecast to drop to 30% in interior Mendocino, Trinity and Lake Counties through the remainder of the week. NBM and mid- range models been trending cooler with <50% probabilities of temperatures >75 degrees even in Mendocino and Lake counties. Regardless, an overall warming trend is expected with highs in the upper 60`s and low 70`s as the ridge builds onshore. A broad trough axis is currently forecast to remain over the northern rockies as several shortwaves train downstream. Another round of minor rain accumulations is appearing more likely with new hi-res model guidance - HREF and NBM are in better agreement on a weak front traversing the north coast early Thursday with potential 0.05-0.20 inches in northern Humboldt and Del Norte counties. Looking ahead, long range cluster analyzes continue to suggest a major change in pattern sometime early this weekend. Members are beginning to align in the portrayal of anomalous lower heights accompanying an upper trough Saturday - Sunday. Surface low pressure moving through the region has potential to produce measurable precip, although the path of this low is still very uncertain. && .AVIATION...VFR expected today (4/30) at all forecast terminals (KACV, KCEC and KUKI). Satellite imagery is showing a layer of broken cumulus clouds approaching from the northwest over the coastal sites, yet this band of clouds is sitting at around 3000- 5000ft height and should have little impact on flight categories from a ceiling height perspective. An inversion has broken this morning allowing for northerly winds and gusts up to 25 kt at coastal terminals (KACV and KCEC) and gusts to around 20 kt at KUKI through the afternoon. As the solar heating begins to dissipate this evening, winds at all sites are forecast to die down with clear skies leading to continued VFR conditions. DS && .MARINE...Winds will continue to strengthen through Wednesday as inland California heats up creating a mesoscale thermal low pressure system driving intense northerly flow along the coast. Near gales with gusts to 35-40kt and large very steep combined seas around 10 feet are forecast for the waters just south of Cape Mendocino. These winds are strong enough to warrant a gale warning which may even be extended as time goes on and newer model guidance becomes available. Northerly wind gusts will probably increase again to near gale again Wed afternoon. Thus, gale warnings are in effect into the late afternoon/evening on Wednesday. North of Cape Mendocino, northerly winds will increase this afternoon through evening. Fresh to strong breezes with gusts to 25-30kt are expected north of Cape Mendocino this afternoon through Wednesday. These strong winds in the northern waters have caused a small craft advisory to remain in effect until late Wednesday night. DS && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Frost Advisory from 1 AM to 11 AM PDT Wednesday for CAZ102- 105>108. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 AM PDT Thursday for PZZ450-470. Gale Warning until 8 PM PDT Wednesday 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