Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
568 FXUS66 KEKA 301202 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 502 AM PDT Tue Apr 30 2024 .SYNOPSIS...Minimal amounts of cloud cover this morning, other than high altitude cirrus, give way to cool morning temperatures in the 30`s. Mild pleasant weather is expected today with colder temperatures expected overnight into Wednesday. Offshore flow and high pressure will promote warming and drying for the interior, late in the week. && .DISCUSSION...The upstream ridging pattern continues although scant amounts of integrated water vapor can be seen rounding the isobars overlaid on the satellite imagery. Most of the moisture remains north of our CWA as it interacts with shortwave features over Washington and Oregon with a surface low cascading down the coast. A similar set up is expected Thursday morning, this time with a bit more of exposure to the wrap around moisture, circulating around the offshore high. Accumulation will be isolated north of Humboldt Bay and very light with probabilities >0.05 inches around 20%. As the Pacific High builds into the PNW, the pressure gradient will continue tightening along the coast and enhancing northerly winds. HREF indicates that winds above 30 mph 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 into Wednesday morning which is looking to be the final opportunity for cold morning temperatures as HREF clears out coastal stratus in the pre dawn hours. Frost or freeze products may be prudent for Trinity, Humboldt, Mendocino and possibly Del Norte. HREF probabilities are 50-75% for temperatures <40 degrees - something to consider for sensitive vegetation. Clearing skies 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 25-30 mph gusts likely across Del Norte, Humboldt, Mendocino and Lake counties and exposed ridges. RH values currently forecast to drop to 30% in interior Mendocino, Trinity and Lake Counties. Models are still without consensus on high valley temperatures Thursday and Friday - the NBM has 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 70`s as the ridge builds onshore. Otherwise, long range cluster analysis continue to suggest a major change in pattern sometime early this weekend, but with very little model agreement at this point. As it stands, long range models suggest a deepening trough may produce measurable precip sometime between Saturday and Sunday. && .AVIATION...VFR expected today (4/30) at all forecast terminals (ACV, CEC and UKI). Satellite imagery did show some clouds over higher terrain of the interior, mainly E-SE Humboldt, western Trinity and far NW Mendocino. Based on scant reports of cloud bases, MVFR cigs are probable. These clouds should dissipate with mixing and solar insolation this morning. High and weak inversion forecast to break late this morning with gusts to 25 to 30kt at coastal terminals (KACV and KCEC) and gusts to around 20 kt at KUKI til about 03z. DB && .MARINE...Northerly winds will continue to strengthen through Wednesday. Near gales with gusts to 35-40kt and large very steep combined seas around 10 feet are forecast for the southern waters. Coverage of gale gusts are marginal at best except for a 3-6 hour window for the inner waters (pzz455) late this afternoon into early evening. Combined seas will remain elevated and borderline for a warning for seas so will continue with a marginal gale warning into Wed morning. Northerly wind gusts will probably increase again to near gale again Wed afternoon. Thus, gale headline has been extended into the afternoon and evening on Wed. 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 Wed. Seas will build up to 10 feet tonight into Wed as NW swell around 8 ft at 11 sec combines with shorter period wind waves near 6 ft at 6 sec. DB && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Freeze Warning until 11 AM PDT this morning for CAZ102- 105>108. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 1 PM this afternoon to 3 AM PDT Thursday for PZZ450-470. Small Craft Advisory until 1 PM PDT this afternoon for PZZ455-475. Gale Warning from 1 PM this afternoon to 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