Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
193 FXUS66 KEKA 191208 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 508 AM PDT Thu Sep 19 2024 .SYNOPSIS...High pressure is building over the area. This will strengthen through the weekend and into early next week bringing above normal temperatures. Some of the warmer valleys may see temperatures around 100 Sunday and Monday. Offshore flow strengthens over the weekend bringing sunny skies and warm temperatures to the coast. && .DISCUSSION...High pressure is building over the area as the upper level pushes to the southeast. The marine layer is already shallow this morning, only around 1500 feet or so. This will likely clear out by this afternoon, but models indicate it may take it`s time and it may not occur until early afternoon.This afternoon inland temperatures are expected to warm by nearly 10 degrees over yesterday with highs in the upper 80s expected. Friday and Saturday most inland areas continue to see some warming with highs getting into the low to mid 90s by Saturday. Northeast winds overnight will help keep much of the coastal areas clear. Breezy northwest winds each afternoon will likely keep temperatures from warming much more than the mid 60s. Sunday and Monday inland temperatures continue to warm with the warmer valleys seeing temperatures near 100. The winds at the coast may be slightly weaker and this could allow temperatures to warm into the 70s, although confidence is low on this. The main area of uncertainty in this forecast is how quickly the ridge breaks down. Tuesday most of the models agree that the ridge axis will have just moved onshore. This will likely change the wind patterns enough to bring a return of stratus and fog to the coast. The ensemble clusters struggle more with how quickly the ridge will break down. One of the clusters keeps a strong ridge over the area while others start to break it down. One cluster has a trough moving onshore by Wednesday afternoon and bringing some rain as early as Thursday. Needless to say this would also bring some differences in temperatures. MKK && .AVIATION...A substantial layer of low ceiling, foggy marine stratus has established itself all along the NW California coast and coastal river valleys. Visibilities and ceilings are showing LIFR conditions at the coastal terminals and should remain as such for most of the morning. NBM Model guidance currently is showing a drop in the probability of stratus <500ft AGL & <1000ft AGL near KACV from 75%(<500ft AGL)& 90%(<1000ft AGL) at 1800Z to 25%(<500ft AGL) & 50% (<1000ft AGL) at 1900Z. These probabilities tell that the low stratus will mostly likely rise up above LIFR conditions, yet is not necessarily going to dissipate entirely from the terminal space during the day. This evening, overcast skies/fog and its associated LIFR conditions are forecasted to return to the coastal terminals. In addition, a southerly wind reversal could lead to some wind shear at the marine layer/free atmosphere boundary. KUKI shows its similar pattern of daytime winds from the W/NW before dying off at or around sunset (0330Z). Some extremely high- resolution models suggest breezy winds along the mountain ridges inland, which could possibly mix down into the terminal space, but confidence remains low on this occurring. No cloud layers are forecast to develop over the inland areas, besides in the coastal river valleys, 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 the outer waters at least through tomorrow at 3pm. However, tomorrow afternoon/evening there is substantially model guidance agreement of a strong low-level jet (winds at 925mb 40-50kts) building over our waters from tomorrow evening 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, or even upgraded, marine hazard statement for Friday evening into the weekend. More confidence on these details will be available within the next 24hrs as more models initialize and extend through this time period of interest. && .Fire Weather...Offshore flow (NE Winds) is ongoing this morning and is expected to continue for the next several days. It looks like it will be the strongest on Saturday morning with winds of 15 to 25 mph and gusts to 35 mph on the most exposed areas of Del Norte county. Winds will be lighter farther south and east, although there is some uncertainty on how much lighter. This will also bring drier air to the coastal mountains and recoveries are only expected to be around 40 percent on the higher terrain. This combination will bring elevated fire weather conditions so will add a headline to the fire weather forecast for this in zones 203 and 204. Late in the weekend and early next week it looks like winds will diminish some, although RH recoveries will remain poor. MKK && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 PM PDT Friday for PZZ470-475. && $$ 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