Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
345 FXUS66 KEKA 092014 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 114 PM PDT Tue Sep 9 2025 .SYNOPSIS...Periods of rain and thunderstorms are forecast to continue today through Wednesday. Locally heavy rain will be possible with storms in the interior each day. Drier weather will be possible toward the end of the week, followed by another chance of rain during the weekend. && .DISCUSSION...A nearly vertically stacked area of low pressure remains off the coast this afternoon. Over the next 24 hours this is expected to move gradually to the south and east. This will keep the clouds around as well as showers and a few thunderstorms. The question will be how much sunshine and afternoon heating there will be before the showers and thunderstorms get started. Today these showers are expected to be the strongest and most widespread in Trinity and eastern Del Norte and eastern Humboldt counties. There is still some uncertainty on how much lightning there will be with these storms. The lapse rates aloft are under 6C/KM and this may limit the convection despite having around 400 j/kg of CAPE. These showers and thunderstorms are expected to produce locally heavy rain. The HREF is showing over a 70 percent chance of 1 inch in 3 hours in N. Trinity county. Today it looks like the shower and thunderstorm may be limited in Mendocino and Lake counties. Tonight there may be a few showers along the coast, but these may be fairly limited. Wednesday the showers are expected to be mainly over the inland areas. The models are showing around 500 j/kg and lapse rates remain under 6c/km in the upper levels. This makes the CAPE fairly skinny and may limit the thunderstorm potential. Locally heavy rainfall is expected again with these showers. The HREF probabilities of over 1 inch in 3 hours moves farther south into NE Mendocino county and northern Lake county. Temperatures are expected to be fairly similar to today. Thursday high pressure starts to build into the area and this will limit the potential for convection. A few showers are possible in the far eastern mountains from Trinity county down to Lake county. There may be fairly widespread fog Thursday night into Friday morning. Dry weather and clearing skies are expected Friday. For the weekend it looks like there will be another weather system bring some more rain to the area. There is still quite a bit of uncertainty on how quickly this will occurs. The GFS keeps Saturday dry and brings the rain in on Sunday. The ECMWF is slightly faster and brings in precip Saturday night. The NBM puts pops in starting Saturday afternoon, but only a fairly low chance with higher chances early Sunday. This may also bring some chances for thunder as well. MKK && .AVIATION....A closed, low-pressure, cyclonic circulation is spinning about 100 miles off the coast of Cape Mendocino. The low has brought bouts of showers and multiple cloud levels creating mostly IFR/MVFR categories and calm, variable winds. For coastal sites, model guidance shows around a 40% probability of IFR conditions (ceilings <1000ft AGL) through 03Z this evening with MVFR conditions much more likely. Tonight, ceilings are expected to drop into LIFR categories with about a 60% confidence level. Inland, capped cumulus is forming in the mountains due to the added moisture in the area. Scattered to Broken ceilings are expected inland through the day. This afternoon, there is a low, but non-zero chance of thunderstorms over NW California. Gusty outflows/inflow winds are possible, as is locally moderate to heavy rain. Turbulence is possible near all terminals due to micro-scale updraft winds. && .MARINE...As an early season low pressure center spins just offshore from the coastal waters, winds are expected to remain fairly light through the day. Isolated showers are possible through the early afternoon, yet confidence remains low timing and location. Wind waves are relatively small from the south today. A small southerly swell at 14 seconds is also being observed. Tomorrow, the low pressure center migrates south leading to the eventual pick up of northerly winds. The models are not in great agreement on how quickly this will happen but once they do, the 10 to 20 kt northerly winds are expected to continue through the work week. The strongest winds are expected to be in the southern waters directly south of Cape Mendocino. Another weather system is expected to approach the area on Saturday generating a NW swell and a calming of winds. A stronger NW swell will build in Sunday/early next week. && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... None. && $$ NOTE: The full forecast discussion is now regularly issued between 10 am/pm and 1 pm/am. Additional updates will be issued as needed. 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