FXUS66 KEKA 262011

AFDEKA



AREA FORECAST DISCUSSION

National Weather Service Eureka CA

111 PM PDT Thu Jun 26 2025



.SYNOPSIS...

A gradual warming trend is expected over the next few days with

highs pushing into the 100s for many interior valley location on

Sunday. Moderate to locally major HeatRisk will occur this

weekend, especially on Sunday. Thunderstorm chances will return

for interior areas Monday into Tuesday.



&&



.DISCUSSION...

Stratus continues to plague the coast, as it often does this time of 

year, but the afternoon breakup is bringing sunshine to most areas 

this afternoon. The stratus will once again spread to many areas 

along the coast overnight except for off the southern Humboldt 

coastline into far northern Mendocino where offshore northerly flow 

should dominate.



There are two main concerns for this week: 1) Heat for this weekend 

and 2) Thunderstorm chances Monday and Tuesday.



As for the heat, models remain consistent with a ridge building over 

the west cost this weekend allowing 1000-500 mb heights to increase 

and 850 mb temperatures to warm. On Sunday an upper low is forecast 

to strengthen off the California coast and begin to move north 

toward northwest California. A shortwave ridge on the north side of 

this low will nose itself over Northwest California leading to a 

brief window for much above normal temperatures across the interior. 

100 degree temps will be possible for many interior valley 

locations, particularly on Sunday, as 850 mb temperatures reach 

25- 30C. At this time the heat is expected to be brief and 

overnight cooling recoveries should keep the HeatRisk from 

becoming too intense. Thus, no heat advisories are anticipated at 

this point. Temperatures will cool several degrees Monday into 

Tuesday as the low moves overhead.



Speaking of this upper low, it is also the system that will pull 

moisture toward our region bringing a chance for thunderstorms, 

primarily over the mountains of Trinity County Monday and Tuesday 

afternoons. There is an approximately 15% chance that storms could

form and move northwest into Humboldt and Del Norte interiors and

additionally farther south into the Mendocino National Forest in 

Mendocino and northern Lake counties on Monday. The flow Tuesday 

will become more southerly to southwesterly keeping storms farther

east. Storms will likely be a mix of dry and wet over this time 

period with guidance showing bullseyes of QPF greater than 0.10 in

the interior but inverted V soundings near the surface. GFS 

precipitable water values are currently forecast to be around 

0.8-1" both days.



Dry conditions are likely to return by Wednesday as the low moves 

east of the area leaving zonal flow over the west coast. /RPA



&&



.AVIATION...

18Z TAFs...The marine layer greatly deepened overnight form a 

passing shortwave. A weaker, more subtle shortwave will pass 

through tonight. Soundings show the marine layer compressing some 

overnight, presenting higher chances for IFR CIGs tonight verses 

the mostly MVFR levels observed over the previous 24 hours. There 

is a chance that the weak shortwave holds the ceilings up higher 

than soundings portray, to more in the MVFR levels. There is 

enough model support and confidence to include IFR levels in the 

18Z TAfs however, with much lower confidence on LIFR levels. A 

brief window for LIFR CIGS does exist, and was included for early 

Friday morning in the TAFs. Current thinking is that subsidence on

the backside of the passing shortwave after 12Z will allow for 

further compression of the marine layer and lower CIGS. 



Overnight weakness in the northerly winds may allow for weak stratus 

intrusion around the Fort Bragg area and inland valleys south 

through Mendocino, but probabilities for IFR levels are low to 

moderate (35-45%). This are also has higher probabilities for low 

level wind shear in this described region with 30 kt north to 

northeast winds aloft through 2000 ft AGL. 



Inland terminals, including UKI will remain VFR through this 18Z TAF 

period with relatively light surface winds.  

  



Forecast Confidence: 



Chance for LIFR CIGS along the Humboldt coastal terminals Low: 

Coastal Terminals have 20-35%, mainly from 13-15Z Friday. 



Chance for IFR CIGS along the Humboldt coastal terminals Moderate to 

High: 65 to 70%



Fog probability Very Low: Coastal Terminals 5-15%.  JJW



&&



.MARINE...

Fresh to strong northerly breezes will continue across the 

southern waters, with isolated gusts over 30 kts downwind Cape 

Mendocino. Gentle to moderate northerly winds continue for the 

northern zones, ranging only up to around 15 kts through Thursday.

A building high pressure ridge and interior heating will 

strengthen a thermal trough near the coast this weekend. Northerly

winds begin to strengthen in response on Friday. Gale force gusts

over 34 kts are probable in the southern zones (61 to 73%), 

mainly fanning off of Cape Mendocino. A Gale Warning has been 

issued for this zone with the higher confidence for the strength 

and sufficient coverage of these winds Friday. 



The thermal trough will strengthen and expand north Saturday. Gale 

strength gusts 34, to up to 40 kts will develop in the northern 

zones Saturday. A Gale Watch is now up for the Northern Outer zone 

470. A narrower band of gale strength northerlies will continue to 

extend off Cape Mendocino in the southern waters on Saturday. 

Looking at modeled coverage of these winds, extension of the Gale 

Warning in the southern waters may be considered through Saturday or 

possibly further into Sunday. 



There is growing indication that the northerlies will increase by 

early next week, potentially significantly as the pressure gradient 

tightens up from building high pressure to the west. Chances for 

greater than 34kt gusts are currently moderate to high (45 to 65%) 

early through at least mid next week for much of the waters. JJW 



&&



.FIRE WEATHER...

Hot and dry conditions are expected over the next several days with 

highs pushing back over 100 degrees on Sunday. This heat will be 

followed by the potential for a mix of wet and dry thunderstorms 

primarily during the afternoons both Monday and Tuesday. Highest 

chances will be in Trinity and Siskiyou counties but there is a 

distinct possibility storms could move farther west into Humboldt

and Del Norte counties and south into the Mendocino National 

Forest on Monday. Some guidance is indicating even a slight chance

of storms early Monday morning out to coastal areas but chances 

of this are too long to include in the forecast. Dry conditions 

will likely return on Wednesday.



&&



.EKA WATCHES/WARNINGS/ADVISORIES...

CA...

None.

NORTHWEST CALIFORNIA COASTAL WATERS...

     Small Craft Advisory until 3 AM PDT Saturday for PZZ455.



     Gale Watch from Saturday afternoon through Sunday morning 

     for PZZ470.



     Small Craft Advisory until 1 PM PDT Friday for PZZ475.



     Gale Warning from 1 PM Friday to 3 AM PDT Saturday for 

     PZZ475.



&&



$$



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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For forecast zone information

see the forecast zone map online:

https://www.weather.gov/images/eka/zonemap.png

