Weather Service Report


821 
FXUS66 KEKA 222144
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
244 PM PDT Wed Sep 22 2021

.SYNOPSIS...Seasonable temperatures arrived with the passing of an 
upper trough. Offshore flow will develop tonight and tomorrow 
night. Temperatures will warm through the end of the week as the 
North Pacific High noses in from the southwest. No precipitation 
is expected through the weekend while the ridge flattens and 
temperatures moderate back down. 


&&

.DISCUSSION...Some morning shallow fog clung along the immediate 
coast today, eventually splashing in and out of the coast with the 
northwest winds before peeling down from the north. An upper trough 
passed by today and allowed the high temperatures to drop 
significantly along the coast, upwards of 20 degrees from what 
was observed yesterday. Offshore winds will develop overnight, 
creating some brief fire concerns. See the fire discussion below. 
The North Pacific High will quickly begin nosing in overnight 
behind the trough. Temperatures will warm in response, though 
coastal temperatures will be moderated by the westerly flow and 
perhaps some coastal stratus. Winds will be lighter Friday and may
have a better chance of warming at the coast if the stratus drys 
out. 

The weekend will feature continued dry and quiet weather, while the 
upper ridge 'flattens' and begins to give way to some gradual 
cooling heading into next week. There continues to be signs in the 
ensemble and deterministic guidance of some rain arriving as early 
as Monday, or possibly Tuesday. Ensemble guidance is homing in on 
some solid chances for at least a wetting rain for that time.
Probabilities increase northward for areas starting from Cape 
Mendocino. There are probabilities for more, but still some spotty
individual members in there, especially GFS. There are hints this
could mark a pattern change more favorable for at least some more
general 'troughiness'.


&&

.AVIATION...Waves of shallow moist air has been rolling onto the
coast today resulting in occasional LIFR in fog at the coastal 
terminals. Surface northerlies offshore will increase this evening 
in the wake of a decaying front, however moist air will likely get 
trapped around Humboldt Bay and Eel Delta, resulting in low clouds 
and possibly fog building back to KACV. Low level wind profiles 
indicate northeast winds just above the ground at both KACV and KCEC 
this evening which may limit the stratus growth and expansion 
especially up to KCEC. Otherwise, VFR conditions are expected to 
prevail across the interior. Smoke and haze from fires has been thin 
and not impactful at this point.  


&&

.MARINE...Northerlies are expected to increase and reach small
craft advisory (21-25kt) this afternoon/early evening across mainly 
the outer waters and near prominent headlands. Northerlies will 
persist through the day on Thu, then ease on Friday. Southerlies 
should also develop for the inner waters on Friday as steep short 
period northerly waves slowly diminish. A series of small (6ft or 
less) mid-period NW swells are forecast to spread into the waters 
through the forecast period as well. Long-range models hint at a 
trough deepening over the NEPAC early next week, possibly sending us 
a larger NW swell around Tue-Wed next week. 


&&

.FIRE WEATHER...RH recoveries have improved after an onshore flow 
push as an upper level trough passed through. Westerly up-valley 
winds picked up this afternoon. Drying northeast winds will pick up 
overnight. Winds will gust to around 20 to very isolated 30 mph over 
the ridges. The southern zones of 264 and 277 are currently 
headlined for the resulting low RH values and locally critical fire 
weather conditions. These winds will ease heading into Thursday 
night and Friday. Dry weather will continue through the weekend, but 
with a gradual cooling trend and improved RH recoveries.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
     Small Craft Advisory until 3 AM PDT Friday for PZZ470-475.

&&

$$

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Western Regional Climate Center, wrcc@dri.edu