Weather Service Report


675 
FXUS66 KEKA 232307
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
407 PM PDT Tue May 23 2017

.SYNOPSIS...
Warm temperatures will continue on Wednesday followed by a
gradual fall back to normal values late in the work week. Coastal
areas will remain more seasonal with morning clouds and afternoon
sunshine. Pop up showers will be possible over the mountainous 
interior the next few afternoons with a slight chance for 
thunderstorms on Wednesday. 

&&

.DISCUSSION...
An upper level ridge is current centered over Northern California 
leaving much of northwest California under clear skies, except for 
the normal stratus along the coast. Stratus/fog has been 
particularly persistent from the mouth of the Eel River and south 
along the Mendocino County coast with a well defined eddy in place 
south of Cape Mendocino. This eddy has weakened over the last few 
hours as northerly winds increase over the coastal waters, but it 
seems unlikely that the southern Humboldt and Mendocino immediate 
coasts will see much clearing at all this afternoon. Stratus will 
likely reform overnight along the rest of the Humboldt and Del Norte 
coastlines only to dissipate more quickly on Wednesday as gales 
intensify over the coastal waters.

Temperatures will decrease significantly on Wednesday as the ridge 
flattens and a shortwave trough moves through the Pacific Northwest. 
Some interior areas will see temperatures fall 10 to 15 degrees as 
compared to today, followed by another potentially 10 degree drop on 
Thursday bringing interior areas back to normal or slightly below 
normal. The upper level ridge will amplify again late in the week 
into this weekend bringing a gradual warmup back to around 10 
degrees above normal early next week. As the shortwave moves inland 
on Wednesday, the cooling aloft may be just enough to trigger a few 
showers or thunderstorms during the afternoon and evening over 
eastern Trinity County.

In addition to the gradual warmup, upper level shortwaves will move 
over the area from the southwest on the eastern periphery of a deep 
trough. This, in combination with the warm temperatures across the 
interior, will support the potential for mountain convection each 
afternoon beginning Saturday through mid next week. There is 
potential that one or two of these days could have scattered 
afternoon showers and storms depending on the timing of the 
shortwaves moving overhead. /RPA

&&

.AVIATION...
Overnight, stratus brought IFR-LIFR conditions to most of the 
airports/airfields near the the immediate coast. By Noon, only 
lingering pockets of stratus continued from Humboldt Bay to Point 
Saint George/Crescent City. However, the entire shoreline of 
Mendocino remained under a blanket of marines clouds as a south 
surge moved up its coast then around Cape Mendocino and sort of 
blended with the stratus north of the Cape. By mid afternoon the 
stratus surge was affecting Humboldt Bay and heading to ACV. The 
surge will allow for another eve/night of IFR CIGS. Inland areas 
will generally remain hot and sunny through the period, with a weak 
threat of convection over Trinity tomorrow. There is also the 
possibility that low clouds may edge near the UKI valley from the 
south on Wednesday.

&&

.MARINE...
Northerly winds will increase substantially tonight into Wednesday as 
high pressure over the eastern Pacific interacts with a strong 
thermal trough over interior California. Model guidance is unanimous 
in producing sustained gale force winds beyond 10 nm north of Cape 
Mendocino and gusts to gale force into the northern inner waters and 
southern outer waters. The gales and potentially a few storm force 
gusts will also produce very steep seas that will propagate into the 
northern inner waters and extreme northern portion of the southern 
waters zone near Cape Mendocino. With seas exceeding hazardous seas 
criteria north of Cape Mendocino and gusts expected to reach near 
gale force, opted to raise a gale warning for the northern inner 
waters. Seas will likely peak between 15 and 20 feet in the outer 
waters and around 10 to 15 feet in the northern inner waters beyond 
5 nm Wednesday into Wednesday evening. The models continue to 
indicate that the majority of the inner waters zone south of Cape 
Mendocino will not experience even small craft conditions, so no 
headlines have been issued.

Winds and seas will decrease through the day Thursday into Thursday 
night as the thermal trough weakens. Additionally, high pressure 
over the eastern Pacific will shift farther north as an upper trough 
approaches. This should result in a period of very light winds late 
Friday into Saturday with coastal areas experiencing light 
southerlies. /RPA

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...
    Small Craft Advisory until 3 AM PDT Wednesday for PZZ450-475.

     Gale Warning from 3 AM Wednesday to 3 AM PDT Thursday for PZZ450.

     Small Craft Advisory until 9 PM PDT this evening for PZZ470.

     Gale Warning from 9 PM this evening to 6 PM PDT Thursday for 
     PZZ470.

     Gale Warning from 3 AM Wednesday to noon PDT Thursday for PZZ475.

&&

$$

Visit us at http://www.weather.gov/eureka

Follow us on Facebook and Twitter at:
http://www.facebook.com/NWSEureka
http://www.twitter.com/nwseureka

For forecast zone information
see the forecast zone map online:
http://www.weather.gov/eureka/zonemap.png

Return to Home page


Western Regional Climate Center, wrcc@dri.edu