Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

FXUS66 KEKA 232308

National Weather Service Eureka CA
308 PM PST Fri Feb 23 2018

.SYNOPSIS...A broad trough over the region will prolong an active 
weather pattern and unseasonably cool temperatures through next 
week. There will be a chance for rain on Saturday with more 
widespread rain, mountain snow, and small hail possible Sunday 
into Monday. 


.SHORT TERM...through Monday. The next upper disturbance to 
impact the region is forecast to arrive on Saturday. This feature 
will aid in generating showers, first across the coast during the 
morning, and then interior areas by midday. The greatest precip 
amounts from 0.05-0.3 inches, will occur from central Humboldt 
northward across Del Norte county. Elsewhere, precip totals will 
be less than 0.05 inch. In addition, snow levels are forecast to 
rise to around 2500 feet by afternoon. Thus, impactful snow 
accumulations are not expected due to the combination of light QPF
and rising freezing levels.

A stronger storm system, characterized by 700 mb temperatures near -
17C, and 500 mb temperatures at or below -30C, will dig south across 
NRN CA Sunday night into Monday. Snow levels near 2000 feet will be 
probable as a result, and could fall as low as 1500 feet. In 
addition, model guidance shows the digging trough yielding a 
substantial amount of deep-layer upward vertical motion augmented by 
a convective environment and westerly upslope flow. Thus, the 
potential for impactful snowfall affecting mountain travel corridors 
exists. In addition, forecast soundings and model hail guidance 
supports small hail along the coast. JG/KML


.LONG TERM...Tuesday morning through Friday. An active weather 
pattern will continue for northwest California as an area of low 
pressure sits over the western US. Cool and wet weather is 
anticipated during this time frame. The latest set of model runs are 
in better agreement about Friday/Day 7 in rainfall intensity; 
however, the placement of the storm is not the same. Confidence 
remains low on the forecast that far out. 


.AVIATION...Post-frontal VFR/Sunny conditions persisted across the
ACV, CEC and UKI air well as the entire reach of 
NW California today. A middle afternoon Visual Sat Picture showed 
a spectacular shot of snow over the region's coastal hills to the 
interior higher ranges. NWLY winds were mostly light to afternoon 
breezy at ACV and CEC especially. Clouds will begin to enter the 
area from the NW in the evening and overnight as the next weather 
disturbance approaches the Redwood Coast. North Coast air 
terminals will most likely slowly deteriorate Saturday morning as 
rain and intermittent MVFR Cigs/VIS move into the region. UKI and 
the more southern interior areas are expected to remain VFR 
through most Friday. /TA


.MARINE...N winds will continue to diminish this evening, but 
advisory level winds will continue over the S waters through 
tonight. After a period of sub-advisory winds this weekend (albeit 
just barely in some areas), N winds are forecast to increase again 
on Monday with gales possible over the S outer waters by Monday 
night. Combined seas will build up to 17 feet in the outer waters 
during this time period.

A small NW swell at around an 18 second period will gradually decay 
through the day on Sunday. A more substantial NW swell will impact 
the area through the forecast timeframe, with periods 8 to 10 
seconds through Saturday, then 12 to 14 seconds on Sunday into next 
week. /SEC/KR


NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until 6 PM PST this evening for PZZ455.

     Small Craft Advisory until 9 PM PST this evening for PZZ475.



Visit us at

Follow us on Facebook and Twitter at:

National Weather Service Glossary of Abbreviations