Area Forecast Discussion
Issued by NWS Eureka, CA
FXUS66 KEKA 291212
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
512 AM PDT Wed Mar 29 2017
.SYNOPSIS...A cold front will bring a chance of rain today through
tonight. High pressure will rebuild on Thursday resulting in dry
weather that will last through Friday.
.DISCUSSION...A frontal boundary offshore has been generating mid
and high layer clouds through the night, but no rain. Rain
chances will increase today as a surface cold front approaches
from the northwest this afternoon. The highest rain amounts and
highest chances will be over Del Norte and northern Humboldt
counties. The front will push through Northwest California this
evening giving the entire forecast area a chance of receiving
measurable rain. Amounts with the front will be fairly light with
a tenth to three tenths of an inch for Del Norte and northern
Humboldt counties. Lesser amounts are anticipated elsewhere.
Southern Mendocino county may not see any measurable rain through
Additional shower activity will spike up later tonight and early
Thursday morning as a mid level shortwave trough follows in the
cooler air behind the front. Convective parameters are unfavorable
for low topped storms and hail. Snow levels will start to fall
late tonight and eventually dip down to 3500 feet to 4000 feet
early Thursday morning. An inch or less will be possible around
3500 ft. With very low snow amounts anticipated, an advisory is
Drying northerly winds and a cooler air mass will settle over the
area by Thursday afternoon and evening. We are probably going to
need another frost advisory for interior Mendocino county
Thursday night. Temperatures are expected to fall into the mid
30s in the coldest valleys.
Another forecast challenge will be the strength of the northerly
winds behind the front on Thursday and then again on Friday as
high pressure builds toward the coast. With northerly flow stacked
up from the surface to 500mb, there is a potential for breezy
(15-25mph) and locally windy (20-30mph) conditions at the coast.
The ridge will flatten out and weaken on Saturday in response to
another short-wave trough. The models continue to struggle on
what to do with this shortwave. The GFS continues to be the most
bullish with driving the shortwave through the ridge and
generating showers over the interior with daytime heating on
Sunday. The ECMWF has the trough developing farther east on
Sunday with much less potential for showers. For now will continue
to maintain fairly low shower chances considering the high level
of uncertainty. Another front should approach around mid next
week and bring a new chance of rain.
.AVIATION...VFR to MVFR conditions and light winds to calm conditions
will continue at KCEC and KACV through this morning. MVFR conditions
and moderate winds will prevail at KCEC and KACV this afternoon
and tonight as a weak cold front moves across the region. The weak
cold front will produce showers at times this afternoon and
tonight reducing ceilings and/or visibilities at KCEC and KACV.
VFR conditions will continue at KUKI through tonight. The winds
will be light to calm at KUKI through this morning. The winds will
become light this afternoon at KUKI.
.MARINE...Light winds will continue today as the high pressure ridge
maintains a weak pressure gradient across the waters. The westerly
swell will continue propagating across the waters this week. The
seas will diminish slightly today. A weak cold front will move
across the waters tonight and early Thursday. Northerly winds will
increase Thursday. Small craft advisories will continue in effect
across the outer waters through Friday afternoon due to the
continuing westerly swell this week and the increasing winds on
Thursday. A small craft advisory will continue across the northern
near shore waters through this evening due to elevated seas. A
small craft advisory will continue across the southern near shore
waters through this afternoon due to elevated seas. Another weak
cold front will move across the waters late Saturday and early
Sunday. Small craft advisories are likely to continue across the
outer waters through this weekend due to elevated winds and/or
seas. Small craft advisories are likely across the near shore
waters Saturday and Sunday.
NORTHWEST CALIFORNIA COASTAL WATERS...
Small Craft Advisory until 9 PM PDT this evening for PZZ450.
Small Craft Advisory until 3 PM PDT Friday for PZZ470-475.
Small Craft Advisory until 3 PM PDT this afternoon for PZZ455.
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