Area Forecast Discussion
Issued by NWS Eureka, CA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34
000
FXUS66 KEKA 231123
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
423 AM PDT Thu Mar 23 2017

.SYNOPSIS...
Gusty winds are likely early this evening through Friday morning
across portions of Humboldt and Del Norte counties. Widespread
rainfall will overspread the region as well during this time, some
of which may be locally heavy at times. A more showery pattern will
commence Friday night through early Sunday, before another storm
system potentially brings more gusty winds and widespread rainfall
to the region in the Sunday through Monday time frame.

&&

.DISCUSSION...
.SHORT TERM...
(Today through Friday)

Enjoy the dry weather today, as it`ll quickly come to an end by
tonight. Early this morning, temperatures have dropped below 37
degrees (the temperature at which frost typically starts to form) at
a few locations of Mendocino County, but so far it`s been pretty
limited. Still, with a few more hours before sunrise and mainly
clear skies dominating the county, will leave the Frost Advisory in
tact through its 8 AM expiration time.

Otherwise, a strong storm system will continue to develop as it
passes by to our northwest. A trailing cold front will approach the
Redwood Coast this evening and cross the area overnight. Ahead of
this feature, a strong 925mb jet in the 55 to 60 knot range will
develop across the outer waters and coastal ridges, with gusts to 55
mph a good bet for coastal Del Norte County. Slightly higher gusts
near 65 mph are also a good bet for portions of the Kings Range and
for interior Humboldt and Del Norte counties. Farther south along
coastal Mendocino County, the latest 06z data also continues to show
a slight upward trend in not only the low-level jet wind speeds but
how far south it extends, with the latest data showing winds of 40
to 45 knots at this level. As such, we were tempted to extend the
advisory down to this area but will defer to the day shift for a
possible late morning update, so we can look at some of the daytime
hi-resolution data and satellite imagery, to ensure enough breaks
will be present in the approaching cloud cover. This could be a
pivotal point as increased insolation would enhance downward
momentum transfer potential via increased mixing.

As if that wasn`t enough, the real "fun" could be with the
approaching cold front, as widespread rainfall develops along and
behind it, some of which may be heavy at times. As you know, the
soils remain saturated to a large extent, and although the heavy
rainfall could result in more mudslides in itself, the prolonged wind
torque on the trees near and west of the coastal ridges could only
exacerbate this concern. With several area roads currently under
construction/repair from this winter, you may want to keep updated
on road conditions if you have any travel plans over the next few
days.

.LONG TERM...
(Friday evening through Wednesday)

Things will start to wind down in the Friday evening through
Saturday night time frame, as precipitation becomes more showery in
nature while decreasing in areal coverage. By Saturday night into
Sunday morning, little if any precipitation should be present
across the forecast area. However, as you might have guessed, this
will be another short-lived "dry spell", as another storm system
will be making in-roads to our neck of the woods by Sunday evening.
A storm system approaching the Pacific Northwest coast will send a
trailing cold front eastward across the area Sunday night/Monday
morning.

Similar to this first system, another strong (albeit slightly
weaker) low-level jet will develop, with current indications showing
925mb winds around 50 knots from Cape Mendocino northward. Should
this solution verify, gusty winds likely at advisory levels would
affect portions of Humboldt and Del Norte counties once again.
Widespread rainfall, some of it of moderate to locally heavy
intensity would develop along the front as it treks eastward.

The weather pattern will start to calm down by the middle of next
week, as an area of high pressure at the surface and aloft develops
across the eastern Pacific, while attempting to build eastward
across Northwestern california. As it stands now, Mendocino County
would see an extended period of dry weather, with perhaps a few
showers developing north of there. We`ll see if this "drier theme"
continues in the numerical forecasts as we head through the weekend.
/PD

&&

.AVIATION...
VFR conditions should continue for majority of the
day before a frontal boundary brings deteriorating conditions as
widespread rain impacts northwest California late this afternoon.
Rain will continue through most of the night into early Friday
morning as the front tracks to the southeast. Expect MVFR conditions
with the onset of the rain later today with periods of IFR. In
addition to rain, south winds will increase through the day bringing
strong gusts this evening with the strongest gusts across exposed
ridgetops. Low level wind shear will also be a concern with the
frontal passage this evening. /kml

&&

.MARINE...
The gale warnings and small craft advisory remain in
effect for late this afternoon as a robust frontal boundary tightens
the pressure gradient across the coastal waters. There was, however,
a last minute change to hoist a new gale warning for the northern
inner waters. This system may be strong enough to bring some
isolated storm force gusts across the northern outer waters thus
more frequent gale force gusts nearshore seems plausible with the
well mixed airmass. The strongest winds nearshore will primarily be
located near Point Saint George, Cape Mendocino, and Point Arena
with occasional gale force gusts expected southward of the Cape.
After this round of potent southerlies, winds will steadily decrease
behind the front on Friday as surface ridging shifts over the region
and turns winds out of the north by Saturday. This will be
shortlived as models show another front bringing fresh winds to near
gales for Sunday.

Wind driven seas will become large and steep with the frontal
passage this afternoon and evening. As steep waves steadily subside
on Friday, a westerly swell will enter the waters and decay through
the weekend. Steep seas will make a comeback with the late-week
front. /kml

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory from 5 PM this afternoon to 5 AM PDT Friday for
     CAZ101-102-104>106.

     Frost Advisory until 8 AM PDT this morning for CAZ110-111.

NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory from noon today to 3 PM PDT this afternoon
     for PZZ450.

     Gale Warning from 3 PM this afternoon to 3 AM PDT Friday for
     PZZ450-470-475.

     Small Craft Advisory from noon today to 9 AM PDT Friday for
     PZZ455.

     Small Craft Advisory from 9 AM this morning to 3 PM PDT this
     afternoon for PZZ470-475.

&&

$$

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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.