Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 041102

National Weather Service Eureka CA
302 AM PST Sun Dec 4 2016

.SYNOPSIS...A broad/flat upper ridge was located over the NERN
Pacific Sunday morning. To the north of the ridge, an upper low
was centered over the NERN Gulf of Alaska. The upper ridge is
expected to yield a storm track oriented from the NW to the SE
through midweek, which will favor a significant cold air
intrusion during the early portions of the upcoming work week. The
pattern then shifts to a W-E storm track during the second half of
the week, which will favor warmer and wetter conditions for NWRN


.DISCUSSION (SUN-TUE)...A shortwave impulse is forecast to eject
SEWD from the previously mentioned upper low positioned over the
Gulf of Alaska; moving onshore across OR/WA Sunday afternoon.
Given this feature is well north of the CWA, relatively light
precipitation is expected for NWRN CA, primarily focused along a
surface frontal boundary moving SEWD across the region this
afternoon and evening.

Of greater significance will be a deep-layer of anomalously cold
temperatures spreading SSE behind the front. This will favor
overnight lows near freezing for interior valleys Monday and
Tuesday morning, particularly if cloud cover is less than
currently forecast. As a result, frost advisories and/or a freeze
warning may need to be issued during future shifts. In addition,
snow levels will fall to around 1500-2500 feet over the northern
half of the CWA. However, a relatively dry airmass and weak
forcing for ascent is expected to preclude anything more than an
inch or two of snow accumulation.

.EXTENDED DISCUSSION (WED-SUN)...An exiting trough will
allow a brief break between weather systems on Wed however residual cool
air will likely promote cold mornings..especially over the interior
valleys where one or two clear nights are expected. A nice day looks
on tap for the coast on wed as offshore flow associated with the short
wave ridge of high pressure occurs. By thursday heights and thickness`s
begin to fall as another pacific low approaches the pacnw coast.  This
feature does not look especially strong in terms of wind but should provide
a decent dose of widespread rain.  The flow will be generally out of the west
and fairly warm thus snow levels look to remain above 5000 ft with the initial
cold front.  GFS is the most aggressive model in terms of expected rain
amounts...showing 1-2 inches possible along the coast and higher amounts
across rain prone areas through thurs night. Once the front goes through a
few showers are possible on friday with lower snow levels. Forecast models
still in flux for how sat and sun will be.  Does appear some type of upper
short waves will move across the area next weekend so cannot rule out
additional chances of precip for that time period but at this point nothing
major for next weekend.


.AVIATION...Conditions will deteriorate at the coastal terminals
today as a weak front from Oregon slides southward. For the most
part, VFR to MVFR ceilings and visibilities are anticipated. Light
rain and misty air conditions will also result in periods of IFR.
The brief IFR will initially develop at KCEC by late morning or
early afternoon, and then at KACV this afternoon through early
evening as an onshore flow develops. At KUKI, VFR will prevail
today, however MVFR ceilings should develop by early Mon morning
as low clouds push over the coastal range.


.MARINE...Long period swell hit 17-21 ft yesterday afternoon and
evening. Large long period NW swell will subside today through Mon,
but remain high enough to satisfy our criteria for a small craft
advisory, 10 FEET or ABOVE. We probably are not going to see another
long period swell that will require a high surf advisory all this
week. There will be a couple of tiny long period groups from the
west and south that may pose a slight risk for sneaker waves all
week. The next significant ramp up is expected mid to late next
week. The latest run from the GFS continues to be hot and heavy with
the winds. Steep southerly waves around 10 ft or higher are likely.
The GFS also has much more westerly winds with the surface low. This
blast of westerly winds offshore will result in another significant
WNW swell toward the latter portion of the week. The periods will be
squared with the wave heights; 13-15 FT at 13-15 seconds that is.


NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until 3 AM PST Tuesday for PZZ450-455-470-



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