Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Eureka California
418 am PST Wednesday Mar 4 2015
Synopsis...high pressure will build over northwest California
this week bringing dry conditions and a gradual warmup through
this coming weekend. However overnight low temperatures will
remain cool with frost developing in some areas of northwest
California through late week.
Discussion...high pressure continues to build over the West Coast
bringing dry conditions and mostly clear skies. Clearer skies than
last night have allowed temperatures to fall more readily tonight as
was anticipated. Thus the frost advisories and freeze warnings
remain on track. A couple more cool nights are anticipated with
strong low level inversions likely to develop beneath the
building ridge of high pressure. Temperatures will slowly moderate
but will still fall into the lower to middle 30s across the interior
valleys of Mendocino County. Thus additional frost/freeze
headlines will be likely for the interior Mendocino County zone
tonight and possibly Thursday night. Near the coast temperatures
should moderate enough that frost advisories will not be required
but still some patchy frost will be possible in protected valley
locations of the Redwood coast and Mendocino coast zones tonight.
The day shift will take another close look at the low temperatures
for tonight near the coast to determine if temperatures need to be
lowered and headlines issued.
With the ridge building over the region...thickness values will
increase and 850 mb temperatures will warm to over 10c by this
weekend. This should allow for decent warming during the afternoon
hours...especially across the interior where Mendocino County valley
locations may top out in the middle to upper 70s f this weekend.
Model guidance indicates that the thermal trough will never make a
real push off the coast allowing coastal areas to warm
..however some southerly downslope flow on Thursday may allow
the Humboldt Bay area to warm above guidance into the middle 60s
before the marine layer returns bringing the potential for some
low clouds on and off into the weekend.
Both the GFS and European model (ecmwf) models indicate a return to cooler and wetter
conditions is in store for the 7-10 day period. In fact...likely
chances for precipitation have been introduced to the forecast for
next Thursday. However it appears that moisture will be limited
restricting rainfall totals. /Rpa
Aviation...other than some very localized early morning Interior
Valley fog...all areas including the coast should remain VFR through
the next taf cycle. /Kml
Marine...winds will continue to ease with the weakening pressure
gradient and responding seas will gradually subside through the day
today. Small craft advisories will persist across the outer waters
as steep seas will be a little slower to subside. Light to moderate
winds will become southerly on Thursday as a ridge of high pressure
currently over the eastern Pacific Ocean shifts over the Pacific
northwest. Then northerly flow will return on Friday as a thermal
trough sets up along the California coast. Winds will increase
slightly over the weekend as the thermal trough interacts with the
shifting ridge yet no advisories are anticipated at this point in
time since conditions look marginal at best. Seas will be relatively
low through the weekend as compared to the past few days. Short
period seas will develop with the increasing weekend winds while two
opposing swell systems, one from the northwest and the other out of the S,
will propagate the waters through early next week. /Kml
frost advisory until 7 am PST this morning for caz001-002.
Freeze warning until 8 am PST this morning for caz076.
Northwest California coastal waters...
Small Craft Advisory until 9 am PST this morning for pzz450-455.
Small Craft Advisory until 9 PM PST this evening for pzz470.
Small Craft Advisory until 3 PM PST this afternoon for pzz475.
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