Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Eureka California
500 am PDT Sat Jul 12 2014

Synopsis...a weak trough aloft will bring a slight chance of
thunderstorms over interior northwest California mountains each
afternoon through the weekend. Coastal areas of northwest California
will continue to see night and morning clouds and fog with some
afternoon clearing through the weekend.


Discussion...satellite showed stratus extending well into the
coastal river valleys early this morning. The stratus will most
likely clear out in the river valleys by this afternoon but hang
around at the coast all day. Sunday is looking very similar. High
pressure will build toward the coast early next week and bring
better opportunities for clearing to the coast.

Vapor channel showed a complex upper trough just outside 130w
this moring. A couple of shortwaves or vorts in SW flow will clip
the area today through Sunday and perhaps trigger a few late day
thunderstorms over the Siskiyou Mountains near del Norte County.
Weak instability will linger around northeast del Norte County
and around The Horn of Trinity on Sunday. Thus isolated thunderstorms will
once again be possible...though middle level moisture looks very
sparse. On Monday the models indicate the possibility for
convection as high pressure over the desert SW builds northwest and flow
aloft GOES southeast late in the day. The middle levels look too
dry and moisture should hold off until Tuesday.

Temperatures over inland areas will slowly warm up this weekend
into early next week as high pressure aloft over the desert SW
expands northwest. Southeast flow aloft will likely bring middle level moisture
and clouds into the forecast area around middle week which should
cool temperatures down if it stays mostly cloudy all day. Models
indicate instability as well as convective we added
a slight chance of showers and thunderstorms to the forecast for mainly
Trinity County Tue-Thu. For Friday and Sat...GFS and European model (ecmwf) indicate
cooling as another trough approaches the region. The GFS was much
stronger with this trough. I stayed close to climatology precipitation chances
and climatology sky cover and the consensus for temperatures.


Aviation...12z satellite imagery and surface observations indicate
another early morning of coastal stratus with conditions ranging
from IFR to LIFR. Coastal areas south of the cape should have the
best chance for scattering out this afternoon otherwise expect
another a mostly cloudy day along the northwest California coast. Interior
areas should remain mostly clear except for a slight chance of
thunderstorms across far eastern del Norte County. Expect coastal
stratus to fill back in later tonight bringing ceilings down to IFR
and LIFR and interior airfields to be mostly VFR. /Kml


Marine...surface low pressure centered off of the northwest California
coast will maintain a weak pressure gradient today and consequently,
marine conditions will be low. Light to gentle winds will continue
today with seas hovering around 3 to 4 feet. Northerly conditions
will begin to build on Sunday as the Pacific Ridge and California
thermal trough strengthen the pressure gradient across the coastal
waters. Expect winds and seas to increase to small craft conditions
by late Sunday and potentially near gales by Monday but will hold
off on issuing any products at this time. Conditions will ease
slightly by the middle of next week as another surface low develops
off of the California coast and pushes higher winds farther
offshore. Otherwise fresh winds and steeper seas will persist
through late in the week. /Kml


Fire weather...isolated thunderstorms will be possible late this
afternoon over northeastern del Norte County near Siskiyou County.
Though middle-level moisture is limited...the GFS does show
increasing 925-850mb relative humidity late today into tonight as a short wave trough
traverses toward the region from the southwest. Boundary layer
convective available potential energy and lifted indices look sufficient to support isolated
storms. SW flow will probably push towering cumulus to the
northeast and limit the lightning threat in zone 203. Not too sure
about the Trinity and Scott mountains as the atmosphere looks too
dry and stable for thunderstorms in zone 283 today. Tonight the GFS
indicates possible convection sparking up as a short wave trough clips
del Norte County. The coverage may need to be expanded if storms
develop during the night-time hours. Instability and moisture
looks to creep a little farther southeastward on Sunday as the short wave
swings by to the north. Any lightning strikes in zone 283 on
Sunday will be on the periphery near Siskiyou County around the
Trinity and Scott mountains next week is looking really interesting.
The models have been trending toward more thunderstorm chances creeping
back into the picture next week. Timing...coverage...duration and
frequency of activity is for now will broadbrush a
slight chance of thunderstorms in mainly zones 283 and 277 Tuesday through
Thursday. Coverage may need to be increased as the event unfolds.


Eka watches/warnings/advisories...
Northwest California coastal waters...none.


Visit US at http://www.Weather.Gov/Eureka

Follow US on facebook and twitter at:

National Weather Service Glossary of Abbreviations