Scientific Forecaster Discussion
fxus66 ksto 131100
Area forecast discussion
National Weather Service Sacramento California
300 am PST Wed Dec 13 2017
dry and mild weather into early next week with chilly nights in
clear skies across interior norcal early this morning other than a
few high clouds spilling over the West Coast ridge. A tight
easterly surface pressure gradient is resulting in some locally
gusty east winds along with very dry conditions in the northern
Sierra Nevada. Current temperatures range from the teens to lower
20s in the mountain valleys, upper 20s to upper 30s in the Central
Valley, and 40s to lower 60s across the foothill and mountain
Strong high pressure will continue the dry and mild weather
pattern through the end of the week. Little overall temperature
change expected through the end of the week with dry and mild
weather continuing under a strong subsidence inversion. Highs will
remain above average.
The ridge will weaken Friday as a short-wave trough brushes by to
the north, but precipitation chances will remain to our north
over the Pacific northwest. This system will bring some cooling
across the area but highs will remain above normal.
Chilly overnight temperatures will continue in the Central Valley
beneath shallow nocturnal radiative inversions that develop each
night with patchy frost likely.
Extended discussion (sunday through wednesday)
upper ridge over the West Coast will bring continued fair skies
with daytime temperatures well above normal for mid December.
Breezy north winds will continue Sunday but will be on the
decrease as surface gradients begin to relax. By Monday afternoon,
upper ridge axis centers over the West Coast with light northerly
gradients bringing only light or light north winds most areas.
Little change is expected on Tuesday as the upper ridge moves
slowly inland with daytime highs remaining on the order of 10
degrees above normal. Extended models show a weakening of the
upper level West Coast ridge by the middle of next week as a weak
low drops into the Pacific northwest. Models differ on timing and
strength but at this time it appears any precipitation will remain
north of the forecast area. Daytime highs will remain above
normal as well.
VFR conditions over interior norcal next 24 hours except local
MVFR/IFR conditions in br/fog southern Sacramento and northern San
Joaquin valleys through 18z today and again after 09z Thursday.
Valley winds generally below 10 knots.