Scientific Forecaster Discussion
fxus66 ksto 191045
Area forecast discussion
National Weather Service Sacramento California
345 am PDT Tue Sep 19 2017
cooler weather this week with a chance of showers into Friday.
initial frontal system remains draped across norcal early this
morning with satellite imagery showing lots of high clouds over
the region slowly moving south. There are low clouds along the
west slopes of the northern Sierra, and only very spotty light
amounts of precip have been reported at a few gages along the
Temperatures are cooler across most of the area compared to
24 hours ago, though they are milder in many of the mountain
valleys due to the cloud cover. Current readings range from the
mid 30s to mid 40s in the mountain valleys to the lower 60s in the
milder portions of the Central Valley.
Little if any precip is expected across the region today as we'll
be in between systems as the current trough shifts east and the
next upstream one moves down the British Columbia coast.
A better chance of showers will return later tonight and continue
into Thursday as a deep trough and associated frontal system
move in. The best chance of precipitation will remain over the
mountains and over the northern Sacramento Valley, but a chance of
showers may spread south through the foothills and possibly the
Sacramento region Wednesday afternoon as the next front moves
As cold air drives further south, snow levels will drop to
5500-6500 feet, so some light snow accumulations could be
possible late Wednesday night into Friday over the mountains.
Temperatures will continue to trend downward through Thursday with
highs forecast to be around 10-20 below average. Moderating
temperatures are expected heading into the weekend.
Extended discussion (saturday through tuesday)
high pressure returns to northern California this weekend with
dry conditions and a warming trend to the afternoon temperatures.
High temperatures Saturday will remain below normal, but
temperatures Sunday into early next week will return to normal or
slightly above normal. Breezy valley and Ridgetop winds can be
expected for the weekend and into next week.
VFR conditions for the valley terminals for the next 24 hours
with light winds. Chances for light mountain rain showers and
increasing clouds tonight and Wednesday.