Scientific Forecaster Discussion
fxus66 ksto 231545
Area forecast discussion
National Weather Service Sacramento California
845 am PDT Tue may 23 2017
triple digit heat continues today in the Central Valley then
cooling Wednesday into Friday with near to slightly below normal
readings by the end of the week. Isolated afternoon showers or
thunderstorms possible over the southern Sierra Nevada today and
over the northern interior mountains Wednesday.
Discussion (today through friday)...
strong upper ridging over interior norcal today will result in
another day of triple digit heat over portions of the Central
Valley. Marine layer is currently around 1400 feet per ft. Ord
profiler and flow through the Delta has increased slightly from 24
hours ago. Delta breeze expected to bring some minor cooling to
the Carquinez Strait and Fairfield areas today. Otherwise most
areas will see high temps similar to Monday. GFS continues to
show a slight chance of deep moist convection possible over the
Sierra Nevada, south of US-50, this afternoon.
Delta breeze ramps up early this evening and will provide low
level cold air advection into the southern SAC/northern San Joaquin valleys.
Marine layer deepens tonight as offshore upper low approaches.
Models showing strong flow through the Delta overnight into
Wednesday providing cooling into the Central Valley.
Upper troughing over the pacnw digs towards the Great Basin
Wednesday as associated weak cold front stalls over northern
portions of California. This may provide enough lift to set off a few
afternoon showers or thunderstorms over the coastal and northern
interior mountains. Increased Delta breeze and synoptic cooling
over the area Wednesday will result in about a 10 degree drop in
Broad upper troughing continues over the forecast Thursday into
Friday providing additional cooling. Highs expected in the 80s
throughout the Central Valley Thu/Fri, 70s in the Delta, and 50s
to around 80 for the mountains and foothills.
Extended discussion (saturday through tuesday)
ridging builds back in for the Holiday weekend with warming
temperatures. Warmest temperatures expected across northern SAC
valley where highs will approach the upper 90s by Sunday and
Memorial Day. Those with outdoor plans should keep an eye on the
forecast as activities may be impacted by the heat. Onshore flow
will keep decent Delta breeze going, so expect much cooler
conditions in that region and possibly into the Sacramento area.
Weak moisture return and instability under dirty ridge may allow
for a few showers and thunderstorms to develop across the Sierra
Saturday and Sunday afternoons, but low confidence in just how
widespread the activity will be. For now, have introduced slight
chance pops, mainly south of Tahoe. Short wave approaching the
coast will shift ridge off to the east for Monday and Tuesday,
bringing additional chances for convection across the Sierra.
Again, low confidence in this but something to watch going
stg high pres ovr intr norcal with VFR conds nxt 24 hrs.
Isold aftn tstm poss tda nr siernev crest, S of US-50, btwn
23z-03z. Swly sfc wnd gsts to 30 kts thru Delta aft 00z Wed.