Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Sacramento California
955 PM PDT Sat Apr 21 2018
dry and warm through early next week. Chance of a few showers or
thunderstorms over the mountains by mid to late next week.
update: isolated storm occurred Sat afternoon near the crest in
Tuolumne/alpine co, and for sun/Mon the instability is forecast to
shift a little swd, although still slightly negative Li's are
forecast in the Yosemite np area. Then, the coverage should become
more widespread over the Sierra from Tue through the middle of the
week as the upper low approaches the California coast.
Temperatures are running a little warmer today than yesterday and
should top out in the low to mid 80s throughout the valley. A weak
dry trough will pass over the northern end of the state Sunday
morning and weak north flow will develop behind the system. (Update:
temperatures are expected to warm a couple of degrees on sun
compared to sat's highs over areas generally S of I-80, but cool
over areas to the north in the wake of the upper trof.)
A ridge will stay over the area through the middle of next week as a
low pressure system deepens off the coast and becomes cutoff from
the jet. Temperatures will be running well above normal in the 10 to
15 degree range through Tuesday with the warmest days Tue/Wed.
(Update: forecast Max temps for rdd anomolous propagation are running at record/near
record levels for the 23rd to the 25th, 86 in 2002, 87 in 2013 and
90 in 2004, respectively.)
Some moisture advects northward from the southwest over the
Sierra Nevada on Tuesday and may bring a few showers or even
some isolated thunderstorms...mainly near the crest.
Extended discussion (wednesday through saturday)
High pressure remains over the western US Wednesday and Thursday
as a closed upper low sits over the eastern Pacific Ocean.
Daytime temperatures will remain 5-15 degrees above normal through
Thursday, and there's a slight chance of afternoon thunderstorms
over the Sierra crest.
Friday into the weekend, uncertainty is high as models diverge
significantly on the speed and direction of the closed low
movement. Generally, the upper low and associated surface cold
front approaches the area on Friday, creating a chance for more
widespread showers and afternoon thunderstorms over the coastal
range and Sierra crests Friday through the weekend. Temperatures
expected to cool down to near normal by Friday as the front
passes through the area. Hec
VFR conditions at the taf sites the next 24 hours. Winds
generally around 10 kts or less except vicinity Delta with winds