Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Sacramento California
922 PM PDT Wednesday Jul 1 2015
very hot weather continues over the northern Sacramento Valley
through Thursday although a few degrees of cooling are Likely.
Mountain thunderstorms are possible each afternoon and evening
through the weekend with the possibility of a stray shower or two
in the valley late tonight and Thursday night. Cooler temperatures
over the weekend and next week but remaining above normal.
unexpected increased cloud cover helped to keep temperatures down
in a number of areas today. We should see even more cloud cover on
Thursday. As a result the excessive heat warning will be trimmed
to just include the far north end of the valley. I will trim the
timing back to 7 PM Thursday evening as well since daytime highs
may only reach around 105 degrees and not around 110 but will
still be hot.
The Delta breeze will not have much of an impact until late
tonight into Thursday when it is expected to start to increase.
Winds should remain up throughout Thursday to help bring some
cooler air for the Sacramento region. We should also see a decent
amount of cloud cover during the day which should help as well.
The morning should feel fairly nice with the cloud cover in place.
Unfortunately the cloud cover will help to keep the overnight lows
up tonight and again Thursday night for most locations absent the
The other thing of concern will be with the increased monsoonal
moisture and increase in thunderstorm potential over the next
several of days. The central part of the high is over Nevada
bringing easterly flow aloft the next couple of days. This will
bring not only clouds but an increased threat for showers and
thunderstorms over the interior. Showers or sprinkles may migrate
down the western slopes into the Central Valley late tonight and
early Thursday mainly from around Marysville to Southern Lake
County and southward. The main thunderstorm activity looks to
remain over the mountains but an isolated thunderstorm at lower
levels cannot be ruled out. There should be an increased push of
moisture towards the Central Valley Thursday night into Friday
The downward trend in temperatures will continue Friday along with
chances of mountain showers and thunderstorms. Some residual
showers or isolated thunderstorms may linger over the north end
of the valley Friday morning but any activity should move north
into the mountains by late morning. Cloud Clover once again will
be our friend during the day helping to keep temperatures down a
Extended discussion (sunday through wednesday)
Interior norcal sandwiched between offshore upper low and Great
Basin upper ridge through early next week. Ec tries to progress
upper low inland midweek, while GFS/Gem keep it quasistationary.
Models showing limited moisture and instability to support showers
or thunderstorms over the higher mountain terrain Sunday. Less
probability for deep moist convection Monday into Tuesday as upper
flow becomes southwesterly.
High temperatures will trend down slightly through the extended
forecast period as upper high weakens and onshore flow increases.
Maximum temperatures expected mainly in the 90s for the Central
Valley, 80s for the Delta and foothills, and 70s for the
Southeasterly flow aloft as upper ridge continues. VFR conds over interior norcal next 24
hours. Afternoon dnsty alt gtr than 3500 feet in portions northern SAC valley. Isolated
-shwrs overnight then afternoon/evening showers/thunderstorm poss over mountains and Sierra Nevada
fthls after 20z.
excessive heat warning until 7 PM PDT Thursday for mountains
southwestern Shasta County to Northern Lake County-northern
Sacramento Valley-Shasta Lake area / northern Shasta County.