216
FXUS66 KSTO 150829
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
129 AM PDT Wed May 15 2024

.SYNOPSIS...
Warmest temperatures of the year so far are still expected to occur
this afternoon, resulting in widespread moderate HeatRisk for the
central and northern Sacramento Valley. Cooler, but still seasonably
warm, weather then looks to continue through the end of the week,
with closer to normal temperatures from the weekend into next
week.

&&

.DISCUSSION (Today through Saturday)...

As of early this morning, temperatures are beginning to cool
diurnally. Early morning low temperatures are expected to dip into
the 50s for most Valley and foothills locations and 40s to low 50s
at higher elevations. Although, with less influence from onshore
flow, portions of the northern Sacramento Valley and adjacent
foothills locations do look to only fall into the lower 60s. The
trough currently progressing through SoCal will continue to meander
eastward today, allowing the rather robust offshore ridge to more
directly influence interior NorCal. This shift aloft will likely cap
any late day shower or thunderstorm potential.

As a result, high temperatures this afternoon look to make a run at
the warmest the area has seen so far this year. Widespread 90s are
expected throughout the Valley, with 40% to 70% probabilities of
reaching triple digits for the northern and central Sacramento
Valley. This is resulting in fairly widespread areas of moderate
HeatRisk across the northern and central Sacramento Valley for
today. Elsewhere at higher elevations, high temperatures also look
to reach the 70s to 80s as well. Along with the heat, a breezy and
dry northerly wind looks to filter through the northern and central
Sacramento Valley, with some gusts of 20 to 25 mph possible through
the afternoon.

Onshore flow then begins to dominate from this evening into the
remainder of the week and the weekend. This regime will help to cool
temperatures slightly and lead to some modest moisture recovery as
well. This cooling trend looks to be further reinforced by a series
of troughs ejecting out of the Pacific Northwest toward the northern
Plains from the end of the week into the weekend. This flow pattern
will indirectly affect interior NorCal by flattening the ridge and
lowering heights aloft. As a result, afternoon Valley high
temperatures generally look to cool into the upper 80s to 90s to
round out the work week, with locally breezy south to west winds.
This slight cooling trend then looks to continue into the early
weekend, although the passing trough to the northeast may lead to a
bit stronger of a south to west breeze on Saturday, with occasional
gusts 20 to 25 mph.

&&

.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)...

As the aforementioned series of troughs continue to progress, a
secondary closed low over the eastern Pacific looks to gradually
translate eastward toward the west coast through the weekend. The
exact timing and resultant interaction with the troughing over the
northern CONUS remains somewhat uncertain, but the majority of
ensemble guidance is in agreement that large scale troughing aloft,
in some capacity, will become the primary upper level influence in
the West through early to mid next week. The exact evolution of the
interaction between the two troughs will dictate the eventual
impacts for interior NorCal, but at the very least, temperatures are
expected to hold in the near to slightly above normal range next
week. Current cluster analysis favors a continuation of mostly dry
weather, but there is nonzero membership indicating some potential
for a slightly wetter pattern (by mid-May standards) as well. As
a result, we will be keeping an eye on the evolution of the
anticipated trough interaction.

&&

.AVIATION...

VFR conditions next 24 hours. Southwesterly surface wind gusts
20-30 kts in the west Delta and local northerly 15-25 kts in the
Sacramento Valley 15Z-21Z, otherwise generally less than 12 kts.
&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$