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737
FXUS66 KSTO 232032
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
132 PM PDT Thu May 23 2024

.SYNOPSIS...
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Seasonably warm, dry, and breezy weather continues today. A brief
cool down is then expected on Friday and Saturday before
temperatures warm back up from Sunday into next week. A few isolated
showers or thunderstorms will also be possible Friday across the
northern Sacramento Valley and northern Sierra.
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&&

.DISCUSSION...
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As the trough responsible for the northerly winds last night-this
morning continues to progress eastward across the northern
Rockies, the northerly pressure gradient will continue to relax
through this evening, resulting in lighter winds.

Another shortwave trough will dig southward from the Pacific
Northwest tonight through Friday, then rapidly transition toward
the intermountain West throughout the day on Saturday. There
remains some ensemble uncertainty on exactly how the shortwave
will evolve, but overall impacts for interior NorCal look to
remain minor at most. Regardless, as this shortwave moves within
the vicinity of interior NorCal late day Friday into early
Saturday, a few isolated showers and thunderstorms may pop up (10%
to 25% chance) across the northern Sacramento Valley and northern
Sierra. Otherwise, the region looks to trade northerly winds for
south to west winds in onshore flow from Friday into the weekend.
Additionally, a somewhat pronounced cool down is anticipated, with
Valley high temperatures in the 70s to low 80s and 50s to 60s at
higher elevations. This cool down looks to remain short lived,
however, as heights aloft begin to rise on Sunday and temperatures
return to near normal by Sunday afternoon.
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&&

.EXTENDED DISCUSSION (Monday THROUGH Thursday)...

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Cluster Analysis and ensembles have upper-level ridging develop
over the Great Basin region through at least mid week next week.
This will allow high temperatures to be in the upper 80s to mid
90s for the Valley. With increased heights aloft, daytime heating
will be enough for some limited instability to develop along
portions of the central/southern Sierra crest early next week,
potentially allowing for some limited isolated showers and
thunderstorms to develop mainly in southern Tuolumne County. By
mid week next week, some notable variance in the clusters develops
with the ridge heights (intensity) and how quickly it is shifted
eastward with weak shortwaves progged to move through British
Columbia/WA late week. Given the location of the ridge axis, some
variation of weak west to southwest flow will be overhead late
week next week, keeping onshore flow, and thus somewhat limiting
the upper-end potential of the NBM forecast highs late week. Even
so, the shortwave trough may not influence our apparent weather
much late next week, allowing for temperatures to be warmer than
currently advertised, especially for areas less likely to be
influenced by onshore flow (central/northern Sacramento Valley).
The NBM forecast high temperature spread between the 25th and 75th
percentiles for Thursday and Friday next week differ by 12-15
degrees. Given these uncertainties, confidence in the temperatures
forecast late week isn`t super high, so stay tuned as the
forecast gets closer and details become more clear.

//Peters
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&&

.AVIATION...

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VFR conditions next 24 hours. Winds in the northern Sacramento
Valley continue to taper off through this afternoon becoming light
by overnight hours. In the afternoon, areas near the Delta will
see gusts 15-20 kts continuing into Friday morning.
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&&

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

$$