NWS Area Weather Forecast Discussion
County Warning Area [CWA]: STO Regional NWS Weather Office: Sacramento, CA
FXUS66 KSTO 241625
Area Forecast Discussion
National Weather Service Sacramento CA
925 AM PDT Wed Apr 24 2019
Dry weather and above normal temperatures through the week. A few
isolated thunderstorms could be possible over the high mountains
this afternoon and Thursday. A cooling trend is possible over the
weekend into early next week.
.UPDATE AS OF 9:24 AM...
Ridge of high pressure remains over NorCal this week with
generally dry conditions and above normal temperatures. Another
very warm day is in store across the region today with widespread
low 90s across the Valley. These temperatures are roughly 10 to 20
degrees above normal for this time of year. Many locations will
again approach or exceed record temperatures this afternoon. Look
for high temperatures to reach the upper 80s to low 90s on
Models are hinting at a few isolated showers/thunderstorms near
the northern Sierra crest this afternoon, but should mainly
remain east of the Sierra crest. A weak disturbance moving across
the Pacific NW may bring some convection to the southern Cascades
and Shasta County late Thursday.
By Friday and Saturday, temperatures will have cooled back down
to the mid to high 80s for the valley as heights lower. However,
daytime highs will remain 10 to 15 degrees above average.
Upper level ridge remains over NorCal this week with dry weather
and warm temperatures. Another day of 90 degree temperatures today
with readings 10 to 20 degrees above normal. Many locations will
again approach or exceed record temperatures, which are in the
A system passing north of the area this afternoon and Thursday
may bring extremely isolated thunderstorms to the Southern
Cascades and northern Sierra near the crest. Model agreement
remains poor, but will maintain low-end precip chances in line
with HREF and mesoscale WRF models.
Temperatures will cool into the 80`s Friday and through the
weekend with lowering heights, as disturbances pass north of the
.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)
To conclude the weekend and entering next week, a split flow
regime is evident in the guidance. A compact upper low within the
southern stream will stay well to the south of the region as it
moves through extreme northern Baja California early Monday. The
northern extent of the precipitation shield could reach Tuolumne
County which affords a risk for a few showers. Have kept the
threat of showers in the forecast into Monday given models have
trended slower with the passage of the trough.
The longwave pattern within the northern stream should remain
amplified into next week. Operational and ensemble solutions favor
further elongation of this flow down into the Central Great Basin
next Tuesday and Wednesday (Apr 30-May 1). If the forcing from
this trough moves far enough west, some showers will be possible
across the Sierra. A tightening pressure gradient should afford an
uptick in dry, northerly winds across the Valley. Given modest
ensemble spread with the pattern, expect some of these details to
change in the upcoming days.
Temperatures should move closer to climatology next week given the
presence of lower heights over the region. Mid to upper 70s will
likely be the norm for Valley highs while mountain and foothill
locations stay in the 50s and 60s, respectively. ~BRO
Generally light west to northerly flow aloft underneath the ridge.
VRF conditions expected over all TAF sites with surface winds
remaining below 10 knots. Isolated afternoon thunderstorms are
possible across the northern Sierra crest between 21Z Wed and 02Z