Mountain House, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

951
FXUS66 KSTO 192010
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
110 PM PDT Thu Mar 19 2026


.KEY MESSAGES...

 - Record breaking heat continues today & Friday, with widespread
   Minor HeatRisk and areas of Moderate HeatRisk.

 - Slightly cooler temperatures this weekend and into next week,
   but temperatures will be 15-20 degrees above-normal.

&&

.DISCUSSION...

...Today-Friday...
Strong high pressure continues to dominate the synoptic pattern
this week, resulting in record-breaking heat across much of the
area. Yesterday, Sacramento, Modesto, and Stockton recorded/tied
their all-time hottest March day on record; and Modesto AP
recorded it`s earliest 90 degree day on record. Today and Friday
will see the hottest temperatures of the week, with widespread
Minor HeatRisk and areas of Moderate HeatRisk. The NBM is
currently forecasting a 70-90% chance of highs 90 or greater
throughout the Valley and Delta today & Friday. If Stockton AP or
Sacramento hits 90 degrees today, it will be the earliest 90
degree day on record at those two sites.

...Saturday-Wednesday...
Temperatures cool down slightly over the weekend, as ridging
flattens out and shifts eastward over the Great Basin.
Temperatures will still be several degrees above-normal, but are
forecast to be slightly cooler than previous days. Minor HeatRisk
will still be widespread especially in the Valley and Delta, but
some areas in the mountains will fall below any HeatRisk concerns.

There is still a degree of uncertainty regarding the eastward
trajectory of the high, which could allow a weak lobe of energy
to bring very light showers over the Shasta County mountains mid
next week. However, probabilities for 0.1" or more are currently
less than 25%. The majority of ensembles favor the redevelopment
of high pressure and rising heights mid next week, which would
yield continued dry weather and above-normal temperatures.

If you are outside or planning outdoor activities this week and
over the weekend, please remember to drink plenty of water and
wear sunscreen. As this is an anomalous heat event, individuals
may not be fully acclimated to the emerging heat. Local waterways
are also running very cold due to snowmelt.



&&


.AVIATION...
VFR conditions are expected for the next 24 hours. Surface winds
below 12 kts and generally from the north. Chances (20-45%) of
lower visibilities tomorrow morning, mainly Sacramento southward
from BR conditions reducing visibility to MVFR conditions. Best
chances from around 11z through 15z Friday. &&

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

$$