FXUS66 KSTO 012129
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
229 PM PDT Wed Jul 1 2020
SYNOPSIS...
Temperatures around seasonal averages this week, with a quiet, dry
pattern continuing.
.DISCUSSION
...
Mid-level water vapor imagery across the western U.S. shows a
positively-tilted trough over the Pacific Northwest while ridging
remains prominent well off the coast. The resultant northwesterly
flow has kept tranquil weather in place with sunny skies over most
locations. Some orographically induced fair weather cumulus fields
are noted in the 0.64 micron visible satellite channel. Otherwise,
much like yesterday, early afternoon temperatures across the
Valley and Delta have reached the upper 80s to low 90s. Given
additional diurnal heating, another 3 to 5 degrees can be tacked
on to these temperatures this afternoon. This should keep readings
with a degree or two of seasonal averages for early July.
For Thursday and Friday, an area of low pressure moving toward the
Washington coastline will turn flow to a more westerly direction.
1000-500 mb thicknesses are forecast to lower by a few dm as this
subtle pattern shift commences. The greater Delta influence will
lower temperatures to slightly below average which is in the mid
80s around the Delta and low 90s across the Sacramento and San
Joaquin Valleys. In terms of expected winds, 20 to 30 mph
southwesterly gusts will be likely around the Delta with 10 to 15
mph southerly winds being more commonplace over Valley locations.
By the start of the holiday weekend, temperatures are forecast to
come back up a bit as heights build in response to a Four Corners
ridge. However, compared to previous model guidance over the last
few days, forecast numbers have come down a bit. This is in
due to the Pacific Northwest trough sagging southward to the
Oregon/California border. Expected Valley highs will be in the mid
to upper 90s which is approximately 2 to 4 degrees above
climatology. ~BRO
.EXTENDED DISCUSSION
(Sunday THROUGH Wednesday)...
For Sunday and heading into next week, only subtle changes are
likely in the large-scale pattern. Global ensemble means maintain
a positively-tilted trough just offshore of the Pacific Northwest
while the Four Corners ridge expands toward Arizona. Ultimately
expecting Valley temperatures to stay in the mid to upper 90s
through Monday before a slight cooling trend ensues thereafter. If
anything, this may take about 3 to 5 degrees off daily
temperatures. The overall dry pattern will continue into next
week. ~BRO
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