Weather Service Report


827 
FXUS66 KSTO 230601
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1100 PM PDT Wed Sep 22 2021

.SYNOPSIS...
Dry and warmer weather this week. Locally breezy north to east winds 
on Thursday. Cooling trend begins this weekend with the potential 
for a pattern change next week.

&&

.DISCUSSION...
Light Delta Breeze able to cool off the KSUU and KVCB areas from 24 
hrs ago but that is about as far as it gets. Upper ridge axis has 
shifted Ewd and the Nly winds will, if not already depending on 
location, begin increasing overnight. 925 mbs winds not nearly as 
strong as Sun nite/Mon, but will still result in poor RH recovery W 
of I-5 and the lee-side of the North Coast Range tonight and then 
low RH on Thu. Upper air support weakens Thu afternoon and winds 
should begin to slacken. Nly winds and rising 5H heights from the 
building EPAC ridge will result in another warm day on Thu. Maxes 
could be 2 to 6 degrees warmer, nearing 100 where adiabatic warming 
effects are realized. A combo of NBM 75 and 90 pct NBM could be a 
reasonable alternative.   

Nly flow will preclude any stratus intrusion in addition to a 
shallow marine layer (~1400 ft).     JHM

.Previous Discussion... 
Latest water vapor satellite imagery shows an upper trough tracking 
through the region this afternoon, bringing slightly cooler 
temperatures to most areas. Current temperatures are running 2 to 5 
degrees cooler compared to 24 hours ago, with upper 80s to low 90s 
across the Valley. This system has also resulted in gusty southwest 
winds across the high Sierra and southern Cascades; current wind 
gusts range from 20 to 25 mph. These winds could bring localized 
fire weather concerns through this afternoon.

Ensemble guidance shows the trough digging into the Great Basin
area Thursday, resulting in breezy offshore winds early Thursday
morning through evening. Gusts of 20-30 mph will be possible in 
the Sacramento Valley and near favored wind-prone mountain areas 
on the west slopes of the northern Sierra and southern Cascades. 
The combination of gusty winds and dry conditions will result in 
elevated fire weather conditions.

Moderate heat risk impacts are possible across portions of the 
southern Sacramento Valley and the Delta Thursday as forecast 
highs climb into the mid to upper 90s. This could impact those 
who are sensitive to the heat.

Lighter winds and warm conditions are expected Friday and 
Saturday as high pressure remains in control.

&&

.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)...
Cluster solutions anticipate a deep trough making its way through
the Pacific Northwest early next week bringing unsettled weather 
to our region. This pattern change will lead to cooler 
temperatures across Northern California with highs forecast to be 
5 to 15 degrees below climatology. Shower chances will also be 
possible primarily for far Northern California with best chances 
over the higher terrain. Current projections indicate this to be a
generally low impact event. Cooler temperatures, passing clouds, 
and breezy onshore winds at times are likely. 

&&

.AVIATION...
VFR conditions persist. Gusts to 25 kts possible through the 
Carquinez Strait and Delta as well as over the high Sierra. 
Elsewhere, winds generally under 10 kts.

&&

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

$$

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Western Regional Climate Center, wrcc@dri.edu