Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 272236

Area Forecast Discussion
National Weather Service Sacramento CA
336 PM PDT TUE SEP 27 2016

A cool down will begin on Wednesday with much cooler temperatures
by the end of the week as a weather system moves toward NorCal.


Last day of hot weather as ridge axis continues to shift east
today. Main story for the rest of the work week will be cooling
trend as upper level trough begins to move toward the coast. As
onshore flow increases, expect Delta Breeze to pick up tonight and
Wednesday. This will mark the beginning of a cool down with
temperatures dropping several degrees each day into Friday.
Daytime highs on Friday will be near the 80 degree mark in the
Valley, nearly 20 degrees cooler than today. As trough moves
toward the coast, breezy southerly winds likely Thursday and
Friday. Increasing moisture return/RH values and cooler
temperatures should limit widespread fire weather concerns but
may hamper ongoing fire fights. CEO


Forecast models in good agreement that an upper trough will deepen
over the forecast area, bringing cooler temperatures and a chance
of precipitation mainly over the northern mountains. Several
shortwaves will rotate around the main feature and reinforce it.
The first shortwave will move late Friday into Saturday, but
precipitation chances will remain over far northern California.
Confidence in the evolution and timing of the system decreases
with additional waves moving over the forecast area early next
week. The ECMWF is the wettest solution, with precipitation
chances as far south as the Central Sacramento Valley. Have kept
only a slight chance of precipitation to account for model

Significant cooling is expected over the weekend, as the trough
moves inland and ushers in a cool airmass aloft. Highs could be
10-15 degrees below normal during the Saturday-Monday period, with
Valley temperatures in the 70s and 50s-60s over higher elevations.
As the trough axis begins to shift east early next week, daytime
temperatures will be trending slightly upward but will remain
below normal.



VFR conditions over interior NorCal next 24 hours. Generally
light winds across TAF sites. Light onshore flow continues through
the Delta.

.STO Watches/Warnings/Advisories...

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