Area Forecast Discussion
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FXUS66 KSTO 212209

Area Forecast Discussion
National Weather Service Sacramento CA
309 PM PDT Tue Aug 21 2018

Gradual cooling with dry conditions expected through the week.
Areas of smoke and haze will continue, especially near wildfires.


Temps trending several degrees cooler than yesterday at 20z (as much
as 5-11 degrees cooler many locations) thanks to a persistent Delta
Breeze and 2800 ft deep marine layer, and suppressed 5H heights from
the positively-tilted Pac NW trof. The cooling trend will continue
on Wed with the passing trof, before leveling off Thu, followed by
additional cooling into the weekend. The continentality of the trof
means that it is devoid of moisture, or even clouds for that matter,
in our CWA.

Most of the energy from this trof will move through during the day
on Wed, but before then, secondary energy will move through the trof
tonite and Wed morning, reinforcing onshore flow. With an extensive
and deep marine layer, we expect another, but even more extensive of
a marine intrusion into the Srn Sac Vly Wed morning. The Delta
Breeze should then weaken later Wed and Thu morning allowing temps
to moderate slightly most locations on Thu.

Another approaching Pac trof will continue a cooling trend on Fri
and into the weekend as it moves through the Pac NW. Some improvement
in smoky conditions away from the fire origin is expected over
Norcal (given current status of WFs) as the succession of upper
level trofs over the region suppresses stagnant high pressure over
the Desert SW.    JHM



Models differ during extended forecast period with EC showing a
series of short wave troughs moving across the PacNW and northern
portions of CA. GFS keeps these waves more confined to the PacNW
with higher heights over CWA. Forecast attm leans between the two
with dry weather and high temperatures around 3 to 8 degrees
below normal Saturday into Tuesday.



Lcl MVFR/IFR conds poss in HZ/FU vcnty of fires. Areas MVFR/IFR in
ST vcnty Delta into Srn Sac Vly btwn 06z-20z Wed. SW-W sfc wnd
gsts up to 30 kts vcnty Delta tngt thru abt 13z Wed and lcly ovr
hyr mtn trrn til arnd 03z Wed.




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