Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 180605
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1005 PM PST Fri Nov 17 2017

.SYNOPSIS...
Dry weather through Sunday. Next system moves through Monday with
another during mid week. Each of these next systems will come
with light to moderate precipitation and high snow levels
generally above pass levels.

&&

.DISCUSSION...
Clear nite for viewing the Leonid meteor showers this evening. In
the wake of the upper trof moving into the Great Basin and into the
Rockys by morning, high pressure will build in behind it and into
Norcal. Nly winds should be subsiding by morning in the valley and a
strong radiative inversion will form. Moisture trapped below the
radiative inversion from the recent rains could lead to some
radiation fog early Sat morning. After 12z Sat, the HRRR surface
winds are progged to shift to light SEly which is a more favorable
direction for some fog. It does not have the ingredients for a
widespread F+ event as dewpoints/RHS have succumbed to the Nly winds
and we expect mainly MVFR vsbys in the morning. Near the river
valley there may be some MIFG (ground fog) causing some brief lower
IFR vsbys.  JHM

.Previous Discussion...
Major weather system of the past few days has moved into the Great
Basin region. Pacific ridge is building over NorCal behind this
system with dry conditions and northerly surface winds. Overnight
and early morning fog chances seem less likely as north wind of 5-10
mph should keep mixing and drying from Sacramento northward. Some
patchy fog could form Sacramento southward, especially in river
valleys.

Ridging with dry conditions will continue into Sunday with near
normal temperatures in the low 60`s. A weak weather system will
bring light showers Monday, best chances northern Sacramento
valley and Shasta county. Precip should be light with this system,
generally less than 0.25 for valleys and less than an inch
mountains. Snow levels will be high generally above 8000 feet.
&&


.EXTENDED DISCUSSION (Tuesday THROUGH Friday)

Forecast confidence remains low through the extended period. The
latest runs of the GFS and ECMWF build a very strong ridge into
the Desert Southwest, which would force the storm track farther
north than previously projected (mainly toward the Pacific
Northwest). It still appears that periods of light to moderate
precipitation will be possible, and could possibly impact
Thanksgiving holiday travel. Our forecast favors a blend of the
GFS and ECMWF models.

Dang

&&

.AVIATION...

Mainly VFR conditions with light north winds the next 24 hours.
Patchy fog may develop from KSMF southward Saturday morning.

Dang

&&

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

$$



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