Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 222240
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
240 PM PST Thu Jan 22 2015

.Synopsis...
Dry weather forecast with areas of night and morning valley low
clouds and fog through Monday. Temperatures expected to remain
well above normal through the early next week. Potential for some
wet weather exists Tuesday into Wednesday of next week.

&&

.Discussion...
Weak upper trough moving through Interior NorCal is bringing some
mid to high level cloudiness and also helping to mix out the
stratus from this morning. Wave will push into the Great Basin
this evening as upper level ridging starts to build over NorCal
in its wake. Stratus expected to redevelop over the Northern San
Joaquin valley tonight and expand northward into the Sacramento
Valley Friday morning. This should hinder dense fog formation
although low visibilities likely again in the foothills at the
base of the stratus deck. Heights/thicknesses begin to increase
Friday as the AMS begins to warm.

Models similar in pumping up upper level ridging over NorCal into
the weekend with 5H heights in the mid 580s DM by Saturday. This
will result in unseasonably warm temperatures, especially in the
Northern Sacramento Valley where guidance is pushing max temps
into the mid 70s for Saturday and Sunday. Forecast highs and
record max temps for Redding and Red Bluff for this weekend are
below:

Date    Location    Forecast    Record
1/24 Redding       75         77
1/24 Red Bluff      73         78
1/25 Redding        76         78
1/25Red Bluff      74         78

Along with well above normal temperatures this weekend, models are
showing some locally breezy north to easterly winds possible, mainly
over the eastern foothills/mountains. This increased low level flow
may help to hinder some valley fog development under increased
subsidence.

PCH

&&

.Extended Discussion (Monday through Thursday)

Not much has changed in the extended forecast thinking over the
previous few models runs. The upper level ridge will shift east
into the Great Basin on Monday, though subsidence will continue to
bring dry weather that day. With southerly flow behind the upper
level ridge, medium- range models continue to suggest that
subtropical moisture from west of Mexico will be drawn northward
toward the Western US. The GFS brings this moisture along the
Great Basin and the Desert Southwest, with the best chance of
NorCal precipitation confined to the mountains. The ECMWF and GEM
are both a bit farther westward with the moisture, and would bring
a better chance of precipitation across NorCal. With this being a
somewhat unusual setup for the wintertime, we blended the
solutions together to give a roughly 25-40% chance of rain across
the area in the Tuesday-Thursday time-frame. Expect the models to
continue to change in timing and strength of this system over the
next several runs.

Model continuity worsens even further beyond Tue-Wed of next week,
and there is little confidence in any particular solution beyond
that point.


&&

.Aviation...

Low clouds gradually lifting over the cent/srn Sac valley this
afternoon. Low clouds and fog will become widespread in the Valley
again tonight with IFR/LIFR conditions expected after 10z to
around KCIC. Conditions will gradually improve to MVFR/IFR again
tomorrow afternoon in some areas.

&&

.STO Watches/Warnings/Advisories...
None.
&&

$$







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