FXUS66 KSTO 240647 AAA
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
1045 PM PST Sun Feb 23 2020
Synopsis...
Dry weather. A slight cool down today then a return to well above
normal temperatures this week.
.Discussion...
The Evening Update: Nly gradients beginning to increase this evening
as the dry cold front moves over Norcal. MFR-RDD gradient has
increased to 6+ mbs near its max value for this modest Nly wind
event. Behind the front, surface high pressure will build across ORE
and into NV increasing Nly and Ely pressure gradients tonight and
through Tue morning. A modest Nly barrier jet is forecast to develop
on the W side of the Sac Vly and into the Golden Gate gap beginning
Mon morning thru Tue morning. Gusts during this time are forecast to
reach 25-30 kts on the W side of the Vly. Late Mon nite and Tue
morning, the Ely gradients will support a katabatic wind down the W
side of the Sierra affecting the SW-NE oriented canyons, i.e. Jarbo
Gap. Doubling the 925 mbs winds gives an estimate of a peak gust up
to 40 kts in the wind favored areas. A very warm stretch of wx is
forecast this week (10-20 deg above average) with possible record
max temps Thu in the Nrn Sac Vly and Wed-Fri in the Srn Sac and Nrn
SJ Valleys.
Addendum: With the developing Nly flow down the W side of the Sac
Vly any low clouds are forecast by the HREF to occur on the E side
of the Nrn San Joaquin Vly Mon morning. JHM
.Previous Discussion...
Cooler temperatures today with temperatures running 5 to 10 degrees
lower than yesterdays values at 2 pm. The cooler temperatures will
be short lived as high pressure rebuilds over the region Monday
through Wednesday. This will bring a warming trend each day through
Wednesday with temperatures warming 10 to 15 degrees above normal
each day. Models are indicating some possible low clouds forming in
the San Joaquin Valley late tonight and early morning. Any that form
should clear fairly early in the morning as the northerly winds
increase and drier air moves into the region.
Northerly flow will develop in the valley and primarily easterly
flow for the Sierra Nevada starting tonight. Winds do not look to
be strong each day but some local gusty winds Monday night for
some of the favored places in the Sierra Nevada will be possible.
Weaker gradients across the Sierra Nevada Tuesday night will
bring the return of lighter winds.
.EXTENDED DISCUSSION
(Thursday THROUGH Sunday)
...
Dry and mild conditions will continue late this week under upper
level ridging. Highs will be around 10 to 20 degrees above
average for late February, with Valley temperatures in the mid to
upper 70s. There are signs that the ridge may break down next
weekend as a system drops south from the Gulf of Alaska into the
region. Therefore, cooling will be possible by next weekend, with
at least some light precipitation on Sunday. Best chances appear
to be over the mountains.
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