Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 220545
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1045 PM PDT Sun May 21 2017

.SYNOPSIS...
NorCal`s first triple digit heat possible Monday and Tuesday
across portions of the Northern Sacramento Valley. A chance of
Sierra thunderstorms Tuesday southward of Highway 50. Delta Breeze
begins Tuesday and becomes stronger Wednesday with cooler
afternoon temperatures.

&&

.DISCUSSION (Today through Wednesday)...

Increasing anticyclonic flow from the Ern Pac high pressure cell has
spread some thin cirrus over the CWA this evening. The NAM RH progs
suggest that most of this cirrus will be leaving/eroding by sunrise
Mon yielding a hot day for Norcal early in the warm season.  JHM

High pressure will continue to build Monday and Tuesday when the
warmest airmass will be over the interior. The warmest day for the
Sacramento region will by Monday while over the north both Monday
and Tuesday will be hot with Tuesday being the peak of the heat.

Dry conditions are expected for Monday but Tuesday a weak low
located near 31N and 130W may help to bring draw some moisture
northward along the crest to bring a chance of thunderstorms south
of US-50. That low will lift northward a little on Wednesday
along 130W while a trough moving through the Pacific Northwest
will help to bring some better synoptic cooling to the region. Any
thunderstorm activity for Wednesday looks to be north of the
forecast area and to the south along the crest so have continued
dry conditions for now.

The delta breeze will be weak through at least most of Tuesday
daytime but should increase Tuesday evening to help bring some
cooler air into the interior Tuesday night and Wednesday.

.EXTENDED DISCUSSION (Thursday THROUGH Sunday)...

Models are consistent in forecasting a pattern change with an
upper level disturbance approaching northern California.
Temperatures are expected to drop to near normal by Memorial Day
weekend. Onshore flow will return to bring cooling into the delta
influenced locations. Instability associated with the passing
upper level trough will create some chances for showers and
thunderstorms for the mountains, but the valley and foothills
should remain dry from Wednesday through next weekend.

&&

.AVIATION...

VFR conditions the next 24 hours. Variable winds less than 10 kts
at valley TAF sites.

&&

.STO WATCHES/WARNINGS/ADVISORIES...

None.

&&

$$



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