Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 040332
Area Forecast Discussion
National Weather Service Sacramento CA
832 PM PDT TUE MAY 3 2016
Period of unsettled weather setting in through this weekend.
Scattered thunderstorms in this pattern will produce a few areas
of heavy rain and small hail, most numerous in the foothills and
Some showers this evening over Burney Basin and places to the
north and east will continue to move northward. A few showers may
pop up east of the crest overnight but most of the area is
expected to stay dry overnight. The HRRR indicates possible
showers popping up in the western delta towards morning and moving
north along the west side of the valley. By 8 am an increase in
showers is expected along the coastal range and over Shasta
As the eastern portion of the low moves onshore instability will
increase in the afternoon and bring a change of showers and
thunderstorms across the interior. The better profiles for
stronger thunderstorm activity looks to occur over the foothills
and mountains. The activity should continue into the evening
before tapering but isolated activity may be able to occur in the
mountains overnight. Snow levels look high so not expecting any
major impacts to trans sierra travel. Temperatures will cool into
the 70s in the valley to the 60s in the mountains.
On Thursday the center of the low will be along the coast to
provide continued instability over the interior and another day
of showers and thunderstorms. The low will begin to drift
southward Thursday night. A couple of inches of snow may occur
over the pass along highway 88 in the evening but the other major
passes should be OK for travel.
On Friday the center of the low will move into Southern
California with warp around moisture continuing showers over the
northern part of the state. It may be unstable enough for some
thunderstorm activity but the amount should be less than the next
two days. Temperatures will cool into the low to mid 70s in the
valley and 50s and 60s in the mountains Thursday and Friday.
.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)
Negative anomaly (minus 3) 5H closed low over Socal on Fri forecast
to track slowly ENEwd across the Great Basin over the weekend...
followed by high pressure building into Norcal early next week.
Cyclonic flow and wrap around moisture will keep a cool and
unsettled weather pattern over most of our CWA through the
weekend...followed by a drying and warming trend early next week.
At times...the models indicate some instability or light precip
developing over a small portion of the Nrn portion of our CWA
spilling over the amplifying ridge. In addition...the last couple
of runs of the ECMWF continue to show a weak trof moving trough
the Pac NW and Nrn Rockys early next week. Given the trend...will
continue some low or "silent PoPs" over the mtns for now.
Temps will gradually warm through the period. Maxes will start
out just a little below normal over the Nrn portion of the CWA to
5-10 degrees or more cooler than normal over the Srn portion on
Sat...before warming to 5-10 degrees above normal on Tue. Forecast
highs in the low to mid 70s in the Central Vly on Sat warm into
the 80s for Mon and Tue. JHM
VFR conditions expected tonight through tomorrow morning with
ceilings lowering to around 10 kft. Isolated mountain
thunderstorms could continue overnight, but expect greater areal
coverage Wed afternoon. The best chances for Wednesday thunderstorms
look to be confined to the mountains but heavier showers causing
MVFR conditions over the Sacramento Valley, especially the
northern half, cannot be ruled out.