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000
FXUS66 KSTO 302221
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
321 PM PDT MON MAY 30 2016

.SYNOPSIS...
Very warm weather expected this week as high pressure strengthens.

&&

.DISCUSSION...
A very warm week ahead with max temps some 10-18 degrees or so above
normal over much of interior Norcal.

High pressure cell just off the CA coast forecast to shift inland on
Tue...with the ridge axis shifting into Wrn NV/SErn CA on Wed. Max
temps this afternoon trending up to 4 deg or so warmer than 24hrs ago
at 20z...so today should warm into the mid to upper 90s in the Valley...
with more warming to come this week.

850 mbs temps are forecast to be in the low to mid 20s deg C through Fri
with the ridge axis persisting over the Desert SW and Great Basin
maintaining the very warm temps after mid week. Dry adiabatic descent
from 850 mbs would yield max temps at least in the mid 90s to around
103 for example. There may be enough of a Delta "trickle" on Wed with
the ridge axis shifting Ewd to allow form some slight cooling through
the Carquinez Strait and into the Srn Sac Vly. However...we don`t
expect maxes to cool as much as the guidance shows...and have
generally adjusted a few of the temps upward and just below 100 in
the Delta-influenced areas. However on Thu...the ridge is forecast
to amplify slightly with a bump in 850 mbs temps which should push
max temps a little higher and up near or little above 100. In
addition...these warm 850 mbs temps also suggest strong "thermal
belt" areas with very mild/warm overnite mins.

Darkening in the water vapor imagery off the coast indicates strong
subsidence which should also move inland on Tue. This will squash
the marine layer...limit the influence of the Delta Breeze and result
in max temps some 10-17 degrees above normal on Tue...and possibly
the first 100+ reading this season. Bias corrected consensus of
the Max T models suggests a >70-99% chance of at least reaching
the century mark in the Valley on Tue. The average date for the
first 100 at DTS is around June 18/19...close to the summer solstice...
and for the RDD area around June 9. Max temp records for the date...
May 31 are for KRDD/KSAC 103 in 2001...for DTS 106 in 2001...and
for KSCK 107 in 2001.

Just a slight chance of some late day shower/storm activity along
the Sierra Crest S of Tahoe and over the Shasta Co mtns on Wed as
the flow turns Wly on top of the ridge...otherwise little if any
late day/early evening shower and thunderstorm activity is expected
over the mtns in our CWA this week until the flow backs to the
SE...possibly this weekend.   JHM

&&
.EXTENDED DISCUSSION (Friday THROUGH Monday)


Strong high pressure will dominate through the end of the work
week into the start of the weekend with well above normal
temperatures...triple digit Valley temperatures. Models continue
to advertise a closed upper low transitioning into a negative-tilt
trough moving northeast onto the central CA coast impacting
interior northern CA this weekend Saturday into Monday with
potential mountain showers and thunderstorms. Regardless, the
region will experience some relief from the heat with
temperatures on Sunday around 5 to 10 degrees cooler than
Saturday and increasing flow through the Delta.      JClapp/CEO

&&

.AVIATION...


VFR conditions for TAF sites with light winds. Density altitudes
will be increasing throughout the week due to hot temperatures.
JClapp


&&

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

$$





000
FXUS66 KSTO 301030
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
330 AM PDT MON MAY 30 2016

.SYNOPSIS...
Very warm weather expected this week as high pressure strengthens.

&&

.DISCUSSION...
Clear skies across interior NorCal early this morning except for
some high clouds spilling over the ridge along 130W. The mountain
valleys are cool - mainly in the 30s and 40s under clear skies
while the valley and foothills are generally on the mild side with
current temps in the mid 60s to lower 70s, except in the mid 50s
to around 60 through the Delta and into the Sacramento and
Stockton region.

The main weather story for the region this week will be hot
weather as the ridge over the eastern Pacific shifts over NorCal
to kick off meteorological summer. Warmest temperatures will be
around the century mark in the Central Valley as 850 mb temps
climb into the lower to mid 20s C and subsidence increases. A
Delta trickle should persist through the week shaving a few
degrees off temps around Fairfield.

Little if any late day shower and thunderstorm activity is
expected over the northern Sierra.

&&

.EXTENDED DISCUSSION (FRIDAY THROUGH MONDAY)...
Strong high pressure will rule the area through the end of the
work week into the start of the weekend with well above normal
temperatures. Models continue to advertise a closed upper low
approaching the CA coast by late Saturday into Sunday. Differences
remain with track of low and how far south into CA it will move
before being ingested into larger scale trough. GFS paints more
widespread precip, mainly across higher elevations. ECMWF with
further south solution/less widespread precipitation. For now,
have included chance of showers and thunderstorms across higher
elevations for the end of the weekend, until discrepancies are
better resolved. Regardless, should lend itself to some relief
from the heat with temperatures on Sunday around 5 to 10 degrees
cooler than Saturday and increasing flow through the Delta. CEO

&&

.AVIATION...
VFR conditions for TAF sites with light winds. A few
thunderstorms near the Sierra crest, south of Lake Tahoe this
afternoon/evening.

&&

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

&&

$$





000
FXUS66 KSTO 291530
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
830 AM PDT SUN MAY 29 2016

.SYNOPSIS...
Very warm weather expected this week as high pressure strengthens.
A few afternoon showers or thunderstorms possible along the Sierra
crest today.

&&

.DISCUSSION...
Mainly clear skies across interior NorCal this morning.
Temperatures will inch up a few more degrees today as high
pressure strengthens a bit. Still enough moisture and instability
for another round of afternoon and early evening showers and
thunderstorms over the Sierra to the south of Tahoe. No updates.

&&

.PREVIOUS DISCUSSION...
Another warm day in store for interior NorCal today as high
pressure ridging over the Eastern Pacific begins building into the
West Coast. Highs today: valley in the low 90s, delta in the mid
70s to mid 80s, foothills in the 80s, mountain highs in the 60s
and 70s. There`s another chance for Sierra convection this
afternoon due to low pressure lingering over SoCal. However, any
showers or thunderstorms that develop will likely be limited to
the higher elevations of the Sierra south of Tahoe.

Memorial Day and Tuesday will kick off the week with hot
afternoons. High pressure will strengthen over NorCal on Monday
and Tuesday causing the peak of this current warming trend.
Valley highs will be in the mid to upper 90s. A few locations may
even top out around 100 degrees on Tuesday when daytime highs
measure 10 to 15 degrees above normal.

By Wednesday, the high pressure will begin to shift eastward and
weaken. This will finally allow temperatures to gradually cool,
but only by a few degrees. Residents should still be prepared for
a hot day with valley highs in the mid to upper 90s with 70s and
80s across higher terrain. Keep in mind to stay well hydrated for
the first half of this week as many of us are not used to the hot
afternoons.  JBB

&&

.EXTENDED DISCUSSION (THURSDAY THRU SUNDAY)...
Models continue to show strong high pressure over the western
U.S. bringing above normal temperatures through the extended
period. Daytime highs will climb slowly to more than 15 degrees
above normal by Saturday. Models fairly consistent in positioning
an upper low off the Socal coast Thursday and Friday. This will
result in southeast flow aloft and GFS, ECMWF and GEM models all
painting some convective precipitation over the northern Sierra
each afternoon. Therefore...have included a slight threat of
afternoon and evening thunderstorms in this region Thursday
through Saturday. Models diverge by next Sunday in both dealing
with the Closed low off the Socal coast and a Pacific frontal
system possibly approaching the Pacific Northwest coast. Depending
on the upper lows position...northern Sierra could see another day
of showers next Sunday. The second feature of approaching frontal
system now not looking as likely with 06z run of GFS already
backing off on this idea. Either way, should see a little cooling
most areas early next week.

&&

.AVIATION...
VFR conditions next 24 hours TAF sites. Isolated thunderstorms
possible afternoon and evening hours over the northern Sierra
crest. Sustained winds generally below 15 knots.

&&

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

&&

$$





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