Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 311728
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1025 AM PDT TUE MAY 31 2016

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

&&

.DISCUSSION...

Early (first of the) season heat wave unfolding over interior Norcal
with max temps some 10-15 degrees or more above normal. Ern Pac high
pressure cell that was off the CA coast yesterday has shifted inland
with strong subsidence squashing the marine layer and suppressing
mtn convection. Forecast max temp trend indicates additional warming
up to 5 degrees from yesterday this afternoon. Initial triple digit
max temps are quite likely in the Valley today with the Bias
Corrected Consensus of the Max T models suggesting a >70-99% chance
of at least reaching the century mark in the Valley today. 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 today are for KRDD/KSAC 103 in 2001...for DTS 106
in 2001...and for KSCK 107 in 2001.

The high pressure cell is forecast to shift into Wrn NV/SErn CA on
Wed as a trof works its way into the Pac NW. However...the heat will
continue as 850 mbs temps are forecast to remain in the low to mid
20s deg C through Sat 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
some of the guidance shows as the marine layer will remain shallow
which reduces the cooling effects in the Srn Sac Valley...aka "no
freon".

For Thu thru Sat...the ridge is forecast to amplify slightly with a
bump in 850 mbs temps which should push max temps a little higher
and up above 100. In addition...these warm 850 mbs temps also
suggest strong "thermal belt" areas with very mild/warm overnite
mins.

Limited convection potential in our CWA mtn areas for the rest of
the week until the flow backs to the SE...possibly during the
weekend.  JHM

&&

.EXTENDED DISCUSSION (SATURDAY THROUGH TUESDAY)...
Strong high pressure will remain in control for the start of the
weekend with well above normal temps (triple digits in the Valley
again on Saturday). Upper level closed low will approach the coast
for the end of the weekend and move inland for the start of next
week. Differences remain between model solutions as low
transitions into negative-tilt trough, but looks like a chance
for showers and thunderstorms across higher elevations for Sunday
through the end of the period. Regardless of precip chances,
relief from the heat likely on the way with temps dropping around
15 degrees from Saturday to Monday. Increasing flow through the
Delta will result in even cooler temps in that region. CEO

&&

.AVIATION...
VFR conditions with light winds under building high pressure.

&&

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

&&

$$



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