Wildfire in California, June 25 to 27, 2019

Area Forecast Discussion
National Weather Service Sacramento CA
312 PM PDT Tue Jun 25 2019

.SYNOPSIS...
Daytime temperatures cooling through mid week with highs on Thursday
12 to 22 degrees below normal. A warming trend begins at the end of
the week with highs gradually climbing to near normal on Monday. No
precipitation expected except for a small chance of showers or
thunderstorms over the mountains of Shasta County. Occasionally
breezy winds through the Delta and over the higher terrain
during the next few days.

&&

.DISCUSSION....
Synoptic pattern over Wrn NOAM/Ern Pac dominated by a seasonably
deep (minus 2.7 anomaly) upper trof off the coast, and will result
in a (comfortably?) cooler than normal stretch of weather over
Norcal for the rest of the week. (Non-scientific survey of selected
co-workers reveals the term "comfortable" applies to these temps.)
The GEFS/EPS 5H anomaly charts suggest this trof will maintain its
cool influence on Norcal into the weekend. By Mon, temps should
rebound to normal. The return interval suggests this cool pattern
occurs about every 5-10 yrs in our region this time of year. Thu
looks to be the coolest day with high temps some 12 to 22 degrees
below normal (mostly 70s in the Valley, and 50s to 60s over the
higher terrain and foothills). The Probability Tool of less than 80
degrees reveals a high probability (50-97% wrt CONSALL) that Valley
temps will not equal/exceed 80 on Thu. This by no means is a lowest
max temp event as a climate data base search reveals temps in the
60s for this date (6/27), most recently in 2001 for RBL and the RDD
area. Overnite lows will drop into the 30s/40s in the mountains, and
50s in the Valley during the mid to latter portions of the week.

The low pressure center is near 50N/140W and is forecast to move
into ORE late Wed. The deepening trof will bring occasional
cloudiness to Norcal through the middle of the week, but it looks as
if convection will be limited or nil in our CWA. The elevated
instability charts suggest a low probability or potential for
thunder in our CWA, with the chances of convection near/around the
Shasta Co border and Lassen NP. In addition, the deepening trof will
increase SWly winds over the region resulting in some gusty ridge
winds over the Sierra, as well as breezy winds in the Valley,
during the middle of the week.

In the short term, the marine layer has deepened to near 2000 ft but
remains mixed-out from around MTR Bay northward. As the trof deepens
offshore, the marine layer should deepen and/or lift with the chance
of seeing some marine cloudiness spreading inland Thu as onshore
flow increases. The low clouds may also be accompanied by higher
level cloudiness from the synoptic upper trof.  JHM

&&

.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)

A gradual warming trend continues from the weekend into early
next week. A general upper level trough is expected to linger
around the West Coast into Sunday. Ensembles suggest this will
weaken, while the latest European tends to keep the trough into
mid week. Confidence remains low given the continued deterministic
and ensemble differences. Will lean towards ensemble and NBM for
temperatures. This means forecast highs are projected to remain
below normal through Sunday, followed by near normal temperatures
early next week. EK

&&

.AVIATION...

VFR conditions with broken cirrus at times and surface winds mostly
less than 10 kts at TAF sites through 18z Wed, increasing to gusts
25-35 kts after 18z Wed. Limited depth and extent of marine stratus
will keep MVFR CIGS to near the coast and immediate coastal valleys
tonight.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&