...COOLER TEMPS ALONG WITH SHOWERS AND THUNDERSTORMS TODAY AS A LOW
MOVES THROUGH...
...LINGERING SHOWERS OVER THE SIERRA INTO NV ON FRIDAY WITH DRY
CONDITIONS THEN EXPECTED FOR MOST AREAS OVER THE WEEKEND ALONG
WITH SOME WARMING...

.METEOROLOGICAL CONDITIONS (THU AM - WED AM)...

The upper low that was traveling along the nrn and cntrl CA coasts
yesterday has reached Point Conception. Radar and satellite imagery
show this system continues to rotate showers and thunderstorms
across the region. Particularly heavy thunderstorm activity can be
observed over the Desert Southwest with large clusters of lightning
being picked up by sensors. Precip came in heavier across southern
CA than anticipated yesterday as observations report 24 hr totals
across the area of 0.50" to over 3". The rest of the region received
anywhere from a few hundredths to 1.50".

The low will progress inland across southern CA today lifting
northeastward into NV by the late afternoon while opening into a
trough. The majority of the precip from the remainder of this system
will fall today as showers and thunderstorms continue. Precip will
then diminish on Friday as the main part of the system exits to the
northeast. Broader troughing will remain overhead as a shortwave
slides down the back of that exiting system and forms a secondary
low somewhere over southern CA by the evening. While this will carry
some moisture near the core, it will not be as wet or widespread as
the current system. Expect a few additional showers over srn CA, but
for the moment it doesn't look like more than a few hundredths or
so. Ensembles over San Diego don't show more than 0.20" for Friday
night to Saturday night while most are less than 0.10". The presence
of the current system and persistent troughing will also act to keep
temperatures below normal across the region the rest of the work
week with anomalies of -5 to -15 deg F.

Behind the trough, an upper ridge will build in over the eastern
Pacific into Saturday while shifting into the west coast. An upper
low just behind it coming in from the Gulf of Alaska will force it
to move quickly through the region to prevent prolonged warming. The
ridge should bring temperatures back up to near seasonal normals the
rest of the period. That upper low from the northwest this time will
not travel down the CA coast but will head into the PacNW some time
on Monday. Models still disagree on the exact path and timing of
this next low. Det models favor the PacNW but some ensembles do send
the system into nrn CA. Ensembles of 24 hr QPF at Arcata range from
0 to 1". Arrival timing of showers, should there be any, varies
amongst the ensemble members as well showing anything from Saturday
night to late Monday morning. The official forecast brings in some
very light scattered showers late Sunday night through Monday and
not more than 0.10".

QPF for the next 24 hours was a blend of WPC, the NBM, and
occasionally the west WRF/HRRR. Much of the remaining precip will be
convective, which models often struggle to nail down the location
and amounts of precip under those conditions. Any amounts in the
official forecast will be higher/lower depending on where storms
develop. QPF through 12z Saturday: 0.50-1.25" Sierra/ne CA, 0.25-1"+
NV, 0.25-0.75" coastal srn CA, 0.10-0.50" around the Bay
Area/valleys/nrn CA, and 0.10" or less elsewhere.

Freezing levels 8.5-11.5 kft west to east this morning with lower
levels spreading across the region into tonight as the low moves
through. They will then rebound from west to east tomorrow as the
ridge approaches rising back to 9.5-12.5 kft across CA by Saturday
morning. Freezing levels will re lower north of Shasta when that
next low moves through the PacNW early next week.

Please Note: This product may NOT be routinely updated.
Please refer to the following product issued by the CNRFC
www.cnrfc.noaa.gov/Daily-Briefing for a graphical summary of
weather and hydrologic conditions.