...AN UPPER LOW MOVING THROUGH THIS WEEK WILL BRING WIDESPREAD
PRECIP AND THUNDERSTORM CHANCES ALONG WITH COOLER TEMPERATURES...

.METEOROLOGICAL CONDITIONS (SHORT TERM: TUE AM - MON AM)...

An upper low now rotates offshore west of the Bay Area this morning,
having traveled south off the nrn CA coast overnight. Observations
report about 0.10-0.30" of precip along the north coast over the
past 12 hours. Satellite imagery and lightning detection show some
flashes near the core of the low. The system will continue to move
towards southern CA offshore the rest of today rotating showers and
possibly thunderstorms over the Sierra and eastward into NV.
Tomorrow, the low will start to shift eastward towards the coast
bringing more moderate precip into coastal srn CA and inland to the
Sierra as the eastern half of the system pushes inland.
Additionally, models show MUCAPE into coastal srn CA Wednesday
afternoon up to 500 J/kg with lesser amounts along other parts of
the CA coast and inland across the Sierra. This means chances of
thunderstorms, particularly in the afternoon. Higher rainfall rates
are also a possibility where WPC has a slight risk of excessive
rainfall across parts of srn CA along the coast over Santa
Barbara/Ventura counties and a bit northward. HREF exceedance
probabilities for Wednesday afternoon have around a 30% chance of
0.50"/hr rates, 15% chance of 1"/hr or even 2"/hr in that slight
risk area. Rain rates of 0.5"+/hr over the Sierra show higher
probabilities of around 50%. Amounts for Wednesday are still
uncertain as the exact path of the upper low may continue to shift
between model runs. Ensemble spread remains high. Looking at 24 hr
QPF ensembles at Santa Barbara Airport for Wednesday, amounts vary
from 0.50" to 3". Models do agree on the main focus of precip from
this system still being over coastal srn CA, the Sierra, and
southern NV.

Thursday, the core of the low will start to move inland near Point
Conception spreading showers across much of the region. Thunderstorm
chances persist as instability continues to rotate inland. Best
chances of thunderstorms over CA south of Santa Cruz to San Diego
and northeastward through NV. The low will open up into a trough
late Thursday and into Friday as the system lifts northeastward.
Best precip totals over the eastern Transverse and San Diego inland
mountains, the Sierra, and eastern NV. Precip will diminish on
Friday over CA as the trough moves through NV with lighter showers
wrapping up over ne NV in the evening. Models then have a low
forming over AZ on Saturday and a ridge building in from the eastern
Pacific. A handful of ensembles are showing some precip along the
north coast and into the nw CA/OR border from a weakening front over
the weekend , however det models remain dry along with the rest of
the ensemble members. Therefore, have kept any precip out of the
official forecast for Saturday and Sunday as ridging seems most
likely at the moment.

The rest of the QPF was mainly a blend of WPC and the NBM with
occasionally a little of the ECMWF/GFS as well. QPF since yesterday
for the duration of the system has increased by 0.10-0.50" over the
southern Sierra and much of coastal srn CA with increases of up to
1" for the San Bernadino mountains. Amounts went down by 0.10-0.50"
around the Bay Area and the northern Sierra into nw NV. Majority of
the precip is still expected for Wednesday/Thursday. QPF through
Friday: 0.50-1.50" coastal srn CA/Sierra, 1.25-2.25" Transverse
Range, 0.10-0.30" Bay Area, 0.10-0.75" central coast, 0.25-1" ne CA
and NV, and 0.10" or less for nw and se CA.

Freezing levels 9.5-12.5 kft today with lower levels spreading
across central CA into Thursday at 8.5-10.5 kft. Levels will rebound
behind the exiting low Friday back up to 10.5-12.5 kft for most of
CA by late Friday afternoon.

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.