358
AGUS76 KRSA 041413
HMDRSA

Hydrometeorological Discussion
National Weather Service / California-Nevada RFC / Sacramento CA
715 AM PDT Fri Sep 4 2026

...LINGERING SCATTERED SHOWERS TODAY AS A COLD FRONT AND UPPER LOW
MOVE THROUGH...
...SHOWERS POSSIBLE FOR SOUTHERN CA/NV AND THE NORTHERN REGIONAL
BORDER SUNDAY...

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

An upper low is slowly making its way into the PacNW as a cold front
continues to traverse southern CA stretching offshore south of Point
Conception and up through into central NV. The moisture that was
ahead of this front continues to weaken diminishing precip chances
for southern CA compared to what nrn CA saw yesterday. Observations
overnight reported 1-1.50+" over the northern/central Sierra and
0.25-1" scattered across the Bay Area and the Smith Basin. 12z
morning sounds across the region now show PW values below 1". A weak
surface trough offshore of nrn CA and the PacNW in combination with
the upper low is generating some showers along the north coast while
the larger main frontal system produces showers over parts of the
northern Sierra and into NV north of I-80. Expecting showers to
linger over these areas the rest of today maybe producing up to
another 0.50" for some areas, but generally 0.10" or less for most.

As for the weekend, the upper low will continue to meander around
the PacNW keeping below normal temperatures in the forecast.
Moisture from Hurricane Marie is still expected to move into srn
CA/NV on Sunday resulting in some precip. There is still uncertainty
on the amounts, models are showing potential for a narrow corridor
of more moderate precip stretching from LA to srn NV as this
moisture moves through. The GEFS ensembles maintain generally less
than 0.25" for Sunday over LA while the ECMWF has at least a few
members exceeding 1". For now it looks like yesterday`s forecast of
a few hundredths to 0.33" remains the most likely, though a few
locations may reach 0.50". Additionally, the low moving through OR
may generate some showers over the northern regional border on
Sunday as well with similar amounts predicted.

The PacNW low is still on track for the northern Rockies early next
week as another system moves in from the northwest. Uncertainty
remains on how close the low will be to the coast and its strength.
Models at this time also show the remnants of Marie moving northward
offshore. The det GFS and ECMWF have this system merging with the
other upper low around mid-week keeping both far enough offshore to
prevent much if any precip over CA/NV. However, some ensemble
members do have what`s left of Marie moving into either southern or
central CA sometime Tuesday or Wednesday. The ECMWF members have the
highest precip totals with the spread anywhere from 0 to 4" over LA
while the GEFS is limited to under an inch. Either way, enough
ensembles show this trajectory that more widespread showers have
shown up in the latest NBM. For now, have kept Tuesday mostly dry
and gone with WPC for Wednesday showing less than 0.10" for
central/southern CA and up to 0.50" for parts of the southern
Sierra. Uncertain at this time on timing/location/amounts of precip
for mid next week as this will depend on the tracks of Marie and the
next upper low.


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.

QPF graphics are available at www.cnrfc.noaa.gov/qpf.php



AS

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