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AGUS76 KRSA 131331
HMDRSA

Hydrometeorological Discussion
National Weather Service / California-Nevada RFC / Sacramento CA
630 AM PDT Sun Sep 13 2026

...LIGHT LINGERING SHOWERS AS A LOW PASSES TODAY ALONG WITH BELOW
NORMAL TEMPERATURES...
...POSSIBLE ADDITIONAL LIGHT SHOWERS OVER NRN CA WEDS WITH OTHERWISE
DRY CONDITIONS THE REST OF THE PERIOD...

.METEOROLOGICAL CONDITIONS (SUN AM - SAT AM)...

An upper low is making its way through the PacNW this morning with
the southern edge of the system scraping northern CA. Not much to
show on radar with just a few light echos along the border.
Overnight observations showed about 0.10" over those locations with
higher totals on the OR side. The low will head northeastward
lifting into ID later today while troughing from the low remains
overhead. Some lingering showers possible along the CA/OR border
into tonight as the low passes. Otherwise, dry conditions and more
widespread below normal temperatures expected for the rest of today.
Models then still show drier air moving in over CA/NV behind the low
tomorrow preventing additional chances for precip.

One thing that has changed from yesterday, now the GFS and the ECMWF
show a low forming over the PacNW on Tuesday rather than just some
broader weak troughing. This low also carries some moisture with it
breaking up the drier airmass that was expected to remain overhead
basically the rest of next week. Both the GFS and the ECMWF then
show the low digging into nrn CA some time Wednesday, disagreements
on exactly when, and dropping some light precip as it arrives.
Models then lift the low back northeastward into OR/ID at the end of
the week with some ridging building in behind it. Don`t have a lot
of confidence on this development but if it sticks around the next
few model runs we`ll see. For now, blended in the ECMWF/GFS into WPC
morning guidance to generate some showers over nrn CA/srn OR on
Wednesday. Amounts look minimal at less than 0.10". Should this low
manifest, it would also act to keep cooler temperatures overhead and
delay a bit of warming from that next ridge.


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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