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AGUS76 KRSA 181408
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
710 AM PDT Wed Sep 18 2024

...CONTINUED COOLER TEMPERATURES WITH PRECIP AND ISOLATED
THUNDERSTORMS POSSIBLE THE REST OF THE WEEK...
...DRY CONDITIONS RETURN BY THE WEEKEND WITH WARMING TEMPERATURES
INTO THE COMING WEEK...

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

Between the previous low and the current one sitting just offshore
of the northern CA coast, showers fell across the northern portion
of the region yesterday dropping generally a few hundredths to a
couple tenths of an inch over northern CA/NV. Isolated locations saw
closer to 0.25-0.50". The low will continue to travel southward the
rest of today with the core of the system just offshore. The center
of the low is expected to pass the Bay Area this afternoon reaching
the central coast by the evening. As it moves offshore, the low will
generate some scattered showers and thunderstorms from the
northern/central CA coast through to the Sierra and into NV. Current
guidance has the low staying offshore longer than previous runs
making for less precip over the region than prior forecasts. The
exception is favorable orographics into the Sierra along with decent
moisture (~1" PW) continue to increase QPF across that area (0.75-
1.25" for some locations). Both the GFS and the ECMWF have the low
stalling when it reaches the Big Sur coast later today sitting in
place until starting to move again Thursday afternoon-ish. The GFS
has the low shifting south of Point Conception in the evening before
moving inland through srn CA near San Diego early Friday. The ECMWF
has it moving inland shortly after passing Point Conception but
slowly enough that the two catch up position wise over soCal mid
Friday morning. All this time scattered showers and thunderstorms
will remain a possibility, though QPF amounts look generally low at
0.10" or less aside from thunderstorms and about 0.50-0.75" over the
western Transverse Range. The low will then move through the
southern tip of NV and start entering AZ by the early evening
refocusing showers/thunderstorms over se CA and srn NV. In addition
to precip, this system is also expected to bring widespread below
normal temperatures through Friday by about 5 to 15 deg F.

Behind the exiting low, a ridge of high pressure will build in over
the eastern Pacific returning dry conditions to the region the rest
of the forecast period along with warming temperatures. Expecting
afternoon highs to rise to as much as 10 or so deg F above seasonal
normals for parts of CA Sunday before becoming more widespread
across the region Monday.


Please Note: This product may NOT be routinely updated Friday
through Sunday between Jun 1 and Oct 1. Please refer to
www.cnrfc.noaa.gov/dailyBriefing.php 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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