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AGUS76 KRSA 041438
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
740 AM PDT Sat May 4 2024

...WIDESPREAD PRECIP ACROSS THE REGION TODAY WITH ISOLATED T-STORMS
OVER NRN CA THIS AFTN/EVE AS A LOW MOVES THROUGH NRN CA AND A COLD
FRONT/MOISTURE PLUME TRAVEL THRU CENTRAL/SRN CA...
...LIGHT SHOWERS ALONG THE NRN REGIONAL BORDER MON BEFORE DRYING AND
WARMING KICK OFF THE REST OF THE WEEK...

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

An upper low is on the approach currently west of OR as a cold front
and moisture plume traverse CA. TPW satellite has the moisture plume
surrounding the Bay Area as radar imagery shows widespread precip
across much of CA north of I-80 and currently spreading across the
bays. Precip overnight came in a bit heavier than models initially
predicted with observations over the past 12 hrs along the north
coast reporting anywhere from 1.50" to over 3". Amounts then taper
off to the south and east down to 0.10-0.25".

The front and moisture plume will continue to sweep through the
region this morning reaching Point Conception in the afternoon and
moving through soCal overnight. Meanwhile, the upper low offshore
will head inland through nrn CA this afternoon before moving into NV
this evening/overnight. As the low moves through nrn CA, chances of
isolated thunderstorms for the afternoon and evening. Heaviest
period of precip will be mainly through this morning as the front
and moisture plume separate further from the parent low the rest of
the weekend. Scattered showers will persist this afternoon and
tonight diminishing across CA on Sunday as the front/moisture plume
exit to the south and the low progresses further eastward through
NV. The low is then expected to start to enter UT/ID in the late
afternoon/evening Sunday. The exiting low and a weak disturbance
moving through the PacNW will keep light scattered showers possible
along the CA/OR border and over ne NV into Monday morning.
Today/tomorrow contain the bulk of the QPF for the next 6 days with
highest amounts expected along the central coast and across the
Sierra. QPF 18z today to 12z Mon: 1-2.50" across the Sierra, 0.25-
0.75" along the north coast, 0.10" to <1" Bay Area/Central
Coast/valleys, and a few hundredths to 0.25" along coastal soCal
(0.50-1" for some of the mountains).

This system will also act to cool temperatures and lower freezing
levels across the region this weekend. Afternoon highs for today are
looking 10-20+ deg F below normal for most of CA with still near to
above normal conditions across se CA and eastern NV. Lower
temperatures will spread into Sunday with most of the region 10-20+
deg F below seasonal normals through Monday. Freezing levels
lowering from nw to se today starting at 3-6.5 kft north of I-80
this morning before lower levels spread across much of the state to
2.5-5.5 kft north of Point Conception by Sunday morning. As the low
exits, freezing levels will rebound up to 4-8 kft north of I-80 and
7-13 kft to the south early Monday.

Some brief transitional ridging then on Monday ahead of a shortwave
approaching OR. Troughing will dig through the PacNW throughout
Monday scraping the northern CA/NV borders resulting in shower
chances for those areas through Tuesday morning. Models also have
the back edge of the trough dipping across NV generating some light
showers further across the state Tuesday morning. At this time, the
low that is currently offshore will have strengthened and joined the
system that moved through the PacNW over the central US while high
pressure builds over the eastern Pacific. This pattern of high
pressure offshore of the west coast and low pressure over the
central U.S. will persist the rest of the period with troughing
occasionally retrograding back into NV and pushing high pressure to
the west. This will keep dry conditions in place and temperatures
for much of interior CA and NV below normal while parts of northern
and coastal CA see above normal temperatures.


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



AS

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