####018005422####
AGUS76 KRSA 051430

HMDRSA



Hydrometeorological Discussion

National Weather Service / California Nevada RFC / Sacramento CA

730 AM PDT Sun May 5 2024



...SCATTERED SHOWERS & ISOLATED T-STORMS TODAY AS A SYSTEM EXITS THE 

REGION FOLLOWED BY SHOWERS ALONG THE NRN CA/NV BORDERS MON INTO 

TUES AS A DISTURBANCE MOVES THROUGH THE PNW...

...WARMING AND DRYING TREND BEGINS EARLY NEXT WEEK...



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



Radar imagery capturing scattered showers this morning, mainly north 

of I-80, as the upper low that began to move through nrn CA 

yesterday enters NV. Most of CA saw at least some rain yesterday 

between the upper low and the cold front/moisture plume. Highest 

precip amounts over the past 24 hrs were across the northern/central 

Sierra at 1" to just over 3" with about 0.50-1.25" across the rest 

of northern/central CA. Several thunderstorms developed over nrn CA 

yesterday afternoon/evening while the cold front/moisture plume 

brought about 0.10-0.50" of precip to coastal soCal and 0.50-1.25" 

in the mountains. Snow was also reported across much of the CA 

mountainous areas.



The cold front and moisture plume will continue to progress to the 

south this morning, exiting into Baja over the next few hours. 

Meanwhile, the upper low will push further into NV allowing 

scattered showers to persist along with chances of thunderstorms 

over northern NV. The upper low will begin to exit to the east later 

this afternoon and into the evening as high pressure builds into the 

eastern Pacific/CA behind it. This will allow for conditions to dry 

out for most of the region. The continued presence of the low today 

will result in another day of far below normal afternoon high 

temperatures by 10 to 25 deg F.



A weak disturbance will pass through the PacNW on Monday resulting 

in chances of showers along the northern regional border through 

Tuesday morning before joining with the current low to become a 

larger system over the north central US. Over the eastern Pacific, a 

stronger ridge will build keeping most of the rest of the region dry 

into early next week and kicking off a gradual warming trend. The 

pattern for the rest of the week will remain high pressure to the 

west and low pressure to the northeast. The ridge will attempt to 

push into CA throughout the week only to be battled back by 

troughing from the larger upper low. This will result in some 

moderation of the warming allowing interior CA and NV to remain 

below normal while conditions rise to near/above normal for the 

coast and into the Sacramento Valley. The large upper low over the 

north central US will then split in two with the western edge 

retrograding back towards the west coast into Thursday and kicking 

the ridge offshore. Most ensembles are dry with the returning low, 

but a handful show the potential for showers over the Sierra and 

eastward into NV Thursday. For Friday, the low and ridge will battle 

for positioning to determine the fate of the west. The 500mb height 

clusters for 00z Saturday (Friday afternoon) are divided on how much 

influence the low will ultimately have with the GFS members (like 

its deterministic parent) more in favor of the low and the ECMWF the 

ridge. The det GFS even shows some showers over the Sierra and 

through to central NV Friday while the ECMWF is dry. This will 

impact temperatures as well should the ridge push more into the 

region, temperatures will be warmer than if the low is the more 

dominant feature.



To summarize, continued scattered shower activity with isolated 

thunderstorms and below normal temperatures today as a system exits 

the region. Light showers along the northern regional border Monday 

into Tuesday as a disturbance moves by to the north followed by a 

warming and general drying trend the rest of the week with high 

pressure to the west and low pressure to the east. Some uncertainty, 

mainly for the end of the week into the coming weekend on how far 

into the region and for how long a low will push in from the east.



Nearly all the QPF in the forecast is expected before Tuesday 

morning. Today's forecast was a blend of the morning WPC guidance 

and the latest NBM. Highest amounts along the northern regional 

border and into the srn OR Cascades with scattered showers of a few 

hundredths to a tenth of an inch or so (higher amounts under 

thunderstorms or heavier convective showers). QPF through Tues am: 

075-1.60" srn OR Cascades, 0.10-0.75" Smith Basin, 0.10-0.50" nrn 

CA/nrn NV borders (higher in the nrn NV mountains), and a few 

hundredths to a couple tenths over the northern Sierra (scattered 

showers possible across the rest of CA/NV).



Lower freezing levels hang around today at 3.5-6.5 kft north of 

Point Conception before higher levels spread northward tomorrow. 

Expecting freezing levels 4.5-9.5 kft north of I-80 Mon am and 7-13 

kft to the south. Higher freezing levels will continue to spread 

northward Tuesday staying generally above 7 kft through mid-week 

(aside from the northern regional border at 4.5-6 kft). By Thurs 

afternoon the entire region will be above 8 kft and up to 12.5 kft.





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







AS



$$