BULLETIN 120: Forecast update

From the Department of Water Resources:

DWR has finished the March 22, 2022 Bulletin 120 (B120) forecast update. The forecast includes observed conditions through the morning of March 22, 2022.

 The forecasts are posted at:

• B120 Update:  https://cdec.water.ca.gov/reportapp/javareports?name=B120UP
• B120 Update WY Distribution:  https://cdec.water.ca.gov/reportapp/javareports?name=B120DIST

Forecast Summary:

The projected median April-July (AJ) runoff ranges in the major Southern Cascades/Sacramento River basins from 36 percent of average for the Trinity River basin to 58 percent of average for the Pit River basin, in the major San Joaquin River basins from 30 percent of average for the Cosumnes River basin to 61 percent of average for the San Joaquin River basin, and in the major Tulare basins from 23 percent of average for the Tule River basin to 55 percent of average for the Kings River basin.

Since the March 1 B120 was issued, the AJ forecasts for all river basins have decreased significantly (between 6 percent and 10 percent) due to the continued dry conditions and pre-April melt, except for larger decreases on the Feather (14 percent), Yuba (13 percent), and American (19 percent). Since last week’s forecast update, forecasts have dropped between 3 percent and 6 percent, except for that of the American which was decreased by 9 percent.

Runoff:

Since approximately March 15, full natural flow rates have increased due to snowmelt.  The increase is more pronounced in the central and southern Sierra.   All rivers are running below half of their respective March average rate except the San Joaquin (56 percent).  Five rivers (Trinity, Shasta Inflow, Sacramento at Bend Bridge, Cosumnes, and Tule) are flowing at a rate less than 25% of normal for the month.

Unimpaired flows in Percent of Average for Water Year 2022 are as follows:

River	Oct	Nov	Dec	Jan	Feb	Oct-Feb	Mar (Month to Date)
Trinity	312	195	40	46	32	59	23
Shasta	104	104	72	67	29	63	22
Sacramento at Bend Bridge	125	115	76	54	25	60	23
Feather	348	137	117	74	45	93	40
Yuba	566	163	115	57	35	87	32
American	814	198	144	58	40	95	39
Sacramento Region	233	131	99	60	33	75
Cosumnes	1334	151	254	51	28	89	18
Mokelumne	732	234	135	58	49	103	40
Stanislaus	432	161	146	47	47	89	42
Tuolumne	384	176	143	45	39	86	33
Merced	277	167	140	42	36	72	30
San Joaquin	282	170	215	71	67	117	56
San Joaquin Region	402	176	165	52	45	93
Kings	96	100	126	53	51	72	37
Kaweah	70	49	99	38	34	49	31
Tule	65	29	95	35	22	40	24
Kern	51	58	72	45	37	50	28
Tulare Region	76	74	104	47	42	60

Precipitation:

March remains well below average with none of the three indices recording more than 1.1” of precipitation.  After 24 days, the Northern California 8-Station and San Joaquin 5-Station Indices for March are 13% and 17% of an average March, respectively.  With the forecast showing no significant precipitation, it is likely that March will conclude a three-month period of well below average precipitation.

Precipitation summary for Water Year 2022 as of March 24, 2022:

Region	Percent of Average							Precipitation (inches)
	Oct	Nov	Dec	Jan	Feb	Mar (Month to Date)	WY to Date	Mar (Month to Date)	WY to Date
Northern Sierra 8-Station Index	453	58	144	14	4	13	77	1.1	33.0
San Joaquin 5-Station Index	314	25	195	0	2	17	68	1.1	21.5
Tulare Basin 6-Station Index	216	7	221	0	9	22	64	1.0	14.5

Snowpack:

The statewide snow water equivalent (SWE) based on snow sensors is 13.3 inches which corresponds to 48 percent of normal for this date.  Since March 1, the statewide snowpack has decreased by 2.5 inches, with 2.0 inches melting in the past 7 days.

The regional snowpack levels as of the morning of March 24, 2022 stand at the following (based on snow sensors): 

Region	No. of Stations	Avg. SWC	Percent of April 1	Percent of Normal
Northern	30	11.8	42	42
Central	42	14.9	50	50
Southern	26	12.5	49	49
Statewide	98	13.3	48	48

 

Weather and Climate Outlooks:

According to CNRFC 6-day forecast, precipitation is forecasted for Sunday and Monday and will impact the entire state.  The central and southern Sierra may see up to one inch of precipitation.   The southern Coastal region is forecast to receive the highest totals – most areas up to 1.5 inches and a few areas of the San Gabriel range to receive up to 2.5 inches.  Currently freezing levels are between 11,000-12,000 feet in the Northern Basins and at least 12,000 feet farther south.  As the front moves across the state on Sunday and Monday freezing levels will drop significantly to 5,000 to 7,000 feet in most areas before returning to between 9,000 and 12,000 feet on Tuesday. 

The NWS Climate Prediction Center (CPC) one‐month outlook issued on March 17, 2022, suggests equal chances of above or below normal temperatures throughout the northern half of the state; it suggests above average chances for higher-than-normal temperatures in the southern half. The southern 2/3rds of the state has increased chances for below normal precipitation whereas the northern third has equal chances of above or below normal precipitation.

The CPC three-month (April-May-June) outlook, issued on March 17, 2022, suggests equal chances of above or below normal temperatures for the central coast and northern third of the state; for the rest of the state increased chances of above average temperatures are expected.  The outlook also shows equal chances of above or below normal precipitation for the southern half of the state and increased chances of below normal precipitation for the northern half.

According to the latest El Niño/Southern Oscillation (ENSO) discussion issued by the Climate Prediction Center on March 21, 2022, La Niña conditions are present. Equatorial sea surface temperatures (SSTs) are below average across the east-central and eastern Pacific Ocean. The tropical Pacific atmosphere is consistent with La Niña.  These conditions are favored to continue into the Northern Hemisphere summer (53 percent chance during June-August 2022), with a 40-50 percent chance of La Niña or ENSO-neutral thereafter.

Next Update:

A Bulletin 120 update forecast for conditions as of March 28, 2022, will be available on Wednesday, March 30th.  If you have any questions regarding this forecast, please contact a member of the Snow Surveys and Water Supply Forecasting staff.

Important Links: 

Full Natural Flow Data:  

• Daily FNF
• Monthly FNF
• Seasonal FNF
• Tableau Dashboard – Historical FNF Comparison (Interactive Data Visualization)  
• Tableau Dashboard – Daily FNF (Interactive Data Visualization)

Precipitation Data:  

• Latest Northern Sierra 8-Station Precipitation Index Tabular Data
• Latest San Joaquin 5-Station Precipitation Index Tabular Data
• Latest Tulare Basin 6-Station Precipitation Index Tabular Data
• Latest Northern Sierra 8-Station Precipitation Index Plot
• Latest San Joaquin 5-Station Precipitation Index Plot
• Latest Tulare Basin 6-Station Precipitation Index Plot

Snow Data: 

• Latest Snow Sensor Report
• Latest Statewide Summary of Snow Water Equivalents
• Tableau Dashboard – Regional Snow Water Equivalent Comparison (Interactive Data Visualization)

 

Extended Regional Forecasts:  

• California Nevada River Forecast Center 6 Day QPF and Snow Level Forecast
• Climate Prediction Center One-Month Outlook Forecasts
• Climate Prediction Center Three-Month Outlook Forecasts
• U.S. Seasonal Drought Outlook
• Weather Forecast Office California Service Area-Products
• El Niño Southern Oscillation (ENSO) Conditions and Weekly Discussion (including La Niña)
• Atmospheric River Scale Forecast Products

Bulletin 120: 

• Tableau Dashboard – Snow Product Comparison for WY2022 (Interactive Data Visualization) *** NEW ***
• Tableau Dashboard – Bulletin 120 Forecast Performance Over Time (Interactive Data Visualization)  
• Historical Forecast Error Plots

Other Useful Links:

• California Water Watch *** NEW ***
• U.S. Department of Agriculture California Climate Hub by California State Climatologist *** NEW ***