FGUS65 KSTR 072008 ESGUT NATIONAL WEATHER SERVICE COLORADO BASIN RIVER FORECAST CENTER SALT LAKE CITY, UT April 6, 2023 SPRING FLOOD POTENTIAL OUTLOOK UTAH Great Salt Lake, Sevier, Virgin, Price/San Rafael, Duchesne and Lower Green River Basins. The 2023 spring runoff flood potential due to snowmelt is high at this time for all major river basins in Utah due to near record or record snowpack. These basins include the Bear, Weber, Provo, Six Creeks,Duchesne,Sevier,Virgin,Price/San Rafael,and Green River basins. It should be emphasized that snow typically accumulates into April,therefore conditions may change before the runoff begins. Currently, the following sites are forecast to have mean daily peak flows at or above the defined flood flow at the given exceedance level: Segment Threshold Exceedance Value (probability) ------- -------- ------------- Blacks Fk-Robertson Flood 10 Green-Jensen Flood 50 Green-Green River UT Flood 25 Duchesne - Tabiona Flood 25 Bear-Utah-Wyoming State Line Bankfull 90 Bear-Evanston Flood 10 Bear-Border Flood 90 Logan-Logan Flood 25 Little Bear-Paradise Flood 90 Blacksmith Fork-Hyrum Flood 10 Weber-Oakley Flood 25 Chalk Ck-Coalville Flood 25 Mcleod Ck-Park City Flood 25 Provo-Woodland Flood 10 Little Cottonwood-SLC Flood 50 Big Cottonwood-SLC Flood 90 Mill Ck-SLC Flood 25 Emigration Ck-SLC Flood 50 City CK-Salt Lake City Flood 90 Sevier-Hatch Flood 50 Specific forecast procedures and flood flow levels do not exist for all streams. Areas that typically experience high water in normal or above normal snow years will be susceptible during peak runoff this year. Instantaneous peaks can be higher than mean daily peaks, especially in headwater basins. Precipitation for all major river basins in Utah was much above average for March and is also much above average for the water year. April 1 snow water equivalent is much above median with many basins having record or near record snow conditions. Temperatures have remained below normal limiting any significant snowmelt which has resulted in much above normal snow conditions at all elevations. PRECIPITATION (% OF AVERAGE) AND SNOWPACK (% OF MEDIAN): SUBBASIN MAR PRECIP OCT-MAR PREC APR 1 SNOWPACK ---------------------- ---------- ------------ ------------- BEAR 205 135 175 WEBER 230 150 220 SIX CREEKS (SLC) 255 160 230 PROVO 245 160 250 SEVIER 195 150 225 VIRGIN 210 170 400 DUCHESNE 210 140 200 PRICE/SAN RAFAEL 220 150 245 Spring temperatures and rain events greatly affect the pattern of snowmelt runoff and consequently the magnitude of peak flows. It is important to keep in mind that an extended period of much above normal temperatures or heavy rainfall during the melt period can cause or exacerbate flooding problems in any year. A list of specific spring peak flow forecasts is available at: https://www.cbrfc.noaa.gov/dbdata/station/peakgraph/list/peaklist.html?type=rank A map of the current spring peak flow forecasts is available at: https://www.cbrfc.noaa.gov/lmap/lmap.php?interface=peakfp The spring runoff flood potential will be re-evaulated in mid April and an updated product will be issued at that time. CBRFC/P.Kormos, B.Alcorn, T.Grout