201 FGUS75 KBOI 072015 ESFBOI IDC001-003-005-007-009-011-013-015-017-019-021-023-025-027-029-031- 033-035-037-039-041-043-045-047-049-051-053-055-057-059-061-063-065- 067-069-071-073-075-077-079-081-083-085-087-080600- Water Supply Outlook National Weather Service Boise ID 114 PM MST Thu Mar 7 2019 ...IDAHO SPRING FLOOD AND WATER RESOURCES OUTLOOK... Spring Flood Potential... The potential for spring flooding due to snowmelt is slightly elevated for much of the central Idaho Mountains, particularly in the Big Lost and Wood River Basins, as well as the Upper Boise, Payette, and Weiser Basins. For the remainder of the state the spring flood potential due to snowmelt is average. The primary factors in the development of spring flooding are the occurrence of persistent above normal temperatures, and rain on snow precipitation events. Even for areas that have low snowpack, spring flooding is possible under the right conditions. Additionally, wildfire burn scars can have a significant impact on local flood potential during spring snowmelt. Water Supply... National Weather Service April through September water supply volume forecasts vary from 90 to 135 percent of average from the Clearwater Basin south to the Snake River Plain and the Snake River Headwaters. Forecasts for Southside Snake River Basins, the Bear River Basin and Idaho Panhandle vary from 70 to 90 percent of average. These forecasts may change considerable over the next couple of months since seasonal snow accumulation and rainfall typically occur during March and April. Temperature and Precipitation... Wet weather early last fall was beneficial in recharging the soil moisture after a very dry and warm summer. However, fall precipitation as a whole was below normal across the state and subpar precipitation continued through most of January. February precipitation was exceptional across west-central and southern Idaho with much of the area receiving 200 to 300 percent of normal. Precipitation for the 2019 Water Year so far (Oct 1, 2018 to March 1, 2019) is normal or above normal for central and southern Idaho, and normal to below normal for the Panhandle Region. Mean temperatures for the 2019 Water Year so far have been close to normal. However, February temperatures were well below normal across the state, especially in northern Idaho. Snowpack... As of March 7, snowpack for the Salmon River Basin south to the Nevada and Utah border, and the Snake River Headwaters Region was above normal. The highest percentages were in the Big Lost Basin, Wood River Basins, Payette Basin, and Weiser Basin, ranging from 134 to 151 percent of normal. Northern Idaho snowpack ranged from 89 to 100 percent of normal in the Northern Panhandle, Spokane, and Clearwater Basins. Idaho snowpack as a whole typically builds through March and peaks in early April. Reservoirs... Reservoir storage across Idaho is in good shape as of early March with major reservoir systems holding near average or above average water. Across southern Idaho, reservoir storage in the Bear River Basin was near 140 percent of average and Southside Snake Basin storage was near 95 percent of average. The Upper Snake Basin, Wood River Basins, and Lost River Basins were near 125 percent of average. Storage in West Central Basins was near 98 percent of average, and the Clearwater and Panhandle Regions were near 97 and 104 percent of average. Weather patterns, irrigation demand, and flood control needs will drive reservoir operations over the next several months. Wet spring weather or extended periods of above normal temperatures resulting in rapid snowmelt and large reservoir inflows could result in significant fluctuations in reservoir discharge and downstream river levels. Drought... Moderate to severe drought plagued portions of Idaho through the fall and early winter, especially across southern Idaho and near the Utah and Nevada border. Drought conditions were eased by well above normal precipitation and a large increase in snowpack during February. The latest U.S. Drought Monitor shows pockets of lingering drought across far southwest Idaho and along the Utah border. Weather and precipitation for the remainder of winter and this spring will determine whether or not drought conditions continue to improve or deteriorate. Seasonal Outlook... The outlook for March through May favors above normal temperatures across Idaho. The precipitation outlook favors wetter than normal conditions across far southeast Idaho, with equal chances of either above normal, normal, or below normal precipitation for the rest of the state. Refer to the links provided below for the latest information on water resources. Water Supply Volume Forecasts National Weather Service-Northwest River Forecast Center www.nwrfc.noaa.gov/ws/ National Weather Service-Colorado Basin River Forecast Center www.cbrfc.noaa.gov/ Snowpack Information National Weather Service-Northwest River Forecast Center www.nwrfc.noaa.gov/snow/ National Weather Service-National Operational Hydrologic Remote Sensing Center www.nohrsc.noaa.gov USDA-Natural Resources Conservation Service www.nrcs.usda.gov/wps/portal/nrcs/main/id/snow/ Reservoir Storage Bureau of Reclamation www.usbr.gov/pn/hydromet/select.html USDA-Natural Resources Conservation Service www.wcc.nrcs.usda.gov/basin.html Drought Conditions U.S. Drought Portal www.drought.gov Peak Flow Forecasts Northwest River Forecast Center www.nwrfc.noaa.gov/peak/ Colorado Basin River Forecast Center www.cbrfc.noaa.gov/rmap/peak/peaklist.php Temperature and Precipitation Outlook Climate Prediction Center www.cpc.ncep.noaa.gov/ $$ TL