May 1, 2026 Spring and Summer Streamflow Forecasts
Upper Missouri Basin
The high elevation snow pack in the Upper Missouri Basin as of May 1
was below average. The snow pack in the St. Mary Basin was 57 percent,
and the Milk River Basin was 55 percent.
April precipitation across the Upper Missouri Basin was below average.
Basin precipitation summaries for the Missouri Basin include: Milk St. Mary,
59 percent; Milk Canada, 42 percent; Lower Milk, 85 percent; above Toston,
104 percent; Toston to Ft. Peck, 75 percent.
April 2026 Upper Missouri Mean Precip Oct-Apr WY2026 Upper Missouri Mean Precip
Stream flow in the Upper Missouri Basin is forecast to be
below average during the upcoming Spring and Summer.
The St. Mary River is forecast to have 53 percent of average
April-September flows. Runoff is expected to range around
76 percent of average for the Missouri Basin above Fort Peck,
Montana.
Upper Missouri May 1, 2026 Spring and Summer Streamflow Forecasts
Of the four major irrigation reservoirs in Montana; Lima
Reservoir had 95 percent average storage, Clark Canyon was
holding 96 percent of average water, Gibson Reservoir had 99
percent of average stored water, and Fresno Reservoir had
49 percent of average stored water.
Yellowstone Basin
The high elevation snow pack in the Yellowstone Basin was near average
on May 1. The snow pack in the Upper Yellowstone Basin was 71 percent
of average. The snow packs in the Wind, Bighorn, and Shoshone Basins were 60,
54, and 55 percent of average, respectively. The snow packs in the Tongue
and Powder basins were 36 and 17 percent of average, respectively.
Precipitation during April was near to below average. The upper Yellowstone
River Basin received 66 percent of average precipitation while the Lower
Yellowstone River Basin reported 69 percent of average. The Bighorn
Basin received 78 percent of average precipitation while the
Wind River Basin received 69 percent of average. The Little Bighorn -
Upper Tongue Basin received 104 percent of average and the Powder River
had 74 percent of average precipitation.
April 2026 Yellowstone Mean Precip Oct-Apr WY2026 Yellowstone Mean Precip
Forecast stream flow in the Yellowstone Basin is below average
for the upcoming Spring and Summer. Stream flow for the
Yellowstone River above Sidney, Montana is forecast to be about
68 percent of average. Flow in the Tongue Basin is expected to be
45 percent of average. Flows in the Powder River are expected
to be about 25 percent of average.
Monthend storage at Boysen Reservoir was 96 percent of average.
Stored water in Buffalo Bill Reservoir was 112 percent of average.
Monthend storage was 99 percent of average at Bighorn Reservoir.
Yellowstone May 1, 2026 Spring and Summer Streamflow Forecasts
Platte Basin
The high elevation snow pack in the Upper North Platte Basin was
29 percent of average on May 1. The snow pack in the North Platte
Basin below Seminoe Reservoir was 74 percent of average. The snow
pack in the South Platte Basin was 54 percent of average.
Precipitation during April in the Upper North Platte Basin was 91
percent of average. In the Lower North Platte Basin, precipitation
was 79 percent of average. The North Platte Plains below Guernsy
Reservoir had 21 percent. The South Platte Mountains had 38
percent whereas the Plains had 31 percent of average April
precipitation.
April 2026 Platte Mean Precip Oct-Apr WY2026 Platte Mean Precip
Stream flow in the Platte Basin is forecast to be below
average during the upcoming Spring and Summer. Runoff
for streams above Seminoe Reservoir are expected to be
about 46 percent of average. Streams in the South Platte
Basin above South Platte, Colorado can expect 42 percent
of average flow. For the remainder of the South Platte
basin, flows are expected near 40 percent.
Stored water in the South Platte Basin was 93 percent of average
on May 1.
North Platte Streamflow Fcst South Platte Streamflow Fcst
WATER SUPPLY FORECAST NWS MISSOURI BASIN RIVER FORECAST CENTER PLEASANT HILL MISSOURI DATA CURRENT AS OF: MAY 01, 2026 .B KRF 20260930 M DH24 /DC202605011200/DVM06/QVVFZZ5/QVVFZZ1/QVVFZZ9 :MISSOURI/YELLOWSTONE/PLATTE RIVER BASIN FORECASTS : 50% % 10% 90% AVG :FORECAST PT PERIOD (KAF) AVG (KAF) (KAF) (KAF) :----------------------------------------------------------- SBDW4 : Apr-Sep : 299/ : 42: 554/ 187: 720 :Boysen Resvr Inflow SBDW4N : Apr-Sep : 751/ : 84: 1054/ 565: 890 :Boysen Resvr Inflow LVEW4 : Apr-Sep : 530/ : 54: 830/ 431: 985 :Bighorn R at Kane LVEW4N : Apr-Sep : 1092/ : 76: 1550/ 837: 1440 :Bighorn R at Kane MEEW4 : Apr-Sep : 87/ : 44: 165/ 60: 196 :Greybull R at Meeteetse MEEW4N : Apr-Sep : 87/ : 42: 165/ 60: 205 :Greybull R at Meeteetse CDYW4 : Apr-Sep : 478/ : 59: 618/ 405: 815 :Buffalo Bill Resvr Inflow CDYW4N : Apr-Sep : 612/ : 67: 753/ 535: 910 :Buffalo Bill Resvr Inflow KEYW4 : Apr-Sep : 5/ : 125: 13/ 3: 4 :Keyhole Resvr Inflow SMYM8 : Apr-Sep : 377/ : 82: 434/ 340: 460 :St. Mary R nr Babb SMYM8N : Apr-Sep : 343/ : 64: 401/ 307: 535 :St. Mary R nr Babb SMBM8 : Apr-Sep : 235/ : 60: 315/ 181: 390 :St. Mary R at Intl Boundary SMBM8N : Apr-Sep : 321/ : 49: 399/ 276: 660 :St. Mary R at Intl Boundary PDBM8 : Apr-Sep : 10/ : 9: 29/ 8: 113 :Milk R nr Western Crossing PDBM8N : Apr-Sep : 15/ : 37: 38/ 10: 41 :Milk R nr Western Crossing ERNM8 : Apr-Sep : 157/ : 73: 226/ 145: 215 :Milk R nr Eastern Crossing ERNM8N : Apr-Sep : 41/ : 37: 148/ 22: 112 :Milk R nr Eastern Crossing NGTC2 : Apr-Sep : 45/ : 18: 83/ 31: 245 :North Platte R nr Northgate NGTC2N : Apr-Sep : 87/ : 29: 130/ 63: 295 :North Platte R nr Northgate ECRW4 : Apr-Sep : 103/ : 66: 125/ 82: 156 :Encampment R nr Encampment ECRW4N : Apr-Sep : 114/ : 69: 135/ 93: 166 :Encampment R nr Encampment KCRW4 : Apr-Sep : 32/ : 60: 38/ 25: 53 :Rock Cr nr Arlington KCRW4N : Apr-Sep : 33/ : 62: 39/ 26: 53 :Rock Cr nr Arlington SETW4 : Apr-Sep : 287/ : 38: 395/ 203: 765 :Seminoe Resvr Inflow SETW4N : Apr-Sep : 426/ : 46: 536/ 330: 920 :Seminoe Resvr Inflow WODW4 : Apr-Sep : 13/ : 12: 27/ 7: 108 :Laramie R nr Woods Landing WODW4N : Apr-Sep : 41/ : 29: 62/ 29: 142 :Laramie R nr Woods Landing SMTW4 : Apr-Sep : 15/ : 27: 24/ 12: 55 :Little Laramie R nr Filmore SMTW4N : Apr-Sep : 17/ : 30: 26/ 14: 57 :Little Laramie R nr Filmore ANRC2 : Apr-Sep : 9/ : 64: 13/ 6: 14 :Antero Resvr Inflow ANRC2N : Apr-Sep : 9/ : 64: 12/ 6: 14 :Antero Resvr Inflow SPYC2 : Apr-Sep : 26/ : 46: 37/ 22: 57 :Spinney Mountain Resvr Inflow SPYC2N : Apr-Sep : 19/ : 42: 34/ 12: 45 :Spinney Mountain Resvr Inflow EVNC2 : Apr-Sep : 34/ : 58: 41/ 31: 59 :Elevenmile Canyon Resvr Inflow EVNC2N : Apr-Sep : 22/ : 44: 41/ 14: 50 :Elevenmile Canyon Resvr Inflow CHEC2 : Apr-Sep : 46/ : 46: 66/ 38: 100 :Cheesman Lk Inflow CHEC2N : Apr-Sep : 46/ : 49: 81/ 30: 93 :Cheesman Lk Inflow SPTC2 : Apr-Sep : 255/ : 106: 272/ 240: 240 :S Platte R at S Platte SPTC2N : Apr-Sep : 87/ : 42: 136/ 56: 205 :S Platte R at S Platte MRRC2 : Apr-Sep : 6/ : 23: 12/ 3: 26 :Bear Cr at Morrison MRRC2N : Apr-Sep : 6/ : 23: 12/ 3: 26 :Bear Cr at Morrison GLDC2 : Apr-Sep : 45/ : 38: 66/ 33: 118 :Clear Cr at Golden GLDC2N : Apr-Sep : 45/ : 34: 66/ 33: 131 :Clear Cr at Golden LNSC2 : Apr-Sep : 36/ : 46: 53/ 25: 79 :St. Vrain Cr at Lyons LNSC2N : Apr-Sep : 47/ : 43: 69/ 34: 109 :St. Vrain Cr at Lyons OROC2 : Apr-Sep : 16/ : 34: 22/ 13: 47 :Boulder Cr nr Orodell OROC2N : Apr-Sep : 23/ : 44: 35/ 19: 52 :Boulder Cr nr Orodell BELC2 : Apr-Sep : 12/ : 34: 19/ 9: 35 :S Boulder Cr nr Eldorado Sprgs BELC2N : Apr-Sep : 12/ : 30: 21/ 9: 40 :S Boulder Cr nr Eldorado Sprgs FTDC2 : Apr-Sep : 114/ : 106: 149/ 91: 108 :Cache La Poudre at Canyon Mouth FTDC2N : Apr-Sep : 140/ : 67: 187/ 111: 210 :Cache La Poudre at Canyon Mouth LRRM8 : Apr-Sep : 26/ : 34: 38/ 22: 76 :Lima Resvr Inflow LRRM8N : Apr-Sep : 26/ : 33: 38/ 22: 79 :Lima Resvr Inflow CLKM8 : Apr-Sep : 32/ : 29: 36/ 30: 110 :Clark Canyon Resvr Inflow CLKM8N : Apr-Sep : 50/ : 25: 72/ 42: 198 :Clark Canyon Resvr Inflow BARM8 : Apr-Sep : 98/ : 49: 104/ 96: 199 :Beaverhead R at Barretts BARM8N : Apr-Sep : 71/ : 25: 95/ 62: 280 :Beaverhead R at Barretts ALRM8 : Apr-Sep : 48/ : 55: 63/ 40: 88 :Ruby R Resvr Inflow ALRM8N : Apr-Sep : 70/ : 72: 85/ 62: 97 :Ruby R Resvr Inflow MLRM8 : Apr-Sep : 524/ : 88: 701/ 461: 595 :Big Hole R nr Melrose MLRM8N : Apr-Sep : 582/ : 88: 755/ 517: 660 :Big Hole R nr Melrose HBDM8 : Apr-Sep : 432/ : 93: 488/ 392: 465 :Hebgen Resvr Inflow HBDM8N : Apr-Sep : 432/ : 93: 488/ 392: 465 :Hebgen Resvr Inflow ELMM8 : Apr-Sep : 491/ : 69: 537/ 465: 715 :Ennis Resvr Inflow ELMM8N : Apr-Sep : 655/ : 90: 759/ 589: 730 :Ennis Resvr Inflow GLGM8 : Apr-Sep : 366/ : 77: 446/ 309: 475 :Gallatin R nr Gateway GLGM8N : Apr-Sep : 366/ : 77: 446/ 309: 475 :Gallatin R nr Gateway LOGM8 : Apr-Sep : 322/ : 64: 446/ 272: 505 :Gallatin R at Logan LOGM8N : Apr-Sep : 470/ : 72: 581/ 417: 650 :Gallatin R at Logan TOSM8 : Apr-Sep : 1307/ : 63: 1666/ 1193: 2060 :Missouri R at Toston TOSM8N : Apr-Sep : 2134/ : 75: 2522/ 1975: 2830 :Missouri R at Toston FBNM8 : Apr-Sep : 1795/ : 59: 1898/ 1738: 3060 :Missouri R at Fort Benton FBNM8N : Apr-Sep : 3144/ : 77: 3725/ 2877: 4100 :Missouri R at Fort Benton VRGM8 : Apr-Sep : 1895/ : 55: 2023/ 1832: 3420 :Missouri R nr Virgelle VRGM8N : Apr-Sep : 3515/ : 77: 4218/ 3241: 4560 :Missouri R nr Virgelle LDKM8 : Apr-Sep : 2030/ : 55: 2171/ 1926: 3680 :Missouri R nr Landusky LDKM8N : Apr-Sep : 3704/ : 76: 4426/ 3431: 4890 :Missouri R nr Landusky FPKM8 : Apr-Sep : 2114/ : 55: 2363/ 1984: 3840 :Missouri R below Fort Peck Dam FPKM8N : Apr-Sep : 3828/ : 74: 4544/ 3514: 5180 :Missouri R below Fort Peck Dam AGSM8 : Apr-Sep : 461/ : 102: 592/ 405: 450 :Gibson Resvr Inflow AGSM8N : Apr-Sep : 461/ : 102: 591/ 405: 450 :Gibson Resvr Inflow SHLM8 : Apr-Sep : 291/ : 67: 439/ 230: 435 :Marias R nr Shelby SHLM8N : Apr-Sep : 341/ : 70: 484/ 271: 490 :Marias R nr Shelby HLWM8 : Apr-Sep : 28/ : 35: 48/ 18: 80 :Musselshell R at Harlowton HLWM8N : Apr-Sep : 37/ : 39: 55/ 24: 95 :Musselshell R at Harlowton YLOW4 : Apr-Sep : 619/ : 76: 674/ 539: 815 :Yellowstone R at Yellowstone Lk YLOW4N : Apr-Sep : 633/ : 75: 732/ 552: 840 :Yellowstone R at Yellowstone Lk CORM8 : Apr-Sep : 1339/ : 68: 1545/ 1163: 1980 :Yellowstone R at Corwin Sprgs CORM8N : Apr-Sep : 1427/ : 69: 1661/ 1250: 2070 :Yellowstone R at Corwin Sprgs LIVM8 : Apr-Sep : 1463/ : 64: 1728/ 1297: 2290 :Yellowstone R at Livingston LIVM8N : Apr-Sep : 1617/ : 66: 1903/ 1424: 2440 :Yellowstone R at Livingston BILM8 : Apr-Sep : 2410/ : 59: 3055/ 2146: 4070 :Yellowstone R at Billings BILM8N : Apr-Sep : 3220/ : 67: 3853/ 2911: 4790 :Yellowstone R at Billings MILM8 : Apr-Sep : 3449/ : 59: 4319/ 3054: 5850 :Yellowstone R at Miles City MILM8N : Apr-Sep : 5341/ : 69: 6616/ 4745: 7690 :Yellowstone R at Miles City SIDM8 : Apr-Sep : 3114/ : 55: 4025/ 2660: 5710 :Yellowstone R at Sidney SIDM8N : Apr-Sep : 5506/ : 68: 6788/ 4829: 8060 :Yellowstone R at Sidney BTMM8 : Apr-Sep : 189/ : 56: 228/ 161: 335 :Boulder R at Big Timber BTMM8N : Apr-Sep : 231/ : 62: 269/ 204: 375 :Boulder R at Big Timber SRAM8 : Apr-Sep : 372/ : 69: 456/ 320: 540 :Stillwater R nr Absarokee SRAM8N : Apr-Sep : 425/ : 71: 507/ 374: 595 :Stillwater R nr Absarokee BFYM8 : Apr-Sep : 551/ : 89: 661/ 493: 620 :Clks Fk Yellowstone R nr Belfry BFYM8N : Apr-Sep : 622/ : 89: 733/ 566: 695 :Clks Fk Yellowstone R nr Belfry STXM8 : Apr-Sep : 786/ : 55: 1073/ 706: 1430 :Bighorn R nr St. Xavier STXM8N : Apr-Sep : 1835/ : 75: 2424/ 1490: 2460 :Bighorn R nr St. Xavier HRDM8 : Apr-Sep : 76/ : 60: 120/ 66: 127 :Little Bighorn R nr Hardin HRDM8N : Apr-Sep : 76/ : 60: 120/ 66: 127 :Little Bighorn R nr Hardin DAYW4 : Apr-Sep : 43/ : 45: 65/ 33: 96 :Tongue R nr Dayton DAYW4N : Apr-Sep : 48/ : 48: 70/ 38: 101 :Tongue R nr Dayton DSLM8 : Apr-Sep : 72/ : 31: 130/ 56: 235 :Tongue R nr Decker DSLM8N : Apr-Sep : 108/ : 45: 169/ 86: 240 :Tongue R nr Decker DKRM8 : Apr-Sep : 60/ : 26: 121/ 44: 235 :Tongue R Resvr Inflow DKRM8N : Apr-Sep : 99/ : 40: 162/ 77: 245 :Tongue R Resvr Inflow MHDM8 : Apr-Sep : 47/ : 21: 135/ 41: 225 :Powder R at Moorhead MHDM8N : Apr-Sep : 68/ : 25: 159/ 55: 270 :Powder R at Moorhead LOCM8 : Apr-Sep : 58/ : 22: 148/ 48: 260 :Powder R nr Locate LOCM8N : Apr-Sep : 79/ : 26: 172/ 62: 305 :Powder R nr Locate .END Locations with an `N` suffix indicate natural flows excluding stream augmentations. KAF: Thousands of Acre-feet %AVG: Current 50%/AVG AVG: Average(50%) seasonal runoff voulme as simulated by the river forecast model considering acontinuous simulation of the basin response to historic climate data (observed precipitation and temperatures) over the period of 1991-2020. The 50%, 10% and 90% columns indicate the probability that the actual volume will exceed the forecast for the valid time period. Beginning April 1, May and June official forecasts include observed runoff volume up to official forecast date. For more information, please visit: www.weather.gov/mbrfc/water $$
