Henry’s Fork, March 12, 2022
Nicer but unsettled weather is predicted for the coming week. With increasing BWO activity on the lower river, some decent top water fishing should take place but river still has limited approaches. Streamer and stonefly nymph patterns remain effective when presented in deeper runs and holes where you can get to them..
Excerpts from Dr. Rob Van Kirk’s Henry’s Fork drainage Snow Water Equivalent (SWE) report of yesterday, March 11th, are below. The data give a grim picture of current SWE in the area.
Headlines:
- More low temperature records were set yesterday, which started out with the coldest minimum in over five years.
- Water-year precipitation dropped to 82% of average, while SWE stayed at 68% of average.
- Reservoir fill rates were even lower yesterday than on Wednesday. Island Park is 86% full, compared with 79% full on average.
- After today, temperature and precipitation are expected to be near climatic normal for the next week or two.
Details:
Yesterday morning was the coldest in the watershed since December 17, 2016. In the 12-station 1989-2021 record I use for the whole watershed, yesterday’s minimum, mean, and maximum temperatures all set new records for the date. The low of -16.5 degrees F broke the old record of -3.2 degrees set in 2006. The daily maximum of 17.0 degrees broke the old record of 21.1 degrees, set in 2009. The daily mean was a whopping 27 degrees below average for the date and the second coldest day of the winter, behind January 1. That beat the old March-10 record by 9 degrees. Even at stations with very long periods of record, yesterday’s low temperature broke records for the date by wide margins. Idaho Falls set a new record low of -7 degrees, breaking the old record of 4 degrees, set in 1969.
No precipitation was recorded yesterday, dropping the water-year total to 82% of average. Snow water equivalent (SWE) stayed at 68% of average. After another day of below-average temperatures, forecasts and long-range outlooks all call for temperature and precipitation near climatological averages. In the short term, light precipitation is expected on Sunday, with slightly heavier precipitation on Tuesday and Wednesday. The latest 7-day precipitation forecast looks a little better than it did yesterday, with 0.25-0.5 inch expected over most of the lower elevations of the watershed and up to 1.25 inches along the Teton crest. If realized (big if), that would be roughly average for this time of year.
As you might imagine, stream gages throughout the watershed remain affected by ice. The Island Park and Ashton gages are the only two that have provided reliable data all winter, and both show natural flow in the upper Henry’s Fork at around 75% of average.
Reservoir fill rates were even lower yesterday than they were on Wednesday. Island Park Reservoir is 86% full, compared with 79% on average, and the three reservoirs in the watershed are 87% full, compared with 84% full on average. The upper Snake River reservoir system is 50% full, compared with 74% full on average.
Rob Van Kirk, Ph.D.
Senior Scientist
P.O. Box 550
Ashton, ID 83420
208-652-3567 OFFICE
208-881-3407 CELL
208-652-3568 FAX