Forecast Outlook
& Flood Fight Update
Blaine County
Serving Idaho Since the 1890s
www.weather.gov/pocatello
Flood Fight Outlook
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Vienna Mine Snowpack
2017 Max 57 Inches
What is Left to Melt
52.5 inches
Just starting to Melt
Out
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Galena Summit Snowpack
2017 Max 36 Inches
What is Left to Melt
26.9 inches
Only ¼ melted out
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Lost Wood Divide Snowpack
2017 Max 38 Inches
What is Left to Melt
21.9 inches
Approaching half melt
out
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Dollarhide Snowpack
2017 Max 52 Inches
What is Left to Melt
36.5 inches
Only ¼ melted out
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NRCS Snowmelt Rules of Thumb
Big Wood River at Hailey, on AVERAGE, peaks
8 days before Vienna Mine SWE reaches half melt,
9 days after Galena Summit reaches half melt, or
4 days before Galena Summit melts out.
** Point of interest – Galena Summit has only melted ¼ of it’s snowpack with
26.5 inches of liquid content left go
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Vienna Mine Snowpack
2017 Max 57 Inches
What is Left to Melt
52.5 inches
Just starting to Melt
Out
www.weather.gov/pocatello
Galena Summit Snowpack
2017 Max 36 Inches
What is Left to Melt
26.9 inches
Only ¼ melted out
www.weather.gov/pocatello
Historic & Forecast Volumes
Current forecasted total volume of water to flow
through Hailey ranks at #1
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Flood Potential – Rivers/Streams
Exceptional Risk
High Risk
Moderate Risk
Lowest Risk
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Key Decision Points – Next 2 Weeks
Big Low Pressure system moved into Western US
snow above 7000 feet – Small Accumulation –Cool Temps
Below Normal Temperatures thru Tomorrow
Warmup as we head for Memorial Day Weekend
www.weather.gov/pocatello
Thursday May 18 through Wednesday May 24
Average:
High: 65
Low: 38
Cool and
Wet More
Mtn Snow
Cool
Slightly
Wet and
Warmer
Warm
Above
Average
www.weather.gov/pocatello
www.weather.gov/pocatello
www.weather.gov/pocatello
River Hydrographs
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Current Snowmelt Flows – Big Wood
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Current Snowmelt Flows – Big Wood
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Current Snowmelt Flows – Big Wood
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Historic & Forecast Volumes
Around 355,000 AF left to pass through MJ&J – Avg Flows must = 2367cfs
Currently 1970 cfs
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Current Snowmelt Flows – Big Wood
Currently 1970 cfs
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Big Wood River Peak Flows
Highest Peak 1983 7.93 ft (6150 cfs*) & 2006 7.92 ft (7880 cfs*) * USGS recently recalibrated CFS so
values are now lower compared to previous years – key point it looking at Feet
2017– 5950 cfs 7.82 Ft
Flood Stages
5.5 Action
6.0 Minor
6.5 Moderate
8.0 Major
1983, 2006 &2017
www.weather.gov/pocatello
This Year’s Peaks
Big Wood River
• We’ve had one peak on May 8 - 7.82 feet
• Second peak Saturday May 13 - 7.19 feet
• Flows will remain reduced thru May 23rd
• Expect final peak sometime May 29 through June 11 – as we
warm up- and it may be (though small chance) the biggest
peak depending on how fast we warm up
• 5 % Chance for Biggest Peak as late as June 19
www.weather.gov/pocatello
Current Snowmelt Flows – Little Wood
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Historic & Forecast Volumes
Around 77,000 AF left to pass through MJ&J – Avg Flows must = 513cfs
www.weather.gov/pocatello
Little Wood River
Little Wood Reservoir
Now 76% full 22,704 acre feet – full at 30,000 acre feet
Inflows ~1000 cfs
USBOR releasing ~800 cfs
Enough Water to fill 2 times in May
Enough Water to fill around 1 time in June
Keep flow levels at least this much - cool temps will help in
releasing water without going to flood stage
www.weather.gov/pocatello
Flood Potential – Rivers/Streams
Exceptional Risk
High Risk
Moderate Risk
Lowest Risk
www.weather.gov/pocatello
Long Range
Outlook
cpc.ncep.noaa.gov
www.weather.gov/pocatello
www.weather.gov/pocatello
www.weather.gov/pocatello
Recorded Weather Briefings
– Available at our webpage every day
– View by 5 am
– At your convenience
www.weather.gov/pocatello
Questions?
FB: US National Weather Service Pocatello
Twitter: @NWSPocatello
[email protected]
208-233-0834
www.weather.gov/pocatello
NOAA’s National Weather Service
1945 Beechcraft Avenue
Pocatello ID 83204
(208) 233-0834
www.weather.gov/pocatello