CBRFC April 2014 CUWCD Briefing/Meeting 1:30pm April 8, 2014 Ashley Nielson

Outline March weather Precipitation Current snow conditions Water supply forecasts Upcoming weather Peaks Discussion

Frequent storms in zonal (east to west) upper air flow pattern Largest storm impacts: Bear River Upper Green River Yampa River Dry again in the south (Duchesne, Virgin River, San Juan, Lower Colorado) March 2014 Upper Air Pattern

Winter Precipitation 77%62%120%

Spring Precipitation Duchesne = 69%

Past 7 day Observed Precipitation Observed % of Normal

November 1 Model Soil Moisture Blue/Green = above average/wet conditions Red/Orange= below average/dry conditions 2013

Snow March 10, 2014 April 7, 2014

Snow: Satellite Derived Snow Cover Grids

Snow 107% of median 148% of median

Snow 119% of median 110% of median

Snow 77 % of median 83% of median

April 1 st Water Supply Forecasts 91KAF 91% 86 KAF 80% 72 KAF 64% 36KAF 51% 72 KAF 97% 193 KAF 60% 106 KAF 84%

Forecast Trend Change in the forecast % of average between March 1 st and April 1 st

Forecasts: Daily ESP w/ Forecast Daily ESP Forecast Official Forecast 10% 50% 90% x Observed data ESP will be a combination of forecast + observed to date

Forecasts: Provo April 1 Forecast: 10% KAF 50% KAF (91% Average) 90% - 84 KAF

Forecasts:Duchesne April 1 Forecast: 10% - 55 KAF 50% - 36 KAF (51% Average) 90% - 24 KAF

Forecasts:Duchesne April 1 Forecast: 10% KAF 50% - 72 KAF (64% Average) 90% - 55 KAF

Forecasts: Duchesne April 1 Forecast: 10% - 18 KAF 50% - 14 KAF (73% Average) 90% - 9.7KAF

Forecasts:Duchesne April 1 Forecast: 10% - 89 KAF 50% - 72 KAF (97% Average) 90% - 58 KAF

Upcoming Weather: Short term warm and dry. Increasing chance of precipitation mid April

5-Day Precipitation Forecast April 8 -13

Long Term Precipitation Outlook Climate Prediction Center April 2014 April-June 2014

Spring Temperature Outlook Climate Prediction Center April 2014 April-June 2014

ENSO Update Web Reference: iri.columbia.edu/climate/ENSO 60% Tend to develop during the period Apr-June Tend to reach their maximum strength during Dec-Feb Typically persist for 9-12 months, though occasionally persisting for up to 2 years Typically recur every 2 to 7 years

Soil Moisture Impacts – Snow conditions more important at this point – Positive in high elevation basin such as Upper Stillwater, Lake Fork – Negative lower elevation basins (Strawberry, Starvation, Great Basin) Snow – Snow near normal (Western Uintas) – Conditions deteriorate moving eastward – Early April storm improved conditions (entire storm not included in forecasts) Forecasts – All forecasts below average – Forecasts better for high elevation basins Weather: Warm and Dry for the near future – Better change of precip next week Summary

What is a Peak Flow Forecast? Maximum Mean Daily Flow due to snowmelt April-July Probabilistic Forecasts Exceedence Probabilities -10%, 25%, 50%, 75%, 90% Regulated flow - accounting for reservoirs and diversions Planned operations if known (hard with diversions) Assumptions based on past operations Only forecast magnitude of peak not time of peak ~60 forecast points Will issue twice a month this year

Where to Find Peak Flow Forecasts Map: – peak peak Special Product (Unreg/Reg) – txt txt List: –

Green = Low probability of reaching flood flow Red = High probability of reaching flood flow Peak Map

Peak List

Special Peak Product

Normal time of peak Minimum peak of record Max peak of record 0 10% 25% 50% 75% 90% Forecast Probabilities Flood Flow Bankfull Flow Current year observed daily streamflow to date Forecast Issuance Date Select to plot min and max year hydrographs Select to plot all historical peaks

Peaks: Strawberry 10%: 650 cfs 50%: 400 cfs (44%) 90%: 250 cfs

Peaks: Currant Creek 10%: 330 cfs 50%: 240cfs (79% of average) 90%: 150 cfs

Peaks: Upper Stillwater 10%: 1400 cfs 50%: 1000 cfs (82% of average) 90%: 700 cfs

Peaks: Big Brush 10%: 280 cfs 50%: 160 cfs (68% of average) 90%: 90 cfs

Discussion Forecast discussion CUWCD Operations discussion Next briefing date? – May 7 th? Or 8 th 1:30 pm

Ashley Nielson CBRFC Hydrologist Phone: Feedback, Questions, Concerns always welcome….