National Weather Service Diane Cooper MPX /DLH Service Hydrologist Steve Gohde DLH Observations Program Leader December 13, 2011

Discussion Points Part 1 – Weather review Jan - Early Dec 2011 (precipitation and temperatures) Current Conditions Part 2 – Winter Short and Long range outlooks Drought outlook Hydrologic long range outlook for Island Lake Reservoir

Part 1 Review of 2011 Weather

Point Observations in the Island Lake Basin.

Rain Gauge Locations Island Lake Basin

T EMPERATURE H IGHLIGHTS S EPT 1 – N OV 30: 3.5 D EG A BOVE N ORMAL Temperatures at Duluth

Precipitation at Duluth P RECIPITATION H IGHLIGHTS U NTIL M ID S EPTEMBER P RECIPITATION NEAR NORMAL. L ITTLE RAIN AFTER S EPT 15 TH AND LATER … NOW BELOW NORMAL

Autumn Precipitation at Duluth P RECIPITATION H IGHLIGHTS F ALL S EASON S EPT 1 – N OV 30 F ALLING BELOW NORMAL SINCE SECOND WEEK IN A UGUST 2011 N ORMAL 9.05 OBSERVED 3.21 DEPARTURE TH LOWEST FALL PRECIP. S INCE 1870 ~6 in deficit

Precipitation at Brimson P RECIPITATION H IGHLIGHTS L IKE D ULUTH B RIMSON IS BELOW NORMAL.

Autumn Precipitation at Brimson P RECIPITATION H IGHLIGHTS LIKE D ULUTH B RIMSON REMAINS BELOW NORMAL N ORMAL 8.13 OBSERVED 2.51 DEPARTURE ND LOWEST FALL PRECIP. S INCE 1948 ~6 in deficit

Precipitation Summary Duluth has seen the most precipitation of the 4 rain gauges in the Basin

2011 Snow Summary Snow Depth near 1” 10 inches of Frost penetration Current Snow Water Equivalents Virtually NIL Rank Value Ending Date / 8/ / 8/ / 8/ / 8/ / 8/ / 8/ / 8/ / 8/ / 8/ / 8/2009, 12/ 8/2008

Regional View of Precipitation and Temperatures.

Precipitation Jan 1, 2011 –Dec 7, 2011 Rain Gauge information only included in MRCC Maps. Roughly 20“ to around ~25” for the last 11 months 75% to 100% of normal.

Fall Precipitation ( Oct - Dec 7, 2011) Roughly around 1.5” to 2.5” of “liquid” for Oct through early Dec. 25% to 50% of normal.

Precipitation for Jan 1 – Dec 9, 2011 Rain Gauge & Radar Estimated Analysis 15 “ (upper basin) to nearly 25” (lower basin) for 11 month period. 50 to ~ 75% of normal for 11 month period.

Precipitation for Oct 1 – Dec 9, 2011 Rain Gauge & Radar Estimated Analysis Less than 2.5” of liquid precipitation in Oct and Nov. Mainly 25% to 50% of normal.

Average Daily Temperatures Jan 1, 2011 – Dec 7, 2011 Temperature averages ranged between 40°F to 45° F. About Normal

Average Daily Temperatures Oct 1, 2011 – Dec 7, 2011 Temperature averages ranged in the mid to upper 30°F. Roughly 1°F to 2°F above normal.

Drought Information Conditions worsened in Nov/Dec.

Current Soil Conditions

Snapshot of the Model Basin WE – state of snowpack (barely existent.) UZTWC & UZFWC– Picture of moisture in upper soil layers. FWC typically wets and dries out quickly. TWC is a slower responding parameter. upper layers are dry.

Snapshot of the Model Basin LZTWC, LZFPC LZFSC – How much water available for base flow – TWC very dry FPC very dry FSC very dry ADIMC – perspective of how much water is stored above the soil (i.e. wetlands): Dry.

Summary of the past year. Precipitation, we were on target for normal….UNTIL Sept. Then rains then stopped!!! Abnormally dry to Moderate Drought (D1) is establishing across the region. With little precipitation, we are now “behind” in establishing a snow pack. While in the long term temperatures have been around normal, in the past few months they have been roughly 1°F to 2°F above normal.

Part 2 Short and Long Range Outlooks

La Niña exist in the Pacific Ocean La Niña means the Pacific Ocean Temps are cooler than normal. La Niña conditions are expected to continue through Spring (Similar to 2011.)

U.S. Precipitation Departures (mm) and Frequency of Occurrence (%) for La Niña Feb.-Apr. Indications from past La Niña years for 3 month averages beginning in Dec – Apr, are a higher likelihood of below normal temperatures. Indication for precipitation do not become apparent until February and March when it is possible increase over normals.

La Niña precipitation at Duluth Historically16 of the past 20 La Niña winters have seen above normal precipitation. Does not include 2010 data.

La Niña Snowfall at St Cloud and Minneapolis Both St Cloud and Minneapolis show an increase in the number of 6+ inch snowfall events during La Nina years. (does not include 2010 data)

North American & Arctic Atmospheric Oscillations Other factors Temperature Connections The NAO and AO tend to be “shorter lived” with a ~ week to 2 week duration of influence. Atmospheric models show the NAO and AO to remain Positive through Dec. This would indicate the potential of above normal temperatures. 1

6 to 10/8 to 14 day outlooks Period of Dec 17 – 21 st Above Normal Precipitation and Normal Temperatures Period of Dec 19 th – 25 th Above Normal Precipitation and Temperatures. Precipitation Temperatures

Dec, Jan, Feb Outlook Above normal Precipitation Normal Precip (liquid) Dec - ~1 inch Jan - 1 to 1.5 inches Feb – ~1 inch Below Normal Temperatures

Jan, Feb, Mar Outlook Below normal Temperatures. On the “edge” of no clear signals to slightly above normal Precipitation Normal Precip (liquid) Jan - 1 to 1.5 inches Feb – ~1 inch Mar 1 – 2 inches

Feb, Mar, Apr Outlook Edge of below normal Temperatures. Edge of above normal Precipitation Normal Precip (liquid) Feb – ~1 inch Mar 1 – 2 inches Apr – 1.5 to ~2 inches

Environmental Canada Forecasts Jan, Feb, Mar Normal Temperatures (But on the edge of below normal temperatures) Normal Precipitation

Anticipated Drought Impacts With the long range outlooks showing the potential of above normal precipitation, some slight improvement possible with the drought.

Potential For Refill of Island lake for Summer 2012

Chance of Reaching Refill Demands (Normal Conditions) Mustard line Mustard line indicates volume of water to fill reservoir under “normal” condition operating rules. So refill by June 1. We are very dry. Considering current lake levels for this time of year, historically we have met Fill volume demands roughly 60% of the time. This year with the dry conditions and delayed snowpack ~15% chance. Another way to view this information is the “chance of reaching the target pool elevation, given the current elevation.” Roughly 60% chance from a historical perspective and ~15% when considering current dry soil conditions and virtually no snowpack yet.

Chance of Reaching Refill Demands (Dry Conditions) Another way to view this information is “chance of reaching the target pool elevation, given the current elevation.” Roughly 80% chance from a historical perspective and 50% when considering current dry soil conditions and virtually no snowpack yet. Mustard line Mustard line indicates volume of water to fill reservoir under “dry” condition operating rules. So refill by July 15 th. Historically we have meet Fill volume demand roughly 80% of the time. This year with the dry conditions and delayed snowpack, it is only a ~50% chance of meeting refill needs/volumes.

Summary Precipitation – Normal through the Spring and Summer, Very dry this fall and very little snowpack now in place. Temperatures – For Jan – Dec average temperatures have been near normal. This fall – 1 to 2 degrees above normal. Soil Conditions – Very dry across the entire basin. Abnormally dry to Moderate Drought D1 status. Short Range outlook (Dec) – Normal to Above normal Temperatures (at least thru the 25 th ) Above normal Precipitation (thru the 25 th ) For Jan – Apr – Broader look CPC – Border of above normal precipitation Below normal temperatures. ***May, June and July are normally the higher precipitation months.