Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Tom Hultquist - NOAA/NWS Twin Cities, MN University of Minnesota Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Event Overview/Summary Climatological Significance Forecast Challenges Reforecast Experiment Outline Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Observed Snowfall Event Overview/Summary: Observed Snowfall LocationSnowfall (inches) Blooming Prairie, MN18.0 Stockholm, WI17.7 Goodhue, MN17.5 Rice Lake, WI17.0 Cameron, WI16.0 Menomonie, WI16.0 Ellsworth, WI16.0 Ellendale, MN15.8 Owatonna, MN15.5 Dodge Center, MN15.4 Rochester, MN14.0 Ladysmith, WI12.9 Albert Lea, MN10.0 Eau Claire, WI9.3

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Synoptic Overview Event Overview/Summary: Synoptic Overview Surface Evolution 00Z 1 May Z 3 May 2014

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Synoptic Overview Event Overview/Summary: Synoptic Overview Surface Evolution 12Z 1 May Z 3 May 2014

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Synoptic Overview Event Overview/Summary: Synoptic Overview 850 mb Evolution 00Z 1 May Z 3 May 2014

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Synoptic Overview Event Overview/Summary: Synoptic Overview 500 mb Evolution 00Z 1 May Z 3 May 2014

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Synoptic Overview Event Overview/Summary: Synoptic Overview 300 mb Evolution 00Z 1 May Z 3 May 2014

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Synoptic Overview Event Overview/Summary: Synoptic Overview Radar Evolution 330 PM CDT 1 May 2013 – 1200 AM CDT 3 May 2014

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Some Minnesota Facts Daily and monthly snowfall records were set in numerous locations. The event went into the record books as depositing Minnesota's heaviest 24-hour May snowfall totals ever. While May snowfalls are not uncommon in northern Minnesota, heavy May snowfall in southern Minnesota is rare. A quick scan of all historical Minnesota May daily snowfall totals greater than or equal to 3.0 inches indicates that May 1938 may have been the last time any southern Minnesota observer reported snowfall totals of similar magnitude. Climatological Significance

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Some Minnesota Facts (continued) Minnesota's previous record statewide daily May snowfall total was 12.0 inches. This threshold was reached twice: May 8, 1938 in Windom (Cottonwood County) and May 3, 1954 near Leonard (Clearwater County). The Minnesota State Climatology Office will now regard the May 2, 2013 snowfall measurement made in Dodge Center as the largest official 24-hour May snowfall total ever recorded in Minnesota. The Dodge Center snowfall observation made at 7:00 AM CDT on May 2 was 15.4 inches. More snow fell after observation time, adding up to a storm total of 17.2 inches. Climatological Significance

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Some Minnesota Facts (continued) A CoCoRaHS observer near Ellendale in Steele County measured 17.3 inches of snow and this establishes a new Minnesota State Record for a three day snowfall in May. Ellendale's May monthly total also was 17.3 inches and this falls just short of Minnesota's all-time monthly May snowfall record of 17.8 inches set in Virginia (St. Louis County) in Climatological Significance

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Eau Claire Tidbits Set new snowfall record for May with 9.3” Set new calendar day snowfall record for May with 8.7” on May 2 nd. Set record daily snowfalls for May 2 nd (8.7”) and 3 rd (0.6”). Set record low maximum temperature on May 2 nd with a high of 34°. Climatological Significance

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Standardized Anomalies Climatological Significance: Standardized Anomalies 500 mb Heights 18Z 1 May 2013 through 00Z 3 May 2014

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Standardized Anomalies Climatological Significance: Standardized Anomalies Mean Sea-level Pressure 18Z 1 May 2013 through 00Z 3 May 2014

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Standardized Anomalies Climatological Significance: Standardized Anomalies 850 mb Temperature 18Z 1 May 2013 through 00Z 3 May 2014

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Standardized Anomalies Climatological Significance: Standardized Anomalies Precipitable Water 18Z 1 May 2013 through 00Z 3 May 2014

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Historical Pattern Type Climatological Significance: Historical Pattern Type Hultquist & Schmit 2009

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Historical Pattern Type Climatological Significance: Historical Pattern Type Gulf-inverted Trough Composite Mean Sea Level Pressure T-48 through T+48

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Significant May snowfall is climatologically rare Large scale pattern was not necessarily eye-catching (standardized anomalies for large scale mass fields were not extreme) However, interaction effects of non-anomalous fields produced highly anomalous results. Model forecasts underwent fairly significant shifts in potential placement of heaviest precipitation during critical watch/warning phases of the event. Precipitation-type forecasting was difficult, with results hinging to a large extent on where the heaviest precipitation occurred. Most significant snowfall occurred overnight May 1 st through the morning of May 2 nd. Forecast Challenges

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Day 2/3 vs Day 1/2 Forecasts Forecast Challenges: Day 2/3 vs Day 1/2 Forecasts GFS 36-hour Forecast MSLP 00 UTC 2 May 2013 GFS 12-hour Forecast MSLP 00 UTC 2 May 2013

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Day 2/3 vs Day 1/2 Forecasts Forecast Challenges: Day 2/3 vs Day 1/2 Forecasts GFS 48-hour Forecast MSLP 12 UTC 2 May 2013 GFS 24-hour Forecast MSLP 12 UTC 2 May 2013

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Day 2/3 vs Day 1/2 Forecasts Forecast Challenges: Day 2/3 vs Day 1/2 Forecasts GFS 54-hour Forecast MSLP 18 UTC 2 May 2013 GFS 30-hour Forecast MSLP 18 UTC 2 May 2013

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Day 2/3 vs Day 1/2 Forecasts Forecast Challenges: Day 2/3 vs Day 1/2 Forecasts GFS 36-hour Forecast MSLP 00 UTC 2 May 2013 GFS 12-hour Forecast MSLP 00 UTC 2 May 2013

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Day 2/3 vs Day 1/2 Forecasts Forecast Challenges: Day 2/3 vs Day 1/2 Forecasts GFS 42-hour Forecast MSLP 06 UTC 2 May 2013 GFS 18-hour Forecast MSLP 06 UTC 2 May 2013

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Day 2/3 vs Day 1/2 Forecasts Forecast Challenges: Day 2/3 vs Day 1/2 Forecasts GFS 48-hour Forecast MSLP 12 UTC 2 May 2013 GFS 24-hour Forecast MSLP 12 UTC 2 May 2013

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Day 2/3 vs Day 1/2 Forecasts Forecast Challenges: Day 2/3 vs Day 1/2 Forecasts GFS 54-hour Forecast MSLP 18 UTC 2 May 2013 GFS 30-hour Forecast MSLP 18 UTC 2 May 2013

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Operational models struggled with precipitation placement leading up to the event, with a general shift eastward. Solutions came into good agreement within hours of the event as upstream precipitation developed and location of precipitation axis became established. Longer range solutions were too broad and diffuse with forcing and resulting precipitation in comparison to shorter range runs of the same models. Reforecast Experiment

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Reforecasts of the event were conducted to investigate how forcing evolved in consecutive simulations as the event time drew closer. In addition, runs were conducted at varying grid resolutions to evaluate how increased resolution would have impacted forecasts. Reforecast Experiment

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Reforecast Experiment WRF-ARW 3.4 GFS Initial & Boundary Conditions 12Z 30 April, 00Z 1 May, and 12Z 1 May initial times 64 km > 16 km > 4 km grid configurations 9 Simulations 60 Vertical Levels Kain-Fritsch used in 64 km and 16 km grids WSM6 Single-moment 6-class Microphysics Scheme Quasi-normal Scale Elimination (QNSE) PBL Scheme Noah Land Surface Model w/QNSE Monin-Obukhov Similarity Theory Surface Layer Scheme RRTMG Long Wave Radiation Scheme RRTMG Shortwave Radiation Scheme Model Configuration

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm 64 km vs 16 km Reforecast Experiment: 64 km vs 16 km 36-hour Precipitation Ending 00Z 3 May hour Forecast 48-hour Forecast 36-hour Forecast 64 km 16 km

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm 64 km vs 16 km Reforecast Experiment: 64 km vs 16 km 60-hour Forecast 48-hour Forecast 36-hour Forecast 36-hour Precipitation Difference Ending 00Z 3 May hour Forecast 48-hour Forecast 36-hour Forecast

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm So, what might be going on? Reforecast Experiment: So, what might be going on? 44-hour Forecast 64 km vs 16 km Potential Temperature at 08Z 2 May 2014 subtle but important differences with the 16 km solution

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm So, what might be going on? Reforecast Experiment: So, what might be going on? 44-hour Forecast 16 km Pot Temp & Pot Vorticity at 08Z 2 May 2014 potential vorticity generation is an indication of latent heat release in the model solution

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm So, what might be going on? Reforecast Experiment: So, what might be going on? 44-hour Forecast 64 km 2-D Frontogenesis at 08Z 2 May hour Forecast 16 km 2-D Frontogenesis at 08Z 2 May 2014

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm So, what might be going on? Reforecast Experiment: So, what might be going on? 44-hour Forecast 64 km & 16 km Omega at 08Z 2 May km solution more narrowly focused and equatorward

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm So, what might be going on? Reforecast Experiment: So, what might be going on? 44-hour Forecast 64 km Geostrophic Saturated EPV & Theta-E Lapse Rate at 08Z 2 May km solution did provide ingredients and a hint of what could occur

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm Resolution vs Precip-type Reforecast Experiment: Resolution vs Precip-type 20-hour Forecast 64 km Precip-type at 08Z 2 May hour Forecast 16 km Precip-type at 08Z 2 May hour Forecast 4 km Precip-type at 08Z 2 May 2014

Ninth Northern Plains Winter Storm Conference Saint Cloud, MN October 2014 Was a historic and challenging event. Forecast challenges arose due to anomalous nature of event, inconsistent model behavior, narrow axis of heavy precipitation, and precipitation-type issues. Improvement in guidance as event drew closer in time was likely only partially due to initial condition uncertainties. Model resolution, and the ability to accurately forecast heavy/convective precipitation at longer lead times, likely played a role in model performance. Sets the stage for additional experiments and evaluation. HopWRF-TS now being run at MPX to provide forecasters with enhanced resolution guidance over a forecaster- specified 36-hour time window between 0 and 174 hours. GFS resolution upgrade coming around the holidays (increase from ~27 km to ~10 km) Concluding Thoughts Observed & Modeled Characteristics 1-3 May 2013 Upper Midwest Snowstorm