Grade Summary
A band of heavy snow developed north of an area of low pressure across central Minnesota into northern and central Wisconsin during the evening of March 30th. It continued into the early morning of the 31st. A narrow band of 8 to 12 inches occurred from Fargo to Hayward and Ladysmith, with amounts tapering off to the north and south of there. The band shifted south as the forecast went on, with most of the guidance keeping it north of the MPX area completely as late as the 29th. Because of the shift to the south, points were deducted for the 6 inch contour error and amounts were under forecasted.
Local conditions and perceptions may vary from the objective grade calculated below. Step through the other tabs to see a breakdown of the scoring.
|
80% |
Graded Element | Possible Points | Actual Points |
| 6 inch contour error | 8 | 5 | |
| Magnitude of snow error | 8 | 6 | |
| Onset timing error | 4 | 4 | |
| Peak wind gust error | 4 | 3 | |
| Probability of Detection/False Alarm Ratio | 8 | 8 | |
| Warning lead time | 8 | 6 | |
| Impact messaging | 4 | 3 | |
| Total | 44 | 35 | |
| Grade | 80% |
6 inch contour error
The forecasted area for 6 inches or greater was produced mainly from a blend of the models. The expectation was the higher amounts would shift closer to the 6 inch contour, as would the lower amounts as the gradient tightened over time. Warnings are issued for areas greater than 6 inches.
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 |
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| Official snowfall forecast at warning issuance | Observed Snowfall | Overlap of predicted and observed 6 inch snowfall areas |
| Error | Points |
| <=15 miles | 8 |
| 16-20 miles | 7 |
| 21-25 miles | 6 |
| 26-30 miles | 5 |
| 31-35 miles | 4 |
| 36-40 miles | 3 |
| 41-45 miles | 2 |
| 46-50 miles | 1 |
| 51+ miles | 0 |
| Actual: 29 miles | 5 |
Magnitude of snow error
The highest amount of snow forecast was between 7 and 8 inches across far northern Mille Lacs and Kanabec counties. The highest totals were 11 inches in Isle, MN and 10.6 inches near Camp Ripley, making for a peak snow error of 3 to 4 inches. Most totals fell into the 6 to 8 inch range though.
Forecast with initial warning issuance
Friday morning, March 30, 2018:
|
 |
 |
 |
| Official snowfall forecast | Low end amount (90% chance for more snow than this) | Median amount (equal chances for more or less than this) | High end amount (10% chance for more snow than this) |
| Error | Points |
| <=2" | 8 |
| 2.1-3.5" | 6 |
| 3.6-5.0" | 4 |
| 5.1-6.5" | 2 |
| 6.6+" | 0 |
| Actual: 3.5" | 6 |
Subsequent Forecasts
Friday afternoon, March 30, 2018:
 |
 |
 |
 |
| Official snowfall forecast | Low end amount (90% chance for more snow than this) | Median amount (equal chances for more or less than this) | High end amount (10% chance for more snow than this) |
Friday evening, March 30, 2018:
 |
 |
 |
 |
| Official snowfall forecast | Low end amount (90% chance for more snow than this) | Median amount (equal chances for more or less than this) | High end amount (10% chance for more snow than this) |
Snowfall reports by county:
Location Amount Time/Date Provider
...Minnesota...
...Anoka County...
3 NE Ramsey 6.0 in 0700 AM 03/31 COCORAHS
1 SSE Andover 5.5 in 0700 AM 03/31 Public
East Bethel 4ENE 5.0 in 0400 AM 03/31 COCORAHS
Oak Grove 4.6 in 0950 AM 03/31 Public
Blaine 2NNW 4.4 in 0600 AM 03/31 COCORAHS
Anoka 1SE 4.3 in 0700 AM 03/31 COCORAHS
Circle Pines 4.0 in 0857 AM 03/31 Public
St. Francis 4.0 in 0720 AM 03/31 Public
1 NNE Columbia Heights 3.5 in 0900 AM 03/31 Cocorahs
...Benton County...
Rice 7.6 in 0700 AM 03/31 COOP
5 W Foley 7.0 in 0424 AM 03/31 Public
1 E Foley 5.5 in 0715 AM 03/31 COCORAHS
...Carver County...
Watertown 4.2 in 0415 AM 03/31 COCORAHS
Victoria 1WSW 3.2 in 0700 AM 03/31 COCORAHS
Victoria 2ENE 3.0 in 0800 AM 03/31 COCORAHS
Chanhassen NWS 3.0 in 0700 AM 03/31 Official NWS Obs
Chaska 2.8 in 0644 AM 03/31 COCORAHS
Carver 1W 1.8 in 0700 AM 03/31 COCORAHS
...Chippewa County...
Montevideo 1.8 in 0700 AM 03/31 COCORAHS
...Chisago County...
Rush City 3NE 10.0 in 0700 AM 03/31 COCORAHS
7 ESE Harris 8.0 in 0645 AM 03/31 Public
Harris 5WNW 7.5 in 0800 AM 03/31 COCORAHS
Chisago City 2ENE 6.8 in 0700 AM 03/31 COCORAHS
Stacy 1W 5.3 in 0700 AM 03/31 COCORAHS
North Branch 1NNW 5.0 in 0600 AM 03/31 COCORAHS
...Dakota County...
Inver Grove Hgts 1ENE 2.9 in 0700 AM 03/31 COCORAHS
Lakeville 2NNE 2.4 in 0700 AM 03/31 COCORAHS
2 SSW Apple Valley 2.2 in 0100 AM 03/31 Public
Rosemount 3WNW 2.0 in 0700 AM 03/31 COCORAHS
Eagan 1NW 1.6 in 0818 AM 03/31 COCORAHS
Apple Valley 3ESE 1.5 in 0700 AM 03/31 COCORAHS
Apple Valley 3SSE 1.3 in 0730 AM 03/31 COCORAHS
Hastings (L/D 2) 0.5 in 0600 AM 03/31 COOP
...Douglas County...
Carlos 3WSW 7.0 in 0530 AM 03/31 COOP
Millerville 6.5 in 0701 AM 03/31 Public
Nelson 2WSW 5.5 in 0700 AM 03/31 COCORAHS
Brandon 1WNW 4.5 in 0800 AM 03/31 COCORAHS
Farwell 5N 4.5 in 0800 AM 03/31 COCORAHS
Alexandria 4.2 in 0832 AM 03/31 COCORAHS
2 SE Garfield 4.0 in 0945 AM 03/31 Public
...Goodhue County...
Red Wing 4W 0.3 in 0700 AM 03/31 COCORAHS
Vasa 5NNE 0.2 in 0700 AM 03/31 COCORAHS
...Hennepin County...
Brooklyn Park 2E 4.1 in 0800 AM 03/31 COCORAHS
Golden Valley 4.0 in 0930 AM 03/31 Public
New Hope 2S 3.8 in 0700 AM 03/31 COCORAHS
Plymouth 2ENE 3.8 in 0700 AM 03/31 COCORAHS
Robbinsdale 3.8 in 0700 AM 03/31 COCORAHS
2 NE Corcoran 3.7 in 1020 AM 03/31 COCORAHS
Golden Valley 3.5 in 0700 AM 03/31 COCORAHS
3 SW Maple Grove 3.0 in 0140 AM 03/31 Trained Spotter
Osseo 1 NW 3.0 in 0800 AM 03/31 COCORAHS
Champlin 3.0 in 0445 AM 03/31 Trained Spotter
Long Lake 4SW 2.8 in 0700 AM 03/31 COCORAHS
Brooklyn Center 1E 2.8 in 0700 AM 03/31 COCORAHS
Minneapolis St. Paul Airport 2.8 in 0700 AM 03/31 Official NWS Obs
Edina 2 ENE 2.6 in 0800 AM 03/31 COCORAHS
1 E Robbinsdale 2.5 in 0715 AM 03/31 Public
Richfield 1WNW 2.3 in 0400 AM 03/31 COCORAHS
Hopkins 2.3 in 0800 AM 03/31 COCORAHS
Edina 1SW 2.0 in 0700 AM 03/31 COCORAHS
Richfield 1NW 2.0 in 0700 AM 03/31 COCORAHS
Minneapolis Dwtn 2.0 in 0600 AM 03/31 COOP
Richfield 2NNW 2.0 in 0700 AM 03/31 COCORAHS
Edina 1SE 1.7 in 0700 AM 03/31 COCORAHS
Eden Prairie 3SE 1.5 in 1047 AM 03/31 COCORAHS
Bloomington 1 ESE 0.5 in 0800 AM 03/31 COCORAHS
...Isanti County...
Braham 1ENE 9.1 in 0715 AM 03/31 COCORAHS
Cambridge 3N 8.0 in 0700 AM 03/31 COCORAHS
Cambridge 6.0 in 0500 AM 03/31 Public
...Lac qui Parle County...
Montevideo 1SW 2.5 in 0700 AM 03/31 COOP
Dawson 1.0 in 0700 AM 03/31 COOP
...Le Sueur County...
New Prague 0.3 in 0845 AM 03/31 COCORAHS
...McLeod County...
Silver Lake 1NNW 1.8 in 0700 AM 03/31 COCORAHS
Glencoe 3NW 1.5 in 0700 AM 03/31 COCORAHS
Glencoe 1.0 in 0800 AM 03/31 COCORAHS
...Meeker County...
Dassel 4.2 in 0700 AM 03/31 COCORAHS
Watkins 3WSW 3.0 in 0900 AM 03/31 COCORAHS
...Mille Lacs County...
Isle 11.0 in 0715 AM 03/31 Public
2 NW Foreston 8.9 in 0955 AM 03/31 Trained Spotter
Princeton 1NE 8.4 in 0700 AM 03/31 COCORAHS
Onamia 4WNW 7.0 in 0930 AM 03/31 COCORAHS
Milaca 7.0 in 0530 AM 03/31 COOP
...Morrison County...
Camp Ripley 4E 10.6 in 0700 AM 03/31 COCORAHS
Little Falls 10.0 in 0700 AM 03/31 COCORAHS
7 SSE Hillman 8.4 in 0745 AM 03/31 Trained Spotter
...Ramsey County...
1 NNW White Bear Lake 4.5 in 0755 AM 03/31 Public
Maplewood 4.2 in 0700 AM 03/31 UCOOP
North St. Paul 1WNW 3.7 in 0700 AM 03/31 COCORAHS
North St. Paul 1NNW 3.3 in 0700 AM 03/31 COCORAHS
Mendota Hgts 2WNW 2.6 in 0700 AM 03/31 COCORAHS
Roseville 2WNW 2.0 in 0600 AM 03/31 COCORAHS
...Renville County...
Lake Lillian 5SE 2.0 in 0715 AM 03/31 COCORAHS
Bird Island 7SSE 1.1 in 0700 AM 03/31 COCORAHS
...Rice County...
Montgomery 3ENE 0.2 in 0600 AM 03/31 COCORAHS
...Scott County...
Jordan 1SW 1.1 in 0530 AM 03/31 COOP
...Sherburne County...
St. Cloud Airport 5.9 in 0700 AM 03/31 Official NWS Obs
Orrock 2SE 4.7 in 0700 AM 03/31 COCORAHS
3 N Becker 4.5 in 0800 AM 03/31 Public
...Stearns County...
St. Cloud (SCSU) 6.1 in 0700 AM 03/31 UCOOP
5 S St. Cloud 6.0 in 0900 AM 03/31 Trained Spotter
Kimball 3N 4.0 in 0600 AM 03/31 COOP
Cold Spring 3.5 in 0700 AM 03/31 COCORAHS
St. Joseph 3.5 in 0700 AM 03/31 COCORAHS
Paynesville 1SSW 2.2 in 0700 AM 03/31 COCORAHS
...Todd County...
Clarissa 9.5 in 0800 AM 03/31 COCORAHS
Browerville 8.5 in 0805 AM 03/31 COCORAHS
Long Prairie 7.3 in 0600 AM 03/31 COOP
...Washington County...
3 N Birchwood Village 4.3 in 0900 AM 03/31 COCORAHS
Stillwater 1NE 4.0 in 0811 AM 03/31 COCORAHS
Woodbury 3.0 in 0700 AM 03/31 COCORAHS
Afton 1E 1.5 in 0820 AM 03/31 COCORAHS
...Wright County...
2 ESE Otsego 5.0 in 0700 AM 03/31 COCORAHS
St. Michael 1E 4.0 in 0800 AM 03/31 COCORAHS
Rockford 3.6 in 0700 AM 03/31 COOP
2 NE Montrose 3.3 in 0737 AM 03/31 Public
Monticello 4WNW 3.0 in 0800 AM 03/31 COCORAHS
...Wisconsin...
...Barron County...
Rice Lake 8.0 in 0630 AM 03/31 Trained Spotter
Chetek 2SE 7.0 in 0700 AM 03/31 COCORAHS
...Chippewa County...
Cornell 4W 7.0 in 0800 AM 03/31 COCORAHS
Bloomer 6.0 in 0800 AM 03/31 COOP
Jim Falls 3NW 4.7 in 0630 AM 03/31 COOP
Chippewa Falls 3.0 in 0800 AM 03/31 COOP
...Dunn County...
Menomonie 5.0 in 0754 AM 03/31 Trained Spotter
Elk Mound 1ENE 4.4 in 0730 AM 03/31 COCORAHS
...Eau Claire County...
Eau Claire 2.5 in 1030 AM 03/31 Official NWS Obs
Eau Claire 1WNW 2.0 in 0500 AM 03/31 COCORAHS
...Pierce County...
River Falls 1SW 1.5 in 0700 AM 03/31 COCORAHS
Ellsworth 1E 1.0 in 0700 AM 03/31 COOP
...Polk County...
Dresser 2SSW 8.0 in 0700 AM 03/31 COCORAHS
Balsam Lake 4SE 6.5 in 0700 AM 03/31 COCORAHS
...Rusk County...
Ladysmith 2WNW 8.1 in 0700 AM 03/31 COCORAHS
13 NNW Weyerhaeuser 8.0 in 0715 AM 03/31 Public
12 E Haugen 8.0 in 0700 AM 03/31 Public
Bruce 1E 8.0 in 0700 AM 03/31 COCORAHS
...St. Croix County...
Clear Lake 4S 6.0 in 0800 AM 03/31 COCORAHS
3 SSE Deer Park 5.5 in 0700 AM 03/31 Trained Spotter
4 SW Roberts 3.0 in 0700 AM 03/31 COCORAHS
New Richmond 1SW 2.5 in 0800 AM 03/31 COCORAHS
Roberts 2.5 in 0800 AM 03/31 COOP
Baldwin 2.0 in 0700 AM 03/31 COOP
Observations are collected from a variety of sources with varying
equipment and exposures. We thank all volunteer weather observers
for their dedication. Not all data listed are considered official.
Onset timing error
The time visibility falls to less than 3 miles due to snow is noted for each warned weather station at an airport. This is considered the time accumulations and impacts begin. It is checked against the time snow becomes likely in the forecast when the initial warning is issued and the difference is calculated.
| Warned Airport Weather Station | Expected time accumulating snow becomes likely | Actual time visibility fell to less than 3 miles due to snow | Error (hh:mm) |
| Alexandria (AXN) | 9:00 pm | 9:12 pm | 0:12 |
| Blaine (ANE) | 11:00 pm | 11:15 pm | 0:15 |
| Cambridge (CBG) | 10:00 pm | 10:55 pm | 0:55 |
| Chetek (Y23) | 12:00 am | 12:35 am | 0:35 |
| Cumberland (UBE) | 12:00 am | 12:35 am | 0:35 |
| Eau Claire (EAU) | 12:00 am | 12:02 am | 0:02 |
| Ladysmith (RCX) | 12:00 am | 1:15 am | 1:15 |
| Lake Elmo (21D) | 11:00 pm | 11:35 pm | 0:35 |
| Little Falls (LXL) | 10:00 pm | 11:15 pm | 1:15 |
| Long Prairie (14Y) | 9:00 pm | 9:57 pm | 0:57 |
| Menomonie (LUM) | 12:00 am | 11:55 pm | 0:05 |
| Mora (JMR) | 10:00 pm | 1:17 am | 3:17 |
| New Richmond (RNH) | 11:00 pm | 11:55 pm | 0:55 |
| Osceola (OEO) | 11:00 pm | 12:15 am | 1:15 |
| Paynesville (PEX) | 10:00 pm | 10:15 pm | 0:15 |
| Princeton (PNM) | 10:00 pm | Not Available | N/A |
| Rice Lake (RPD) | 12:00 am | 12:35 am | 0:35 |
| Rush City (ROS) | 11:00 pm | 11:55 pm | 0:55 |
| Sauk Centre (D39) | 9:00 pm | 9:35 pm | 0:35 |
| St. Cloud (STC) | 10:00 pm | 11:05 pm | 1:05 |
| Average: 0:49 |
| Error | Points |
| <1 hr | 4 |
| 1-2 hr | 3 |
| 2-3 hr | 2 |
| 3-4 hr | 1 |
| 4+ hr | 0 |
| Actual: 0:49 | 4 |
Peak wind gust error
Wind gusts of 30-40 mph were predicted throughout the warned areas. The forecast was high by about 6 mph.
| Warned Airport Weather Station |
Expected peak wind gusts (mph) |
Actual peak wind gust (mph) |
Error (mph) |
| Alexandria (AXN) | 40 | 33 | 7 |
| Blaine (ANE) | 40 | 32 | 8 |
| Cambridge (CBG) | 40 | 26 | 14 |
| Chetek (Y23) | 30 | 26 | 4 |
| Cumberland (UBE) | 30 | 31 | 1 |
| Eau Claire (EAU) | 30 | 33 | 3 |
| Ladysmith (RCX) | 30 | 31 | 1 |
| Lake Elmo (21D) | 35 | 29 | 6 |
| Little Falls (LXL) | 35 | 29 | 6 |
| Long Prairie (14Y) | 35 | 29 | 6 |
| Menomonie (LUM) | 35 | 28 | 7 |
| Mora (JMR) | 35 | 28 | 7 |
| New Richmond (RNH) | 35 | 32 | 3 |
| Osceola (OEO) | 30 | 28 | 2 |
| Paynesville (PEX) | 40 | 30 | 10 |
| Princeton (PNM) | 35 | Not Available | N/A |
| Rice Lake (RPD) | 30 | 31 | 1 |
| Rush City (ROS) | 30 | 28 | 2 |
| Sauk Centre (D39) | 40 | 29 | 11 |
| St. Cloud (STC) | 40 | 34 | 6 |
| Average: 6 mph |
| Error | Points |
| <5 mph | 4 |
| 5-8 mph | 3 |
| 9-12 mph | 2 |
| 13-16 mph | 1 |
| 17+ mph | 0 |
| Actual: 6 mph | 3 |
Probability of Detection (POD)/False Alarm Ratio (FAR)
Probability of Detection (POD) is event-based, meaning that each confirmed event is checked to see if a warning was issued and in effect at the time of the event. The national goal for winter storms is 0.90 or greater (90%).
False Alarm Rates (FAR) are computed based on warnings. For each warning issued, did an event meeting warning criteria take place? There is not a set national goal for FAR. The higher the decimal, the more counties were warned for that didn't need them.
With this event, warnings were issued for all counties that had greater than 6 inches so POD was perfect. FAR was low because only one county of 19 never reached criteria.
| POD | Points | FAR | Points | |
| 0.90+ | 4 | <0.11 | 4 | |
| 0.80-0.89 | 3 | 0.11-0.20 | 3 | |
| 0.70-0.79 | 2 | 0.21-0.30 | 2 | |
| 0.60-0.69 | 1 | 0.31-0.40 | 1 | |
| <0.60 | 0 | 0.40+ | 0 | |
| Actual: 1.0 | 4 | Actual: 0.05 | 4 |
Warning lead time
Lead time is considered the amount of time between the warning issuance and when criteria is met (typically when 6 inches of snow was measured or less snow with a wintry mix). This category is the average lead time of all the verified counties and unwarned counties.
| Lead Time | Points |
| 20+ hours | 8 |
| 15-19 hours | 6 |
| 10-14 hours | 4 |
| 5-9 hours | 2 |
| <5 hours | 0 |
| Actual: 15 hours | 6 |
Impact messaging
The main message was a narrow band of heavy snow expected to graze the northern portion of our area with strong winds elsewhere. However, the band set up a bit further south and thus impacts were a bit worse than expected. A point was deducted for not conveying the possibility of a bigger shift in the snow band.
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| Watches, warnings, and advisories in effect on the evening of March 30th. | Radar loop of the storm. | Travel conditions during the early morning of March 31st. |
| Impact messaging | Up to 4 points |
| Impacts were clearly conveyed and partners responded accordingly. Positive feedback was received. | 4 |
| Overall, impacts were conveyed well, but some impacts were over or underestimated. Mostly positive feedback was received. | 3 |
| Impacts could have been more clearly stated. Feedback was mixed. | 2 |
| Impacts were not clearly defined. Mostly negative feedback was received. | 1 |
| Impacts were opposite of what was forecast. Feedback was negative. | 0 |
| 3 |
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