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A light snow event: Feb 2-4, 2003

A light snow event: Feb 2-4, 2003. 2/3/03 – 6Z (midnight) Small storm passes to the SE, cold front to the NW. +. NWS Forecasts, 4am (9Z) Feb 4. BLACK HAWK-BREMER-GRUNDY-MARSHALL-STORY-TAMA- INCLUDING THE CITIES OF... AMES ...MARSHALLTOWN... WATERLOO/CEDAR FALLS 352 AM CST MON FEB 3 2003

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A light snow event: Feb 2-4, 2003

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  1. A light snow event:Feb 2-4, 2003

  2. 2/3/03 – 6Z (midnight)Small storm passes to the SE, cold front to the NW +

  3. NWS Forecasts, 4am (9Z) Feb 4 BLACK HAWK-BREMER-GRUNDY-MARSHALL-STORY-TAMA- INCLUDING THE CITIES OF...AMES...MARSHALLTOWN... WATERLOO/CEDAR FALLS 352 AM CST MON FEB 3 2003 ...WINTER WEATHER ADVISORY FOR THIS AFTERNOON AND THIS EVENING... .TODAY...CLOUDY WITH A CHANCE OF FREEZING DRIZZLE OR DRIZZLE THIS MORNING...THEN WIDESPREAD SNOW THIS AFTERNOON. ACCUMULATION 1 TO 2 INCHES. TURNING COLDER. BRISK. TEMPERATURES FALLING INTO THE UPPER 20S. NORTH WINDS 15 TO 25 MPH...GUSTING TO 30 MPH FROM LATE MORNING ON. CHANCE OF PRECIPITATION 80 PERCENT. .TONIGHT...WIDESPREAD SNOW EARLY...THEN PARTLY CLOUDY. ACCUMULATION 1 TO 3 INCHES.BRISK WITH BLOWING AND DRIFTING SNOW. LOW IN THE MID TEENS. NORTHWEST WINDS 15 TO 25 MPH...GUSTING TO 30 MPH. CHANCE OF SNOW 80 PERCENT. .TUESDAY...PARTLY SUNNY. HIGH NEAR 20. NORTHWEST WINDS 10 TO 20 MPH. DALLAS-MADISON-POLK-WARREN- INCLUDING THE CITIES OF...DES MOINES...INDIANOLA 352 AM CST MON FEB 3 2003 ...WINTER WEATHER ADVISORY FOR THIS AFTERNOON AND THIS EVENING... .TODAY...CLOUDY WITH A CHANCE OF FREEZING DRIZZLE OR DRIZZLE THIS MORNING...THEN WIDESPREAD SNOW THIS AFTERNOON. ACCUMULATION 1 TO 2 INCHES. TURNING COLDER. WINDY. TEMPERATURES FALLING INTO THE UPPER 20S. NORTH WINDS 15 TO 25 MPH...GUSTING TO 35 MPH FROM LATE MORNING ON. CHANCE OF PRECIPITATION 80 PERCENT. .TONIGHT...WIDESPREAD SNOW EARLY...THEN MOSTLY CLOUDY WITH SCATTERED FLURRIES FROM LATE EVENING ON. TOTAL ACCUMULATION...1 TO 3 INCHES. BRISK WITH BLOWING AND DRIFTING SNOW. LOW IN THE MID TEENS. NORTHWEST WINDS 15 TO 25 MPH...GUSTING TO 30 MPH. CHANCE OF SNOW 80 PERCENT. .TUESDAY...PARTLY SUNNY. HIGH IN THE LOWER 20S. NORTHWEST WINDS 10 TO 20 MPH.

  4. RWFS Forecast9Z – 3 Feb 2003 RUN

  5. RWFS – predicted storm totals Snowfall (inches) QPF (inches)

  6. PRETREAT w/110 brine– 17Z (11am) Forecast at Ames (reprocessed)

  7. PRETREAT w/110 brine – 17Z (11am) Forecast at Des Moines (rep.)

  8. The event – 2/3/03, 12-15Z + AMW: 1oC, OVC DSM: 2oC, OVC + AMW: 1oC, OVC DSM: 1oC, OVC

  9. The event – 2/3/03, 18-21Z + AMW: 1oC, OVC DSM: 1oC, OVC + AMW: -2oC, +SN DSM: -1oC, SN

  10. The event – 2/4/03, 0-3Z + AMW: -5oC, BLSN DSM: -5oC, BLSN + AMW: -9oC, “UP” DSM: -8oC, BLSN

  11. A closer look – important features

  12. Forecast vs. Observed 2/3/03 – 9Z RUN QPF SNOW

  13. Temperature forecast: Ames 6am mid 6pm noon 6pm noon

  14. Treatment comparison: Ames noon 6am 6pm noon mid 6am

  15. Temperature forecast: Des Moines 6am mid 6pm noon 6pm noon

  16. Treatment comparison: Des Moines noon 6am 6pm noon mid 6am

  17. Light Event Summary • RWFS forecast • Temperature: Fine during event, rapid cooling after SN • Precipitation: location, timing, amount, type • All reasonable • Treatment • Reasonable given forecast • Matched reality well, except for… • Late plowing & salting due to roads icing over & BLSN • Lessons • Use a “whole storm” perspective for rec. treatments • Method to handle or alert for blowing snow treatments • Wind speed, direction – local knowledge is key for treatment

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