A light snow event: Feb 2-4, 2003
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A light snow event:Feb 2-4, 2003
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2/3/03 – 6Z (midnight)Small storm passes to the SE, cold front to the NW
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NWS Forecasts, 4am (9Z) Feb 4BLACK 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.
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RWFS Forecast9Z – 3 Feb 2003 RUN
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RWFS – predicted storm totals
QPF (inches) Snowfall (inches)
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Forecast at Ames (reprocessed)
PRETREAT w/110 brine– 17Z (11am)
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Forecast at Des Moines (rep.)
PRETREAT w/110 brine – 17Z (11am)
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The event – 2/3/03, 12-15Z
AMW: 1oC, OVC
DSM: 2oC, OVC
AMW: 1oC, OVC
DSM: 1oC, OVC
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The event – 2/3/03, 18-21Z
AMW: 1oC, OVC
DSM: 1oC, OVC
AMW: -2oC, +SN
DSM: -1oC, SN
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The event – 2/4/03, 0-3Z
AMW: -5oC, BLSN
DSM: -5oC, BLSN
AMW: -9oC, “UP”
DSM: -8oC, BLSN
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A closer look – important features
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Forecast vs. Observed 2/3/03 – 9Z RUN
QPF
SNOW
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Temperature forecast: Ames
-16
-14
-12
-10
-8
-6
-4
-2
0
2
4
6
6 8 10 12 14 16 18 20 22 0 2 4 6 8 10 12 14 16 18 20 22 0 2 4
Time (UTC)
Tem
p (
°C)
METAR w/o FSL
METAR w/ FSL
AMW_METAR_OB
Precip Type
RWIS w/o FSL
RWIS w/ FSL
AMW_RWIS_OB
noon 6pm mid 6am noon 6pm
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Treatment comparison: Ames
6am noon 6pm mid 6am noon
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Temperature forecast: Des Moines
-16
-14
-12
-10
-8
-6
-4
-2
0
2
4
6 8 10 12 14 16 18 20 22 0 2 4 6 8 10 12 14 16 18 20 22 0 2 4
Time (UTC)
Tem
p (
°C)
METAR w/o FSL
METAR w/ FSL
DSM_METAR_OB
Precip Type
RWIS w/o FSL
RWIS w/ FSL
DSM_RWIS_OB
noon 6pm mid 6am noon 6pm
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Treatment comparison: Des Moines
6am noon 6pm mid 6am noon
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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