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Blowing SnowBlowing SnowClimatology StudyClimatology Study
WFO La Crosse Climatology Series #12WFO La Crosse Climatology Series #12
Todd SheaTodd SheaWFO La CrosseWFO La Crosse
MethodologyMethodologyMethodology
• Hourly Surface Observations (1961-90)– La Crosse, WI (LSE)– Rochester, MN (RST)– Mason City, IA (MCW)
• Observations compared– BLSN Only– SN & BLSN
BLSN ObservationsBLSN Observations• All observations (vsby 0-6 miles)
– LSE 182 hours– RST 761 hours (4x LSE)– MCW 1698 hours (9x LSE)
• Visibility 1 mile or less– LSE 15 hours– RST 144 hours (9x LSE)– MCW 439 hours (29x LSE)
Blowing Snow / MonthLa Crosse, WI (LSE)
0 0 0 0 2
32
122
178 1 0 0
0
20
40
60
80
100
120
140
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
Month
# of
Hou
rs
Blowing Snow / MonthRochester, MN (RST)
0 0 0 0 11
180
395
10855
12 0 00
50100150200250300350400450
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
Month
# of
Hou
rs
Blowing Snow / Month
0
100
200
300
400
500
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
Month
# of
Hou
rs
LSERST
Blowing Snow / Hour of DayLa Crosse, WI (LSE)
0
5
10
15
20
1 3 5 7 9 11 13 15 17 19 21 23
Hour
# of
Hou
rs
Blowing Snow / Hour of DayRochester, MN (RST)
010203040506070
1 3 5 7 9 11 13 15 17 19 21 23
Hour
# of
Hou
rs
Blowing Snow / Hour of DayMason City, IA (MCW)
020406080
100120140
1 3 5 7 9 11 13 15 17 19 21 23
Hour
# of
Hou
rs
Wx Obs Taken by Hour of DayLa Crosse, WI (1961-1990)
400050006000700080009000
10000
1 3 5 7 9 11 13 15 17 19 21 23
Hour
# of
Hou
rs
Wx Obs Taken by YearRST (1961-1990)
20003000400050006000700080009000
61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90
Hour
# of
Hou
rs
Normalized BLSN Reports by Hour (1961-1990)
0.01
0.10
1.00
10.00
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hour (LST)
Nor
mal
ized
Hou
rs
LSERST
Blowing Snow / Wind DirectionLa Crosse, WI (LSE)
05
101520253035
10 40 70 100
130
160
190
220
250
280
310
340
Wind Direction (degrees)
# of
Hou
rs
Blowing Snow / Wind DirectionRochester, MN (RST)
0
50
100
150
200
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35
Wind Direction (degrees)
# of
Hou
rs
Blowing Snow / Wind Direction
0
50
100
150
200
10 40 70 100
130
160
190
220
250
280
310
340
Wind Direction (degrees)
# of
Hou
rs
LSERST
Blowing Snow / Visibility
020406080
100120140
0 0.2 0.4 0.6 0.8 1 1.2 1.7 2.5 3 5
Visibility (miles)
# of
Hou
rs
LSERST
Blowing SnowLa Crosse, WI (LSE)
0.01.02.03.04.05.06.07.0
0 5 10 15 20 25 30 35
Wind Speed (mph)
Vis
ibili
ty (m
iles)
Blowing SnowRochester, MN (RST)
0.01.02.03.04.05.06.07.0
0 10 20 30 40 50 60
Wind Speed (mph)
Vis
ibili
ty (m
iles)
Blowing Snow (≤1 Mile)La Crosse, WI (LSE)
0.0
0.2
0.4
0.6
0.8
1.0
0 5 10 15 20 25 30 35
Wind Speed (mph)
Visi
bilit
y (m
iles)
Blowing Snow (≤1 Mile)Rochester, MN (RST)
0.0
0.2
0.4
0.6
0.8
1.0
0 10 20 30 40 50
Wind Speed (mph)
Visi
bilit
y (m
iles)
Blowing Snow (≤1 Mile)Mason City, IA (MCW)
0.0
0.2
0.4
0.6
0.8
1.0
0 10 20 30 40 50
Wind Speed ( mph)
Visi
bilit
y (m
iles)
Snow & Blowing Snow (≤1 Mile)La Crosse, WI (LSE)
0.0
0.2
0.4
0.6
0.8
1.0
0 5 10 15 20 25 30 35 40
Wind Speed (mph)
Vis
ibili
ty (m
iles)
Snow & Blowing Snow (≤1 Mile)Rochester, MN (RST)
0.0
0.2
0.4
0.6
0.8
1.0
0 10 20 30 40 50 60
Wind Speed (mph)
Vis
ibili
ty (m
iles)
Snow & Blowing SnowLa Crosse, WI (LSE)
0
2
4
6
8
0 10 20 30 40 50
Wind Speed (mph)
Visi
bilit
y (m
iles)
SN/BLSNBLSN
Snow & Blowing SnowRochester, MN (RST)
01234567
0 10 20 30 40 50 60
Wind Speed (mph)
Visi
bilit
y (m
iles)
SN/BLSNBLSN
Blowing SnowLa Crosse, WI (LSE)
0.01.02.03.04.05.06.07.0
0 10 20 30 40 50
Snow Depth (in)
Vis
ibili
ty (m
iles)
Blowing SnowRochester, MN (RST)
0.01.02.03.04.05.06.07.0
0 10 20 30 40 50 60 70
Snow Depth (in)
Vis
ibili
ty (m
iles)
Blowing SnowLa Crosse, WI (LSE)
0.01.02.03.04.05.06.07.0
0 2000 4000 6000 8000 10000 12000 14000 16000
Ceiling (ft)
Visi
bilit
y (m
iles)
Blowing SnowRochester, MN (RST)
0.01.02.03.04.05.06.07.0
0 5000 10000 15000 20000 25000 30000
Ceiling (ft)
Visi
bilit
y (m
iles)
Blowing SnowRochester, MN (RST)
0.01.02.03.04.05.06.07.0
0 1000 2000 3000 4000 5000
Ceiling (ft)
Visi
bilit
y (m
iles)
0100200300400500600700
# of
Rep
orts
(hou
rly)
0 1 2 3 4
Days
Days Since Last Snow
RSTLSE
Blowing Snow / VisibilityLa Crosse, WI (LSE)
0.01.02.03.04.05.06.07.0
0 1 2 3 4
Days since last snow
Visi
bilit
y (m
iles)
Blowing Snow / VisibilityRochester, MN (RST)
0.01.02.03.04.05.06.07.0
0 1 2 3 4
Days since last snow
Visi
bilit
y (m
iles)
Aviation Climatology of BLSNAviation Climatology of BLSNWind Sp (kts)Ave/Min
Snow Age (Days)
Hours
RST <1 mi 14/9.3 0.80 96
1 to <3 mi 12.5/6.7 0.56 227LSE <1 mi 9.8 0.42 7
1 to <3 mi 8.9 0.16 36
-Do not forecast BLSN at KLSE in the TAF.-Newer snow is better for IFR BLSN.-No great difference between LIFR and IFR BLSN wind speeds.-Lower threshold for 0 to <3 mi BLSN is about 12 knots.
% BLSN Observations% BLSN Observations
% BLSN Observations% BLSN Observations
BlizzardsBlizzards
MethodologyMethodology
• Hourly Surface Observations (1961-90)– LSE, RST, MCW
• Criteria searched:– ½ mile visibility or less– 30 mph wind speeds or higher– SN or SN/BLSN
Blizzard ObservationsBlizzard Observations• Near Blizzard
– ½ mile or less visibility– 30 mph wind speeds or higher– SN or SN/BLSN
• Blizzard– ¼ mile or less visibility– 35 mph wind speeds or higher– SN or SN/BLSN
• “True” Blizzard– 3 hours or more
Near Blizzard Observations(1/2 mi / 30+ mph)
020406080
100120140160
NOV DEC JAN FEB MAR APR TOTAL
Month
# of
Obs
erva
tions
LSERSTMCW
143
113
5
Blizzard Observations(1/4 mi / 35+ mph)
0102030405060
NOV DEC JAN FEB MAR APR TOTAL
Month
# of
Obs
erva
tions
LSERSTMCW
1
27
54
““TrueTrue”” BlizzardsBlizzards• La Crosse – 0
• Rochester – 3– January 11, 1975– April 5, 1979– January 10, 1982
““TrueTrue”” BlizzardsBlizzards• Mason City – 7
– February 26-27, 1971– January 11, 1975– January 10, 1982– April 3, 1982– December 24, 1983– December 1, 1985– March 28-29, 1987
AcknowledgementAcknowledgement
THANKS to Dan Baumgardt (ARX SOO) for retrieving data and assistance with review !
