Cloud Comparison for Feb 9, 2004
1
AMW
OVC
AMW METAR OB
AMW METAR wFSL
0.9
AMW METAR woFSL
AMW RWIS wFSL
AMW RWIS woFSL
0.8
0.7
BKN
0.6
0.5
0.4
SCT
0.3
0.2
0.1
0
CLR
18 20 22 0 2 4 6 8 10 12 14 16 18 20 22 0 2 4 6 8 10 12 14 16 18
Feb 10, 2004
Feb 11, 2004
Time (UTC)
Fig. 10.29. Cloud cover time-series plot comparing the Ames METAR
only to the RWFS forecasts (both with and without the FSL supplemental
models) for the METAR and RWIS site. The vertical lines represent the
time period that the Ames METAR was reporting falling precipitation.
The very light snowfall was not predicted by the RWFS at all (Fig. 10.30). The POP did
increase during the time of the event however the QPF never increased enough to trigger
a forecast of precipitation. The NWS office forecast for the case at 330 PM CST on 9
February stated:
.TONIGHT...PARTLY CLOUDY. SCATTERED FLURRIES. LOW NEAR 15.
WEST WIND AROUND 15 MPH.
.TUESDAY...PARTLY SUNNY. HIGH IN THE MID 20S. WEST WIND
AROUND 10 MPH.
.TUESDAY NIGHT...PARTLY CLOUDY. SCATTERED FLURRIES. LOW
15 TO 20. SOUTHWEST WIND AROUND 10 MPH.
.WEDNESDAY...PARTLY SUNNY. BLUSTERY. AREAS OF BLOWING
SNOW. HIGH IN THE MID 20S. WEST WIND 10 TO 15 MPH SHIFTING TO THE
NORTHWEST 15 TO 25 MPH IN THE AFTERNOON.
According to this forecast the NWS scattered flurries were expected during the overnight
hours. Blowing snow was also forecast for 11 February two days in advance.
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