Case: February 11, 2003
The first significant snowfall of the season finally fell in southern
and central Wisconsin during the afternoon of February 11. Some links to images
and information about the storm are presented here, along with
forecast ingredient maps.
Ingredient maps and discussion
For more information about the ingredients approach and these diagnostics
Although moisture was limited above 800hPa, moderate to strong QG forcing and
frontogenesis combined with a layer of instability led to enhanced
precipitation rates in this storm. White-out conditions and some
lightning was reported
in southern Wisconsin. Temperatures were around -15F in the region of
ample moisture, forcing, and instability, ideal for maximum
depositional ice crystal growth.
Ingredient maps are shown in the table below from the ETA model forecasts
initialized at 12UTC February 11 (the morning before the event), and at
00UTC February 11 (the evening before the event). At 850hPa, both forecasts
valid at 00UTC February 12 show moderate forcing coincident with instability
(area highlighted by the PVQ and PVF parameters) in the presence of 80% RH
over southeastern Wisconsin. Instability coincident with forcing (as
indicated by PVQ and PVF) also existed at this time at 700hPa. Moisture
was more limited at this level, but advection of moisture from
below likely contributed more moisture at this level.
Table of Ingredient maps
For access to more ingredient maps from these ETA model runs, click here.
Return to Winter Forecast Ingredients Page