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.

Satellite images and
surface observations, by Scott Bachmeier (CIMSS, UW-Madison)

Graphic of snow totals and text listing of snow totals, by Steve Davis (NWS Sullivan)

Text from Wisconsin State Journal article about the storm

Ingredient maps and discussion

For more information about the ingredients approach and these diagnostics see http://speedy.meteor.wisc.edu/~swetzel/winter

click to enlarge

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

		850mb	700mb	600mb
12UTC 11 February 2003 ETA Model	06 hour forecast	Traditional PVQ & PVF Cross-Section	Traditional PVQ & PVF	Traditional PVQ & PVF
	12 hour forecast	Traditional PVQ & PVF Cross-Section	Traditional PVQ & PVF	Traditional PVQ & PVF
00UTC 11 February 2003 ETA Model	18 hour forecast	Traditional PVQ & PVF Cross-Section	Traditional PVQ & PVF	Traditional PVQ & PVF
	24 hour forecast	Traditional PVQ & PVF Cross-Section	Traditional PVQ & PVF	Traditional PVQ & PVF

For access to more ingredient maps from these ETA model runs, click here.

Return to Winter Forecast Ingredients Page