To support your use of the EPV chart, consider the following synoptic elements that are favourable for CSI and slantwise convection:

1. Strong horizontal temperature gradient aloft (and not necessarily at the surface), which results in windspeeds increasing with height in a moderate to strong speed shear
   
   
2. Usually southerly to southwesterly upper flow, with little directional shear at those levels – anecdotal evidence suggests that westerly flow can also be favourable over downstream regions far enough from the mountains that the westerlies can be moist.
   
   
3. Gravitational stability near neutral but slightly stable – the vertical profile is generally close to the moist adiabatic lapse rate at lower to middle levels
   
   
4. Atmosphere near saturation
   
   
5. Generally weak large-scale upward motion present
   
   
6. Upper absolute vorticity small or close to zero (neutral or even anticyclonic upper pattern)
   
   
7. Often occurs ahead of a surface warm front, but may also be found north or northwest of a surface cold front oriented W-E or SW-NE
   
   
8. May be more frequent on the anticyclonic shear side of an upper-level jet streak
   
   
9. Frontogenetic forcing acting as a lifting mechanism – CSI situations are related to strong horizontal temperature gradients, which can be related to frontogenesis
   
   

According to Wiesmueller and Zubrick (1998), "CSI often occurs near a warm front and ahead of a large-scale upper trough in regions of strong, moist southwesterly midtropospheric flow. In these regions, the atmosphere has a disposition for weak large-scale ascent, which is important for saturating the airmass. CSI is then released by parcel perturbations, of which the slantwise displacements are unstable." Furthermore, they state that "CSI may operate in an otherwise seemingly innocuous synoptic setting and may contribute to unexpectedly large precipitation amounts." Also, several authors have noted that frontogenetical forcing can be an important mechanism for generating banded mesoscale precipitation patterns, such as those that can occur with the release of CSI.

In general, modern NWP models generally forecast some precipitation in areas where slantwise convection occurs, but the mesoscale banding and maximum amounts are not accurately represented. One possible explanation for this weakness is that it may be related to inadequate model resolution. If so, operational forecasters should see improvements with increasing model resolution.

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