Light to Moderate Snowfall Across Northern Indiana: 9 January 2024

A zone of strong low to midlevel warm air advection aided in moderate precipitation rates across the northern half of Indiana during the pre-sunrise hours of January 9th, 2024. The airmass in the lowest couple of kilometers hovered very close to freezing, with surface temperatures at Fort Wayne slightly above 32F. Nevertheless, strong upward vertical motion through a deep layer favored moderately heavy snowfall rates that overcame the marginal low-level temperatures. However, the period of heavier snowfall was short-lived, as above freezing air near 850 mb quickly spread north across Indiana, bringing an end to snow and initiating a quick transition to rain.

A shield of precipitation forced by intense low to midlevel warm air advection spread north across northern Indiana a few hours before sunrise during 9 January 2024. The narrow band of higher reflectivity moving north marks the transition from snow to the north and rain to the south.

Composite radar reflectivity with surface observations overlaid. Note the marginal surface temperatures within the zone of heavier precipitation over northern Indiana. Dewpoints in the 20s likely aided in enhancing wet bulb cooling that maintained a sufficiently cold low-level airmass for snow.

Surface wet-bulb temperatures ranging from 32 to 33F over northern Indiana were marginally cold enough for snow.

850 mb temperatures show a robust transition from sub-freezing to above-freezing air going from north to south across the Midwest.

850 mb temperature advection.

Short term model guidance, such as the RAP (shown above) did a good job predicting a band of 2-5 inch snowfall occurring across northern Indiana during the early morning hours of 9 January 2024.

RAP forecast sounding valid 10 UTC 9 January 2024 near Fort Wayne, Indiana. Note the saturated isothermal layer hovering near 0C from the surface to around 850 mb. Strong ascent was also present within the -10 to -20 C layer, likely forced by intense low to midlevel warm air advection inferred by the strongly veering wind profile.

A few inches of snow observed in southern Fort Wayne, Indiana at around 5 AM on 9 January 2024.