Here is what the National Weather Service is saying:
Area Forecast Discussion National Weather Service Indianapolis IN 822 AM EST Thu Dec 28 2023 .Key Messages... - Fog this morning in places, mainly north and east portions of the CWA - Chances for rain and snow through Friday - A coating of snow is possible, mainly western parts of the CWA - Seasonable temperatures persist through the week into the weekend && .Mesoscale Update... Issued at 822 AM EST Thu Dec 28 2023 A band of snow across far southwest portions of central Indiana has resulted in around an inch of snowfall accumulation in a few spots, mainly on grassy surfaces. Additional minor snowfall accumulation on grassy surfaces is possible as the band is nearly stationary. Latest radar observations show the band has weakened slightly in intensity over the past hour. Look for this trend to continue as the deformation zone associated with this band of snow dissipates. Marginal road temperatures near or just above freezing have limited impacts across this area, but a few slick spots and reduced visibilities will be possible over the next few hours. && .Short Term...(Today and tonight) Issued at 301 AM EST Thu Dec 28 2023 SYNOPTIC OVERVIEW AND EXPECTED SYSTEM EVOLUTION Surface and upper-air analysis show a mid to upper-level low over Missouri and southern Illinois. Another wave/vort max is taking shape over Michigan and southern Ontario. These two features are expected to interact while inducing surface cyclogenesis over Indiana this afternoon and evening. No notable trends in guidance since midday yesterday. Models now seem in good agreement regarding the evolution of the upcoming system. Current analysis shows a band of precipitation intensifying as it enters our southwestern counties. Surface observations place the air mass ahead of this band in the upper 30s to low 40s. In the band itself, temperatures have dropped into the mid to low 30s with some reports of snow coming in. Behind the band, temperatures remain in the 30s. The contrast in temperatures and wind shift suggest that frontogenetical forcing is the primary driver of this band. Hi-res guidance slowly brings this feature northward into our CWA, slowing it down and allowing it to pivot in place for a time while weakening. Will introduce snow/rain mix in locations under band going forward. This afternoon, model soundings show moisture increasing through the column. Clouds heights lower to under 1000 feet for most locations, with some fog possible at times this morning. By 20z, hi-res guidance allows precipitation to break out across our northern and western counties as low pressure begins forming just to our north. As the low wraps up and slowly drifts southward around the primary mid/upper level system, precipitation should spread southward as well. PRECIPITATION TYPE AND AMOUNTS The biggest challenge of the short term is precipitation type. Snow is favored where precipitation intensity is greatest, at least initially. Model soundings show a very marginal profile most of the day today, with temperatures in the mid to upper 30s across the region. Even if snow mixes in, or fully changes over within heavier bands...snow ratios will be quite low and accumulations will be difficult to achieve. By sunset, model soundings indicate further cooling of column which greatly increases snow chances. Still, almost every member of guidance retains above-freezing surface temperatures through tonight. Will introduce snow to the forecast for most locations after 00z, and keep it rain/snow mix through the period. The best chance of going all-snow will be near the Illinois state line and westward. In turn, these places also have the best chance of seeing snowfall accumulations. In terms of amounts, current expectation for total liquid equivalent QPF ranges from a couple hundredths of an inch to a few tenths (some ambitious model runs show around a half of an inch or slightly greater across our northwest). Ensemble means show the lowest values across our eastern counties and the highest in our west and northwestern counties. Regarding snowfall...given the very marginal surface environment, warm ground, and overall light precip amounts...am thinking the most likely scenario for any given point is no accumulation to a coating. If any mesoscale banding occurs, then a coating to an inch or two is not out of the question. The location of any such banding is quite variable within guidance. && .Long Term...(Friday through Wednesday) Issued at 301 AM EST Thu Dec 28 2023 Today`s system continues into the long range, with a few lingering showers / snow showers possible. Model soundings point towards low clouds and dreary conditions persisting well into the weekend. Upper-level flow is modeled to become a bit more progressive and quasi-zonal. Guidance continues to hint at a weak cold front passing through late this weekend, with minor precip chances (less than 20 percent). Overall, the long range looks quiet with few, if any, opportunities for significant precipitation and near-average temperatures. Beyond day 7, some hints in ensemble guidance of a trend towards a more active pattern. While not a strong signal, a period of cooler than average temperatures are possible as well. NAEFS experimental 8 to 14 day probabilities point in this direction while the ECMWF mean is less aggressive.
