355 FXUS63 KIND 031959 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 259 PM EST Wed Jan 3 2024 .Key Messages... - Cloudy tonight with low chance for flurries and/or freezing drizzle north this evening. - Light rain and/or snow expected for most areas Saturday - Potential for a significant storm system next Monday night through Wednesday. Primary threats as of right now are strong winds and high QPF && .Short Term...(This evening through Thursday) Issued at 259 PM EST Wed Jan 3 2024 Expect cloudy and cool conditions the rest of this afternoon and tonight, with a low chance (10-25%) for some scattered flurries and/or patchy drizzle/freezing drizzle north. Forecast profiles continue to depict saturation trapped beneath a substantial inversion based around 5kft across central Indiana overnight. Thus, expect that widespread cloud cover will likely persist through at least daybreak on Thursday, although a few breaks in the clouds may develop in spots very late tonight. Some weak low level upward motion is present within this saturated layer at times through this evening, and will carry a mention of scattered flurries and/or patchy drizzle/freezing drizzle late this afternoon into this evening, primarily north, where some lake enhancement may play into some light precipitation making it into central Indiana. Ongoing cold advection may allow the top of the saturated layer to get cold enough to support ice nucleation and thus flurries (and lake enhanced precipitation would be likely to fall in frozen form as well owing to deeper updrafts generated off the lake), but expect that anything falling this afternoon into the early evening would be predominantly drizzle with a tendency toward more flurries late in the evening. Significant impacts are not expected at this time, as pavement temperatures are largely in the mid 30s, but conditions will require close monitoring tonight, as a trace of freezing drizzle can easily cause slick spots on vulnerable areas, such as bridges and overpasses. Any drizzle or flurries will come to an end by late tonight as moisture begins to shallow a bit. Forecast profiles suggest dry advection with the encroaching surface high should allow low clouds to begin to break up around or after daybreak Thursday, with ample sunshine later in the day. Persistence of cloud cover tonight will keep lows from dropping as much as might otherwise be expected, despite ongoing cold advection - blend numbers appeared a bit too cool as a result, and have trended more towards upper 20s across the area - near 75th percentile. For highs on Thursday, despite the afternoon clearing, morning clouds will limit warming, and should keep highs largely in the 30s across the area, save for perhaps the far south/southwest, where some 40 degree readings may sneak in. && .Long Term...(Thursday night through Wednesday) Issued at 259 PM EST Wed Jan 3 2024 Friday... Quiet weather is expected in this period with surface high pressure in control. Low clouds are expected to have some partial clearing by Thursday night. If clouds clear out enough, lows around 20 are possible for parts of the area. Clouds will increase again on Friday with highs in the mid 30s. Round 1: Friday night through Saturday... The initial threat for impactful weather will be early this weekend as a trough advances eastward through the Midwest and Ohio Valley. A strong subgeostrophic subtropical jet over the Gulf on Friday will lead to rapid cyclogenesis, supported by strong diabatic processes. As this moves to the NE Friday night, another low pressure center will develop over the Appalachia region within the diffluence region of the upper trough. Model soundings show a well saturated surface to 500mb layer over the Ohio Valley, however lift becomes concentrated in the 600-400mb layer over central Indiana. This could lead to some light rain/snow, but greater QPF should remain south of our CWA. Any snow that does fall will be wet/dense, and given near to above freezing ground temperatures, minimal impacts to roadways are expected. Total accumulations between 0.1-1 inch(es) are possible, primarily over SE portions of the region where lower level vertical lift is possible Round 2: Sunday... There will likely be a brief period of quiet weather before a weak clipper system passes through on Sunday. Both lift and moisture look to be marginal with this trough, but it wont take much to squeeze out a few snow showers. Once again, minor accumulations are possible, but will likely result in little to no travel impacts. Ensemble mean temperatures are running a little too high for Sunday given cloud cover and evaporative cooling; highs are more likely to be in the mid 30s than upper 30s and 40s. Round 3: Monday night through Wednesday... A much deeper low is set to approach Great Lakes and Ohio Valley regions on Monday with a wide array of potential impacts. There are currently many uncertainties with this low passage, but there are a few variables that look likely: 1. Strong wind gusts. Ensemble members have been very consistant on significant pressure depression over the region Tuesday and Wednesday. This will lead to very strong low level jets and breezy surface conditions. At a minimum, sustained winds near 20MPH with gusts up to 30mph look likely for Tuesday and Wednesday. Higher gusts are possible depending on mixing depth each day. 2. Consistant precipitation. Strong LLJs out ahead of the low and continuous easterly jet north of the low will lead to a broad area of intense lift. This along with a deeply saturated profile will allow for widespread precipitation late Monday night through most of Tuesday. The bigger unknown will be precipitation type and will be heavily influenced on low track. Amounts/rates will vary depending on low position/track as well. Precipitation type is the primary remaining uncertainty that could drastically alter magnitude of impacts. Trends have been pointing towards a warmer solution and therefore rain as the primary precipitation type, but this could change with still 6 days until the low arrives. Not only does North America have an impending deep low, but there also is a simultaneous strong high pressure system over the Quebec region that will likely play a major role in storm track, further complicating the forecast. Current advice is to continue to monitor for updates, and have a winter preparedness plan in place in case of a shift towards a colder solution. && .Aviation...(18Z TAF Issuance) Issued at 1225 PM EST Wed Jan 3 2024 Impacts: - Borderline IFR/MVFR ceilings all sites becoming widespread MVFR much of the period. Discussion: Widespread stratus deck associated with a prefrontal trough continues to slowly work its way southeast across central Indiana this afternoon, and has already overspread 3 of the 4 TAF sites. BMG remains clear but should become MVFR by around 19Z. Guidance has struggled with ceiling heights all day and continue to be too optimistic. Expect high end IFR/low end MVFR at IND/LAF through the afternoon, with perhaps some modest improvement by dusk. HUF/BMG are more likely to remain MVFR but cannot rule out brief periods of IFR there either. Ceilings will become widespread MVFR by this evening and should remain so much of the night. Improvement to VFR should hold off until no earlier than very late tonight, but likely more toward the daybreak hours Thursday. Some spotty MVFR visibilities are noted, primarily at LAF, but expect that most areas will see visibilities remain VFR. Winds are generally westerly or northwesterly at 5-8KT, and will gradually veer northwesterly and then northerly with time, remaining below 10KT throughout the period. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ Short Term...Nield Long Term...Updike Aviation...Nield