437 FXUS63 KIND 300801 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 301 AM EST Sat Dec 30 2023 .Key Messages... - Some snow showers Sunday into early Monday. These could produce some slick spots on roads. - Seasonable temperatures persist through next week. && .Short Term...(Today and tonight) Issued at 301 AM EST Sat Dec 30 2023 Early this morning, a surface trough was moving southeast across central Indiana, with some light rain and snow along and ahead of it. An area of drizzle and fog extended to the northwest of the rain and snow. The trough and associated precipitation will continue to move southeast in the predawn hours, exiting the forecast area. The drizzle and fog will linger behind for a while this morning. There's still some uncertainty on how long these will linger. For now plan to have these out of the area by 12Z, but will continue to monitor latest trends and data. Satellite showed the low clouds extended back into Illinois, with some clearing noted near Lake Michigan. Low clouds will likely become trapped for a while as warm air advection aloft reinforces an inversion. Will thus go pessimistic with sky cover today, keeping skies cloudy to mostly cloudy through the morning hours. Winds not far off the surface will create some mixing which should create some breaks in the clouds this afternoon. These breaks will aid in warming temperatures a bit from around 40 to the lower 40s most areas. Tonight, an upper level low will begin its approach toward the area from the northwest. A pre-frontal surface trough will move into the area. However, forcing with the surface trough is weak, and any decent forcing from the upper low remains northwest of the area through 12Z Sunday. Will thus continue a dry forecast tonight, but with thickening cloud cover. Low temperatures will be in the upper 20s to lower 30s. && .Long Term...(Sunday through Friday) Issued at 301 AM EST Sat Dec 30 2023 The long term period features a few weak systems passing through the region bringing occasional chances for light precipitation across Central Indiana. The greatest threat for wintry precipitation and potential travel impacts within the next week will be Sunday into early Monday morning along and north of the I-70 corridor. Overall near normal to above average temperatures are expected to persist over the next week before much cooler, winter-like temperatures arrives Mid January. .Sunday into Monday... **Potential for snow showers, falling temperatures, and slick conditions Sunday afternoon through Monday Morning** An upper level low and associated surface low drop south out of Canada into the Southern Great Lakes region on Sunday brining a reinforcing shot of cold air and the next chance for snow showers across Central and North Central Indiana. Surface cold front pushes through the region Sunday morning with southwesterly winds becoming west-northwesterly. Expect an increase winds through the day with gusts of 25+ mph as forecast soundings show steepening low level lapse rates due to cold air advection aloft and an increasing low level jet. Short term guidance shows quite a strong temperature gradient associated with this front as 850mb temperatures drop from near 0C in the morning to -9 to -13C by the evening hours. Highs will likely struggle to make it out of the 30s across the region with temperatures stuck near freezing for portions of North Central Indiana. This pattern also supports snow shower developing over the region within the cyclonic flow around the approaching surface low. Forecast soundings indicate increasing low level moisture Sunday morning, with deep enough saturation in the lower levels and dendritic growth zone by the afternoon to support snow. Steepening low level lapse rates and 0-1km and 0-3km shear approaching 20 kts in addition to moisture advection in a cold enough atmosphere will create good conditions for snow showers. Ample lift within the cyclonic flow around the low, enhanced by the exit region of a 110kt jet streak just to the south will likely be enough to lead to the formation of snow showers across Central and North Central Indiana within this environment. Timing for the most widespread show shower activity will likely be Sunday afternoon through Sunday evening, then diminishing activity towards Monday morning. Currently, not expecting significant snow accumulations with these snow showers. Brief periods of heavier snow under the strongest showers may lead to minor accumulations at times. Guidance does show the positively tilted upper trough hanging back through Monday afternoon. With surface high pressure approaching from the west, it is likely moisture will be trapped in the boundary layer resulting in low clouds and flurries/drizzle through Monday. Will have to watch for slick spots and travel impacts Sunday night through Monday morning as falling temperatures into the 20s may cause icy spots to develop. .Tuesday through Friday... Surface high pressure becomes centered over the Southeast CONUS middle of next week while upper ridging builds ahead of the next system organizing in the Plains. Uncertainty still exists in the overall evolution of the midweek system. A few areas in question are how much influence the southern and north stream branches of the jet will have on the area and where/if will they phase. Latest ECMWF and GFS ensemble runs look to phase the systems east of the Appalachians, resulting in a drier forecast locally with cooler air for the end of the week within a northerly flow pattern. For now, keeping PoPs quite low and temperatures closer to normal or just above in the mid 30s to low 40s. Higher confidence exists in Tuesday's forecast with dry conditions and above normal temperatures. Uncertainty increases Wednesday into Thursday. .Beyond day 7... Some hints in ensemble guidance of a trend towards a more active pattern. Longer range guidance has been hinting at a sudden stratospheric warming event occurring in the Arctic come early to mid January. This correlates nicely with the Arctic Oscillation going negative as shown by many ensembles. Will be watching this closely as this could lead to a period of winter-like weather and colder temperatures come mid January into February.. && .Aviation...(06Z TAF Issuance) Issued at 1200 AM EST Sat Dec 30 2023 Impacts: - Generally IFR conditions will persist through they daylight hours Saturday morning then gradual improvement to VFR - Patchy fog/drizzle early in the period - Return to MVFR conditions Saturday night for KIND 30 hour TAF Discussion: Bulk of precipitation will be east and south of the sites by valid time, leaving behind some patchy fog and drizzle for a few hours. IFR cloud deck extends well northwest of the area, so expect IFR ceilings to continue into the daylight morning hours Saturday. Mixing will then improve conditions during the afternoon. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ Short Term...50 Long Term...CM Aviation...50