HEADLINES
– Weak system brings the potential for a mix of snow shower and freezing drizzle this afternoon and evening. Little or no accumulation.
– Quick moving cold front/upper wave may produce light snow up to an inch on Tuesday.
– Temperatures as low as -5 with wind chills as low as -15 Tuesday night. Multiple nights of single digit or lower lows expected this week.
– Rain changing to snow Saturday morning. No big snow storms appear likely for awhile.
TODAY’S MAP
NWS TECHNICAL DISCUSSION
Moisture profiles are more impressive ahead of the front to our west through midday but as the wave aloft deamplifies...moisture will become progressively shallower in nature as it translates east into the region. There remains a narrow window immediately ahead of the front by mid to late afternoon where slightly stronger isentropic lift on the 280K level aligns with the axis of deeper moisture. Model soundings capture this thinking with near saturation into the 600-500mb layer and are suggestive of the potential for light snow for a brief period focused over the northwest half of central Indiana. However...the moisture and isentropic lift will both decrease as they shift east through late day with the saturated layer becoming confined to the boundary layer as much drier air advects into the region through the mid levels. This scenario would limit ice crystal formation and transition any scattered light precipitation from snow to freezing drizzle into the evening hours. Air temperatures may be able to climb above freezing for a few hours but the combination of the extended period of subfreezing temperatures over the last week plus and the current deep snowpack could lead to ground temps peaking at 32F at best with light icing a possibility from any drizzle. Overall precip amounts will only be a couple hundredths focused primarily across the northern half of the forecast area but could see some slick spots form on roads late afternoon into the evening. Winds will become gusty this afternoon and evening as the front approaches and then moves into the region. Any light precipitation will end during the evening as the cold front sweeps across the region. Cold advection will commence behind the front as winds veer to a brisk westerly direction. RH progs and model soundings continue to highlight deep moisture lingering in the near surface layer through much of the night which should translate to lower stratus persisting into the predawn hours Monday if not through daybreak. Temps...warm advection ahead of the cold front will enable temperatures to rise to their warmest levels in 9 days with low level thermals supporting low to mid 30s from north to south. This is likely the one opportunity for Indy to make it back to the freezing mark for the first time since January 3 before the bitterly cold air returns to the Ohio Valley beginning tonight and into much of the upcoming week. Temperatures will hold near steady into the evening but once the front passes...expect a quick tumble back into the teens by daybreak Monday. && .LONG TERM (Monday through Saturday)... Issued at 300 AM EST Sun Jan 12 2025 Another shot of Arctic air is expected early to mid week, with lows as low as 0 to -5 Tuesday night, and wind chills as low as -15. With the arrival of this airmass, first this evening and with another reinforcing shot Tuesday, temperatures will return to well below normal through mid week. A compact upper wave will pass through the area on Tuesday, ushering in the reinforcing cold blast, and forecast profiles suggest enough low to mid level moisture will be present for what should be a light, fluffy, high-ratio snowfall, given both the thermal profile and a potentially extremely deep dendritic growth zone (up to 200mb deep), partially co-located with modest forcing for ascent through midday/early afternoon. Even in the afternoon as the midlevels dry out, steep low level lapse rates may produce additional snow showers and perhaps even a few weak snow squalls. This may produce minor travel impacts during the day on Tuesday and will bear monitoring over the next couple of days. In the wake of this wave, the arrival of the secondary cold intrusion, along with another addition to the existing snowpack, will likely drive low temperatures down to near or below zero Tuesday night, as mostly clear to partly cloudy skies and relatively light winds are expected. Any wind will push apparent temperatures well below zero. Another weak wave skirting the area to the northeast may be able to produce some flurries or light snow showers Wednesday night, and then focus shifts to the next more substantial system late week into the weekend. At this point, there is significant model disagreement on storm track, but it appears that most precipitation for the event would be likely to fall as rain, changing to light snow for a brief period on the back end as another cold front pushes through the region. Guidance continues to suggest another quite substantial Arctic outbreak in the week two period, though models disagree significantly on the intensity of the cold airmass. Nonetheless, well below normal temperatures are likely to remain the rule for the next couple of weeks. && .AVIATION (12Z TAF Issuance)... Issued at 541 AM EST Sun Jan 12 2025 Impacts: - MVFR ceilings return by midday - Scattered snow showers or drizzle Sunday afternoon with a period of IFR or lower conditions by late day into this evening - Cold front and associated wind shift this evening with gusts up to 20kt afternoon and early evening Discussion: Mid level clouds remain over the region early this morning with southerly winds near 10kts. A cold front will approach from the northwest this afternoon...bringing widespread MVFR ceilings to the terminals through the first half of the afternoon. Dry air aloft will limit precipitation to scattered light snow or perhaps freezing drizzle as the front approaches then passes the region by early this evening...with highest confidence in seeing light precip at KIND and KLAF. Southwest winds will gust to around 20kts this afternoon ahead of the front then shift to westerly as it passes this evening. Ceilings will fall to IFR levels late today and persist through the evening before recovering to MVFR overnight. With trapped moisture in the near surface layer...any clearing of lower stratus will likely hold off until after daybreak Monday.
INDY SEVEN DAY FORECAST
Today: Clouds thicken. Later afternoon snow showers, possibly mixed with drizzle or freezing drizzle. High 34.
Tonight: Mostly cloudy, with a few flurries and snow showers. Snow showers may be mixed with drizzle or freezing drizzle early. Low 16.
Monday: Mostly cloudy morning. Partly sunny later. A few flurries possible. High 19.
Monday Night: Partly cloudy. Low 9.
Tuesday: Partly to mostly cloudy, with snow showers. High 16.
Tuesday Night: Clouds diminish. Low 0.
Wednesday: Mostly sunny. High 18.
Wednesday Night: Partly cloudy. Low 10.
Thursday: Partly sunny. High 32.
Thursday Night: Partly cloudy. Low 24.
Friday: Partly sunny. High 38.
Friday Night: Chance of rain and snow after midnight. Low 29.
Saturday: Morning chance of snow and rain. High 40.





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