Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000 FXUS63 KIND 041510 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 1010 AM EST Sun Dec 4 2016 .UPDATE... The NEAR TERM Section has been updated below. && .SYNOPSIS... Issued at 333 AM EST Sun Dec 4 2016 An upper trough will move across central Indiana today bringing rain and some snow to the area. A stronger system will bring mainly rain to the area Monday night into Tuesday. Much colder air will move in mid week and could bring some snow with it. More snow is possible next weekend. && .NEAR TERM /Rest of Today/... Issued at 936 AM EST Sun Dec 4 2016 UPDATE... Current radar mosaic shows highest reflectivities to the west of forecast area...and current observations are indicating light snow. However, precipitation is struggling to reach the ground across Central Indiana at this time, expect best chances to be this afternoon when forcing intensifies. By that time, warm advection from the south should result in mainly an all rain forecast across the majority of the forecast area. The exception will be the far northwestern counties, which could be cool enough for some light snowfall accumulations later today. Current temps across the area are generally in the mid to upper 30s. Updated grids have been sent. PREVIOUS DISCUSSION... Isentropic lift will increase across central Indiana today as an upper level wave moves into the area. Q-vector convergence progs show decent forcing as well. Moisture looks good. Thus expect the area to see precipitation today. Went categorical PoPs all areas. Timing of the best forcing and moisture is this afternoon, so that is when PoPs will be highest. For the early to mid morning, dry low levels will eat away at precipitation that develops across the area. Main problem is precipitation type across the northwest forecast area today. Temperatures will be cold enough this morning for any precipitation that reaches the ground to be a mix of snow and rain across much of the area, with snow more favorable northwest where temperatures will be coolest. Across the far northwest (Warren, and northwest portions of Tippecanoe and Carroll counties), temperatures will struggle to get above the mid 30s. Forecast soundings show temperatures remaining below freezing for all but the near surface layer. Unfortunately even a small change in forecast temperatures could have big impacts on precipitation type there. For now feel that readings will be cold enough for perhaps around 1 inch of snow today in the extreme northwest. Will have to watch closely. Elsewhere mostly rain is expected so little or no snow accumulation is expected. && .SHORT TERM.../Tonight through Tuesday night/ Issued at 333 AM EST Sun Dec 4 2016 Models are close enough that the SuperBlend initialization was accepted for most items. Dry air will work in quickly tonight behind the departing upper trough. Went low PoPs during the evening, with most of the area dry by midnight. Temperatures may cool enough for some snowflakes to mix in across the north before precipitation ends. High pressure will then build in briefly for Monday. However, lift will increase Monday night as an upper low approaches the area from the southwest. This system will have good forcing as the upper system moves across, including pretty good frontogenetical forcing. Will go likely to categorical PoPs by Tuesday morning. PoPs will quickly lower Tuesday afternoon as the system exits. Temperatures might be cold enough for some snow to mix in with the rain Monday night as the system moves in. However, readings should warm enough for all rain by late Monday night. && .LONG TERM /Wednesday Through Saturday/... Issued at 333 AM EDT Sun Dec 4 2016 Ensembles suggest the main weather feature during this period will be a short wave trough that is expected to push across the Great Lakes around Wednesday into Thursday. Will go with chance PoPs for Wednesday night into Thursday morning to cover this feature. Ensembles suggest snow will be the predominate precipitation type with this system, although some mixed precipitation possible Wednesday evening over the southern and eastern zones. Light accumulations are possible. Next upper trough is expected to move into the middle of the country by next Saturday, although timing and location differences are large at this time. Ensembles suggest some snow is possible within the warm advection pattern ahead of this trough by next Saturday. Will go with chance PoPs at that time. && .AVIATION /Discussion for the 041500z IND Taf Update/... VFR Conditions are expected to deteriorate to IFR and LIFR during the course of the day. Ongoing forecast appears on Track as Radar trends shows a wave of virga moving across Central Indiana. With better forcing and eventual deep saturation this afternoon...trends toward IFR/LIFR appear reasonable. Previous Discussion Below (Discussion for the 041200Z TAF Issuance)... Issued at 548 AM EST Sun Dec 4 2016 Conditions expected to deteriorate to IFR and LIFR during the course of the day and then generally remain IFR during the night. Mixed rain/snow is possible, especially at KLAF. Patchy light rain, with some light snow perhaps mixed in, will move into the area during the first six hours of the TAF period. Widespread precipitation is expected through the afternoon. A rain/snow mix is possible anywhere this morning, with mainly rain this afternoon (except for KLAF where a mix may continue). Precipitation will end by early evening. Conditions will deteriorate into IFR/LIFR with the widespread precipitation. IFR ceilings will likely continue tonight after precipitation ends. && .IND WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...50 NEAR TERM...TDUD SHORT TERM...50 LONG TERM....JAS AVIATION...50/JP

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