947 FXUS63 KIND 180907 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 407 AM EST Thu Feb 18 2021 .UPDATE... The AVIATION Section has been updated below. && .SYNOPSIS... Issued at 253 AM EST Thu Feb 18 2021 Light snow will impact central Indiana through this morning with 1 to 2 inches expected. Subseasonal temperatures are expected to continue through Saturday with below zero wind chills tomorrow and Saturday morning. The next chance for precipitation will be Sunday into to Monday with chances for a rain/snow mix at times overnight. More seasonal temperatures are on the horizon with high projected to be in the low 40s early next week. && .NEAR TERM /Today/... Issued at 253 AM EST Thu Feb 18 2021 Central Indiana is slowing becoming enveloped with light snow this morning. Heaviest snow fall rates are to the SW/S where visibilities are less than 2 miles. This will progress ENE along the mean 500mb flow. 0.25" an hour rates are likely at times. An area of dynamic alignment between vertical lift (WAA/CVA) and upper level diffluence is expected to induce moderate, low to mid level height falls this morning, enough to assemble an organized cyclonic field and pressure center. In return, the enhanced E/NE flow north of the pressure center will create a zone of deformation and enhanced lift for a few hours over eastern central Indiana later this morning. As this occurs, snowfall rates should increase leading to slightly higher snowfall totals over this area. Overall, around an inch is expect over most of central Indiana, with areas to the far south and east receiving closer to 2 inches. A few isolated locations could seed totals between 2-3 inches toward the SE, depending on where snowbands pass over. Snow fall should begin to decrease late this morning with only a few lingering light snow showers around this afternoon. Areas to the NE may experience a lightly longer snow duration depending on where the deformation zone propagates. Mostly cloudy to overcast skies are expected through most of the day with central Indiana influenced by a strong upper level jet and cyclonic flow aloft. Temperatures are expected to remain fairly stagnant due to a constant snow pack and decoupled PBL. Temperatures rises of 5-10 degrees are still likely within inefficient diurnal warming leading to highs in the mid 20s. Temperatures below zero and thick cloud cover will limit road temperatures and therefor slick road conditions are expect for most of the day, but this will be especially true during the morning commute with light snowfall expected through 10am. && .SHORT TERM /Tonight and Friday/... Issued at 253 AM EST Thu Feb 18 2021 Snow should be well east of central Indiana by nightfall as high pressure moves in at the surface. CAA will further enforce surface height rises leading to dry conditions and breaks in the cloud cover. This CAA will also impact temperatures overnight, with lows expected to be back into the single digits. Central Indiana will start to experience influence from an approaching upper level ridge friday, and large scale subsidence inhibits cloud growth and dries out the PBL. With this in mind, mostly clear skies are expected by Friday afternoon. Enhanced incoming SW radiation will increase temperatures and reduce the snow depth slightly; high temperatures should reach the low to mid 20s even with a cold air mass overhead. && .LONG TERM /Friday Night through Thursday/... Issued at 253 AM EST Thu Feb 18 2021 Friday night will be quiet with high pressure in control. Skies won't be clear with some warm advection beginning aloft, but there should be enough clearing for some radiational cooling off the snow cover. Winds will lessen too, so another cold night is expected. Will cut guidance some and up with lows below zero north to low positive single digits south. Warm air advection will continue aloft on Saturday, but any forcing from this will be weak and moisture lacking. Will continue a dry forecast. Brief upper ridging ahead of an approaching system will keep the area dry into early Sunday. A large upper trough, good upper and lower level jets, and a surface low pressure system will bring forcing to the area Sunday afternoon and night. The low level jet will bring plentiful moisture as well. Thus expect precipitation across the area, especially Sunday evening. Will up guidance PoPs. Precipitation type still remains in question. Models try to warm things up quickly on Sunday, but still feel this might be overdone some at the surface given the snow cover. Cut guidance highs a bit, which leads to mainly snow north and a rain/snow mix south. As noted previously, will have to watch ground temperatures where rain falls. Lows Saturday morning will be in the single digits and in the teens Sunday morning. If the ground doesn't warm fast enough, some freezing precipitation may be possible even with warmer air temperatures. Quiet weather returns for the remainder of the forecast. More zonal flow aloft will lead to warmer temperatures (maybe even above normal). Quick moving pieces of upper energy moving through will bring clouds at times, but moisture doesn't look adequate for precipitation. && .AVIATION /Discussion for 18/09Z TAF Update/... Issued at 404 AM EST Thu Feb 18 2021 Widespread light snow ongoing and should continue through 12Z. Mainly 2-3 mile visibilities with isolated snow bands at 1-2 mile visibilities. MVFR ceilings becoming more likely with most snow bands having around 2500ft ceilings. Previous discussion as follows... IMPACTS: Ceilings, and at times visibilities, will deteriorate to MVFR and worse in light snow 08z-11z. Winds will back from northeast to north 10 knots or less 12z-18z. DISCUSSION: A low pressure system will lift from the the southern Plains and Ozarks to the Ohio Valley today. This will bring deteriorating sky cover and visibility in light snow overnight and today. && .IND WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...Updike NEAR TERM...Updike SHORT TERM...Updike LONG TERM....50 AVIATION...Updike