058 FXUS63 KIND 122255 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 555 PM EST Wed Jan 12 2022 ...Updated Aviation Discussion... .Short Term...(This evening through Thursday night) Issued at 247 PM EST Wed Jan 12 2022 Mostly benign weather can be expected through Thursday night across central Indiana. A broad upper level wave and associated very weak surface low will move through the region later today into Thursday, but ample dry air below about 10kft will preclude any precipitation, resulting instead in plenty of mid and high level cloudiness through the rest of the day and overnight into early Thursday. As the low pushes east tomorrow, low level cold advection and a strong surface high off to the northwest will produce a stout low level inversion, which should allow for the development of a low stratus deck which may persist through the remainder of the short term. Some guidance is quite aggressive in producing fog near daybreak on Thursday into Thursday morning in the convergence zone associated with the weak surface low, but given the midlevel cloud cover, and expected winds overnight, this seems a bit too aggressive, but bears watching. Will hold off on any mention for now. Low level thermal progs suggest temps over the next 36 hours should be trending a bit cooler, and NBM appears to be handling this well. Will make only minor adjustments. && .Long Term...(Friday through Wednesday) Issued at 247 PM EST Wed Jan 12 2022 Predictability of the synoptic-scale pattern in the long term is below average, and this leads to a range of possibilities for precipitation coverage and amounts in Indiana this weekend. Deterministic and ensemble guidance has trended substantially westward in recent cycles for Friday into Saturday with a close midlevel low also evolving sooner. Our area will be on the downstream end of developing warm conveyor belt and warm/moist advection regime, mainly yielding increase mid-high clouds. There is some signal of approaching PV/forcing resulting in midlevel frontogenesis across southwest Indiana. Although exact placement of this will be a function on how specifically the synoptic scale system evolves, it does seems that a west-northwest to east- southeast band of snow will bringing light amounts. Greatest chances are south of Terre Haute to Bloomington to Seymour, through early Saturday. Ensemble spread increases into Sunday with a dipole in medium-range ensemble cluster analysis owing to many members being out of phase. However, the mean in both the GEFS and EPS has shifted more closed/deeper and northwestward in the most recent cycle. Thus, we adjusted precipitation probabilities from lagging blended guidance upward introducing low probabilities of snow for much of central Indiana Sunday. These may need to be adjusted upward given the trend. Given the trend toward a fairly deep closed system, a well-developed TROWAL structure, frontogenesis, and deformation band north of the track of the midlevel closed low are likely. This will potentially result in significant snowfall amounts in a relatively narrow swath somewhere in the Ohio Valley, but this is most likely southeast of our area as it appears now. Trends will need to be monitored closely, however. Predictability of mid-latitude systems of this nature are often relatively low, with a northwest trend sometimes common and often tied to better resolution of latent heating/PV adjustments from warm sector convection. This was first seen in the deterministic GFS, but now has support from many GEFS members, as well as the ECMWF/EPS camp. && .Aviation...(00Z TAF Issuance) Issued at 555 PM EST Wed Jan 12 2022 IMPACTS: -IFR vsbys/cigs after 09Z tonight. Discussion: Ceilings will begin to fall late tonight as radiational cooling brings temperatures down to near 30 and RHs approach 100%. Depending on how strong the cooling is with the abundant high level clouds, there may be periods of patchy fog/freezing fog from 11Z to 15Z. Confidence is increasing but not currently high enough to mention in the TAF but confidence is highest at LAF and IND where the low level moisture is most robust. Will continue to monitor, but for now will leave vsbys at 1SM. These conditions will improve by late morning but expect at least some lowered vsbys through the early afternoon. Cigs will improve during the afternoon hours tomorrow but will remain MVFR. Winds will shift from the SW to NW after 15Z tomorrow but will remain less than 7kts. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ Short Term...Nield Long Term...BRB Aviation...White