218 FXUS63 KIND 221617 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 1117 AM EST Wed Dec 22 2021 ...Updated Aviation Discussion... .Forecast Update... Issued at 950 AM EST Wed Dec 22 2021 Surface analysis this morning shows high pressure in place over the mid Mississippi valley with a surface ridge axis extending north to western WI. This was resulting in continued NW surface flow to central Indiana of cool and dry air. GOES16 shows clear skies across the state. Some mid cloud over MN/W WI/NW IL was advancing SE toward Indiana within the flow aloft. Forecast soundings and time heights tonight show a dry column across the area this afternoon as the surface high pressure system advances eastward into the Ohio Valley. Forecast soundings also show a strong inversion in place aloft that will keep cooler air trapped near the surface and prevent any CU development. Thus will continue with a mostly sunny sky this afternoon with chilly highs in the low to mid 30s. Overall...the forecast remains in good shape. && .Short Term...(Today through Thursday) Issued at 249 AM EST Wed Dec 22 2021 A cold front had quickly moved across the region late Tuesday evening and was now off to the southeast of the area. Colder air was rushing into the region behind the front with gusty northwest winds. 07Z temperatures had fallen into the upper 20s and lower 30s over the forecast area with gusts occasionally up to 30-35mph. The weather will remain quiet through late Thursday but with a brief backward slide to temperatures today before we resume the warming trend set to peak at the end of the week. An amplified upper trough trailing the cold front will track across the lower Great Lakes early this morning with a quasi-zonal regime in its wake for later today gradually transitioning to a broad upper level ridge over much of the country on Thursday. At the surface...high pressure already in the process of resuming its hold across the region in the wake of the Tuesday evening frontal passage. The high will track across the Ohio and Tennessee Valleys later today into tonight maintaining a cold northwest flow across the region for much of today before winds back late. The gusty winds immediately behind the frontal passage will linger for the next few hours before dropping back later this morning as the strongest cold advection diminishes and surface pressure gradient relaxes. Periodic mid and high clouds will drift across the area through the afternoon in what otherwise should be a day filled with abundant sunshine. Skies will remain mostly clear tonight with low level flow backing to a return southerly flow on the back side of the departing high pressure. Winds will steadily increase on Thursday in response to a sharpening of the pressure gradient between the retreating high and low pressure moving out of the upper Midwest. Increasing warm advection will aid in increasing clouds within the boundary layer as an inversion likely organizes. Some uncertainty with respect to how widespread the cloud coverage becomes...but the increase in moisture underneath the inversion supports at least partly cloudy skies focused especially across the northern half of the forecast area Thursday afternoon. Temps...chilly day in store today with cold advection well established across the region. Even despite sunshine...low level thermals support only low to mid 30s for highs for much of central Indiana. The arrival of warm advection and brisk S/SW flow on Thursday will bring a nice bump in temperatures on the order of 10- 15 degrees over today. Lows tonight will fall largely into the lower and mid 20s. && .Long Term...(Thursday Night through Tuesday) Issued at 249 AM EST Wed Dec 22 2021 The long term period will largely be characterized by fast quasizonal to weakly anticyclonic flow over the CONUS, becoming more amplified with time to a western trough/eastern ridge pattern, placing central Indiana under the influence of southwest flow aloft. Weak disturbances in this fast upper level flow will keep multiple chances for precipitation in the forecast, with most if not all of it falling as rain thanks to the above normal temperatures expected throughout the period. Introduced some slight chances for rain on Christmas day that was not in the NBM given models the last couple of nights have continued to depict some QPF with a weak surface wave moving through the area. Otherwise, stuck fairly close to initialized PoPs. && .Aviation...(18Z TAF Issuance) Issued at 1117 AM EST Wed Dec 22 2021 IMPACTS: - VFR conditions are expected this TAF period. - No impacts expected throughout the forecast period Discussion: Surface high pressure over the middle Mississippi valley will build east across Indiana this evening before moving east of Indiana overnight. GOES16 shows clear skies arriving through the period as forecast soundings continue to show a steep inversion aloft preventing any diurnal CU. Overnight as the surface ridge builds east...a weak upper level disturbance is expected to push east from the upper midwest. This may result in some mid and high cloud arriving overnight...but any CIGS will remain VFR. NW winds are expected this afternoon ahead of the passing high but are expected to become southerly overnight as the High passes to the east of Indiana. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ Update...Puma Short Term...Ryan Long Term...Nield Aviation...Puma