608 FXUS63 KIND 221428 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 1028 AM EDT Thu Oct 22 2020 .UPDATE... The AVIATION section has been updated below. && .SYNOPSIS... Issued at 402 AM EDT Thu Oct 22 2020 Warm air advection will return temperatures to near 80 today. The remainder of the forecast period will see multiple frontal systems return cooler temperatures and more rain, particularly tomorrow and again for the start of next week. Lows mid to late next week will drop back down to the 30s. && .NEAR TERM /Rest of Today/... Issued at 947 AM EDT Thu Oct 22 2020 Update... Current obs are showing visibilities of 10SM over the majority of central Indiana, so the dense fog advisory has been allowed to expire. Meanwhile, the warm front is still draped across northern Indiana with all convection confined to the Great Lakes area. Will continue to trend toward a dry forecast for today with highs in the upper 70s/low 80s and strong southerly flow. Currently, temperatures across the area are generally in the low to mid 60s with dew points varying from the upper 50s to mid 60s. Updated grids have been sent. Previous Discussion... Widespread dense fog is impacting the area this morning due to warm moist air advecting in behind a northward moving warm front, saturating the atmosphere near the surface. This has prompted a dense fog advisory until 9am. Visibilities will improve from south to north as time goes on as greater mixing will occur further south from the front. That mixing will expand across the area due to daytime mixing increasing as the sun rises. The northward track of the warm front will cause temperatures today to be well above normal, with highs near 80 across the area. Gulf moisture will also advect into the area, increasing dew points to the mid 60s throughout the day. Clouds will thin out as well into the late evening hours as the warm front continues lifting north. && .SHORT TERM /Tonight through Saturday Night/... Issued at 433 AM EDT Thu Oct 22 2020 High dew points and continued southerly flow will keep lows in the mid to low 60s tonight. Ahead of an approaching cold front, cloud coverage will start to increase from the NW and expand to the SE. This increasing cloud coverage tonight should limit fog formation despite the warm saturated surface layer, but it can't be completely ruled out at this time either. Warm temperatures will continue Friday ahead of the cold front, leading to highs in the mid 70s, that will then drop off as the front passes. At the moment, the frontal passage looks to occur midday into the early overnight hours. Rain and thunderstorms will predominately occur along and behind the front, but given the deep moist layer, a few showers could form in the morning, ahead of the front. The best instability will be just ahead of the front with CAPE values around 800 J/kg, bringing at least some embedded lightning with these storms. Otherwise, the best shear will be well behind the front, lapse rates look good but not great, thus not expecting much in the way of any severe weather... but a stray stronger wind gust can't be ruled out at times. Above normal PWATs, of 1 to 1.5, are expected with this line of storms, bringing heavy rain at times Friday. Behind the front, subsidence will move into the area, allowing the remainder of the period to be dry although there will be some lingering post frontal clouds. && .LONG TERM /Sunday through Wednesday/... Issued at 345 AM EDT Thu Oct 22 2020 Although, the forecast will start off with unsettled weather Monday and Monday night as strong southeastward expanding Canadian high forces yet another cold front southeast across central Indiana. Deep moisture and moderately strong dynamics, including the area being in the right rear quadrant of a 140 knot upper jet over southern Ontario, suggests widespread and then good chance PoPs in the wake of the cold front Monday and Monday night. After that, not a lot of forcing as weakening Canadian high pressure builds in. That said, would not rule out a shower or midweek with cyclonic flow overhead. Finally, late in the long term, the eyes will be focusing on a potent upper vortex, that will be an early cold season wintry weather maker over the southern Plains. At this point, the GFS is trending way to fast so, so much so that even the GEFS is discounted. Prefer the slower ECMWF and ECENS, that typically verify better with these early cold season harbingers. That said, the blend was painting small PoPs through most of the rest of the long term and if there is precipitation around during the pre-dawn, some brief non-accumulating snow could briefly mix in over northwestern sections of central Indiana starting Monday night. In general, thick cloud cover and thermals support 5 to 10 degree below normal blend temperatures with afternoon highs mostly in the 50s and overnight lows in the 30s. && .AVIATION (Discussion for the 221500Z TAF Update)... Issued at 1028 AM EDT Thu Oct 22 2020 Some VFR ceilings around 6000FT may move into KIND for a couple of hours late this morning. Otherwise no significant changes made. Previous discussion follows.... The warm front has moved through which will allow an increasing southerly wind flow and should result in the fog dissipating by 13z. Winds will increase to 10 knots or more with gusts 20 knots or more after 17z, as the atmosphere heats up and mixes down. Otherwise, good confidence in VFR this afternoon through Friday morning. Convection could make it to KIND before 18z Friday, but chances too low to mention. Finally, more non-convective low level wind shear after 06z Friday as 40 knot low level jet moves in. && .IND WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...KH NEAR TERM...KH/TDUD SHORT TERM...KH LONG TERM...MK AVIATION...MK/50