849 FXUS63 KTOP 071747 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 1247 PM CDT Thu Jun 7 2018 ...Update to aviation forecast discussion... .SHORT TERM...(Today and tonight) Issued at 324 AM CDT Thu Jun 7 2018 07Z water vapor imagery shows an upper ridge over the central plains with an upper trough over the west coast. At the surface, an outflow boundary has pushed south and west across the forecast area to near CNK and EMP. A meso high was centered over the MO river with a second meso high over southwest NEB. A surface trough was located across the southern high plains from southeast CO through west TX. The forecast for today is shaping up to be complex. Just about every solution has a different answer for convective trends through this morning and any redevelopment later in the day. In the short term, think the MCS across western KS will probably hold together long enough to move into western sections of the forecast area as southerly winds continue to pump moisture north ahead of the outflow boundary. Through the rest of the morning, most guidance shows the associated MCV propagating east across the area. There are a few convective allowing models (CAMs) that linger scattered showers and storms into east central KS by the late morning and think it may be due to this MCV. The HRRR clearly is behind the curve timing wise, but the ARW and NMM support this idea of storms holding together into eastern KS. The big unknown is how the storms will evolve as they encounter the meso high over northern KS. The expectation is as they run into the cooler air to the east they would become more elevated and weaken. So I keep some scattered wording through the morning with storms moving east, but have POPs gradually diminishing thinking storm coverage will lessen as they move east and become more elevated. For later in the afternoon and tonight, confidence in the forecast is not that great. Models suggest there will once again be quite a bit of instability (at least 4000 J/kg) developing in an undisturbed airmass with temps in the lower 90s and dewpoints holding in the upper 60s. However it is not clear that there will be an undisturbed airmass as there could be some weak subsidence in the wake of the morning convection as well as cooler temps. Additionally there is not an obvious forcing mechanism for storm development this afternoon. So I only carry some small POPs through the afternoon with the expectation the MCS will limit the recovery somewhat. The forecast has chance POPs for tonight. The thinking is areas west could recover enough for renewed development by this afternoon. These storms would likely move across the forecast area through the night. The reason for only going with chance POPs is there is no consensus among any of the models for timing or location of the storms. So think storms tonight may remain scattered in coverage, and there simply isn't enough confidence to go with likely POPs. Deep layer shear remains marginal this afternoon and tonight, but the potential for a very unstable airmass suggests a risk for large hail and damaging winds late this afternoon and overnight. Highs today are expected to be in the middle 80s to near 90. Cloud cover early in the day along with some overturning of the airmass should keep highs somewhat cooler than yesterday. Also models show some cooling in the 1000-500MB thicknesses and 850MB temps. Lows tonight will again depend on coverage of thunderstorms. Given the uncertainty have not strayed to far from a model consensus with lows in the upper 60s to around 70. .LONG TERM...(Friday through Wednesday) Issued at 324 AM CDT Thu Jun 7 2018 Mid-level ridging over the central Plains continues through the weekend with multiple pertibations in the flow through this period allowing for chances for precipitation. Models continue to vary on spacial coverage of any storms Friday and Friday night with the GFS the most robust with precipitation potential. Like previous days, ample CAPE will exist Friday although shear appears to be marginal near 20-30 knots across northeast Kansas. Soundings indicate a cap in place across northeast Kansas Friday afternoon and evening which would need to be overcome before storms can develop. Even so, if storms do form, steep lapse rates will allow for a any storms to become severe with damaging wind gusts and hail the main hazards. This pattern continues through the weekend with low-predictability storms that would be capable of becoming severe. For now, models hint at very northeastern Kansas and east central Kansas have the best chances for precipitation. A mid-level trough advances across the northwest CONUS Sunday into Monday and a frontal boundary moves into northeast Kansas Monday afternoon. There are some chances for precipitation with this frontal passage, but the better chances remain north of Kansas at this time. Model solutions diverge towards the end of the period making confidence in precipitation chances low after Monday. As for temperatures, highs look to remain in the 90s from Friday through Wednesday. Heat indicies creep up near 100 degrees Friday through the weekend, but temperatures do not look advisory level at this time. && .AVIATION...(For the 18Z TAFS through 18Z Friday afternoon) Issued at 1245 PM CDT Thu Jun 7 2018 Mid/high-level clouds will spread across the region through the period, though predominantly VFR conditions are expected at the TAF sites. Isolated to scattered showers and thunderstorms may develop this afternoon across the area, with additional showers/storms entering and crossing the region through tonight into Friday morning. While localized visibility/ceiling restrictions, along with gusty winds, may accompany this activity, confidence in these impacts affecting any given TAF site is too limited for inclusion in the TAFs at this time. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Wolters LONG TERM...Heller AVIATION...Cohen