595 FXUS63 KTOP 121753 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 1153 AM CST Sat Jan 12 2019 .UPDATE... Issued at 740 AM CST Sat Jan 12 2019 Have trimmed the central counties, including Topeka, out of the winter storm warning and transitioned them to a winter weather advisory with the heavy snow having shifted east of the area due to the arrival of a dry slot and the deformation zone not expected to move into the area until later today in a weakened state. Total snow amounts in these areas were around 2 to 4 inches overnight. Also have upgraded the northwest CWA into a winter storm warning with the deformation zone lingering for the next 3-4 hours that could bring storm total snow amounts of up to 8 inches in these areas that are already pushing 6 inches of snow. && ...Update to aviation forecast discussion... .SHORT TERM...(Today and tonight) Issued at 400 AM CST Sat Jan 12 2019 Snow--mixed occasionally with freezing drizzle--gradually winds down today. Early morning water vapor satellite imagery depicted a maturing extratropical cyclone wrapping up over the Central Plains with a dry slot punching northward into central Kansas. With an omega block impinging on its northern flank, the negatively-tilted H300 wave and attendant 1001 mb surface low are progged to take a more easterly trajectory over the next 24 hours. Broad isentropic upglide ahead of the H700-600 low has fueled a widespread swath of light to moderate snowfall over mostly eastern portions of the forecast area overnight, with the mid-level deformation zone wrapping back to the southwest over portions of north-central and western Kansas. The heaviest snow should be done by around 12-15Z as the dry slot spreads eastward and the mid-tropospheric low shifts eastward. Lift maximized in the -5 to -10 C range, coupled with surface wet bulb temperatures hovering right near the freezing mark and reinforced by an ESE flow of similar theta-e characteristics, has produced snow ratios around 5:1 to 10:1 with the snow taking on a slushy consistency that is compacting quickly with time. As the deformation zone swings through and the lift source moves up towards the DGZ, we may see snow ratios increase right as the snow comes to an end. However, the combination of solar insolation (even through the cloud deck) and surface wet bulb values lingering in the 30 to 32 degree range should help compact and melt some snow today. With the dry slot swinging up into central Kansas and the cloud tops warming, there is a chance that p-types could oscillate between light snow and freezing drizzle east of a line from Manhattan to Marysville today. There are a few time steps in the RAP profiles that could conceivably lose ice introduction, and to account for this (albeit) low possibility, did introduce slight to chance periods of freezing drizzle for the remainder of the event. The overall impacts of any freezing drizzle will be minimal given the warm nature of the snowpack, incoming solar radiation during the day, and wet bulb temperatures around the freezing mark. The precipitation comes to an end by this evening as the upper wave shifts into the Mid-Mississippi River valley. However, with a secondary northern stream trough laying out along an axis from Iowa to Colorado, low stratus clouds should persist through the day on Sunday and possibly Sunday night. Did increase lows tonight to account for these clouds and may need to do the same for tomorrow night if it appears that they will linger. .LONG TERM...(Sunday through Friday) Issued at 400 AM CST Sat Jan 12 2019 Quiet and near seasonal temps are forecast for much of the upcoming work week with the focus turning to a another potential winter storm late in the week. The broad, zonal trough lingers over the forecast area well into Monday before upper level ridging builds over the Rockies. A 1034 mb surface high pressure ridge centered over the forecast area Sunday evening shift east for Monday, with WAA starting Monday afternoon as the upper trough decays. Highs on Monday have been lowered 3-5 degrees from yesterday's forecast to account for the new snowpack with raw guidance solutions hinting that this may still be too warm. A low-amplitude wave races through in a zonal flow pattern late Tuesday into Wednesday, driving a cold front through the area on Tuesday night. Increasing clouds will be the main sensible weather impact from this boundary passage, but there is a non-zero chance of some light rain as well. Looking towards late in the week, a strong extratropical cyclone pulls off the Rockies ahead of a digging upper level trough. While it is too soon to resolve the exact impacts of this potential winter storm, it bears watching over the coming days. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 1141 AM CST Sat Jan 12 2019 For the 18Z TAFS, light snow will continue to be possible at terminals until around 21-00Z as an upper low transitions further east of the area. MVFR cigs will continue through the period with times of IFR cigs possible after 06Z as the back edge of the system moves through. Winds will be breezy this afternoon but will decrease overnight as high pressure moves over the region. && .TOP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 6 PM CST this evening for KSZ010>012-021>024-035>039-054-055-058-059. Winter Storm Warning until 6 PM CST this evening for KSZ008-009- 020-026-034-040-056. && $$ UPDATE...Skow SHORT TERM...Skow LONG TERM...Skow AVIATION...Teefey/53