537 FXUS63 KTOP 021148 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 548 AM CST Sat Feb 2 2019 ...Update to aviation forecast discussion... .SHORT TERM...(Today and tonight) Issued at 517 AM CST Sat Feb 2 2019 As of 09Z Saturday morning a negatively- tilted, midlevel trough was progressing eastward across the TX Panhandle. Surface low/lee trough continues to deepen across the High Plains with continued low-level mass response across the Southern and Central Plains. Nearly the entire CWA has seen surface temperatures and dew points rise into the low 40s. Patchy drizzle and fog have been noted across the CWA, primarily the southeastern half. The combination of weak low-level ascent and shallow moisture has resulted in less-coverage of drizzle through the night than previously anticipated. Dense fog has been expanding across portions of Central KS and East-Central KS, as a result have issued a Dense Fog Advisory through 10 AM for Morris, Lyon, Coffey, Osage, Anderson and Franklin Counties. Transitioning into the daytime hours today expect any patchy drizzle to come to an end as ascent further decreases and some mixing of the boundary layer ensues. High temperatures this afternoon will hinge on the depth of mixing through the day. At this point have went with a model average for highs with temperatures ranging from the low 50s along the NE border to the upper 50s along and south of I-70. If trends of latest RAP/HRRR come to fruition with stratus lifting above 2kft and mixing heights reaching 900 mb, low 60s would be possible. Given the expansive stratus shield extending to the TX/OK border and continue moisture advection, tending to think mixing heights will be closer to 925 mb and keep temperatures in the 50s. Low stratus is expected to persist through the night tonight with patchy fog and drizzle possible. Temperatures will are expected to remain steady through the night with lows ranging from the low 40s in North-Central KS to the low 50s in East-Central KS. The current forecast low of 44F and 50F at Topeka and Concordia respectively would set records for the "warmest low temperature" on February 3rd at each site. Records: Topeka (43F in 2012) and Concordia (42F in 1992). .LONG TERM...(Sunday through Friday) Issued at 517 AM CST Sat Feb 2 2019 For Sunday models continue to show a low level warm air advection pattern with some isentropic upglide over northeast and east central KS. Because of this have maintained a slight chance for measuring a hundredth of an inch through the day Sunday. Otherwise the main question is whether the stratus will remain solid across the area. The NAM shows little chance of the stratus mixing out, but the GFS hints at the possibility over parts of north central KS. Think the warm air advection will be good enough to help highs into the lower and middle 60s for most areas. If the sun breaks out, highs may make a run at the upper 60s. A shortwave is progged to move through the central plains Sunday night. All of the guidance seems to be coming in line with the wave passing mainly north of the forecast area with the surface low tracking along the NEB/KS state line. With the better forcing focused to the north, chances for measurable precip look to be to low to mention in the forecast. Lows Monday morning could be tricky as models show a cold front passing through the region by noon. In general think temps on Monday will not see much of a diurnal trend as cold air advection increases through the day with highs occurring in the morning before the front passes through. Dry air moving south with the surface ridge should bring an end to precip chances through Monday night. Things could get a little messy for Tuesday through Thursday as models prog a shallow Canadian airmass setting up over the forecast area while 850MB winds become more southerly with increasing saturation. Large scale forcing looks to be lacking until Wednesday night and models do not have much in the way of QPF for Tuesday and Wednesday. But there is some agreement in a strong warm nose advecting as far north as northern KS while temps remain around freezing or cooler. With a reasonable signal from the models for freezing rain, have included a mention for it in the forecast. The main uncertainty continues to center around the timing of the upper wave on Thursday. The ECMWF and Canadian remain fairly progressive, keeping the wave phased with the northern stream. Meanwhile the GFS wants to lag energy over the southwest, finally lifting it across the region Friday morning. With the ECMWF and Canadian showing pretty good consistency with a progressive solution, think that is the more likely outcome, but have held onto some token chance POPs for Thursday night and Friday morning to account for the GFS solution. At this time, the expectation is for increasing POPs into Wednesday night with a wintry mix, including freezing rain, probable across some part of the forecast area. I anticipate a strong cold front to push through during the day Thursday changing the precip type over to snow. Then depending on the timing of the system, precip ending by Thursday evening or some light snow persisting into the morning Friday. Adjustments to this forecast will likely be needed as it gets closer in time. && .AVIATION...(For the 12Z TAFS through 12Z Sunday morning) Issued at 539 AM CST Sat Feb 2 2019 Dense fog continues to overspread the area from south to north. LIFR vsby have already arrived at the Topeka sites and expect IFR to LIFR vsby to arrive at MHK within 1-2 hours. VSBY and cigs are likely to improve after 15Z with MVFR conditions likely by 19-20Z. Southerly winds are likely to remain 10-15 kt through the remainder of the period. Uncertainty arises for the late afternoon into the early evening as some short term solutions have a brief period of VFR returning at all sites. Given the large swath of stratus across the Central US, would tend to think MVFR cigs should prevail through the remainder of the period. && .TOP WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until noon CST today for KSZ008>010-020>024- 026-034>040-054>056-058-059. && $$ SHORT TERM...Baerg LONG TERM...Wolters AVIATION...Baerg