982 FXUS63 KTOP 081803 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 1203 PM CST Fri Mar 8 2019 ...Update to aviation forecast discussion... .SHORT TERM...(Today through Saturday) Issued at 348 AM CST Fri Mar 8 2019 As of 09Z Friday morning zonal midlevel flow was present across the Central Plains with an embedded shortwave trough traversing KS. Scattered showers and sprinkles were noted earlier this morning, although all precipitation has pushed east of the forecast area. Nighttime microphysics satellite reveals an expanding area of low cloud cover and fog. Generally visibilities have remained greater than 1 mile, although brief periods of <1 mile are possible through the morning, especially south of I-70. Cloud cover is likely to remain stubborn through the day with mostly cloudy skies anticipated, which will make for a tricky temperature forecast this afternoon. GFS/RAP/HRRR forecast soundings depict boundary mixing heights nearing 925-900 mb which could translate to temperatures near 50 for areas along/south of I-70. Given the persistent stratus, have opted for highs in the mid 40s along/south of I-70, with 30s/40s northward where several inches of snow depth remains. Our attention then turns toward midlevel trough which is currently along the CA coast. WAA is progged to rapidly increase after 00Z this evening across the entire forecast area. Given the pre-existing low-level moisture in the form of stratus, drizzle is expected area- wide through 06Z. As the main midlevel trough axis encroaches the area overnight, the stout EML should erode allowing for a transition to rainfall to occur area-wide. Model solutions continue to progress the surface low from Salina to St. Joseph overnight into Saturday morning, allowing dew points to surge into the upper 40s to low 50s southeast of its track. As the EML erodes, 100 to 400 J/kg of MUCAPE is likely to be realized across the southeastern half of the CWA, with the highest values across Anderson County. Considerable uncertainty remains with the near-surface temperature profile and the strength of the inversion. GFS and CAM forecast soundings depict a weak surface inversion by 12Z, while the NAM and ECMWF maintain a stronger surface inversion. With the strongly shear environment expected Saturday morning, if the GFS/CAM solutions come to fruition a few damaging wind gusts would be possible. As the midlevel trough ejects northeast of the forecast area late Saturday morning/early afternoon, precipitation will end from southwest to northeast. Total rainfall amounts are likely to range from near 0.1" in North-Central KS to near 0.75" in far Eastern KS. A strong surface pressure gradient (8-10 mb across the CWA) combined with 850 mb winds near 50 kt will yield windy conditions late Saturday morning through sunset. Current expectation is for sustained winds between 25-35 MPH with gusts 40-50 MPH. A wind advisory may need to be considered in subsequent forecast issuances. A brief period of "spring-like" temperatures is anticipated early Saturday afternoon with highs in the 50s across Eastern KS, 40s elsewhere. CAA will increase by late afternoon, decreasing temperatures into the 30s and 40s area wide by sunset. .LONG TERM...(Saturday night through Thursday) Issued at 348 AM CST Fri Mar 8 2019 Models are in agreement that as a surface ridge builds south Saturday night, shortwave ridging develops aloft over the central plains through Sunday night. Additionally there is expected to be dry air moving into the area with the surface ridge. So with little in the way of moisture or forcing for precip, the weather is expected to remain dry Saturday night and into Monday morning. Temps are expected to be 5 to 10 degrees below normal with lows in the 20s and highs in the 40s. By Monday afternoon, the surface ridge is expected to begin weakening while a low level return flow develops over the surface ridge. There is good consensus for a strengthening warm air advection pattern Monday night and through the day Tuesday as moisture gets lifted along the isentropic surfaces. So precip chances should be on the increase late Monday afternoon and through the night. With the warm air advection pattern, models develop a decent warm nose over the forecast area by Tuesday morning, and as a result it looks like snow is less likely than perhaps some freezing rain where temps do fall below freezing. Although it is not clear temps will fall significantly below freezing Monday night or Tuesday morning as overcast skies limit radiational cooling while the low level warm air advection pattern persists. So have trended Tuesday morning lows a degree or two warmer with areas near the NEB state line and where there could still be some snow pack around freezing. With this in mind, have a wintry mix of freezing rain and sleet for areas along and north of a line from Concordia to Holton. The stronger dynamics are progged to lift across the forecast area Tuesday night and Wednesday morning. There are still some timing differences among the models with the upper low and how quickly the dry slot works its way into northeast KS. But the overall trend in POPs should be to lower through the day Wednesday. Models show a bit of a negative tilt to the wave as it lifts north Wednesday morning. While GFS forecast soundings show limited instability until the dry slot moves in Wednesday afternoon, have kept a slight chance for thunder late Tuesday night and into Wednesday given the pattern and somewhat steeper mid level lapse rates ahead of the wave around 6.5 C/km. Models develop a strong pressure gradient on Wednesday as the surface low lifts north of the forecast area. This is expected to promote good mixing of the boundary layer while 925MB temps potentially increase to around +14C across eastern KS. Thinking there could be some partly sunny skies by the afternoon as well, so have increased highs to around 60 which may still be on the conservative side if the warm air advection is as strong as the models indicate. For north central KS, the warm air advection looks to be weaker and only have highs in the lower and mid 50s. For Thursday, dry air is forecast to move in as the surface pressure rises. Aloft models suggest a broad cyclonic pattern develops with no obvious shortwave. With this in mind think precip chances are to low to mention. Renewed low level cold air advection should hold temperatures generally in the 40s. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) Issued at 1139 AM CST Fri Mar 8 2019 For the 18Z TAFS, visibilities and CIGS will improve slightly this afternoon. An upper level trough and associated surface low will approach the area this evening. Rain and thunderstorms will develop and overspread the forecast area tonight. Damaging wind will be possible with stronger storms. Visibilities and CIGS will drop into the low-end IFR category with precip around. Periods of LIFR will also be possible at times. Rain and storms should exit the area by midday Saturday. Surface winds will increase as the precip exits and will be very gusty through the day. && .TOP WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until noon CST today for KSZ008-020. && $$ SHORT TERM...Baerg LONG TERM...Wolters AVIATION...Teefey