482 FXUS63 KTOP 152325 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 625 PM CDT Mon Apr 15 2019 ...Update to aviation forecast discussion... .SHORT TERM...(This evening through Tuesday) Issued at 335 PM CDT Mon Apr 15 2019 Continued warm and quiet weather continues into Tuesday. Broad longwave ridging is established across the western two- thirds of the CONUS this afternoon with southerly surface flow throughout the Central Plains. Over the next 24 hours, the upper ridge begins to amplify as a West Coast trough digs into the Great Basin. WAA within the return flow sector boosted highs into the 70s today and will push readings into the low 80s on Tuesday as H850 temps eclipse +17 C. Lee cyclogenesis taking place along the Front Range strengthens a baroclinic zone arching eastward-- bifurcating Kansas from southwest to northeast by this evening. This warm front lifts to along the KS/NE border by Tuesday afternoon. There is some signal of low clouds developing along this trough during the morning, with the 12Z NAM by far the most aggressive in developing low stratus throughout the forecast area by sunrise. This solution seems quite unlikely given the synoptic setup and the NAM's boundary-layer over-saturation bias. For the going forecast, have gradual increased high cirrus clouds as Pacific moisture streams northeastward on an 80 kt subtropical jet. .LONG TERM...(Tuesday night through Monday) Issued at 335 PM CDT Mon Apr 15 2019 Strong to severe thunderstorms remain possible on Wednesday afternoon--mainly along and southeast of the Kansas Turnpike--with a brief cool down late week. The aforementioned warm front gradually rotates into a more meridional orientation Tuesday night/Wed morning in north-central Kansas and south-central Nebraska. There is some signal in the 12Z GFS/NAM that elevated inhibition north of the warm front decays within a region of H925-H850 theta-e advection and steepening mid- level lapse rates and promote convective initiation, but the window of opportunity is limited and almost entirely north of the forecast area. A region of mid-level theta-e advection and weak frontogenesis could generate shallow showers early Wednesday morning area-wide, but these showers (rooted under the EML cap) should not amount to much and quickly track northeastward and out of the area. There will likely be a break in the precipitation Wednesday morning into early afternoon with a +19 C warm nose serving as a very effective cap on any convective initation. Attention then turns to how the convective threat evolves during the late afternoon and evening hours. As with last night's model runs, there continue to be signs that the northern and southern stream impulses will fail to phase until late Wednesday night, past the window of opportunity for severe weather in eastern Kansas. This favors the best threat of severe weather being farther south in the Southern Plains closer to the southern wave. The forward motion of the surface boundary has also increased with the latest 12Z guidance suite, with the front along a Seneca to Council Grove line at 18Z and a Lawrence to Burlington line at 00Z. Steep mid-level lapse rates will still promote MLCAPE values of 1500-2000 J/kg, but the lack of a strongly veering hodograph and unidirectional shear above the LFC oriented parallel to the orientation of the boundary does not instill confidence in the ability of convection to remain discrete for long. As with earlier forecasts, still expecting any convection to rapidly grow upscale to clusters or line segments with wind, heavy rain (there will be some element of training cells), and hail being the main threats. There is a non-zero threat of a tornado in the proximity of the surface boundary, but this threat hinges on multiple mesoscale features aligning just right in a very short window. The boundary shifts out of the forecast area by 03-06Z Wednesday night with CAA and wrap-around moisture spilling into the region for Thursday. Highs on Thursday fall to around 60 degrees F with winds pushing 20 to 30 kts with higher gusts possible. Large scale subsidence will keep precip chances low for Friday into Saturday, with a gradual rebound in temperatures into the mid to upper 60s Friday and 70s on Saturday as the surface ridge passes through and return southerly flow settles in ahead of a late weekend southern stream wave working through the Four Corners region. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 625 PM CDT Mon Apr 15 2019 Main concern for this forecast will be LLWS developing this evening by 04Z as the low level jet increases to around 45 kts. Southerly surface winds are expected to decrease to around 10 kts or less at the surface. The jet migrates southeast overnight ending LLWS at MHK around 08Z and by 12Z at TOP and FOE terminals. Otherwise VFR conditions are expected for this forecast period. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Skow LONG TERM...Skow AVIATION...53