201 FXUS63 KTOP 210412 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 1112 PM CDT Thu Jun 20 2019 ...Update to aviation forecast discussion... .SHORT TERM...(This evening through Friday) Issued at 349 PM CDT Thu Jun 20 2019 Main focus in the short-term will be chances for thunderstorms and the timing of convective activity across the area. The upper level pattern is characterized by a trough of low pressure over the northwestern CONUS and slight mid and upper level ridging over the central Plains. A broad area of surface low pressure was located over the Colorado Rockies/Four Corners region. Closer to home, skies remained clear as temperatures warmed into the upper 80s and low 90s over northeastern KS this afternoon. Dewpoints as of mid-afternoon were holding in the mid to upper 60s for much of the area with low 70 degree dewpoints located primarily over the southeastern quadrant of the state. Most of the evening hours are expected to remain dry with the best chance for convective initation occurring near the KS/NE border. If storms are able to get going, all modes of severe weather will be possible given that instability has reached 3000+ J/kg of CAPE and effective bulk shear values exceed 50 kts in northeastern KS. The better chance for thunderstorms across the CWA will occur during the overnight hours. CAMS model guidance has come into better agreement with a squall line of storms developing over northwestern KS as a nocturnal low level jet increases and interacts with an area of low pressure and associated surface boundary located near the NE border. The primary hazards with the storms overnight will be strong winds and hail. Storms should exit the area by mid- morning tomorrow. Attention then turns to very hot conditions developing tomorrow. Temperatures will soar into the low 90s by the mid-afternoon hours. When combined with ample low level moisture and surface dewpoints in the low to mid 70s, the heat index will increase to near 100 degrees for a few hours during prime heating. Current thinking is that rain and storm chances will remain very low throughout the day and evening hours of Friday. Additionally, the better chances for thunderstorms overnight into Saturday look to remain north of the area. .LONG TERM...(Friday night through Thursday) Issued at 349 PM CDT Thu Jun 20 2019 Active weekend in store as seasonably strong short-wave trough expected to move from Utah Saturday morning to western Kansas by Sunday evening. Deepening surface low ahead of upper trough will continue to draw very high theta-e air in the boundary layer northward into eastern Kansas. MLCAPE values forecast to be in excess of 5000 J/kg by late Saturday afternoon with little (if any) convective inhibition. One key question is how far west storms will initiate. In general prefer GFS positioning of surface features as it seems NAM pushes weak surface high too far south and east given approach of upper trough. Once storms form, some will likely become severe, although mid-level winds and deep-layer shear are somewhat marginal. Probably will see mostly outflow-dominated storms, although could be a narrow window/corridor where better shear to west becomes roughly co-located with better instability. Surface dewpoints in the low 70s and precipitable water values nearing 2" should set the stage for efficient rain-producing storms. Wouldn't be surprised if flood highlights are eventually needed for late Saturday and possibly Sunday. Primary question for Sunday seems to be where effective boundary will set up. Not surprisingly, NAM is more aggressive in pushing (and keeping) boundary to the southeast with the rain-cooled air from Saturday night's activity. GFS allows airmass to recover again with axis of mid-level trough still over eastern Colorado by midday Sunday. At this point will play middle-of-the-road scenario and carry highest PoPs in the east. If GFS scenario is correct, heavy rain threat will be present again with very moist airmass in place. Cooler, drier weather expected Monday as upper trough lifts to the northeast. Could see some warm-advection activity again by Tuesday night as mid-level heights rise. Summer-like ridging starting to build in by Wednesday which should mostly shut off any organized precip chances. Should also mention heat potential for Saturday. Some convective cloudiness debris may keep temps in check a bit, but highs near 90 and dewpoints in low 70s yield heat indices around 100. That's below advisory criteria, but warmest of season so far, so will continue to keep this as part of the forecast message. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1102 PM CDT Thu Jun 20 2019 Increasing high clouds in advance of a TSRA cluster with uncertainties lingering on how far south and east it will impact terminals. Current radar and short term models are trending a bit later in timing with MVFR cigs and scattered TSRA in the 11Z to 13Z time frame onset for all sites. There is a possibility for light showers and MVFR stratus to linger during the morning period before lifting to VFR with increasing strong, southerly winds in the afternoon. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Teefey LONG TERM...Manion AVIATION...Prieto