259 FXUS63 KFSD 252249 AFDFSD AREA FORECAST DISCUSSION National Weather Service Sioux Falls SD 549 PM CDT Tue Jun 25 2019 .SHORT TERM...(This Evening through Wednesday) Issued at 212 PM CDT Tue Jun 25 2019 Pleasant but breezy conditions continue across most of the region this afternoon. These winds will slowly subside this evening a ridge of high pressure moves through the area. For tonight, we'll be watching convection rolling off the Northern High Plains late this evening and into Wednesday morning. Nearly all convective allowing model solutions indicate one or more clusters of storms moving eastward later this evening as low-level flow begins to back and EML starts to move eastward. Now this activity should begin to weaken as it slide east along an advancing corridor of 800-1000 J/KG MUCAPE into central South Dakota. That said, certainly an increased potential, looking at soundings, for enhanced winds to persist even as this activity weakens given very dry sub-cloud layer under high based storms. Unfortunately, with such low certainty on where activity will develop and the potential for scattered development along a broad axis from North Dakota to central Nebraska on the edge of the advancing EML, have spread a broad 20-30% PoP into Wednesday morning for most locations. Continued uncertainty on Wednesday, as we'll really need to see where the eventual evolution of overnight convection takes place. It's certainly possible that diminishing activity sends out a few outflow boundaries that could serve as afternoon focus points for redevelopment in the afternoon. However, a broad EML will advance northward through the day, and could certainly cap off convection potential into the evening as shortwave ridging briefly arrives. Temperatures should climb into the 80s in most areas as warmer and more humid air starts to lift northward. .LONG TERM...(Wednesday Night through Tuesday) Issued at 212 PM CDT Tue Jun 25 2019 Wednesday night: No matter which solution you look at, all guidance indicates a shortwave will cross the Central Rockies and move into the Plains either late Wednesday evening (ECMWF) or after dark (NAM/GFS/CMC). As a large reservoir of CAPE in excess of 2500 J/KG remains in place by Wednesday evening, it will certainly be possible to see two areas of redevelopment. One area will be along any retreating outflow or on the edge of thermal ridge across SW MN and NW Iowa, and a second area along the High Plains tied more closely to the shortwave. Both areas will certainly have the ability to turn severe given pool of instability, although there is a little more uncertainty with the activity that tracks east of the Plains late Wednesday night into Thursday morning. Upgrades in the SPC risks may be possible if more certainty can be pinned down on locations. Thursday-Friday: Mid-level heights begin to build quickly on Thursday, as morning convection slides to the east, and we'll begin to head towards our first heat wave of the Summer season. Temperatures approach 90 in portions of the CWA by Thursday afternoon, with 90s building east on Friday. Saturday-Sunday: The peak of this upcoming heat wave will arrive Saturday and Sunday. Latest guidance pushes temperatures will into the 90s, and unfortunately, a good setup for high dew points is arriving. Have bumped up highs a couple degrees with fairly high expectation of heat headlines for the weekend as heat index values jump over 100 degrees. Monday-Wednesday: A bit of disagreement begins in medium range models to start next week. The GFS indicates falling heights across south central Canada to start the week, allowing a front to drop into the region. The ECMWF holds the ridge a bit stronger to start the week, but then does sink a boundary closer to the Dakotas by Tuesday. Will not make any adjustments to the forecast for next week given the uncertainty. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 545 PM CDT Tue Jun 25 2019 Primary aviation concern over the next 24 hours will be potential for isolated-scattered thunderstorms moving into the region from western SD late tonight into Wednesday morning. Confidence still rather low on timing/location, but with growing consensus toward focus in southern portions of the forecast area, will include brief mention of thunderstorms for KSUX toward daybreak. Low chance of redevelopment of storms in the late afternoon Wednesday, but better chance looks to hold off until after 17/00Z. Otherwise expect VFR conditions will prevail, with winds remaining less than 20kts. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ SHORT TERM...Dux LONG TERM...Dux AVIATION...JH