947 FXUS63 KFSD 031136 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 636 AM CDT Mon Jul 3 2017 .SHORT TERM...(Today and Tonight) Issued at 358 AM CDT Mon Jul 3 2017 A few areas of concern regarding the forecast for today and tonight. We have a broad area of isentropic lift nosing across the Missouri Valley this morning. Light east to southeast low level flow today will tap into increased moisture through the day, with dewpoints expected to rise to 60 to 70 degrees by afternoon for much of the forecast area. Meanwhile, a weak shortwave is crossing the Wyoming border into western SD early this morning, and is expected to follow a slightly more northerly track than previous model runs suggested. Ongoing Scattered showers and thunderstorms will continue to track east, but so far this morning, activity has been struggling to move into south central SD. Models generally fizzle out this activity this morning as it moves eastward, however cannot rule out some weak isolated showers or thunderstorms to survive into our western border. Meanwhile some very isolated shower or thunderstorm activity to pop up near the isentropic lift along our southern border later this morning into the afternoon near the Missouri Valley into the highway 20 corridor. With the leading shortwave tracking into south central SD this afternoon, and aided by the heat of the day, activity may reinvigorate enough across southeast SD and the highway 20 corridor for scattered thunderstorm mention. CAPE profiles remain quite skinny, while shear is once again fairly weak, especially in the mid levels. Severe weather is unlikely, but a few stronger storms may have small hail, heavy downpours, and gusty winds. Additional activity is expected to develop late evening into the overnight hours as the main shortwave finally digs across southeast SD and the low level jet cranks up along the I-29 corridor by midnight. Showers and thunderstorms will spread eastward across the forecast through the overnight hours. Precipitable water values are pretty high at around 1.75, so could see some heavy rainfall with this activity. .LONG TERM...(Tuesday through Sunday) Issued at 358 AM CDT Mon Jul 3 2017 The upper level trough/shortwave continues to slide across the Northern Plains on Tuesday, keeping thunderstorm chances going into the evening. Not expecting it to rain through the entire day, as there will probably be a lull in the activity by mid morning, before heating and increasing instability results in redevelopment in the afternoon. The better chances for this still appears to be from the I-29 corridor and eastward. There will be plenty of instability around by Tuesday afternoon with ML CAPE values running 1500-2000 J/KG, but shear is on the weaker side, though cannot completely rule out an isolated severe storm with large hail/damaging winds in the afternoon and early evening. Highs on Tuesday will be mainly 80s, though touching on 90 over south central SD. By Wednesday the upper level trough pulls off into the Mississippi Valley with decreasing thunderstorm chances across our area. In conjunction with that, an upper level ridge over the western CONUS begins to nudge eastward. This will be reflected in temperatures as highs climb into the mid 90s over portions of the James River Valley/south central SD. On Thursday upper level heights continue to rise with the thermal ridge sliding across the region and 850 mb temps in the range of 25 to 30C. With that, stayed on the high side of guidance which will bring highs into the 90s over most of our area, closing in on 100 over south central SD. For the end of the week, upper level energy drops out of Canada into the western Great Lakes/Mississippi Valley region, dampening the ridge over our area and bringing temperatures back into the 80s for Friday and Saturday. It looks to remain dry both days. May begin to see more warming by next Sunday as the ridge begins to build back into the region. && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 630 AM CDT Mon Jul 3 2017 Main concern will the potential for isolated to scattered thunderstorms developing this afternoon along the Missouri Valley and into south central SD. Right now it looks like this activity is too spotty for mention in the HON or SUX TAF. Later this evening and tonight, additional storms are expected to develop in south central SD and spread east through the overnight hours. Have added VCTS and VCSH mention to the TAFs for this evening and tonight. Models suggest that with this activity late tonight, MVFR ceilings will become prevalent at times. Expect the potential for reduced visibility and ceilings in thunderstorms as well. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ SHORT TERM... LONG TERM...JM AVIATION...