Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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349 FXUS63 KFSD 230344 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 1044 PM CDT Sat Jun 22 2024 .KEY MESSAGES... - Ongoing flooding may worsen as the runoff from the last 24 hours makes its way to the waterways. Record river flooding is likely on several basins. - Dry conditions with seasonal temperatures are expected Sunday, however a hot and humid air mass returns on Monday. Monday high temperatures are expected to rise into the 90s with heat indices nearing or exceeding 100 degrees, especially for the SD/NE/IA tri-state region. - The pattern through mid week doesn`t favor any long duration rain, but several brief risks for passing convection exist. A more prominent low pressure system moves in later in the week and weekend. && .DISCUSSION... Issued at 220 PM CDT Sat Jun 22 2024 Shortwave energy responsible for morning/early afternoon convection continues to exit the region, although can`t rule out an isolated diurnally driven shower or thunderstorm over parts of south central South Dakota this evening. Otherwise, high pressure and large scale subsidence is expected for the overnight hours and into Sunday, resulting in dry conditions. The progressive upper level pattern will continue into next week. Another low pressure system will develop out of the Rockies on Monday. Return flow winds and strong WAA advection is expected out ahead of the system Monday afternoon. Model dew point temps rise back into the upper 60s/low 70s with NBM giving a 99% probability of CAPE values soaring above 2000 J/KG. That said a healthy CAP and lack of forcing should prevent thunderstorm activity during the afternoon hours. Afternoon max temperatures will be on the rise, with highs into the 90s. Combined with humidity, apparent temperatures will be nearing or exceeding 100 degrees in some locations, especially along and south of I90. 500 MB height falls/shortwave energy are more prominent during the late Monday night into Tuesday morning time frame however. A low POP exists in this time frame and the region is outlooked for a marginal (1 out of 5) chance for severe weather. High pressure will again build in for Wednesday. However, the end of the workweek appears to be active once again. Near zonal upper level flow on Thursday will transition to southwest flow aloft for Friday and into the weekend. This pattern will again set up the return flow/gulf moisture tap and WAA on Thursday with a fairly well organized low pressure system moving through Friday and Saturday. Multiple rounds of showers and thunderstorms are possible. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1044 PM CDT Sat Jun 22 2024 Potential for fog is the main aviation concern tonight. With winds already calm and variable, as we cool towards our crossover temperatures patchy to areas of fog are expected to form during the overnight period into Sunday morning. This appears most likely for areas along and east of the James River Valley, and given the wet antecedent conditions, patchy to areas of fog are expected with visibilities below 1 mile possible. Given spatial uncertainties, kept mention of fog limited to tempo groups for the TAF sites. VFR conditions return after any remaining fog dissipates Sunday morning. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...AJP AVIATION...APT