Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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763 FXUS63 KFSD 032329 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 629 PM CDT Fri May 3 2024 .KEY MESSAGES... - Rain is expected to move through after dark and into Saturday morning. Rainfall amounts from 0.25" to 1" may be possible. Highest amounts in Northwest Iowa could lead to minor increases in already ongoing flooding. - Cooler temperatures on Saturday (low 60s), with middle and upper 60s on Sunday. Dry conditions expected both days. - Winds approaching advisory criteria may arrive Monday, prior to the arrival of late afternoon and overnight thunderstorms. - The greatest severe weather risks continue to remain focused south of the Missouri River and Highway 20 corridor, however continue monitoring of the forecast is recommended. && .DISCUSSION... Issued at 623 PM CDT Fri May 3 2024 Surface obs indicate the location of the cold front to be in a line roughly from Mission South Dakota northeast through Redfield South Dakota. This front will continue to advance southeastward through the afternoon and evening. Strong frontogenesis in concert with the front will trigger showers and maybe even some thunder. Current radar indicates light rain showers over central South Dakota. These showers will advance along with the front. There is little in the way of instability tonight, so we do not expect these showers to become severe. However, some of the rain showers could produce significant rainfall, especially over northwestern Iowa, where a half to an inch is possible. Elsewhere, totals are expected to be around a quarter to a half inch. Rain showers will be well east of our area by mid Saturday morning. Lows for tonight will be cool, in the upper 30s to 40s. Clouds thin as high pressure builds in Saturday, revealing sunny skies for the afternoon. Winds will be northwesterly bringing a healthy dose of CAA southward, limiting our highs to the upper 50s and 60s. The overnight lows will again be cool, in the upper 30s and 40s. As the high moves to the east, winds will swing around to the southeast Sunday. WAA in the 850 mb level warms temperatures there into the 6-10 deg C range. This indicates that highs at the surface will warm into the mid 60s to low 70s. Sunday night, a low pressure system begins to push through the Rockies, tightening the SPG in front of it. Winds will increase overnight and through the day Monday. I felt that the NBM winds were too strong after considering the model soundings. After collaboration with neighboring offices, went with a 50/50 blend of the NBM and CONSALL. Even after knocking winds back a bit, we are still looking at strong winds for Monday. Sustained at 30-35 mph with gusts 40-45 mph. It may be necessary as we get more information to include a headline for winds, but at this time confidence is too low. Monday morning the surface low ejects out of the Rockies into the north-central Plains, bringing the next round of showers and thunderstorms. Models this round have come into better agreement on the low exiting Colorado and taking a sharp northeasterly track through western Nebraska and South Dakota. As it does so, it will drag a warm front across eastern Nebraska and South Dakota. Instability in the warm sector increases to 500-1000 J/kg of CAPE. Enough to support some thunderstorms. The more favorable environment for severe weather remains over the central Plains, however, a few strong to severe thunderstorms are still possible over southeastern South Dakota and northwestern Iowa Monday night into early Tuesday. Rain totals are still a question mark, with ensembles indicate 80- 100% probability of exceeding 0.1 inches, and 30-60% probability of exceeding 0.5 inches. Rain is expected to be east of the area by Tuesday afternoon. Highs will be 70s for Monday and 60s for Tuesday. The low pressure system then hangs out over the northern plains for the rest of the week, gradually occluding and then moving off to the southeast. Multiple shortwaves form and pass through the area off of that main system, bringing multiple chances for showers through the week. Temperatures will be in the 60s. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 623 PM CDT Fri May 3 2024 VFR conditions with scattered sprinkles continue this evening. Gradually we`ll see the arrival of rain after dark, moving from west to east throughout the Tri-State area into the pre-dawn hours. Ceilings may fall to MVFR levels with visibility dropping towards 3SM at times. MVFR ceilings may linger through Saturday morning as breezy northwest winds prevail. Skies may break into a scattered VFR CU field in the afternoon. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...AJP AVIATION...Dux