Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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902 FXUS63 KABR 280851 AFDABR Area Forecast Discussion National Weather Service Aberdeen SD 351 AM CDT Sun Apr 28 2024 .KEY MESSAGES... - Active pattern continues with chances for moisture today, Tuesday, and Thursday. Rainfall amounts for today and tonight range at about an inch in northeast South Dakota/western Minnesota while western/north central SD will see around quarter inch or less. - Less moisture is expected with the other systems during the week. - Below to near normal temperatures through the extended. && .SHORT TERM /TODAY THROUGH MONDAY AFTERNOON/... Issued at 350 AM CDT Sun Apr 28 2024 Next round of rainfall is moving northward across NE and has recently moved into far southern SD. Main surface low center is down in KS, set to move north-northeast through the day while spreading rainfall northward into the CWA. Models may have slowed down precip onset a bit compared to 24 hours ago, but still expect precip to overspread the region through the morning hours. Little to no instability to speak of, so just looking at general rainfall with this system. Forecast rainfall totals are fairly close to NBM means, which are around 1 inch across the eastern CWA, to around 0.25 or less across central/north central SD. Higher end scenarios (75th/90th percentiles) top out around 1.25-1.50 inches for eastern areas, while central SD is more around 0.75 inches. There is some question where exactly the western edge of precipitation sets up with this system, which models show could be around the CWA border with UNR. In this scenario, it`s interesting to note some drier outcomes (25th percentile) show only about 0.10 or less (maybe nothing at all?) across north central SD and west of the Missouri River. Late tonight into early Monday morning, temperatures try to cool into the mid to upper 30s. NBM lows were generally from 34-36 degrees across the CWA, but felt this might be a touch too cool given the cloud cover and lack of strong cold air advection. Leaned more towards NBM 75th, which still gave lows from 35-38 degrees. This is still cool enough to entertain the mention of a rain/snow mix perhaps, especially for higher terrain areas like the Leola and Sisseton hills regions. NBM probs for precip type (snow) generally show 30-50% from the Leola hills south to Hand/Hyde counties, eastward into the Coteau region. Official wx grids do show a rain/snow mix by early Monday morning, but with little to no snow accumulation. System begins to depart the region on Monday, but it will take some time to erode the cloud cover from west to east according to HREF low-level cloud cover ensemble means. By Monday afternoon, it still shows the eastern CWA stuck in clouds while central SD beings clearing out. Where sun does manage to emerge on Monday (central SD), look for temps to rebound into the 60s as lower level temperatures begin to warm from 925-850mb with an approaching warmer air mass. && .LONG TERM /MONDAY EVENING THROUGH SATURDAY/... Issued at 350 AM CDT Sun Apr 28 2024 Start out the long term with one departing system, weak ridging overhead and an approaching trough from the west. This upstream trough deepens over Montana, ejecting a shortwave eastwards that quickly crosses South Dakota Tuesday, before making a sharp turn northwards up into northern Minnesota. The resulting surface low will have a tight gradient and southeast low level flow as it moves in from the west Tuesday morning, and a north south cold front that crosses into Minnesota by the afternoon. There will be limited moisture return, despite a well defined warm tongue. Its within this warm tongue, and along the cold front, where we see the potential for convection. NAM BUFKIT profiles support skinny elevated CAPE in a high unidirectional shear environment, with the core of highest CAPE in southeast Minnesota. NAM MUCAPE is around 2-3k j/kg in the aforementioned corridor, however NBM 25th/75th range is much lower, between a few dozen to around 500j/kg. Winds on the back side of the system is the result of cold advection (about a 5C drop in 850mb temperatures) though pressure rises are only about 3-5mb over 6 hours. West of Mobridge continues to be the focus for highest winds with the NBM 25th/75th range between ~45 and 50-55mph, but elsewhere that range is much lower. The next system to contend with is a more typical type Colorado low that tracks into Kansas and Iowa, similar to the more recent systems. Pretty similar outcomes between deterministic guidance in the track/timing of the low, though NBM 25th/75th range of QPF is still about 1/2" with a similar range between GEFS plumes. As for temperatures, with the moisture and airmass changes, still looking at readings near to below normal. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1238 AM CDT Sun Apr 28 2024 Terminals KABR,KATY,KPIR,KMBG A mix of MVFR/IFR CIGs will become predominately IFR through the morning hours. -RA/RA will also be spreading northward during the morning hours, generally around 12Z and after. VSBY is forecast to become MVFR/IFR in RA and BR as the storm system overspreads the area. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ SHORT TERM...TMT LONG TERM...Connelly AVIATION...TMT