


Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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085 FXUS63 KABR 271511 AAC AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 1011 AM CDT Fri Jun 27 2025 .KEY MESSAGES... - The entire forecast area has been classified as SLIGHT RISK (2 of 5) for severe weather this afternoon/evening. Large hail (2- 3")/Winds (60-80mph) are the main threats, however we also have the potential for tornadoes mainly between the Missouri and James Rivers. - SLIGHT RISK (2 of 5) again for Saturday, mainly east of a line from Aberdeen to Pierre, with a large hail and wind threat. && .UPDATE... Issued at 1009 AM CDT Fri Jun 27 2025 Allowed the dense fog advisory to expire this morning. Stratus is hanging on across the east, but visibilities have generally improved. Models are not handling the morning convection well. Hourly pop tweaks are expected. && .DISCUSSION... Issued at 235 AM CDT Fri Jun 27 2025 Stratus and some fog are already in place across the CWA, but for how long? Low level flow transitions from northeasterly to south- southeasterly, a trajectory from which the stratus cu-off now resides. Looking at the 00Z ABR RAOB its noted that the cloud thickness is only about 1.5kft, so if we get any breaks they would erode quickly. Thus, the premise that CAMS should dissipate stratus rather quickly this morning with some pretty big jumps between 16- 18Z to the northeast in the HREF seems adequate and the expectation is that stratus will not play a significant part in the hindrance of the later day severe weather threat. 500mb flow this afternoon is marked by a departing shallow mid-level ridge and a western CONUS/Rockies shallow trough. Embedded within this flow is a very subtle wave over western North Dakota tailing down into northwest South Dakota, and while its subtle at least aloft is primarily neutral flow aloft. As for the storm environment, shear in the mid/upper levels is mainly unidirectional at 20 to 45kts, with light low level southeasterlies around convective initiation. 0-6km shear is about 50kts with a core in central/north central SD of 0-1km SRH thats running up to about 100m2/s2 this afternoon/evening... however a transition will occur with loss of daytime heating, and 0-1km SRH will be on the increase overnight as 1/2km winds increase to 45-50kts by 06Z, up to around 200m2/s2. HREF probability of CAPE in excess of 3500j/kg is 60-70% so plenty of instability. So what`s the MO for convection later today? Shear profiles suggest supercell characteristics, with strong RFD thanks to westerly mid-level flow and dry air at 10kft. Tornado potential isn`t anything to write home about with the low 0-1km shear, but a transition in the evening with that low level jet means there is a window in which discrete storms would have a tornado potential before becoming elevated. High CAPE and shear also presents us with a large hail threat. As for timing/locations, the Missouri valley will be the focus primarily this afternoon/evening. A lee low sets up in Wyoming, with broad southeasterly low level flow presenting a slight upslope across the state. The lack of low level focus and generalistic upper level support means confidence on timing/location is generally low, though CAMS support plenty of evidence that storms will develop and move across the Dakotas this afternoon/evening. Storms continue east into the early morning thanks to the low level jet, although weak upper level support again means low confidence on coverage/timing. Saturday, shear remains strong at about 40kts in the HREF. CAPE is also again up around 4000j/kg. So the main question is where has the lee low/inverted trough stalled as the focus for convection to develop? We also have the issue of the flow aloft only being weakly diffluent and relying on another weak/subtle shortwave to provide the upper level support. Focus remains as per previous forecasts across far eastern South Dakota/western Minnesota. A more pronounced trough moves through Sunday with early frontal passage. This is followed by a weak, shallow and slow moving high pressure system so later half of Sunday through into early Tuesday should be dry. That is followed by some ridging with northwest flow aloft for mid-week. && .AVIATION /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 639 AM CDT Fri Jun 27 2025 Terminals KABR,KATY,KPIR,KMBG Widespread IFR CIGs across the region this morning will slowly erode from west to east through the day, while perhaps improving to MVFR as this happens. Areas of FG/BR are also affecting parts of the region, especially central SD where VSBY has been down to IFR as well, even below 1SM at times. After the fog and low clouds become less of an issue by this afternoon, focus then shifts to TSRA/+TSRA potential across much of the region. Areal coverage may be somewhat limited, so used PROB30 to handle this. Severe storms are possible though, and if one were to move over a TAF site, strong surface wind gusts over 50 knots are possible, along with large hail (GR) and IFR VSBY. Timing for this is somewhat uncertain, so low confidence timing within PROB30 groups, unfortunately. Looking at the evening hours mostly. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...20 DISCUSSION...07 AVIATION...TMT