Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
782 FXUS63 KABR 250920 AFDABR Area Forecast Discussion National Weather Service Aberdeen SD 420 AM CDT Sat May 25 2024 .KEY MESSAGES... - Seasonal temperatures return this weekend with daytime readings back into the upper 60s to mid 70s. - Unsettled pattern continues with a 20-50% chance for showers and thunderstorms south and east this afternoon and evening. Some storms could be strong to severe late this afternoon, especially across south-central SD. - 20-55% chance for rain Sunday night and Monday. 20-40% chance for rain Wednesday night through Friday. && .SHORT TERM /TODAY THROUGH SUNDAY AFTERNOON/... Issued at 417 AM CDT Sat May 25 2024 The main concern in the short range is storm chances the next couple of days and whether or not our forecast area will see any strong to severe storms out of the deal. More to come on that in a moment. For the time being, our weather across the forecast area remains relatively quiet early this morning. Partly to mostly cloudy skies are the prevailing sky condition with rather cool temperatures in the upper 30 to low 40s north to upper 40s to low 50s south. A few showers remain across our northeast zones thanks to a little subtle vort energy working through a quasi-barotropic zone set up basically in the vicinity of the ND/SD border. These will exit the CWA by daybreak. Dry conditions will be the rule at least until around midday or so before a frontal boundary or sfc trough nudges east and north across the southern part of SD. This in combination of mid lvl s/w energy working through the region will aid in shower and thunderstorm development this afternoon. By late afternoon/early evening across our far southern zones, increasing instability on the order of 1000-1200 J/kg of MLCAPE, 40-50kts of 0-6km bulk shear and steep low to mid level lapse rates will lead to the potential for seeing strong to severe thunderstorms. Several CAM solutions depict storms developing after about the 5-6 PM CDT hour across the I-90 corridor of Lyman County in our forecast area and moving east to northeast into the evening hours. SPC`s Day 1 severe weather outlook nudged the Marginal Risk(1 out of 5) northward to include the southeastern tip of Lyman County This activity looks to persist in our south and east until mid-late evening before shifting out of our area. We`ll see a break from the precip chances overnight into Sunday morning before another disturbance shifts into the region by Sunday night. Could see some patchy fog in parts of the Missouri Valley including the Pierre area thanks to an increase in boundary layer moisture and an easterly wind fetch just off the sfc and light sfc winds. Another s/w trough will work east-southeastward from the Northern High Plains by Sunday afternoon. A sfc trough or cold front is progged to shift east across the Dakotas Sunday afternoon into Sunday night. This will lead to another round of scattered thunderstorms that look to impact the Missouri Valley as soon as early-mid afternoon Sunday. At this point, instability and shear aren`t quite as favorable as today`s set up, so we aren`t expected any organized severe weather, but it will be something to keep an eye on going forward. Temperatures will return closer to seasonal normals for late May today and tomorrow with highs in the upper 60s to mid 70s. Overnight lows tonight won`t be quite as cool with readings in the mid 40s to around 50 degrees. && .LONG TERM /SUNDAY EVENING THROUGH FRIDAY/... Issued at 417 AM CDT Sat May 25 2024 Not a ton of change in the mass fields from 24 hours ago in the out periods. Still dealing with the formation and translation eastward over the region of an upper level ridge (ensemble clusters analysis) mid-week. Until then, the pattern takes on a northwest flow look and feel, scouring out any lingering shortwave energy Sunday night and Monday (25-55% chances of rain), and quite possibly into Tuesday. After a dry period as the ridge moves across the region, return flow southerly low level winds and west-southwest winds aloft set up by Wednesday evening, and usher a return to low PoPs in the forecast from Wednesday night through the end of the period (a general 20-40% chance which is almost climo for this time of year; ie...no strong signal to hang a hat on right now). Typically, the better set up for convection shows up after mid-upper level heights have a chance to fall some and warm mid-level temperatures cool a few degrees. Perhaps the best chance for rain will come by the end of peak heating on Thursday, with the door remaining open for additional WAA-forced rain chances within a mid- level baroclinic zone that sets up across the region into Friday. There are still some wrinkles that need ironed out in the models for timing/strength/track of the main upper circulation within the longwave trof out west that develops in the wake of the upper level ridge working across the region mid-week. The faster, more progressive envelope of solutions have the region going dry by Saturday as a weaker, more transient upper circulation sweeps eastward through the region. The slower, stronger camp of solutions would have the upper circulation slowing down and undergoing cyclogenesis over the central/northern plains on Saturday, turning the aforementioned baroclinic zone into a deformation zone with additional precipitation chances persisting beyond the range of the 7-day forecast. It does appear as though Thursday could hold some rather strong (25 to 35+mph with higher gusts) southerly winds. It also still looks as though temperatures throughout the extended will remain anchored within ~5 to 10 degrees either side of climo normal (ie...no extremes in temperature noted in the models in the out periods). && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1233 AM CDT Sat May 25 2024 Terminals KABR,KATY,KPIR,KMBG VFR conditions are expected through the TAF period. LLWS (low-level wind shear) is forecast at KATY Saturday morning. Also, guidance suggests a few scattered -SHRA/-TSRA are possible near and south of KPIR around 22Z or after. For now, have a VCSH mention as confidence on areal coverage and placement of any precipitation is low. As for KPIR`s wind forecast, some uncertainty here too as a surface frontal boundary looks to be splayed out over the region during the afternoon hours, with NE winds north of the front, and SE winds south of the front. This front may hang out in the KPIR region during the afternoon, with potential for winds to waffle from SE to NE at times. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ SHORT TERM...Vipond LONG TERM...Dorn AVIATION...Vipond