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Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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527 FXUS63 KABR 072327 AAA AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 627 PM CDT Sun Jul 7 2024 .KEY MESSAGES... - There is a 30-40% chance of precipitation in the form of showers and thunderstorms through the evening, diminishing by sunset. Severe weather is not expected at this time, however, brief funnel clouds remain possible through the evening. Some stronger storms could produce small hail, mainly pea to nickel sized. - Isolated shower and thunderstorm chances (15-25%) remain in the forecast on both Monday and Tuesday, mainly during the afternoon and evening hours across northeastern SD into west central MN. - Heat and humidity will be on the increase through the week into the weekend. By Friday/Saturday temperatures will be about 5 to 10 degrees above average, with highs in the upper 80s to mid 90s and lows in the upper 60s to near 70 with dewpoints well into the 60s to near 70 degrees. && .UPDATE... Issued at 623 PM CDT Sun Jul 7 2024 See updated aviation discussion below. && .SHORT TERM /THIS EVENING THROUGH MONDAY NIGHT/... Issued at 208 PM CDT Sun Jul 7 2024 The longwave trough remains over the central and northern CONUS with the axis from northern MN and southwestward through the Southern Plains through 00Z. As of 1PM, satellite imagery indicates a vort max/mid low spinning over northern MN along with a vort max/shortwave over north central SD. This shortwave and energy behind the low/vort max in MN will aid in lift for convection. Still pretty moist out as PWAT values are around an inch which is around average for this time of year, according to NAEFS. Surface dewpoints are currently in the upper 50s to the lower 60s this afternoon with 700mb temps around 2-3 degrees. Daytime heating continues to steepen low level lapse rates with MU/MLCape values reaching to around 1000- 1300 j/kg or so with values up to around 1500 j/kg over far northeastern to eastern SD into west central MN per HREF. Rap values seem to be running a little higher. Several soundings indicate more skinny CAPE profiles with mid level lapse rates marginal around 6- 6.5C/km-1 and minimal shear. It is interesting to note that NST parameter at 18Z ranges from 0.5 across the CWA to values of 2-3 over northeastern SD into southeastern ND. So cold air funnels/landspouts could be possible as we have surface vorticity/0- 3km ML Cape values of 100-170j/kg (highest over northeastern SD) on top of each other, per SPC meso page. HREF/CAMS indicates convection chances over much of the CWA through this evening with pops ranging from 30-40%. Storm mode will be more pulse "hit and miss" summer type thunderstorms, with storm motion cyclonically around vort max and behind the low which is why the grids are more widespread in coverage. Severe threat remains low as 2-5UH>75m2s2 does not show anything exciting compared to yesterday. With the cooler air aloft and thermodynamics mentioned above, some of these storms could produce small hail (if strong enough) with the main threat being lightning. Pops will diminish with sunset. For Monday, the longwave trough pushes just a bit east with a high pressure system centered over the Rockies in the morning and over the central and northern Plains by the evening. Once again daytime heating and Cape up to 1000 J/kg (which is mainly limited over the far eastern CWA, closer to northern axis of trough) along with dp`s in the lower 60s, could bring some isolated storms in the afternoon and evening. With this limited instability and skinny cape profiles, pops chances are a bit lower ranging around 15% (manually added). Lows tonight will be in the mid to upper 50s/60 and highs for Monday ranging from the upper 70s to the mid 80s. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 208 PM CDT Sun Jul 7 2024 With minimal differences among ensemble clusters, confidence in the large scale pattern for the long term is relatively high and this carries over to the other mass fields such as the temperature and wind forecast. There is greater uncertainty in the precipitation potential however. The northern plains will initially be in an upper level northwest flow pattern as a SW CONUS high builds. The surface pressure pattern remains weak but models suggest low level moisture, with 60+ dewpoints (especially across our eastern CWA) will be fairly persistent. This does introduce some uncertainty into the blended model depiction of a mostly dry forecast through mid week. Instead, we could be on the repeat cycle of afternoon pulse convection. Either way, coverage and POPs would be quite low. Continued the previous trend of including at least a low POP on Tuesday, however this may need to be considered Wednesday and Thursday as well. It will be late in the week before the ridge of high pressure traverses eastward and above normal air spreads across the plains states. Definitely not a high amplitude ridge however, and models suggest a parade of ridge riders traversing the pattern. LREF probabilities of 700 mb temps exceeding 14C are highest on Saturday and Sunday, generally ranging from 70-80% from our southwest CWA to 30-50% across our northeast CWA. This suggests a fairly healthy CAP for the weekend. Likewise, probabilities of surface temps exceeding 90 degrees is greatest for our western CWA, however current ensemble progs suggest a 50% chance or less of realizing heat advisory temps. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 623 PM CDT Sun Jul 7 2024 Terminals KABR,KATY,KPIR,KMBG Scattered showers and thunderstorms will continue across the area this evening. Once the sun goes down, the precipitation will come to an end with the loss of daytime heating. Periods of MVFR vsbys are possible with the thunderstorms. Otherwise, VFR conditions will prevail across the area tonight and through the day Monday. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ SHORT TERM...MMM LONG TERM...Serr AVIATION...Parkin