Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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310 FXUS63 KABR 171148 AAA AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 648 AM CDT Mon Jun 17 2024 .KEY MESSAGES... - Strong to severe thunderstorms are possible tonight into early Tuesday morning over the entire forecast area. Large hail, quarter to golfball size, will be the main threat along with wind gusts between 60-70mph. - The excessive rainfall/flooding risk has been downgraded to a slight risk (15%) over the eastern half of SD into MN through Tuesday morning. Probability of rainfall over an inch is 40-60%, from Sisseton to Watertown and eastward for locations in west central MN. West of these locations range from 20-30%. - After a break in the active weather Tuesday night and Wednesday, look for increasing chances for precipitation again Thursday night through Saturday. && .UPDATE... Issued at 637 AM CDT Mon Jun 17 2024 Aviation discussion updated below for the 12Z TAFs. && .SHORT TERM /TODAY THROUGH TUESDAY AFTERNOON/... Issued at 347 AM CDT Mon Jun 17 2024 As of 330AM, radar indicates a strong line of showers and thunderstorms to our south, extending from NE through southeastern SD into MN. The CAMs struggled this morning on convection as they all showed the possibility of these storms being more north and hitting our southern CWA when in fact this occurred much further south. They look to still struggle on the overall outcome today, so I left the pops closer to the NBM. The overall trend is for this entire "blob of stratiform rain" to continue pushing northeast today as the nearly stationary continues to stall out over NE through northern IA into WI. There looks to be a break in the precip for portions of central SD this afternoon. Our attention then turns to late tonight into early Tuesday for the possibility of severe weather once again. HREF indicates winds increasing out of the southwest overnight, per a speed max on PVA side of trough, that still settles over the western CONUS today and shifts east tonight. A LLJ develops tonight with speeds increasing to 40-60kts, highest over the Coteau into southeastern SD, ahead of the 700-850mb low (southwest flow). The front lifts slightly north this evening with the broad low over southern SD/northwestern NE at 06Z. Higher MUCAPE surges northward into the CWA this evening with values maxing out around 2500 J/KG over our central and southern portions of the CWA at 00Z. Higher amounts of 3000 J/kg looks to stay south of the CWA. Between 00-06Z Tuesday, 1500-2500 J/kg surges more northward over much of the CWA. NAM ML cape of 1000-2000 J/kg looks to stay over our extreme southeastern CWA into FSD WFO. RAP mid level lapse rates look impressive ranging from 7 to areas of 9C over southeastern SD. Bulk shear is between 50-60kt then decreasing over the eastern CWA overnight. HREF probability of max 2-5km UH>75m2s2 is 10-30% , highest over north central SD overnight and even the chance of left moving storms clipping the CWA as prob of min 2-5km>UH is up to 40% over the eastern CWA. Dewpoints will range in the upper 50s to the lower 60s this afternoon through Tuesday morning. CAMs/HREF show the convection moving in, on the PVA side of the shortwave, from WY/western SD as well as from the south and southwest and southeast. So expect thunderstorms to be clustered and pretty much splattered across the CWA late tonight into Tuesday morning. With the dynamic forcing, the SPC has a slight risk (2/5) for the entire CWA with the main threats being large hail, up to golfball size, and 60-70mph winds. THe tornado threat looks low as prob of STP>1 is 0-10% over our extreme southeastern counties with the 50-80% chance staying over FSD WFO (where there is better ML cape and low level SRH) Precipitable Water satellite imagery continues to show warm/moist air from the surface-700mb surging northward from the Gulf of Mexico, creating quite the moist environment. However, there is quite the spread in guidance (and with this morning`s system being further south) there is low confidence on higher rainfall. With such the scattered nature of the storms tonight, it is hard to tell where exactly areas could see heavy rain/training. NBM prob of 24 QPF>1" ending Tuesday 12Z ranges from 40-60% over the far eastern CWA. WPC has downgraded the excessive rainfall/flooding risk to a slight risk (15%) over the eastern half of SD into MN through Tuesday morning. By 12Z Tuesday, the center of the low is forecasted to be over northeastern SD as the cold front will be positioned south of the low as the low and front lift northeastward through the day. Models indicate ongoing precip over the northern and northeastern CWA ,closer to the center of the low, with the precip shifting over the eastern CWA behind the front. More showers and thunderstorms will move in over north central SD as well Tuesday afternoon with the next shortwave and low. && .LONG TERM /TUESDAY EVENING THROUGH SUNDAY/... Issued at 347 AM CDT Mon Jun 17 2024 Surface frontal boundary will be exiting the CWA into MN to start off the extended period at 00Z Wednesday. PoPs drop off through the night and are reduced to just 20-30% chances between 06Z and 12Z Wednesday, and even this may be overdone. Surface high pressure, and drier/more stable air will be working into the region and would not be surprised if PoPs get reduced even more during the next forecast cycle. Wednesday looks to be mostly dry with the surface high still in place. A return to active weather looks to return Thursday night through Saturday. Low-level moisture will be on the increase, especially by Friday with NBM dewpoints in the 60s. An area of low pressure looks to track northeast across the Northern Plains Friday night into Saturday, with still some differences remaining on exact track and timing. That said, the setup looks to be in place for fairly good coverage and several rounds of showers and thunderstorms at the end of the week into Saturday. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 637 AM CDT Mon Jun 17 2024 Terminals KABR,KATY,KPIR,KMBG VFR conditions are holding in place at the start of the TAF period, with areas of -RA/-SHRA across the region. As the day progresses, MVFR/IFR CIGs are forecast to overspread the region, with continued areas of SHRA/TSRA. Areas of precipitation should continue into tonight as well. LLWS (low-level wind shear) will also be a concern across the region and have inserted mention of this when and where appropriate. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...TMT SHORT TERM...MMM LONG TERM...TMT AVIATION...TMT