Area Forecast Discussion
Issued by NWS Aberdeen, SD

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000 FXUS63 KABR 122323 AAA AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 623 PM CDT Wed Aug 12 2020 .UPDATE... Issued at 622 PM CDT Wed Aug 12 2020 Forecast is on track this evening. No major changes are planned. && .SHORT TERM...(This Evening through Thursday Night) Issued at 352 PM CDT Wed Aug 12 2020 Forecast challenges include temperatures and precipitation chances Thursday and Thursday night. Currently, it`s partly to mostly sunny over the CWA, with temperatures in the 70s and 80s east of the Missouri River valley. Throughout and west of the Missouri River valley, temperatures are warming through the 80s and 90s. There is also a lee-of-the-Black Hills surface trof hanging out over the region, extending from the Black Hills east toward Huron and southeast toward Sioux City, Iowa. There appears to be a small window of time this evening, when one or two thunderstorms could develop on the nose of a low level jet forecast to form over the CWA this evening and spread north/east through the region overnight. Low/mid-level thermal advection and low level moisture advection is continuing across central/south central SoDak this evening where the nose of the developing low level jet is forecast to be. Although, by late this evening, the atmosphere, aloft, may be too warm to support convective development. Even if a storm could get going, deep-layer shear is progged at less than 20knots. So, other than a pulse-threat for perhaps some hail, severe weather potential tonight is rather limited. Otherwise, the forecast appears to be a dry one until Thursday afternoon/night when a boundary begins to move into the CWA. Plenty of instability around and better deep-layer shear along/behind the boundary. Some GSM output and hi-res CAM output supports a few thunderstorms trying to go up right on the boundary Thursday afternoon/evening while the mid-level thermal capping inversion is slowly eroded by falling heights aloft as the large western NOAM upper trof approaches the region. If convection develops on this boundary, mainly the eastern half/third of the CWA would potentially be impacted for a few hours. A second/separate round of potential convection could be approaching/working into the western CWA late in the Thursday night period. A stronger shortwave/upper jet streak may be supporting the development or furtherance of convection out over the northern high plains along or on the northern fringe of a surface low progged to be edging into the western Dakotas by early Friday morning. The nose of a low level jet is progged to be over the CWA late Thursday night as well. Operational model thermal progs and ensembles 850hpa standardized anomalies support temperature tonight through Thursday night remaining above normal. .LONG TERM...(Friday through Wednesday) Issued at 352 PM CDT Wed Aug 12 2020 The extended period begins with an upper level shortwave trough sliding across the area Friday into Friday night. A surface front will also be moving through, with fairly warm and moist air being pulled northward ahead of it. This combination of factors looks to allow for the front to become the focus for thunderstorm development Friday afternoon and evening, mainly across the eastern part of the CWA. The one hindering factor may be a bit of a cap, with H7 temps of +11 to +13 C across the far east during the afternoon hours. SPC has highlighted the eastern CWA with a marginal to slight risk for now. Conditions then look fairly quiet for the Saturday through Tuesday time frame as the upper level flow remains out of the northwest, but with little in the way of shortwave energy moving through and with surface high pressure dominating. The high exits to the east Tuesday night, with some models hinting at the potential for a few showers or storms on Wednesday. High temperatures will be in the 80s everywhere Friday, Saturday and Sunday, then will range from the mid to upper 70s east, to the mid to upper 80s west Monday, Tuesday and Wednesday. Overnight lows will be in the mid 50s to lower 60s through the period. && .AVIATION...(For the 00Z TAFS through 00Z Thursday Evening) Issued at 622 PM CDT Wed Aug 12 2020 Terminals KABR,KATY,KPIR,KMBG VFR conditions are expected through the period. Winds will become breezy out of the south on Thursday. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Wise SHORT TERM...Dorn LONG TERM...Parkin AVIATION...Wise

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