Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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653 FXUS63 KFSD 101951 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 251 PM CDT Mon Jun 10 2024 .KEY MESSAGES... - Weakening storms will push into locations along and west of the Missouri River this evening. Gusty winds are possible with the weakening storms. - Severe weather remains possible on Wednesday but uncertainty remains regarding where storms develop. - Near to above average temperatures are expected for the next week. The warmest day will be Wednesday with high temperatures into the 90s. && .DISCUSSION... Issued at 250 PM CDT Mon Jun 10 2024 Quiet conditions continue this afternoon as shortwave ridging resides over the area aloft. An upper level wave on the heels of the overhead ridge is pushing into western South Dakota. A cold front tied to the upper level wave will serve as a focus for convection initiation. Sufficient CAPE and shear are in place which will allow storms to grow into a line of storms as they move eastwards. However, the western edge of the warm sector will reside across central South Dakota. The storms will outrun the warm sector this evening. Thus, the storms are expected to weaken as they approach the Missouri River. As the storms weaken, gusty winds are possible in any outflow produced from the storms. While the storms will continue to weaken into the evening and overnight hours, light showers look to persist through the overnight hours. Light rainfall amounts are expected with the showers ranging from a tenth or so along the Missouri River to a few hundredths east of the river. Lows overnight will fall to the 60s. Tuesday will be a quiet day as upper level subsidence prevails on the backside of the departing upper level wave. High pressure will swing through the Northern Plains, keeping marginally breezy northwest winds going for the day. 850 mb temperatures will reside in the mid to upper teens tomorrow afternoon. Mixing this to the surface will result in high temperatures into the 80s across the forecast area. The lighter winds and warm temperatures will make for a beautiful day for outdoor activities! Especially since humidity will be lower, down to around 30-40%. Low temperatures will fall to the upper 50s to low 60s overnight. The next chance for strong to severe storms arrives on Wednesday as a mid level wave pushes into the Northern Plains. A strong upper level jet streak will reside overhead with the core of the jet anchored over North Dakota. This will place the right exit region over the forecast area. Given how this is a straight jet streak, the four quadrant conceptual model will work in this scenario. However, the low level jet (LLJ) will remain modest beneath the right entrance region at 20-30 knots. The LLJ will further contribute to warm air advection (WAA) across the Northern Plains / Upper Midwest in tandem with the approaching mid level wave. While the right exit region typically isn`t the quadrant that see`s severe weather, sufficient lift in the low levels may be able to overcome the upper level subsidence via the jets indirect thermal circulation. With the upper level jet in the vicinity, adequate vertical shear will be in place with 0-6 km shear values up to 40-50 knots. A quick look at hodographs shows that vertical shear profiles remain mainly straight with a large magnitude of shear above 6 km. This will result in adequate updraft/downdraft separation, supportive of severe storms. At the surface, southerly flow will result in mass response due to the exit region of the jet which will pull higher moisture air northwards. Dew points will moisten up to the 60s beneath very steep mid level lapse rates on the order of 7-8 degrees C/km. This will contribute to large instability on the order of 2,000-3,000 J/kg of MLCAPE. A cold front will be passing through the afternoon hours, providing a potential trigger for storm to develop on. The main catch with this setup is the timing of the mid level wave. Medium range guidance still varies on how fast the wave pushes through the forecast area and struggles where convection develops. If the wave pushes through the area faster, then a smaller area for severe storms will be possible, mainly across southwest Minnesota into central and eastern Minnesota as the nose of the LLJ will reside in this area. If the wave is slower, then the severe threat will remain over the bulk of the CWA as convection fires on or just ahead of the cold front. Still too early to say which scenario is favored but a look at cluster analysis shows the highest probabilities for exceeding a tenth of an inch of rain is across Minnesota from the most favored cluster. Will continue to watch trends. In terms of severe hazards, large to very large hail, damaging winds, and an isolated tornado are all possible. Aside from storm chances, Wednesday will be a hot day with high temperatures into the upper 80s and 90s with breezy southerly winds. The end of the work week looks to be mostly quiet as high pressure returns to the area. High temperatures will be a bit cooler in the upper 70s to 80s with low temperatures falling to the 50s and 60s. The next chance for rain will push into the area Friday night as another upper level wave ejects into the Plains. As of now, convection that does develop just east of the Rocky Mountains looks to outrun the warm sector, keeping a low severe weather threat for the CWA. Confidence decreases going into the weekend as medium range guidance shows increasing variance in the upper level pattern. For now, have kept model blended PoPs through the weekend. In terms of high temperatures, highs will remain in the 80s with lows falling to the 60s overnight. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 1223 PM CDT Mon Jun 10 2024 VFR conditions are expected for the TAF period. Clear skies and light southeasterly winds begin the TAF period. Showers and storms will develop across western South Dakota this afternoon and push eastwards through the evening and overnight hours. Any instability that will fuel the storms will run out by the Missouri River, leaving just showers as they move into the area. Ceilings will remain at VFR levels as the showers pass through during the evening and overnight hours. A stray lightning strike and brief wind gusts cannot be ruled out but confidence is too low to include in a TAF at this time. Winds will turn northeasterly as the showers exit the area early tomorrow morning. Marginally breezy northwest winds will finish out the TAF period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...Meyers AVIATION...Meyers