FXUS63 KFGF 200023 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 723 PM CDT Sun May 19 2024 .KEY MESSAGES... - Isolated severe thunderstorms are possible between 9 pm and 11 pm in a small part of southeast North Dakota, including Ransom and Sargent counties. Hail to 1.5 inches is the primary threat. - The probability for greater than 1 inch of rainfall is 50% Tuesday into Wednesday across parts of northwest and west central Minnesota. && .UPDATE... Issued at 714 PM CDT Sun May 19 2024 As expected severe storms have initiated on north edge of instability gradient into far south central ND south of Bismarck with other storms south along the Missouri River in SD. Instability parameters and forecasts via SPC meso page indicates a sharp drop off in instability surface and aloft as it gets closer to our far SW fcst area (Ransom/Sargenty ND). Not out of the question a strong/severe storm will sneak into that area but chance for severe is at this time 10 percent or less. New severe t-storm watch is to our southwest. Otherwise will see the area of thunderstorms weaken as they move into E ND and form an wide band of showers and t-storms as they move into the central and south RRV after 10 pm...more so toward midnight. && .DISCUSSION... Issued at 249 PM CDT Sun May 19 2024 Synopsis: Southwest flow aloft will allow a notable upstream upper wave to move through the Dakotas out of MT/WY this afternoon and evening. This upper wave will bring showers and thunderstorms through our area, including the chance for strong to severe storms late afternoon into early evening within southeast North Dakota. Overall, upper troughing lingers over south-central Canada through the rest of the week allowing several upper and mid level waves across the Dakotas and Minnesota. One strong, notable shortwave moves out of the Central Plains into Upper Midwest around Tuesday. The current track progged by most guidance of this wave brings center of low pressure through NE/IA/southern MN area, keeping more unstable, robust convection displaced from our area. Rather this places our area under the deformation zone- type rain shield of the wave, bringing high confidence in wetting rainfall to the region. There remains a 50% chance of widespread 1 inches of rainfall Tuesday to Wednesday, with up to 3 inches locally not out of the question should multiple and/or extended period of thunderstorms reside within the deformation zone/TROWAL. Additional waves thereafter move through the region. Although spread within ensemble guidance increases in synoptic details, lowering confidence timing, placement, and magnitude of convection and rainfall amounts. Overall this pattern would support near average temperatures. Isolated Severe Storm Potential Southeast ND: This evening's approaching upper wave is helping pull higher low level moisture this afternoon northward into lee troughing/sfc low in western and Dakotas. Lee troughing and upper support from the wave aloft will help spark convection near the Missouri River from south-central ND through central SD by mid afternoon. All guidance brings this convection east in the form of clusters toward eastern Dakotas. By the time this convection makes its way toward our area near and just after sunset, instability will be waning. This thought is reinforced by the lack of any instability over 500 J/kg in eastern ND as of 3 PM this afternoon. Some additional WAA ahead of the sfc low will help pull some weak instability to 1000 J/kg into southeast ND, but likely be elevated in height as a surface warm front is stalled near the SD/ND border. Regardless of the marginal instability, sufficiently strengthed shear in the cloud bearing layer will allow for organization of convection. Additionally, elevated instability over a stable surface layer will help push updraft depth deeper into the HGZ. Thus there will remain the potential for hail up to the size of ping pong balls (1.5 inches) in convection that moves into southeast ND from the west. The window for strong to severe thunderstorms in this area is quite small, between 8-10 PM. Additional thunderstorms will be possible elsewhere within the area this evening, however after 10 PM and away from southeast ND, the chance diminishes markedly based on the expectation of waning available instability. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 714 PM CDT Sun May 19 2024 VFR this evening and then potential IFR or low end MVFR cigs forming late tonight into Monday AM as low pressure moves thru SE ND into MN and low levels saturate. Showers and a few t-storms anticipated so put in approx timing in TAFs for all but DVL region where chance is a tad lower. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...Riddle DISCUSSION...CJ AVIATION...Riddle