704 FXUS63 KFGF 170900 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 400 AM CDT Thu Apr 17 2025 .KEY MESSAGES... - There is a 40% chance for weak thunderstorms this afternoon, mainly within Minnesota. && .DISCUSSION... Issued at 319 AM CDT Thu Apr 17 2025 ...Synopsis... Broad and expansive upper troughing is viewable on water vapor satellite imagery extending from central Canada southwest into the northern High Plains and Great Basin. Additionally, there is an upper, cut off low off of the southern California coast. This latter feature will help entice a more notable, embedded shortwave trough over the Northern Rockies southward today through Friday, helping keep overall upper troughing in a positively tilted orientation. Energy moving through the lee of the positively tilted trough is forecast to move over the Northern Plains and Upper Midwest, helping provide forcing for ascent to our area. At the surface, a front is moving through the eastern Dakotas, and will eventually push into Minnesota by this afternoon. This will be the catalyst for thunderstorm chances this afternoon (more details found below). Ensemble guidance is strongly suggesting the presence of frontogenesis to move over our area juxtaposed with subtle impulses as well as the surface trough/front. This indicates the likelihood of rain bands to move southwest to northeast over our area, with locations like central and northern Red River Valley into northwest Minnesota holding relatively best chance of seeing banded rainfall. Most likely amounts under this will result in 0.25 - 0.75 inches of rainfall. Forcing for ascent wanes tonight, ending widespread rain chances. Behind the surface front this afternoon, daytime mixing will help tap into gusty north winds, particularly in the southern Red River Valley into west-central Minnesota where gusts to 35 mph are forecast. As broad upper troughing migrates east, cooler air will continue to be reinforced feeding into our area. This will make for a blustery Friday with temperatures not exceeding 50 and continued breezy northerly winds, contributing to wind chills near and below freezing. Reinforced cooler air mass over the area and surface high pressure building into the region will also allow for cold Saturday morning with lows in the 20s, potentially into the teens within North Dakota. Temperatures begin to rebound into next week as flow aloft turns more zonal to southwesterly, with potential for progressive wave pattern to set up for next week. Ensembles highlight Monday and Tuesday, and then again late next week with next chance for appreciable rain chances, including potential to see thunderstorms, although this is low in confidence. ...Thunderstorm chances this afternoon... Near the surface front heading into Minnesota by early afternoon, increasing temperatures and moisture overrunning the front underneath marginally steep lapse rates will contribute to instability aloft. This combined with increasing forcing for ascent into the area, there introduces around a 40% chance to see thunderstorms. Based on current and forecast location of the front, locations closer to central Minnesota hold relatively best chance to see thunderstorms. Some convective allowing models indicate potential to see upwards of 1000 J/kg of instability atop a stable and relatively cool lower levels behind/west of the front. Additionally, increased flow aloft near the upper portions of the updraft region will help promote venting/tilting of updrafts. These factors (and potentially saturated updraft environment) will introduce a low, but present chance for stronger thunderstorms to produce hail. While hail is more likely to be small/sub-severe, there could be large accumulations of it and/or instances where hail could reach severe criteria - contingent on updrafts utilizing all available instability and shear aloft. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1245 AM CDT Thu Apr 17 2025 Aviation impacts are forecast within TAFs through 06Z Friday. These impacts stem from very strong LLWS and lowered CIGs. A very strong low level jet is being measured by KMVX radar, sampling 60kt winds between 1.5 to 2 kft out of the south- southeast. This will gradually shift east into Minnesota tonight, ending at KBJI last at around 10-12Z. A front moves through tonight into Thursday, bringing gusty winds out of the north behind/west of the front around 20-30kt, highest within southeast ND into west-central MN. As the front moves through, areas of virga will be present, along with eventually rain making it to the surface this afternoon. Cannot rule out an isolated lightning bolt with today`s activity before 12Z. The front will also bring lowering ceilings into the MVFR category, mainly after 18Z within the Red River Valley and Minnesota. Confidence is low in start time of lowered ceilings, however, mainly due to uncertainty regarding low level moisture. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ DISCUSSION...CJ AVIATION...CJ