083 FXUS63 KFGF 021451 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 951 AM CDT Fri Aug 2 2024 .KEY MESSAGES... - There is a level 1 out of 5 risk for severe thunderstorms Saturday afternoon and early evening across southeast North Dakota and west central Minnesota. && .UPDATE... Issued at 951 AM CDT Fri Aug 2 2024 All signs of shallow fog have dissipated and clear skies remain across the region under high pressure. Temperatures still seem on track to top out in the mid to upper 80s. UPDATE Issued at 629 AM CDT Fri Aug 2 2024 Automated surface observations and area webcams are showing some patchy shallow ground fog, particularly along the eastern edge of the Red River Valley in west-central Minnesota, into the hills of lakes country. This will diminish by 9 AM. Otherwise, no change to the forecast or previous thoughts mentioned in the Discussion. && .DISCUSSION... Issued at 423 AM CDT Fri Aug 2 2024 ...Synopsis... Large anticyclone currently over the Southern Plains into the Southwest will remain anchored itself over the Great Basin region over the next several days. This will continue broad upper ridging extending into the Northern Plains today allowing for another warm, summer-like day today with temperatures well into the 80s, and a surface high pressure to keep conditions dry and mostly sunny. Ensembles develop an upper low near the Hudson Bay this weekend into next week, helping heights aloft decrease over our region starting around Saturday. The deepening upper low will also help increase winds aloft, with one or two shallow midlevel shortwave trough moving through ND into northern MN within northwest flow aloft. This will also bring a cold front through our area Saturday, with a notable change in air mass behind the front. This cold front and parent shortwave/s will serve as the catalyst for eventual thunderstorm development Saturday, including the potential for severe storms Saturday afternoon into evening in the Northern Plains and Upper Midwest. By early next week, temperatures will trend toward below average, with daytime temperatures remaining in the 70s and nighttime temperatures in the 50s, perhaps touching into 40s for some locations by midweek. Notably less humidity compared to recent weeks also accompanies these temperatures. Ensembles continue to favor the passage of a progressive but notable shortwave within the crest of the upper ridge over the northern tier of the CONUS, aided by upper divergence within the entrance region of an upper jet extending behind the aforementioned Hudson Bay upper low. This wave has potential to bring some banded-type showers and embedded thunderstorms into the Dakotas and Minnesota. Clusters in ensemble guidance favor a precipitation footprint draped over the southern portions of our area. While most likely rainfall amounts as offered by 10th-90th percentile QPF keeps amounts in the 0.5-1.5 inch range over 24 hours, there are indications mesoscale forcing such as fgen and influence of nearby instability may help focus precipitation production that may bring amounts locally over 2 inches. At this time, the risk for flooding is very low in the absence of signal for more robust convection, but this potential may increase some should instability favorable interact with fgen circulations. ...Severe Potential Saturday... Timing of the cold front will be a major key to whether or not our area sees potential for severe storms Saturday. Most guidance, particularly CAMs, depict a cold front that sweeps through our area before peak heating. Should this occur, the potential for severe storms decreases in our area, with initiation of storms more into South Dakota and central/southern Minnesota. There is still a few solutions that tracks the cold front slow enough to allow for potential initiation of robust thunderstorms during peak heating in southeast North Dakota into west-central Minnesota. This scenario would bring potential for isolated severe storms in these locations during the mid-late afternoon into early evening hours Saturday. Regardless of timing, strong instability will likely be in place ahead of the cold front, aided by some pooling of boundary layer moisture in addition to daytime heating pushing temperatures into at least the mid 80s. Increasing winds aloft will also provide the shear need to organize convection, progged to be around 35 kts of effective shear. The vast majority of guidance depicts the orientation of the cold front to shear to favor initially discrete supercells. However, the speed of the cold front (which remains somewhat in question) may also influence storm mode, with faster front favoring less discrete and perhaps more cluster-type. Despite storm mode, large to potentially very hail and gusty winds will remain the forefront of hazards given the magnitude of overall instability coupled with largely unidirectional shear, most of which is in the mid- upper portions of cloud bearing layer in addition to relatively higher LFCs and lowered boundary layer RH. Discrete supercells increase the potential for large to very large hail, while clusters favor large hail and relatively wider footprint of gusty winds to 70 mph. While not likely, can't rule out the potential for a tornado or two with any storms holding well maintained mesocyclones, especially if storms can latch themselves on ambient vorticity rich boundaries like the cold front itself. && .AVIATION /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 629 AM CDT Fri Aug 2 2024 Confidence is high in VFR conditions throughout the TAF period, save the low chance of LLWS at KDVL between 05Z-12Z tonight into Saturday morning. Chose not to include this in the KDVL TAF due to low chance and low magnitude of potential LLWS at around 40kt at 2 kft. Otherwise, high pressure over the area will keep skies mostly clear and winds light, under 10kt. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...CJ/JR DISCUSSION...CJ AVIATION...CJ