Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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462 FXUS63 KFGF 190851 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 351 AM CDT Sun May 19 2024 .KEY MESSAGES... - Isolated severe thunderstorms are possible this evening in far southeast North Dakota. Hail to 1 inch 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. && .DISCUSSION... Issued at 351 AM CDT Sun May 19 2024 Southwest flow is beginning to build into the central/Northern Plains in response to building mid/upper level troughing over the Pacific Northwest. This trough is expected to continue to amplify and deepen southwest flow over the plains and a series of waves ejecting through this flow (along with increase moisture advection) will keep periodic rain/thunderstorm chances in our forecast area, with confidence reasonably high through mid week despite some variations with timing/evolution of some of these waves. By late next week this trough breaks down and a more zonal/progressive flow featuring lowered heights aloft as the northern storm track shifts south. There is lower confidence in evolution of any waves and low confidence in any potential impacts). Temperature trends will be seasonably mild in the mid 60s to lower 70s the next several days, but below average temperatures (50s/lower 60s) become favored during the later periods. Severe risk today: Several impulses bring scattered showers/isolated thunderstorms during the day, with a more organized mid level shortwave passing south of our region late this afternoon and evening. THe norther extent of this will feature a near by baroclinic zone where southerly flow will help increase BL Tds. Mid level lapse rates are shown to steepen enough to support an axis of elevated instability near our forecast area by late afternoon/evening. Consensus is favoring better instability farther west and southwest based on the surface pattern and with increasing low/mid clouds resolved by all current guidance there isn`t currently a risk for surface based parcels (elevated parcels will support hail/wind as primary threats if there is any threat). As current guidance shows lowered instability towards our area (around 1000 J/KG max MUCAPE) confidence is lowered in any strong/severe storms. There is still high shear (40-60kt effective shear) and some CAMs try to hold some organized/embedded cells together as they approach far southeast ND during the 6pm-10pm period. 0-3km shear is in the 30-35 kt range, so while profiles are not that supportive of a wind risk (DCAPE less than 800 J/KG) there is still a low threat for downburst winds if a cell takes on brief/orthogonal linear structures (as some CAMs show). Midweek rainfall (Tuesday-Wednesday): There is increased consensus on a stronger negatively tilted mid level trough passage through SW flow over our eastern forecast area, with the potential for organized/deformation and widespread moderate to localized heavy rainfall. Excessive rainfall isn`t expected as any higher totals (1-3") would fall over a longer duration. Impacts to possibly delay any planting operations are possible though across northwest MN/west central MN as 24hr probs for at least 0.5" is near 80% and 1"+ is 50%. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1151 PM CDT Sat May 18 2024 VFR into Sunday, but potential for MVFR or IFR conditions in vsbys in showers or t-storms late Sunday aftn or Sunday evening. Otherwise skies clear overnight with increasing mid clouds Sun AM and thickening and gradually lowering ceilings into the aftn. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ DISCUSSION...DJR AVIATION...Riddle