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Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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879 FXUS63 KFGF 162039 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 339 PM CDT Fri Aug 16 2024 .KEY MESSAGES... - Wildfire smoke may impact sensitive groups within northwest Minnesota and eastern North Dakota this afternoon into the weekend. && .DISCUSSION... Issued at 252 PM CDT Fri Aug 16 2024 ...Synopsis... Current satellite reveals broad upper troughing within the Upper Midwest and western Great Lakes with embedded lobes of vorticity, one of which resides over our area on the backside of the upper trough. Lingering low level moisture and associated broad scale lift within the trough is continuing areas of light rain/drizzle in the southern Valley into Minnesota. Guidance generally migrates the upper trough to the east as upper ridging currently in the Canadian Prairie Provinces into the Intermountain West. Low stratus is scouring out in some locations allowing heating to generate isolated showers, of which may generate weak lightning activity (20% chance of occurring). Surface high pressure behind the exiting upper trough/attendant surface low is contributing to gusty northerly winds to 30 mph within the Red River Valley into eastern ND. This northerly flow will also help pull smoke from Manitoba into our area. More on this potential impact below. Lingering northerly wind and scattered clouds tonight should help mitigate widespread fog development, although local areas that can clear out and calm may see morning fog. Another opportunity for isolated to scattered showers and perhaps weak thunderstorms comes Saturday afternoon. These chances (30%) currently reside within northwest Minnesota as most high resolution guidance indicates enough surface convergence between an incoming wedge of high pressure and the exiting surface low pressure gradient to generate enough lift for convection after convective temperatures in the mid 70s are reached. Ensemble guidance favors upper ridging to build into the Northern Plains and Upper Midwest from the west, helping re- introduce summer-like temperatures, with medium-high chances of seeing temperatures in the 80-90 degree range next week. This ridging will also allow increased moisture content and potential for more unstable air mass to develop into our area. This may help set the stage for additional strong to perhaps severe convection, although confidence in strength of storms is quite low given uncertainties into the degree of unstable air mass as well as details revolving around potential forcing and moisture. One potential forcing mechanism for eventual thunderstorms comes from a potential shortwave trough rounding the crest of the upper ridge through the Dakotas into Minnesota around the Tuesday. This brings our next appreciable chance for precipitation to our area, but again, confidence is low on potential for strong to severe storms during this episode. ...Potential Smoke Impacts... Visible satellite and air quality sensors reveal surface wildfire smoke from Canadian wildfires over portions of western ND and southern MB. Overall northerly flow lends credence into most available smoke guidance bringing this smoke into eastern North Dakota and the Red River Valley this afternoon and evening. Nocturnal inversion tonight will likely trap surface smoke near the surface at least through early morning hours. Confidence decreases in smoke residing in our area through the weekend as the surface high pressure builds into our region, and guidance depicts different levels of smoke concentration meandering within the anticyclonic flow (likely owing to differences in handling smoke mixing within the boundary layer during the diurnal cycle). Despite this lowered confidence into the weekend, we will maintain messaging of potential impacts from smoke this weekend, with sensitive individuals holding the risk of being impacted, especially if exposed to smoke for relatively long periods of time. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 100 PM CDT Fri Aug 16 2024 Ceiling Impacts: Lingering aviation impacts from lowered CIGs into MVFR and IFR categories will continue through at least 21Z for KFAR and KBJI. Overall, low CIGs behind an exiting low pressure system will start to scattered out as cloud layer moisture retreats with the system. There will still be scattered cumulus and shallow cumulus congestus before 01Z for areas that do lose CIGs. There is uncertainty in whether or not CIGs return across the region after 06Z tonight into Saturday morning, although guidance indicates relatively better chance (60%) for this to occur within MN, namely at KBJI. For this reason, decided to maintain MVFR/IFR CIGs at KBJI throughout the TAF period. Potential Smoke Impacts: Smoke will spread into eastern North Dakota into the Red River Valley out of Canada this afternoon into tonight, potentially impacting KDVL, KFAR, and KGFK. Confidence in vsby reductions being low enough to present impacts (ie less than 3SM) remains low, but does remain as a potential outcome after 00Z. For now, kept vsby reductions at 6SM for now with the anticipation of updating/amending as needed. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ DISCUSSION...CJ AVIATION...CJ