Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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059 FXUS63 KFGF 171529 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 1029 AM CDT Fri May 17 2024 .KEY MESSAGES... - Isolated to scattered severe thunderstorms are possible this afternoon and evening. Damaging wind gusts to 70 mph and hail up to 1 inch in diameter are the main concern. - There is a 70 percent chance for wind gusts greater than 40 mph Saturday afternoon and early evening. && .UPDATE... Issued at 1029 AM CDT Fri May 17 2024 Still trying to time out the potential for severe storms today. The cap may break around 2100z allowing for convection to develop. Looking at the available CAPE and low level shear today`s main threat still looks to be hail and wind. With our scattered to clear skies this morning we shouldn`t have an issue with daytime heating. Currently thinking the convection may start around 23-00z but some of the CAMS had convection starting as early as 20z but that conditional upon our CAP to erode become weaker to allow storm development. UPDATE Issued at 707 AM CDT Fri May 17 2024 There are still some lingering showers early this morning as a warm from list northeast, but there is already a clearing/drying trend behind this. Other than lingering shower mention during the morning hours, precip timing is still on track. && .DISCUSSION... Issued at 402 AM CDT Fri May 17 2024 Zonal flow is favored through the next 7 days, with a trend towards broader troughing in Canada eventually resulting in "cooler" but still seasonably mild temperatures. The general zonal/progressive flow will allow for a series of mid level trough passages and periodic shower/thunderstorm chances through next week. The focus of the period is in the shorter range periods where predictability in impacts is higher. Severe thunderstorm potential today: Strong WAA develops as BL flow increases from the south, while westerly flow brings deeper dry air aloft. Deep mixed layers are advertised and initially forcing is less organized before the main mid level trough moves east. Surface convergence during peak heating near several subtle surface troughs could support discrete initiation (as CINh decreases) and within that environment a brief/elevated supercell with severe hail main be possible. These high bases, dry mid level air, and marginal shear do lower confidence initially in earlier impacts. Main period of focus will be upstream activity expected to develop near the main wave in eastern Montana/western ND which CAMs show evolving into a cluster or linear MCS. Considering the high inverted-V profiles, very steep low level lapse rates, dry mid levels (resulting in likely dry air entrainment) and initial 0-3 and effective shear values 30-35kt this cluster or linear MCS would support severe wind as a primary threat. Elevated instability may remain high enough as low levels decouple while a stronger LLJ increases effective and 0-3kt shear (35-43kt) during the late evening severe wind potential main continue through midnight as this activity transitions east (threat ending as mid level lapse rates decrease and elevated instability drops off). Saturday winds: The main cold front associated with the negatively tilted mid level trough will have exited the region by Saturday morning, but in its wake strong unidirectional westerly flow develops with mixed layer winds 35 to 40kt shown by model soundings during the daytime/early evening period Saturday. NBM probs highlight the potential for advisory wind gusts (45mph) with the probs for gusts over 40 mph 30-70% along and west of the Red River Valley (higher probs west of the valley). && .AVIATION /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 707 AM CDT Fri May 17 2024 VFR conditions should prevail, with some potential for brief MVFR conditions if a stronger shower or thunderstorm moves over a TAF site late afternoon/evening (better chances in eastern ND but coverage still uncertain for severe in vicinity of TAFs). There are a few light showers this morning, but more widespread shower and thunderstorm activity by the evening period. Winds will tend to shift from the southeast to south and eventually to the west as a cold front arrives later tonight. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...MM DISCUSSION...DJR AVIATION...DJR