Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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361 FXUS63 KFGF 070839 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 339 AM CDT Tue May 7 2024 .KEY MESSAGES... - Isolated thunderstorms mainly this afternoon over northeast North Dakota and northwestern Minnesota. && .DISCUSSION... Issued at 317 AM CDT Tue May 7 2024 500 mb low at 08z as over northwest South Dakota. Moisture feed around this system is from northern Arkansas to central Minnesota then back west-northwest across parts of North Dakota and into southern Saskatchewan and Alberta. What has been noticed is that moisture from the south as been weakening the past 6 hours, perhaps due to convfection from Iowa to northern Arkansas. The trends in radar with showers moving NNW from central MN is for diminishing returns as they move toward the RRV. Thunderstorm chances have dropped greatly since 06z and likely to remain thru 16z based off of SPC HREF Calibrated Thunder fcst and HREF lightning prog via DESI. So through 16z shower activity looks to be on the light side moving NNW thru MN into eastern ND. This afternoon will see upper low move a tad east to west of Bismarck with sfc low drifting a bit NNE into southwest ND near Hettinger. A trough rotating around this upper low/sfc low will move into NE SD midday and then into SE ND mid to late aftn with a subtle wind shift from southeast to south. Also drier airmass moves in. Clearing chances appear limited and in this area of SE ND/far WC MN (Valley city-Fargo-Fergus Falls-Wadena) chances for afternoon showers or t-storms is quite low. Farther north, north of the boundary 0-6 km shear is quite strong near 40 kts due to stronger 850 mb winds but by 20z 850 mb winds are in the 35-40 kt range vs 50-55 kt currently. So some shear exists but instability looks very weak...barely 100-250 j/kg and no sfc heating is anticipated with aftn temps in the low 60s. With upper low sufficiently far enough west and colder 500 mb temps wrapping around the system and more into Nebraska thinking is that some t-storms will form in a narrow axis from near DVL-GFK-BJI area mid aftn and move north, but lack of instability, lack of cold air aloft, will prevent much development. Bufkit soundings for GFK show a nearly vertical temperature column from sfc to 500 mb with very limited CAPE (50-100 j/kg). This is from both NAM and GFS models. So net result is thinking any chance of a stronger storm is very low (5 pct). Chance for showers Wednesday as upper system drops south but drier air also moves back in from the north. Instability is focused in southern MN, so covearge of showers look scattered. Clearing Wed night into Thursday. GFS/ECMWF ensembles show 500 mb ridging into Alberta and Saskatchewan Thu-Fri period and enough to height falls over the Great Lakes for an upper level wave to drop south-southeast into Minnesota Friday. This will give chances for showers, and with some colder air aloft with wave several hundred CAPE and a chance for a few t-storms mainly in nothern or central MN. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 1142 PM CDT Mon May 6 2024 Kept with the same ideas from the 00z set of TAFs. Still trying not to chase the showers/storms with too many TEMPO groups. Showery activity tends to have on and off periods, but think for at least most of the first 6 hours of the TAF period there will be more "on" periods. Therefore, will just mention -SHRA in the predominant group and leave the TEMPO`s off. There has been some lightning, but overall think that will stay isolated enough that will leave that mention out too. Put the LLWS in the TAFs with the 00z issuance, and will keep that through most of the night as well. Wind speeds have been very challenging, as some stations are still seeing breezy winds, while others have lost their gusts. Think those that have lost gusts will get them back again, and that is really not worth chasing too much either. Beyond that, have gone with VFR conditions arriving again by mid to late Tuesday morning, but don`t have much confidence that it will scatter out. If it does scatter out, some instability could form again south of the highway 2 corridor, leading to isolated shower/storm development again. The breezy conditions will return by mid Tuesday morning, before they decrease again by late afternoon and early evening (although much less than today). && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ DISCUSSION...Riddle AVIATION...Godon