Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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767 FXUS63 KFGF 171821 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 121 PM CDT Tue Sep 17 2024 .KEY MESSAGES... - There is a level 1 out of 5 risk for severe storms Wednesday afternoon and evening, including the potential for supercells. - Additional chance for showers and storms between Saturday and Monday, with potentially heavy rain. && .UPDATE... Issued at 112 PM CDT Tue Sep 17 2024 More cloud cover than previously expected in northwest MN, thus increased coverage here. Lessening in coverage of clouds here is anticipated as daytime mixing continues. Additionally, added some slight chance PoPs this afternoon in northwest MN for the off chance convective temperatures and subtle mesoscale forcing helps spark a few showers. This is where capping is weakest and convective temps are liable to be reached. UPDATE Issued at 1002 AM CDT Tue Sep 17 2024 Low stratus and fog lingers north of a stationary front in northeast North Dakota, and will continue to linger into the afternoon for some locations. Otherwise, expecting mostly clear skies with breezy winds out of the south and continuation of summer-like temperatures well into the 80s, potentially touching 90 for some in the southern Red River Valley. Very little evidence suggesting for thunderstorms this afternoon in our area, with the exception of near the international border where scattered showers and weak thunderstorms may exist. This morning`s high resolution guidance attempts at resolving the mesoscale environment tomorrow continue to reveal potential for supercells, of which could include tornadoes in addition to hail and gusty winds. More details on this to follow in this afternoon`s AFD Discussion. UPDATE Issued at 706 AM CDT Tue Sep 17 2024 The thunderstorms have moved out of NW MN and the narrow line of showers and t-storms that was developing from SD into MN made up to near Morris and is moving east and not likely to affect our area. So updates to pops were made. && .DISCUSSION... Issued at 358 AM CDT Tue Sep 17 2024 ...Synopsis... Very complex 500 mb pattern to evolve as upper low in Nevada moves northeast into southeast Saskatchewan by 06z Thu and then moves northeast followed by a second 500 mb low that moves southeast from northwest B.C. into southern Manitoba 00z Sun. The location, track of these upper lows will play a huge role in t-storm potential, location, timing the next several days. ...Today... T-storms that have brought heavy rain the past 24 hours to areas along the Manitoba/North Dakota/Minnesota border area will exit the area, though western edge of a few storms may linger thru the day around Lake of the Woods. Also seeing mid level convection forming in far eastern SD into western MN and this will track north-northeast and is likely to affect parts of the far southeast or east areas this morning and maybe into the aftn. Thus pop wise kept some pops in Lake of the Woods area and also from Bemidji to Wadena region thru the day. Mostly sunny elsewhere and warm and humid with highs in the 80s. ...Tonight into Wednesday... Uncertain about tonight as will start to moisture associated to the east of the upper low that is moving north well west of the area. Some support for mid level showers and t-storms thru tonight. Wednesday will see a band of showers and t-storms that is behind pushed ahead of the upper low move into E ND and NW MN during the morning or afternoon, depending on timing of low movement and location. It is once the band of showers/t-storms moves out that some heating will occur in an mid/upper level dry slot, but still sfc dew pts will hold near 70 thru Wed eve. Some potential for storms to re-fire in this moist airmass that with temps near 80 will bring MUCAPE 1500-2500 j/kg. Sufficient 0-6 km shear as well 35+ kts in E ND so that isolated supercell development is possible. Per SPC narrow zone of severe storms may form given the right conditions with level 1 out of 5 risk noted for the Red River valley for the late aftn/eve hours. ...Rest of the period... Thursday will see the upper low move from SE Sask to central Manitoba and a frontal system push east into Minnesota in the aftn. Where this front is located will be key to potential severe t-storm development in a narrow zone just ahead of this front. At this time it would appear best chc for strong/severe storm development is in region from Intl Falls to Brainerd. This weekend into early next week is another headache. Models have been differing greatly on how to handle potentially another upper low that would lift north or northeast from the central Plains into Minnesota. Per extended discussion from WPC low confidence in any one solution due to varying ideas and changes day to day from the models and ensembles. Latest idea is for now to have pops much of the weekend into Monday, but not high as of now and QPF from WPC on the lower end. But NBM QPF is quite high and significantly higher than WPC so some heavy rain threat is indeed possible in the RRV Sun-Mon. NBM has totals 1-2 inches in a wide area. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 112 PM CDT Tue Sep 17 2024 VFR conditions are forecast at all sites this afternoon through Wednesday morning. LLWS is forecast to develop at KGFK, KFAR, KTVF, and KBJI, generally around 35-45kt at 020 kft. Winds will become gusty out of the south 1-3 hours after sunrise Wednesday, gusting between 20-30kt, and likely continuing into the day. There is a chance for scattered showers and thunderstorms between 03-15Z across the region, 15-18Z for Minnesota, as a low pressure system approaches. However, confidence wasn`t high enough in timing of potential impacts from these to include TAFs for now. Thunderstorms are not anticipated to be severe, although could still hold gusty erratic winds over 30kt in addition to lightning. KTVF still holds an AMD NOT SKED due to AWOS outage at the site. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...CJ/Riddle DISCUSSION...Riddle AVIATION...CJ