Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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185 FXUS63 KFGF 291130 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 630 AM CDT Sat Jun 29 2024 .KEY MESSAGES... - There is a low chance for a strong thunderstorm to move into the Devils Lake basin late Sunday night. - There is a level 2 out of 5 risk for severe thunderstorms Monday afternoon and evening. - A system may bring numerous showers and thunderstorms to parts of the Northern Plains on Independence Day Holiday, with a low chance for severe thunderstorms. && .UPDATE... Issued at 630 AM CDT Sat Jun 29 2024 The main area of rain has transition well east of our area, however there is still lingering light rain or drizzle mainly in northwest MN where lower level moisture is pooling closer to the cold front that is almost out of our CWA. Drier air is starting to filter into northeast ND and stratus is beginning to clear a bit faster as a result. Where highest 925MB CAA and max winds aloft are transitioning through the RRV behind the front winds have occasionally gusts to around 38 mph, but as expected we are seeing a downward trends in our northwest. Near term adjustments were made to reflect these trends, otherwise the forecast remains on track. && .DISCUSSION... Issued at 358 AM CDT Sat Jun 29 2024 ...Synopsis... A mid/upper trough is activity transitioning east of our region, with shortwave ridging expected to build over the Northern Plains today into Sunday. The larger scale flow/pattern remains progressive and active with several additional mid/upper level waves bringing high precipitation chances and at least conditional severe thunderstorm chances. Ensembles show strong consensus on the mean 500 MB pattern keeping highest mean heights to the south into the end of next week. There is a signal for a pattern shift later next weekend, which could result in amplified/strong ridging building across either the western US or even into the central US (4 ensemble clusters split between these solutions). Depending on the evolution of that pattern above average temperatures and less organized precipitation chances would be expected. ...Strong thunderstorms late Sunday night... There is a signal for a strong mid/upper level wave to build near the Pacific NW with SW flow bringing higher moisture into the region late Sunday night as the shortwave ridge transitions east. The main axis of instability and forcing will remain well west towards the Montana and western Dakotas where initial severe thunderstorms develop. As a LLJ develops Sunday night this has a chance to organize into either clusters of showers/storms or a possible MCS. The timing favors a general weakening and elevation of any activity as it moves towards our area, however there is a low chance as highlighted by SPC marginal risk for this to hold together into the Devils Lake Basin. Confidence is low based on the current timing (after 06Z) and sounding profiles. With the increase in deep layer shear and potential for modest elevated instability strong storms can`t be ruled out. Timing and upstream trends will be key. ...Severe thunderstorms Monday... The main mid/upper level wave will be pushing east along with a weak cold front/surface trough axis. Stronger surface low pressure continues to be favored south of the region placing the warm from with most clusters south (SD/NE). North of the warm front parcels will tend to be highly elevated, lowering confidence in impacts and severe coverage despite the dynamics at play. Widespread showers and lower stratus may be in place due to strong moisture advection within WAA across our area, however isolated severe threat would still be expected considering the magnitude of deep layer shear and decent elevated CAPE, with more robust/higher CAPE the close to the warm front. More breaks in cloud cover or a farther north surface low (not currently favored) would increase the potential for supercells. High PWATs (greater than 1.5") and potential deformation could create areas of higher rain totals once again (50% probs for 1"+). The signal for flash flooding isn`t as high at this time, but this could result in localized excessive runoff and additional rises on rivers. ...Independence Day Rain and Severe Threat... Yet another mid/upper wave dives into the Northern Plains towards Wednesday night into Thursday night. This carries another increased signal for showers and thunderstorms, locally heavy rain, and a low probably for severe thunderstorms (5% on CSU GEFS machine learning). Even with increasing consensus on the general pattern, impacts/details are still uncertain with slight variances in track/timing between clusters. As this will be a period of interest and impacts are possible it is worth monitoring despite the uncertainty at this range. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 630 AM CDT Sat Jun 29 2024 IFR and MVFR ceilings across eastern ND and northwest MN are starting to clear from the northwest as drier air arrives out of Canada and VFR should eventually prevail by late morning or early afternoon (may take longer near KBJI). Northwest winds will be strongest in the morning with a gradual reduction in max speed and gusts through the afternoon as higher winds aloft transition out of the region. Surface high builds into the region tonight and with loss of daytime mixing we should see calm winds over much of the region. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...DJR DISCUSSION...DJR AVIATION...DJR