Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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618 FXUS63 KFGF 020457 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 1157 PM CDT Mon Jul 1 2024 .KEY MESSAGES... - Numerous showers and thunderstorms tonight. Severe weather is not expected. - A system is expected to bring numerous showers and thunderstorms to parts of the Northern Plains on Independence Day, with a low chance for severe thunderstorms. && .UPDATE... Issued at 1032 PM CDT Mon Jul 1 2024 Numerous showers and thunderstorms continue across the Red River Valley into Minnesota as of around 10 PM. Overall the forecast is panning out as expected, with thunderstorms holding brief periods of heavy rainfall and lightning. The chance for severe weather has diminished with the waning of remaining instability. Additionally, the chance for minor flooding from heavy rainfall is also waning as thunderstorms have and will remain progressive enough. Latest guidance on tomorrow`s chance for scattered showers and storms reveals some potential for semi-organized storms capable of producing small hail. Best chance for this to occur is in northwest Minnesota where there is some overlap between sufficient shear and instability. UPDATE Issued at 727 PM CDT Mon Jul 1 2024 As of around 7 PM, widespread showers and thunderstorms are entering into eastern ND from central ND. These showers and storms will continue northeast through the rest of the afternoon into evening. Overall, the chance for severe hazards is turning out to be very low given general lack of better instability and shear, as well as elevated nature of convection. There has been a noteworthy amount of lightning, in addition to heavy rainfall rates. So there is still a chance for storms to be strong bringing frequent lightning and brief heavy rainfall potentially causing minor urban flooding. This convection has displayed progressive forward movement keeping heavier rainfall rates relatively brief. Latest guidance continues to show this will be the case through the rest of the afternoon into evening. This progressive nature of heavy rainfall will keep chance for flash flooding rather low. However, cannot discount it completely given earlier day heavy rainfall priming areas with fully saturated grounds allowing for efficient runoff. Most sensitive areas are within the northern and central Red River Valley into northwest Minnesota, particularly from near Warren/Alvarado to near Thief River Falls where 2-3 inches have recently fell. An additional quick 1-2 inches of rainfall is reasonable under heavier thunderstorms. While not currently expected, this is where there would be relatively higher chances for minor flooding from compared to other areas. && .DISCUSSION... Issued at 248 PM CDT Mon Jul 1 2024 ...Synopsis... A decent low level jet will remain mainly east of the Red River late this afternoon and into the evening. This has been the primary forcing for the showers and thunderstorms across northwest Minnesota. Precipitable water values have been very high, around 1.70 inches, and the rainfall rates have been quite impressive as well. Here at the NWS in Grand Forks, almost an inch of rain fell in an hour or so. There could be another round of showers/storms this evening, with another 700mb wave that is moving into eastern Montana/western North Dakota right now. This is where the weak surface front is as well. However, there is no low level jet support out in that area tonight to help sustain stronger convection too far into the evening. The 500mb low will be located over southern Manitoba by 18z Tuesday, meaning there is some support for redeveloping Tuesday afternoon showers/storms. There should still be somewhat of a break on Wednesday, before another stronger wave moves in for the July 4th holiday. Beyond that, northwest flow looks pretty well entrenched, with a few additional waves possible. ...This Evening... There is a weak surface boundary east of a Williston to Dickinson line, but there has been extensive cloud cover across that area most of the day. There has been some developing convection across the western Dakotas with a little lightning activity as well. There is ample effective shear out in that region, but instability has been held down somewhat. As mentioned in the paragraph above, there is no low level jet support tonight for anything that does try to move into this FA. CAMs do still show some sort of line of storms forming from Minot to Bismarck by late afternoon, potentially moving into our western FA by 7 pm or so (eastern North Dakota following that). The HREF shows any UH tracks pretty much ending to the west of this FA. Therefore think storms may continue to move into our FA tonight, but on a weakening trend. However, these could still be efficient rain producers, so will have to watch to see if any of these move into areas that have seen highers totals up to now. For the most part, the highest totals have been over the northern Red River Valley into adjacent areas of northwest Minnesota. ...Independence Day... Have been watching this potential for a few days now. If anything, have seen a slight shift southward with the heavier precipitation axis in the latest ensembles. Yesterday at this time, our FA was right in the middle, now it appears eastern South Dakota into southern Minnesota (where they definitely don`t need it) are more in the middle. Either way, will have to keep an eye on this next system over the next few days. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 1155 PM CDT Mon Jul 1 2024 MVFR to IFR ceilings are forecast at TAF sites through 10Z, with some lingering longer in MN. Additionally, some mist/drizzle/fog will lower vsby into the 1-4SM range before 10Z as well. These are the main hazards that will impact TAF sites through 12Z. There is a chance for scattered showers and thunderstorms in the afternoon Tuesday. Decided to leave out of the TAF for now due to confidence in impacts to any particular TAF site remains low. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...CJ DISCUSSION...Godon AVIATION...CJ