491 FXUS63 KFGF 172337 AFDFGFArea Forecast Discussion National Weather Service Grand Forks ND 637 PM CDT Wed Sep 17 2025
.KEY MESSAGES...
- A wet period is setting up from tonight through Friday night, with the focus for the highest rainfall potential across southeast North Dakota and west central Minnesota. Outdoor activities and ongoing harvest will be impacted to varying degrees.
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.UPDATE... Issued at 637 PM CDT Wed Sep 17 2025
Dry air at the surface is keeping the handful of radar returns in our far south from reaching the ground. However, the atmospheric column will continue to saturate over the next several hours, with rain expected to begin in the far south around midnight. From there, it will slowly inch northward overnight, reaching about I94 by sunrise. Outside of short term adjustments to match this idea in the grids, the rest of the forecast remains on track.
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.DISCUSSION... Issued at 246 PM CDT Wed Sep 17 2025
...Synopsis...
A pair of upper lows to our west will wobble east and rotate around each other as we head into the later part of the work weak. The southernmost upper circulation will lift northeastwards towards the ND/SD border tomorrow, remaining over the Dakotas through Friday before moving off into the upper midwest over the weekend. Another upper low starts to move into the Dakotas for Monday, and then down into the central MS Valley by the middle of next week.
...Rain tonight into Friday night...
ECMWF EFI has a fairly robust wet signal for the Dakotas from tonight through 00Z Saturday, then again for Monday. Instability looks fairly weak, although some ensemble members bring some CAPE into our southern counties for tomorrow, with probability of over 1000 J/kg around 25 percent. With not a lot of CAPE and deep layer shear around 30 kts, the main issue continues to be heavy rainfall. Probabilities for over an inch of rain through Friday night are still highest in southeastern ND, ranging from 50 to 80 percent. Chances for heavy rainfall trail off significantly further northeast, with less than half an inch expected near Lake of the Woods. The rainfall is expected over several days and should not all come at once, with the 75th percentile for 6 hourly QPF not getting above half an inch. At this point, think rain should soak in pretty well and will not message much more than we already have.
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.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 637 PM CDT Wed Sep 17 2025
Conditions will go downhill at all TAF sites tonight into Thursday morning. VFR will give way to MVFR by Thursday morning. Pockets of IFR are also expected, particularly at KFAR and KDVL, likely prevailing for a period on Thursday. IFR may become more widespread then current TAFs show, and may necessitate PROB30s or TEMPOs at other sites as we get closer. Rain will accompany lowering ceilings, hampering visibility into the MVFR range as well. MVFR will persist through the end of the TAF period, likely continuing into Thursday night, or even lowering again into IFR.
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.FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None.
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UPDATE...Rafferty DISCUSSION...JR AVIATION...Rafferty
NWS FGF Office Area Forecast Discussion