FXUS63 KFGF 211141 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 641 AM CDT Mon Sep 21 2026 .KEY MESSAGES... - Frost chance exists Monday night/early Tuesday for northwest MN and possibly northeast ND. - Next rain chance is Wednesday night/early Thursday and Saturday. && .UPDATE... Issued at 359 AM CDT Mon Sep 21 2026 Broad 500 mb low moving slowly south-southeast into northern Nebraska this morning. Clouds and leftover sprinkles, very light rain showers perist in north central ND around Minot and does extend east toward Rugby and near Devils Lake where sprinkles are in grids thru 6 am. Overall though today will see this upper low move farther away and an upper level ridge begin to build from western Montana into Saskatchewan and Manitoba. This will aid in pushing the upper level system farther south and eventually allow the clouds to clear out over the area today into tonight. Surface high will be well east of our area and we will have no fresh supply of cool air. But sufficiently dry airmass and winds under 5 kts should lead to at least a chance for frost for NW Minnesota, and possibly even parts of northeast ND. The 20-30 percent probabilities of temps below 36F exist in areas east and west of the RRV overnight in northeast ND and northwest MN. The biggest signal of frost is in northeast MN. && .DISCUSSION... Issued at 220 PM CDT Sun Sep 20 2026 ...Synopsis... Upper low currently rotating over WY will push out into South Dakota and Nebraska tonight, weakening and moving into the Upper Midwest tomorrow. Some high clouds from this system for our area, but all models keep most of the precipitation to our south. At the surface, center of high pressure over Ontario will move only very slightly east, allowing light east to southeast surface winds over our CWA. While can't completely rule out some fog formation tonight, it will be hampered by higher clouds and a little bit of mixing. Right now best chances are up against the escarpment or Turtle mountains where the southeasterly winds will bring some upslope. The upper low pulls off to the east and leaves blocky ridging over the region through Tuesday. Upper flow starts to become more southwesterly Wednesday, with one shortwave coming out into the Northern Plains late Wednesday and into Thursday. There is decent consensus on southwesterly flow with various weak shortwaves continuing into next weekend. Can't really pin down precipitation at this point, but temps look like they will be above seasonal averages. ...Frost chances for Monday night into Tuesday morning... With the upper low moving east of our area by the first part of the work week, clouds look to be decreasing for at least some period Monday night, and a bit drier air moving in from the east. Probability of temperatures below 36 degrees range from below 20 percent in most of the central and western CWA, but get up to around 40 to 50 percent along our far eastern border. Advisory level temperatures dropping into the mid 30s are possible, although much will depend on exact cloud cover trends. ...Next precipitation chances Wednesday night and Thursday... Shortwave trough moving into the western Dakotas Wednesday will progress quickly into the Great Lakes by Thursday. Instability is pretty weak at less than 500 J/kg, so severe is not expected although some thunderstorm activity is not completely out of the question. Main impacts look to be rain, with 40 to 60 percent probabilities of over a quarter of an inch in portions of our western and southern counties. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 638 AM CDT Mon Sep 21 2026 VFR conditions thru the period. Overall a broken mid and high cloud deck gradually being pushed south today with clearing working southward too into the evening. Winds ESE 7-10 kts. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...Riddle DISCUSSION...JR AVIATION...Riddle