NWS Forecast Discussion
224 FXUS63 KMPX 132346 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 646 PM CDT Sun Sep 13 2026 .KEY MESSAGES... - Widespread rain arrives Monday with additional chances later in the week. - A cooler pattern has arrived with highs in the 60s to low 70s through next week. && .DISCUSSION... Issued at 215 PM CDT Sun Sep 13 2026 Now that the clouds are clearing, we`ve get a spectacular fall weather day with high pressure that came out of the Canadian Rockies moving overhead. However, all one needs to do is look at the h5 low over the northwest CONUS to see what will bring this pleasant weather to an end on Monday. Tonight, We`ll be under the influence of the surface high. Cloud cover will move into western MN, but skies will remain clear in western WI, which will setup a decent gradient in lows tonight, with clouds keeping temperatures up in the 50s in western MN, but the clear skies and light winds allowing for some places out around Mora, Rice Lake, and Ladysmith to drop into the upper 30s. Given current forecast lows with isolated upper 30s, there`s no need for any frost headlines in the MPX area at this time. For Monday, the h5 low currently out around Idaho will deepen while moving to along the NoDak/Canada border. A lead shortwave ahead of this low will take on a negative tilt, with h85 winds responding accordingly, getting up over 50 kts as the LLJ moves across the Upper MS Valley. PWATs will increase to around 1.8", which is pushing near the top of climatology for this point in September. With that kind of moisture and the strong LLJ already noted, IVT values are near climatology max as well. This will support some efficient rain producers, but that lack of instability will really limit the heavy rain threat on Monday. The main uncertainty for tomorrow deals with where the heaviest rain falls, most of the guidance shows a large band of 1-1.5" inches of rain falling with this LLJ forced rainfall, but placement of that band ranges from west central through central MN and south central MN through western WI. With the uncertainty in placement of the heaviest rain, we stuck with the NBM for now, which favors the northern solution. What we did change from the NBM were the highs Monday. We took a good 5-10 degrees off of NBM highs for Monday, with cloud cover and rain holding highs back in the 60s for most of the MPX area. Going into Monday night, the LLJ and plume of high PWATS will continue shifting east, largely moving east of the MPX area. Even though the surface cold front will be lagging to the west of the deeper moisture plume, the fact that the LLJ and plume of high PWAT air moves east of the MPX area means that the next round of heavy rain and storms that develops Monday evening through Monday night will be largely east of the MPX area, falling along and east of a line from roughly Omaha Nebraska to Wausau, WI. Next week, this front will run into an unseasonably strong blocking high over the southeast CONUS. This will cause the front to stall out from lower MO River Valley to between the Great Lakes and Ohio Valley. We`ll see multiple wave ripple across this front through the week. The first one comes Tuesday night through Wednesday night. This looks to largely impact northeast KS to southern Lake Michigan, though the northern fringe of this rain shield does look to get up into at least southern MN, which drives the PoPs Wednesday afternoon through Wednesday night that are highest across south central and southeast MN. The next wave arrives for Friday into Saturday and this one looks to take a more northerly track, bringing better precipitation chances to the MPX area. We`re again seeing models pumping out another 1+" rain event with this system, so there`s potential for some beneficial rains to both begin and end the work week. Next weekend, confidence in the forecast, at least for precipitation chances, drops off. The intense southern ridge will finally start to break down as a slow moving long wave trough moves across the north central CONUS. The NBM PoPs are under 20%, but the Canadian and ECMWF are starting to come around on the idea of a stronger wave embedded within this trough driving another chance of rain across the region Sunday/Sunday night, so it`s likely that we`ll start seeing PoPs increase for the end of next weekend as the NBM starts picking up on this newer development in the models. && .AVIATION /00Z TAFS THROUGH 06Z TUESDAY/... Issued at 627 PM CDT Sun Sep 13 2026 VFR conditions continue through the evening and overnight with light and VRB winds. Winds will becoming southeasterly during the early morning hours as the next storm system moves across the area on Monday. A band of precipitation will move SW to NE across the forecast during the morning and afternoon hours, with precipitation starting across west/southwest MN between 12-14z before tracking east/northeast through the morning. Precip coverage will be widespread with moderate rainfall rates at times. MVFR cigs can be expected as well during the duration of precipitation, with isolated instance of IFR. Winds will be gusty as, with gusts up to 30 knots possible. KMSP...Only concern is the arrival of precip during the morning on Monday as well as gusty SE`ly winds. Prevailing light rain to start as early as 15z with moderate rainfall falling between 16-20z. Light rain showers will linger beyond the moderate rain rate window through 00z. Cigs fall to MVFR heights by tomorrow evening. Winds will be out of the NW for the remainder of today and becoming light and variable overnight. Winds shift SE`ly tomorrow morning with speeds increasing to 25-30kts as early as 16z. /OUTLOOK FOR KMSP/ TUE...VFR. Wind NW 10-15kts. WED...VFR. Chc MVFR/-SHRA PM. Wind E 5-10kts. THU...VFR. Chc MVFR/-SHRA AM. Wind E 5-10kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION...MPG AVIATION...LPR
NWS MPX Office Area Forecast Discussion