426 FXUS63 KMPX 091955 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 255 PM CDT Wed Sep 9 2020 .SHORT TERM...(This evening through Thursday night) Issued at 255 PM CDT Wed Sep 9 2020 It's a lovely early November day out there, with most of our area still in the 40s even at 2pm. A broad band of light rain continues to fall as well, in response to fgen in h7 to h6 layer. If MSP fails to reach 50 today, it will be the earliest we've seen a sub-50 high in the fall on record (Sep 10, 1918 is currently the earliest such occurrence). If you've had enough of this weather already, take a look at the forecast for next week, you'll like the way it looks, I guarantee it! The positively tilted trough that has been setup from the Dakotas to Hudson Bay the last couple of days is finally starting to push east toward MN. This will finally push this band of moisture over us off the the east, taking the rain and likely cloud cover with it. How quickly and how much we clean these clouds out will determine how cold we get tonight and how bad the fog becomes. All models are pretty aggressive with clearing things out this evening. With the high overhead, this will set the stage for a rather chilly start to the day Thursday, with 10th percentile lows tonight down into the 20s from Mora over toward Ladysmith. Didn't change forecast lows much, so kept frost advisory unchanged, with this area forecast to get down into the 33 to 37 range outside of the urban core of the Twin Cities metro. Beside the cold, dense fog is looking like a potential issue, with the HREF showing pretty good probabilities of dense fog developing from south central into east central Minnesota and western WI. This moist atmosphere in place will also mean we should develop a heavy dew, which if cold enough, will be a good frost. Thursday, with high pressure overhead we'll see nothing more than fair weather cu and milder conditions, with highs getting back above 60, though still around 10 degrees below normal. Thursday night, high pressure will still be centered over WI, so another night of frost and possibly even a freeze looks likely in west central WI. South of I-94, increasing southwest winds and cloud cover will keep lows up in the mid 40s. Though clouds will be on the increase, we don't have to worry about any precip until likely Friday afternoon. .LONG TERM...(Friday through Wednesday) Issued at 255 PM CDT Wed Sep 9 2020 There are two main stories for the long term period: rain on Friday into Saturday morning and a return to near to above average temperatures. This warming trend will be present through the long term period bringing us from our much below normal temperatures up to temperatures in the 70s and 80s. Friday and Saturday... The upper level cutoff low over the southwest CONUS finally begins to move east towards the Upper Midwest on Friday. This upper level pattern will provide synoptic lift along a broad area of positive vorticity advection. This system should also bring a plume of moisture up from the Gulf of Mexico providing precipitable water values in the 90th percentile per NAEFS across southern and central Minnesota. Different deterministic and ensemble systems remain in good agreement on the probability of precipitation Friday into Saturday. What remains more variable is QPF, but widespread totals of over a half inch is likely. Some higher totals could occur with thunderstorms as weak instability will be present. Sunday to Wednesday... Surface high pressure and ridging moves in on Sunday bringing with it a drier weather pattern. The main story here will be the warmer temperatures as warm air continues to advect into the Upper Midwest with highs in the 70s and 80s each day. By midweek some shortwaves will pass through the Midwest and could lead to some rain showers. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 1256 PM CDT Wed Sep 9 2020 The last band of precip will slowly pull out to the east this afternoon, with main uncertainty the rest of the period dealing with how quickly will skies clear out this evening. Models are certainly aggressive with clearing out the skies, which would set the stage for widespread dense fog. HREF goes this route for south central and east central MN into western WI, highlighting fog potential for all but AXN. Have played into the clearing idea, with a pretty aggressive fog forecast Thursday morning. Once fog clears off, there will be no additional issues Thursday. KMSP...Fog tonight will be purely radiational. It's pretty rare to get that, but when MSP does have it, it doesn't start to impact the field until sunrise, so that would put the fog risk at MSP greatest between about 1230Z and 1400Z. Current thinking is that fog will form down in the river valley and may impact the southeast portion of the field closest to the valley, but probably won't encompass most of the airport, hence the BCFG (patchy fog) in the tempo group. /OUTLOOK FOR KMSP/ Fri...VFR. Wind SE 5-10 kts. Fri night...MVFR/-shra. Chc IFR/-TSRA. Wind SE 5 kts. Sat...MVFR/-SHRA, chc TSRA early. Bcmg VFR. Wind bcmg NW 5-10 kts. Sun...VFR. Wind N 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...Frost Advisory from 1 AM to 7 AM CDT Thursday for Anoka-Benton- Brown-Carver-Chippewa-Chisago-Dakota-Douglas-Hennepin- Isanti-Kanabec-Kandiyohi-Lac Qui Parle-Le Sueur-McLeod- Meeker-Mille Lacs-Morrison-Nicollet-Pope-Ramsey-Redwood- Renville-Scott-Sherburne-Sibley-Stearns-Stevens-Swift-Todd- Washington-Wright-Yellow Medicine. WI...Frost Advisory from 1 AM to 7 AM CDT Thursday for Barron- Chippewa-Dunn-Pierce-Polk-Rusk-St. Croix. && $$ SHORT TERM...MPG LONG TERM...NDC AVIATION...MPG