363 FXUS63 KMPX 131954 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 254 PM CDT Sat Apr 13 2019 .SHORT TERM...(This evening through Sunday night) Issued at 253 PM CDT Sat Apr 13 2019 Lower clouds slow to thin to the east. Drier air is trying to work east as surface ridge builds in slowly from the Dakotas. A couple of moisture starved weak short waves remain embedded in the westerly flow aloft over the area. The first wave over South Dakota is moving east and is weakening as it moves into confluent flow aloft over the western Great Lakes. The other over Saskatchewan Canada is moving east and is weakening. Models suggest some form or a trough aloft will move into southern MN overnight. At the moment, limited high clouds are associated with the short waves. It may slow erosion of the lower clouds to the far east overnight, but we anticipate clearing trend over most of the area. With the light winds and clear sky to the west, we will likely see at least some patchy fog develop over the area overnight. After the patchy fog during the morning, we expect mostly sunny conditions for Sunday and temperatures warming through the 40s regionwide. Models trend the next western wave to approach western MN later Sunday night. We should see increasing clouds and we continued the small chance PoP for a light mix far west after 06z Tue. .LONG TERM...(Monday through Saturday) Issued at 253 PM CDT Sat Apr 13 2019 The main focus of this forecast period is the potential for a spring storm starting Wednesday and perhaps lasting into Friday morning. Confidence is high that most if not all locations will see precipitation from this event. Confidence is medium/high that nearly all of the precipitation will fall as a cool rain. Confidence is low in how the storm system will track across the region, and therefore how much rain will fall and for how long. Did have the confidence to increase pops to 80 and 90 percent for Wednesday and Wednesday night, and in all likelihood this will be too low. In other words, you should expect more rain for the middle of this week. Rain could start as early as Tuesday night, but it appears that the best agreement for when you can expect to see rain is starting Wednesday morning and lasting at least through Wednesday night. There is strong H850 theta_E advection, and upper level support in the form of positive vorticity advection down stream of a longwave trough. How this trough evolves will determine how quickly the precipitation moves out. The GFS has been consistent in taking on a negative tilt, which means slower motion, stronger forcing, and much higher precipitation amounts as the deformation band lingers over the Upper Midwest into Friday. Meanwhile the ECMWF has more of a neutral tilt to it is a bit faster, and the GEM is positively tilted and races the system east of the forecast area by Thursday morning. The slower solution would pose more of a flooding threat, with widespread 1 to 3 inches of rain possible. However, this could be overdone even if the models are right with the storm track. The reason being the robust convection that is expected to take place to the south in the warm sector of this system. This tremendous amount of latent heat release could alter the synoptically forced precipitation. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 1225 PM CDT Sat Apr 13 2019 We maintain cyclonic flow over the eastern area through the afternoon. Should see VFR periods of MVFR cigs farther east. May see a brief -shra/sprinkle as well. Expect clearing to central and into the far eastern area overnight. Still late night fog possible, with light winds and mainly under the surface ridge. Some drying today should limit widespread fog. Usually need a couple days of significant snow melt to get more widespread fog/stratus under the ridge. KMSP...Expect mainly VFR trend through the period. May see cig drop to near 3k feet for a time, but overall trend VFR. Cant rule out a sprinkle, but better shot at that farther into west central WI. Clearing into the evening with perhaps some fog in the river valley late. Not sure how much that would affect the airport proper at the moment. /OUTLOOK FOR KMSP/ Sun night...VFR. Wind SE 5kt. Mon...Chc MVFR cigs. Wind SE 5-10 kts. Tue...VFR. Wind ESE 5kt. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ SHORT TERM...DWE LONG TERM...JRB AVIATION...DWE