349 FXUS63 KMPX 201731 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 1231 PM CDT Fri Sep 20 2019 .SHORT TERM...(Today through Saturday) Issued at 526 AM CDT Fri Sep 20 2019 Main weather concerns this morning will be with a line of showers and thunderstorms extending NW-SE across southern Minnesota, and with dense fog across west-central Wisconsin. The precipitation across southern Minnesota is associated with a subtle shortwave, along an area of enhanced low-level warm-air advection. Expect this forcing to diminish somewhat through the morning and showers/thunderstorms to dissipate before reaching the I-94 corridor, but it is an uncertain forecast as convection-allowing models have performed quite poorly with resolving this boundary already. Isolated to widely scattered showers and thunderstorms will also be possible this afternoon as the remnants of this feature continues north into central Minnesota, but warming temperatures aloft should generate enough of a cap to prevent anything widespread. Elsewhere this morning, calm winds and relatively clear skies have resulted in areas of fog developing, with the densest and most widespread fog across western Wisconsin where visibilities are below one quarter mile. This fog will dissipate by mid-morning, with another warm and humid day expected as temperatures warm into the 80s and dewpoints approach the upper 60s to low 70s. More widespread showers and thunderstorms are expected to develop later tonight and continue through Saturday, as a broad area of low pressure moves through the Upper Midwest. Forcing for thunderstorms will be focused along the cold front, with guidance coming in slower in bringing the front through the area. Expect precipitation to now hold off until after midnight across western Minnesota, and spread east through the area through the morning. Strong to severe weather is still a possibility with shear values of 30-40 kts along the front, but looks to be limited overall by the limited instability during the morning hours. Precipitation/cloud cover from this morning round of storms may then limit additional thunderstorms during the afternoon, with models trending dryer as the dry slot of the surface low works into the area. With the dry slot working in Saturday afternoon/evening, the potential for heavy rainfall looks lower as well. Expect the heaviest rainfall to remain closer to the upper level low across northeast ND/northwest MN. .LONG TERM...(Saturday night through Thursday) Issued at 526 AM CDT Fri Sep 20 2019 The longer term begins with precipitation exiting the area Saturday night as one short wave departs, then another wave arrives Sunday with upper west-northwest flow. The short wave Sunday delivers slightly cooler air to start the week, but temperatures will still be around or slightly above normal. Another short wave arrives midweek, then finally a deep trough develops over the western states late next week. All this spells quite a few periods when there could be showers and storms, but overall probabilities are not too high at this point. Deterministic models are in reasonable agreement through the coming week, and a sizable portion of gfs and ecmwf ensemble members paint a similar picture. Therefore confidence is above average for the overall pattern, with the usual modest timing differences. Once the lead short wave exits Saturday night, another one arrives Sunday, and with cooler temps aloft, there may be a few showers in northwest Wisconsin, but most areas will just experience slightly cooler and drier air along with northwest winds. Timing of the next trough and front remain in question with the deterministic models bringing them through in the Tue/Wed time frame. We will retain the smaller end PoPs for this at the moment and see if models come into better agreement on timing. Finally, many GFS and ECMWF members show a significant western trough developing late next week. The ECMWF members are deeper and sharper with the trough, with some suggestion of nearly meridional flow. This would bring a return of warm temps and humid air and possibly heavier rainfall. The CPC currently flags our area for the potential of heavy rain a week from now. But there is a lot of time for things to change. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) Issued at 1230 PM CDT Fri Sep 20 2019 Through 00z, cigs will remain VFR with isolated TSRA/SHRA near the MN/WI border, and into west central Wisconsin. This evening, SHRA/TSRA will become more numerous in western Minnesota, and slowly spread north and east across the state toward morning. SHRA/TSRA are likely Saturday morning along with IFR/MVFR cigs/vsbys. Winds will remain SE today, with occasional gusts at times. Winds will become more S/SW Saturday and continued gusty through 18z. KMSP... Confidence is still low on TSRA/SHRA this afternoon. If any develop, it will be brief and last only 30 minutes or less. Late tonight, and into Saturday, SHRA/TSRA will become more numerous with cigs/vsbys lowering to MVFR/IFR at times. /OUTLOOK FOR KMSP/ Sun...VFR. Wind W 10G20 kts. Mon...VFR. Wind VRB03 kts. Tue...VFR. Wind SW 10G20kt. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ SHORT TERM...ETA LONG TERM...TDK AVIATION...JLT