Scientific Forecaster Discussion

000 fxus63 kmpx 220919 afdmpx Area forecast discussion National Weather Service Twin Cities/Chanhassen Minnesota 419 am CDT Mon Apr 22 2019 Short term...(today through tuesday) issued at 419 am CDT Mon Apr 22 2019 Surface analysis early this morning shows a low pressure center near koma with a quasi-stationary front extending northeast into northeastern WI and a cold front extending southwest across Nebraska into western Oklahoma. Aloft, split flow has nearly zonal flow along most of the Canadian international border while a pivoting 500 mb trough lumbers east over South Dakota through Kansas. This trough, taking on a negative tilt, will nudge the surface low east-northeast today through tonight, moving it to the Iowa/Wisconsin border by this evening and into northern Michigan by Tuesday morning. The trough will open up and evolve over the Minnesota/WI border by Monday evening, helping push the surface low away from the weather forecast office mpx coverage area Monday night. Drier northwest flow aloft will then accompany incoming high pressure for Tuesday. Kmpx radar this morning shows plenty of rain/thunderstorm activity over western through central Minnesota in a generalized SW-NE orientation, Akin to the frontal boundary orientation over the area. Moisture depth is certainly not an issue as pwats over much of the coverage area is around 1". Given the orientation of the upper trough and fairly deep southerly flow off the surface in advance of the surface low, additional moisture advection is not much of an issue for this low. Pockets of heavy rain are certainly viable thru the rest of this morning and the first half of the afternoon as the low slowly shifts east across northern Iowa and the leading front punches north into southern Minnesota and central WI. Spotty 0.5"-1.0" hourly rates would not at all be unreasonable, with overall totals in the 1-2" range feasible through this event. The spotty nature of the heavy rain plus relatively drier soils after the snowmelt precludes any kind of Flood Watch but mention of heavy rain is made in the hazardous weather outlook (hwo). As for thunderstorm potential, MUCAPES this morning are only in the 250-500 j/kg range and much of that is elevated. So while some spotty cirrocumulus/cloud-to-ground lightning strikes are certainly possible, no strong/severe thunderstorms are expected. There may be some clustering of storms which may also lead to heavier rain and possibly some stronger wind gusts but all activity is expected to be sub-severe. The precipitation will gradually diminish in terms of intensity and coverage as the afternoon progresses, with only scattered showers remaining for far eastern Minnesota into western WI this evening. By midnight, all precipitation looks to be east of the weather forecast office mpx coverage area, thus no longer an issue. Skies will then gradually clear out late tonight through Tuesday morning, allowing for plenty of sunshine and mild conditions for the rest of Tuesday as drier high pressure moves into the area. As for temperatures, the warmer and more unstable conditions will remain to the south of the frontal boundary and low pressure system, thus keeping cooler low level east-northeast flow in place today. Highs will only range from the upper 40s to around 60 degrees today. As the system exits to the east tonight, modest cold air advection will kick in, helping drop lows into the 30s area-wide. On Tuesday, plenty of sunshine will aid in allowing highs to climb into the 60s area-wide. Long term...(tuesday night through sunday) issued at 419 am CDT Mon Apr 22 2019 Wednesday will start out warm, with highs expected to warm back into the 70s as 850 mb temperatures increase to 10-12 c ahead of a frontal boundary to our northwest. This front drops through the area Wednesday evening, but brings little cold air behind it along with fairly dry air to work with. Some scattered showers look possible Wednesday night as the front passes and divergence aloft increases, but precipitation amounts are expected to remain light. Models have come into a bit more agreement with handling the next system, as split flow aloft transitions into an active jet stream setting up overhead towards the weekend. The first of these waves look to approach on Friday, but little moisture in place should keep US dry. A stronger wave approaches sometime on Saturday, with a surface low developing over the Central Plains and skirting across southern Minnesota/northern Iowa. This system looks to be our next shot at widespread precipitation, and potentially heavy precipitation as precipitable water values again surge above 1". Temperatures are still all over the place with this system however, with a 20-30 degree spread between the GFS/CMC/ECMWF Saturday afternoon. The GFS brings the warm sector into southern Minnesota along with a thunder threat, while the European model (ecmwf) keeps temperatures in the 30s and 40s along with a cold steady rain. Until models converge on these details, it's tough to mention any specifics, but the precipitation does now appear more likely on Saturday. The active jet remains overhead into early next week along with continued unsettled weather. && Aviation...(for the 06z tafs through 06z Monday night) issued at 1057 PM CDT sun Apr 21 2019 VFR conditions continue late this evening. Showers and thunderstorms are beginning to develop across western and central Minnesota, which will continue overnight. A heavier round may develop Monday morning from SC to ec Minnesota. IFR cigs are possible Monday before rapid clearing moves in Monday evening. Kmsp...the best chance for showers and storms will be from 07-11z tonight, then after 15z Mon. The rain should end late tomorrow afternoon with quick clearing later Monday evening. /Outlook for kmsp/ Tue....VFR wind north 5-10 kts. Wed...VFR. Wind SW 10-15 kts. Thu...VFR. Chc -shra. Wind northwest 5-10 kts. && Mpx watches/warnings/advisories... WI...none. Minnesota...none. &&

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