This is the word from Chanhassen
Hello from NWS Chanhassen:
The weather pattern will remain active through Wednesday. The threat for severe weather, including large hail, damaging winds and isolated tornadoes, heavy rain, flash flooding and river flooding are all of concern through this period.
With the exception of parts of West Central Wisconsin, A slight risk of severe weather exists across most of the area through Wednesday morning. In the discussion issued at 258 pm, SPC they indicated the possibility of upgrading to a moderate risk across parts of central Minnesota with the concern of damaging winds.
Please forward this to those whom you think can benefit from the information (e.g. spotter groups, law enforcement including PSAPs, fire departments, and others who may need to plan).
More details below.
What: The main severe weather threat is damaging winds; however large hail and isolated tornado are possible. The question is whether or not we will be able to break the strong cap that is currently across much of southern Minnesota. If we do break the cap, thunderstorm growth will be explosive as CAPES are between 3000 and 4000. The wind shear is also strong near the warm front in west central and central Minnesota.
In addition, the rains overnight Monday night have kept the ground very saturated, especially in central Minnesota and West Central Wisconsin. Most of the rain overnight quickly moved into creeks and streams and rivers responded rapidly. While some locations have started to recede, most rivers are still rising. So the rain expected tonight and into Wednesday will lead to higher river levels. Additional Rainfall amounts through Wed Late Afternoon will be widespread ranging from 0.75 to around nearly 3 inches. Localized higher amounts of 4+ inches will be possible. Rain rates of up to 2 inches an hour can be expected which will cause creeks and streams to rise quickly. Flash flooding will especially a concern in the concrete/urban locations where most of the rain will run off as well as in areas that have recently received heavy rainfall. River flooding is also expected especially on the South Fork of the Crow where River flood warnings are in effect for Mayer and Delano. River Flood watches are in effect for Long Prairie on the Long Prairie River and Rockford on the Crow River.
Where: Severe weather is possible Tonight for all of Central Minnesota and West Central Wisconsin. The more likely area for strong winds and isolated tornadoes is along a Madison, MN to Benson to St Cloud to Cambridge, MN to Luck, WI line. This would be the area of focus for tornado development.
The main area for a flooding/flash flood concern is across central Minnesota, including the Twin Cities Metro area and parts of far western Wisconsin. A flash flood watch is in effect through Wednesday for much of NWS Chanhassen's area. Rivers that remain of concern include the Crow system, Long Prairie, Sauk, Rum, and the Mississippi River for Minnesota and in Wisconsin the Apple, St Croix and the Chippewa River basin.
A 4 pm CDT...A low pressure system was centered in southeastern South Dakota with a warm front extending northeast into Minnesota from Dawson to Willmar to just south of St Cloud and near Cambridge . The front will move into northeastern Minnesota and North Western Wisconsin as the low remains anchored in Southeastern South Dakota. Much of the activity this evening will be along and north of the warm front and in the vicinity of the cold front in Western Minnesota. The storms that are able to develop to the south of the warm front will have plenty of energy to tap into and hence the concern for explosive development.
The cold front will slowly move into western Minnesota late tonight and push across Central and Eastern Minnesota and West Central Wisconsin on Wednesday. The main upper level energy will be in eastern Wisconsin and Michigan hence the severe weather threat is diminished on Wednesday. Showers and thunderstorms will move west to east with through the day.
Intense heavy rain will be a concern leading to localized flooding/flash flooding with the stronger storms.
Focus on River Flood Threat
With river levels already high, widespread heavy rain could lead river flooding. River flood watches and warnings are have already been issued for the Crow system and the Long Prairie with Moderate stage forecasts expected for Delano. Other basins of concern include the Sauk, Mississippi, St Croix and Chippewa Rivers are the main once of concern. The heavier rain is not expected to fall in the Minnesota basin and its tributaries and mainly minor flooding is the concern. While not as likely, moderate flood levels are also possible, especially if we see more widespread and even heavier rains than anticipated. Please look at the Contingency River forecasts for possible scenarios.
This e-mail applies only to the 42 MN and 9 WI counties in the Chanhassen National Weather Service area (much of central and southern Minnesota and west central Wisconsin). For other parts of Minnesota or Wisconsin, check with your local NWS Office.
Web Links for your Quick Reference
Severe Weather Outlook from SPC (Day 1)
Forecast Rainfall through Wednesday evening
Near real-time hourly precipitation information
Official River Forecasts (include 24 hours of forecast rainfall for issuance of the forecast...so today from 7 am Mon - 7 am Tue)
Contingency/Ensemble experimental River Forecasts (A potential worst case scenario)
http://www.crh.noaa.gov/crh/rfc/mapgraphicdisplay.php (not this page works best in Mozilla Firefox and this data is not well QC'd s and is not the official River Forecast. Only use for decision making purposes.)
Excessive Rainfall Outlooks
NWS Twin Cities/Chanhassen home page
Watches and Warnings Page
Please feel free to call us if you have any questions, and like always, we'll try to keep you updated. If you have questions or comments, please contact our forecasters at 952-361-6671.