Full Notification

Bottom Line for the Weather:
Showers and thunderstorms will become more widespread across central and southern Minnesota this this evening and overnight. For west central Wisconsin, the activity will develop late tonight and into Tuesday. Heavy rain is a concern with the thunderstorms and hourly rainfall accumulations of 1.5 to approaching 2 inches will not be out of the question. Widespread rainfall amounts of 0.5 to 1.25 inches can be expected through 7 am on Tuesday with an additional 1.0 to 1.5 inches expected on Tuesday. Higher amounts can be expected in the thunderstorms especially for locations that thunderstorms train over the same area for several hours.

Given that he ground is already saturated, especially across Central and Southern MN and West Central WI, from the rains received over the last week, these rainfall rates will lead to localized urban flooding and quick rises in area creeks and streams. Hence a Flood Watch is in effect for South Central and West Central MN from 7 pm this evening through Wed morning. River flooding may become a concern as we move into mid-week depending on the basins that receive the heavy rainfall.

Severe weather is also a concern and Storm Prediction Center has outlined a slight risk for severe thunderstorms across central and southern Minnesota and parts of west central Wisconsin. The main threat will be for damaging winds and large hail for tonight. The severe weather threat will shift east on Tuesday impacting mainly South Central east central and parts of West Central Wisconsin. Again this is a slight risk with the main concerns being damaging winds and large hail. Isolated tornadoes will also be possible especially along and south of I 90 tonight and Tuesday morning.

Overview:
A low pressure system and associated warm front will gradually lift north today and into tonight. The warm front is expected to become nearly stationary across far southern MN late tonight and into Tuesday. Along and north of the front will be the area of focus for training thunderstorms which will produce heavy rainfall. In addition, a boundary on the northwestern side of the low pressure is will extend into West Central MN which will be a secondary focus for heavy rain.
As mentioned above severe weather is also a concern, mainly for tonight and into Tuesday. While isolated tornadoes are possible the main concern is large hail and damaging winds.

There is still some question on the exact location of where the front and boundary will become stationary. This location will have an impact on the amounts and areas that will receive the heaviest rain.

The implications of the rainfall to the river level forecast are still being evaluated. As a reminder, we include 24 hours of forecast rainfall in the official forecasts. Thus, the forecast issued this morning will include the rainfall expected through 7 am on Tuesday and the forecast issued this evening will include the rainfall through Tuesday evening. The "Contingency River forecast" (links provided below) is a resource for insight on the potential implications of the heavy rain to the rivers. This is still reliant on our accuracy of the location, intensity and amount of the precipitation but the can provide some insight on possible "what if" scenarios. As a reminder the Contingency forecasts are for your internal use only and are not to be distributed to the media or public. The official river forecasts are available on the NWS AHPS webpages. If you have not used them in the past, a short tutorial is available on the main website.

Recommendation for severe weather preparedness:
Spotters, emergency management, and other public safety officials should continue to monitor outlooks, graphics, and forecasts. Spotter activation is not anticipated at this time however.

Useful Web Sites:

NWS Twin Cities/Chanhassen home page
http://www.weather.gov/twincities

NWS Twin Cities/Chanhassen River information page (AHPS) http://water.weather.gov/ahps2/index.php?wfo=mpx

Link to the Flood Watch product
http://forecast.weather.gov/wwamap/wwatxtget.php?cwa=mpx&wwa=flood%20watch

Storm Prediction Center Outlooks
http://www.spc.noaa.gov/

Link to the Contingency River Forecast website http://www.crh.noaa.gov/crh/rfc/mapgraphicdisplay.php

Watches and Warnings Page
http://www.crh.noaa.gov/hazards/?wfo=mpx

Severe Weather and Heavy Rain Outlooks
http://www.crh.noaa.gov/outlooks/mpx

NWS Twin Cities/Chanhassen Weather Safety Page http://www.crh.noaa.gov/mpx/safety.php

For a tutorial on how interpret this information please reference.
http://www.crh.noaa.gov/crh/ensemble_hydrographs/Ensemble_QPF_Hydrographs_for_EMs_final1.html
(REMINDER the contingency Forecast are used for decision making purposes only is not to be shared/redistributed with the media or public.)

Some quick links for Flooding Situational Awareness.
Flood Briefing webpage:
http://www.crh.noaa.gov/mpx/?n=springflooding