Update 3pm: Wave #1 slides just mostly south of the metro. The larger system is still on track and should send a second wave our way tonight into Friday.
Time to clean the weather lab gutters.
Radars are lighting up around the Upper Midwest today as a potent wave of low pressure takes aim. This system has all the ingredients to produce widespread and potentially heavy rainfall totals over the next 48 hours.
NAM model 84 hour rainfall paints 2″ to 4″+ over southern Minnesota.
Call it a gully washer, frog strangler or goose drowner…the idea is the same. Sustained tropical downpours are likely to produce some muti-inch rainfall totals by Friday afternoon.
NWS and forecast modles cranking out a good 2″ soaking.
Various forecast models are cranking out rainfall totals for southern and central Minnesota into Wisconsin by the inch. The general trend is for 1″ to 3″ rainfall totals by the weekend. Some of the more aggressive forecasts produce a street flooding 5″ by Saturday evening.
NOAA rainfall forecast puts a 5″ bull’s eye over the metro by Sunday morning.
The set up is nearly ideal. A slow moving warm front and low pressure combo will set up shop over northern Iowa and southern Minnesota. Waves of instability will ride along the front, producing batches of rain and embedded thunderstorms. Tropical moisture with dew points in the 60s to 70 will surge north from Iowa and trigger heavy downpours.
The biggest threat for severe weather appears to be just south of the metro, from southern Minnesota into Iowa. Still any of the stronger storms that do form will contain vivid lightning and booming thunder. High winds are not out of the question with the stronger storms over southern Minnesota overnight.
Rain will increase in the metro this afternoon and tonight. The so called “flash flood guidance” issued by NWS hydrologists indicates that 2.5 inches of rain could cause flash flooding on smaller rivers and streams in southern Minnesota. It may take closer to 3.5″ in central Minnesota. Flash flood watches and warnings may be issued if rainfall totals approach these limits.
Keep an eye out for heavy rain and the potential for localized flooding over the next 48 hours.