AN ACTIVE, BUT UNCERTAIN, WEEK AHEAD

Severe risk areas have already been outlined by the Storm Prediction Center for late this week.

Trends are favoring a more active weather pattern later this week in to the weekend with showers, thunderstorms and a limited severe weather threat. Several days in advance the Storm Prediction Center has already outlined a few areas to watch on Thursday and Friday with a Level 2 of 5 Risk, a Slight Risk. Overall confidence is limited at this point, there are increasing chances for thunderstorms.

Instability forecast for Thursday evening on the GFS.

A warm front is forecast to lift northward across the state Thursday bringing a moist and unstable airmass. The GFS is indicating instability pushing well over 1000j/kg across southern Iowa and northern Missouri. At this point in time this appears to be a hail and wind threat, but trends will be closely watched.

The question is whether storms can form and tap into this environment. The environment will be rather "capped" with a temperature inversion in place that could put a lid on any thunderstorm development. I think the current Slight Risk (Level 2 of 5) could change once confidence in storms swings one way or another.

Friday afternoon and evening a slowly-approaching cold front from the west will likely lead to another round of thunderstorms, some strong. Instability will be somewhat limited as of this point, but given the sufficient wind shear forecast over the region we could see a few strong storms. The likelihood of storms is higher on Friday given better forcing in place.

Moisture will be pushed into the region with fairly strong southerly flow Thursday and Friday. Any time I see the moisture transport in the 90th percentile in relation to history, as its currently forecast, is a strong signal for thunderstorms, and potentially heavy rainfall. One limiting factor to heavy rain is the fact this system will likely be moving rather quickly.

Five-day precipitation forecast from the Weather Prediction Center has a quarter of an inch to a half inch of precipitation across much of Iowa and Missouri, and into northern Illinois. Heavier precipitation will be farther north across northern Minnesota and Wisconsin due to the aforementioned moisture "overrunning" a warm front that will be parked over the region late this week.

The European ensemble is showing a pretty broad area of rain Thursday into Friday across the Upper Midwest which at least shows the chance for storms, but I do not think it will be as widespread as this ensemble mean shows. There will be a smaller, more localized area of storms indicated by the higher-resolution models once they are in range. This ensemble forecast is, notably, higher than the current operational forecast showing some wiggle room and possibilities for an upside surprise in precipitation totals.

This will not be the end to the stretch of active weather for the central US. As I discussed yesterday, the pattern looks rather classic for severe weather chances to end the month of April. A stronger storm system is forecast to move from the Southern Plains into the Great Lakes Saturday through Monday. We will likely see more areas outlined by the Storm Prediction Center for the upcoming weekend.

Analogs are heavily pointing to above-normal precipitation for the central US as we head into the end of the week and next weekend. This would certainly be beneficial as we head into the spring planting season.

Moderate to Severe Drought covers much of the Central Plains and Midwest during the first week of April. More than 78 percent of Iowa and 90 percent of Minnesota are dealing with drought conditions. Hopefully the active pattern brings beneficial rains without the widespread severe weather.

-Meteorologist Nick Stewart