Return of Thunderstorm Outlook - Warm, wet week ahead

An old friend returns today - the thunderstorm outlook! We actually did have a general thunder delineation on February 2nd, but it was short lived and didn't manifest. Tonight, we actually have a better chance for some flashes of lightning as the warm front comes in and collides with the cold airmass that has been in place for some two weeks now. This will cause some slight instability, but it should be enough for some showers to manifest, and some of the stronger ones have been given about a 10% chance of turning into a thunderstorm:

This morning's NAM4KM predicts some potential thunderstorms overnight tonight. Taken from the 06z (1am) run.

This week is going to make the last couple weeks feel like a completely different season. By mid Tuesday we're looking at temps in the low 60s. This is based on several of the latest runs of the NAM, culminating in the latest NAM4KM shown below:

Taken from the 12z (7am) run.

This actually backs off a bit from the early morning run, which predicted temperatures in the mid-to-upper 60s. I'm thinking low 60s is a bit more realistic at this point, due to ground temps and the influence of the lakes (the lake shore areas may only see temps in the 50s, if that - they could be closer to 45°). Wednesday is looking just as warm if not warmer (again, much warmer in the early morning run, with temperatures much cooler near the lake shore), but that's when the rain is going to start. And when I say rain, I mean, rain:

A very moist airmass is on the way. 

These are "precipitable water" values forecast by the NAM for this Wednesday evening. That's 1.3 to 1.5 inches of potential rainfall in the atmosphere for that point in time. That doesn't necessarily mean that's what's going to fall, but we're going to be the end of what weatherfolk refer to as an "atmospheric river" - a very long and wide area of high water vapor content that can bring enormous amounts of rain across a wide swath, especially near a coastline. The coastline involved this time around is the Gulf coast, and areas there may see as much as 8-12 inches of rain in the coming days. We're not going to get anywhere near that much, thankfully, but we're still looking to get a bunch. By Friday we could be looking at widespread areas of 1-2 inches of rain throughout the lower peninsula, with locally higher amounts present for any thunderstorms that do form. Our greatest chance for thunder right now appears to be Wednesday, but this type of rain is mostly going to be stratiform, as well as remnants of storms which form over the Great Plains this week.

To summarize:

• This week is going to feel like mid-April to early-May, with temperatures pushing 65°, possibly isolated 70° in the southernmost regions. I expect records to be challenged if not outright broken.

• A very wet airmass is going to be moving into the area Tuesday into Wednesday, which will cause significant rainfall across the state. Accompanied with snowmelt, this could cause localized flooding in some areas, but I don't anticipate anything too noteworthy.

• A rumble of thunder is not out of the question throughout the week as pockets of instability will be present.