A RAINFALL FEAST FOR SOME

As anticipated as did see some widespread precipitation across the region on Saturday that brought some high-end totals for some, and unfortunately not much for others. Such is the game of summertime storms in the Midwest. Totals topping 3" were reported across the region fueled by somewhat slow-moving thunderstorms and a highly-anomalous, moisture-laden atmosphere.

RAINFALL REPORTS - IOWA (As of Midnight)

• Pella - 5.0"

• Monroe - 4.5"

• Fort Dodge - 4.25"

• Hiawatha - 3.0"

• Vinton - 2.5"

• Cedar Rapids - 2.21"

• Iowa City - 1.70"

• Riverside - 1.5"

RAINFALL REPORTS - IL/WI (UPDATED)

• Platteville, WI - 2.10"

• Mount Carroll, IL - 1.94"

• Taylor Ridge, IL - 1.41"

• Coal Valley, IL - 1.24"

No formal rainfall reports were in as of midnight Saturday night for Illinois or southern Wisconsin as storms were slowly still moving through the area. Pella, Iowa topped the list at 5" of rainfall following multiple rounds of thunderstorms.

Precipitable water, or PWAT, values across the Midwest were pushing 1.8" to 2.1". This value is essentially the rain that would accumulate if you squeezed out all the moisture from the surface to the upper atmosphere. Generally, values over 1.5" are an indication of heavy rainfall concerns, and 2.0" are extremely high values. This creates an environment capable of very heavy rainfall in a short period of time.

Daily weather balloons are critical to collecting this data and really are the only way we can get this information for our models and forecasting. This is why these launches are critical. Not only can we see the values, but we also have a historical dataset to compare this to. So Saturday evening's balloon from the Quad Cities office tallied a measured PWAT of 2.20" - obscenely high!

For some context, the 2.20" values measured is a record for July 6 at 00z (7 p.m. central time on July 5). The previous record for that specific time was 1.96". Looking at the entire date, it is the third-highest values measured on July 6 behind 2019 and 2010. It is also the 16th-highest for a July day on record, with data back to 1995 (905 July days total). That means this was in the top 2% of all July days on record.

This observed data matches really well with climatology data that was modeled for Saturday. You can see there were clearly signals for near-to-record-breaking PWAT values off the NOAA NAEFS product. For Eastern Iowa it was in the 99th percentile, or top 1% of all days, which matches the observed data quite well.

The tropically-induced air is leaving the region, however, which is good news. We will have enough moisture sticking around to generate a few isolated storms Sunday before we likely have dry days Monday and Tuesday. Temperatures will remain seasonally hot across the region.

In terms of the Sunday storm threat, model guidance is quite bearish on storm potential with low-end probabilities across the area in the afternoon. Only about a quarter of the high-resolution thunderstorm models show any signs of life in the late afternoon and evening.

For what it's worth the HRRR, which has performed rather well the last couple of days, does show a few isolated storms pop up in the region Sunday evening. It's something to watch for but not plan around, in my opinion. Most of the area likely remains dry, and if a shower or storm does pop up, it will likely be brief.

Highs in the mid/upper 80s remain commonplace across the region through the week and into the weekend as zonal flow, to somewhat northwest flow, takes over. This pattern aloft will be slightly agitated and we are watching a chance for storms midweek to late week. Overall the confidence is low and coverage will likely be limited, but we cannot rule out a strong storm threat mixed in.

WEDNESDAY

THURSDAY

FRIDAY

Ensemble guidance keeps a daily chance of accumulating precipitation across much of the Midwest, especially Wednesday-Friday. Again, the confidence is somewhat low but it's enough to talk about the risk of storms. Unlike yesterday (Saturday) in which we had pretty high confidence in storms since early in the week last week, this is a little more blurred with more limited upper air support.

Analogs and machine-learning forecasts we have used show a subtle hint, but not as clear as some other recent events. We are watching it closely and hope to share the feast of rain with those that have missed it, and keep it form those who could use more dry time. Hope you all had a great Fourth of July! Stay cool out there...

-Meteorologist Nick Stewart