The Weather Prediction Center is forecasting a very wet week for the state with round one last night dumping localized heavy amounts. The forecasted image is valid up till Friday evening with the highest totals shown just to our southwest, but significant totals up into Iowa. We certainly could use the rain at this point, but it will probably mean flooding for some locations. When it rains, it pours, as the saying goes.

A large complex of thunderstorms are expected to fire to our west today and bring heavy rainfall and severe weather into Iowa on Tuesday evening and night. Nighttime precipitation is a very important part of Iowa's annual total. The featured map displays an IEM computed percentage of total precipitation during June, July, and August that falls during the twelve hours between 8 PM and 8 AM local time. All things being equal, we'd expect half (50%) of the precipitation to fall over a twelve hour period (50% of the day), but it does not work out that way for much of the country. A clear maximum appears over southwestern Kansas thanks to a phenomena known as the low level jet, which drives thunderstorms during the overnight hours and helps push them west through places like Iowa. Minimums appear over the deep south and desert southwest. These locations get summertime thunderstorms driven by peak heating from the sun driving instability.

Numerous rounds of intense thunderstorms dumped hail and heavy rainfall over southwestern Iowa Tuesday evening. The featured map presents estimated precipitation totals from the NOAA MRMS project. While totals exceeded five inches in some locations, the analysis shows amounts varying tremendously even within a single county. Page County (second county from the left on bottom row) missed out with most amounts shown under an inch. The forecast for the rest of this week has temperatures a bit on the cool side with highs in the 70s and lows in the 50s.

The featured chart displays one minute interval precipitation from the Lamoni Airport weather station Tuesday evening. In total, over five inches of rainfall was reported by the sensor for the day. This large total of rainfall was thanks to thunderstorms that "trained" over the location during the evening. Just as train cars pass over the same point along the tracks, so too can thunderstorms behave like this when the winds in the atmosphere are oriented in such a conducive way. The chart shows the intense rainfall rates spike with each passing storm over a number of hours for the event.

The Storm Prediction Center issued a tornado watch for portions of northwestern Iowa on Thursday evening. Thankfully the tornado threat did not materialize and no warnings were issued for Iowa after the watch came out. How common is it to have a tornado watch and then not a warning for a given county in the state. The featured map attempts to answer just that question with the percentage of events whereby a county under a tornado watch gets a tornado warning issued. While the percentages may appear low, they do roughly match the spatial confidence of a watch issuance. The overall map average is near 15%. Winneshiek County has the lowest percentage (0%: only 3 tornado warnings since 2005 and all not within a tornado watch) and Pocahontas County has the highest percentage (29%).

Our weather pattern has been unsettled with numerous rounds of showers and thunderstorms. The featured image shows the Iowa areal average tailing 14 day precipitation totals for each of the past three years and this year to date. This year appears to be mimicking the previous with wet conditions for spring and early summer. The highlighted area shows the rapid drop off that has happened for the past three years in early July. Will this same situation happen again this year?

The featured chart presents a climatology of 500 hPa (millibar) temperatures from the morning sounding for Omaha along with this year's observations. This pressure level in the atmosphere is some over 3 miles above the ground surface and is one of the important levels meteorologists look at to forecast the weather. The chart clearly shows the significant dip around mid May that accompanied the very cold temperatures. Recently temperatures have been on the decrease, which helps promote thunderstorm activity as colder temperatures aloft create unstable situations.

The featured chart presents the daily climatology of precipitation for Ames using period of record data. The blue line represents the simple daily average of precipitation using all days and the red line is the simple average over only the days on which precipitation was reported. These two lines answer the question what is the average daily precipitation and what is the average daily precipitation when it actually precipitates that day. While the blue line peaks in early June, the red line plateaus through the summer. The nature of the summer time thunderstorms is rather consistent over the summer months, but their frequency decreases as the summer passes. So the blue line peaks during the peak in thunderstorm activity, while the red line decreases once we are out of summer and into September.

The thermostat hit 80+ degrees for many parts of the state on Wednesday. The featured chart totals up the 80+ degree days for Ames year to date for this year and past years. The overall plot average is 16 days, so this year's total (14) is only slightly below that. We are well ahead of 2013, but less than half of 2012's total. Cooler temperatures with highs back in the 70s are expected for the rest of the week with a return to the 80s next week.

The featured map displays estimated precipitation departures for the state since the first of May. This analysis shows a large contrast between eastern and southern Iowa with percent of normal departures below 60% and above 130% respectively. Heavy rainfall is in the forecast, but the largest amounts are expected over northwestern Iowa, which could use the rainfall as well. The drought situation in the state is very complex at the moment with dryness on different timescales currently occurring.

The typical IEM expansion involves adding new observation stations, but today's early morning expansion involved adding a new helper. Robert Lee is already producing outputs on par with the software program quality produced by his daddy. The entire family is doing well and daddy is so happy with his Father's Day gift.

The Storm Prediction Center had a categorical moderate risk of severe weather forecasted for much of Iowa on Monday and there was plenty of severe weather that lasted on into the night time hours. The featured map is from the "Local Storm Report" application which you can find on the IEM website. It displays reports of high winds, hail, tornadoes, storm damage, rainfall reports, and other significant weather!

The rainfall over northern Iowa has recently been quite intense with the featured map displaying the previous 72 hour estimated totals. A few observations over 10 inches have been reported, so the estimates do not appear to be too far off. Drought concerns have been replaced by flooding in the area. Our unsettled pattern will continue today with more severe weather and heavy rainfall expected on Thursday.

The concern this summer was if it would resemble the past few years with dry conditions leading to a quickly developing drought. Instead, it is starting to resemble the recent flood years of 2010 and 2008 as illustrated by the featured chart. The chart presents the Iowa areal averaged precipitation for the first 18 days of June since 1893. This year is only one of seven total years with a value over five inches. More rain is falling this morning with another round expected this evening.

The drought situation over northern Iowa has been mostly eliminated this week thanks to estimated rainfall totals over 11 inches in limited areas as shown by the featured map. These estimates are provided by the NOAA MRMS Q3 project, which uses high resolution RADAR information and other data to derive values. Most of the northern Iowa is analyzed over five inches, which is about the expected total for all of June. The forecast has more chances of rain, but at this point the heaviest totals are expected over southern Iowa.

More rainfall fell on Iowa over the weekend with some of it falling in areas that have received too much rainfall already this month. The featured chart shows the June precipitation departures as reported by the National Weather Service. The largest values on the map appear in the Sioux City and Sioux Falls area with departures for the month over 10 inches! In Eastern Iowa, Cedar Rapids is shown 5.4 inches above average while just to the south Iowa City is only 0.9 inches above. Des Moines is the slightly negative number in the state. More rain is in the forecast this week, but after a few mostly dry days to start.

The June precipitation totals have been piling up with some locations in Iowa approaching a record accumulation for the month. For this analysis, Sioux City is shown besting its previous largest June total but long term data does not exist at the site. Other locations like Dubuque, Burlington, and Esterville are just a few intense thunderstorms away from besting their respective records. And then there is Des Moines, which needs over a foot more to break the record (not likely!). The blue circles on the map are a cheesy attempt at illustration the percentage the current June total is to the previous monthly record for June.

The significant rainfalls this June have mostly missed central Iowa leaving quite the disparity between the total precipitation for Des Moines versus other locations in the state. The featured chart compares the average precipitation for four cities in Iowa vs the Des Moines Airport total. This June appears far away from the 1to1 line and unlike anything we have seen since 1951. There is still days left this June, so perhaps the difference will be made up with further storms expected.

The featured chart is a bit complex to understand, but tells a great story of the interplay between temperature and precipitation departures with time. The line connects fourteen day trailing departures evaluated every seven days. Since temperature and precipitation are related, they tend to form circular cycles that trace arcs with time. The most recent point on the chart shows up at a very wet departure and slightly below average temperature departure. In fact, all but three points are shown to the cool side of average. So our year has generally gone from cool and dry to cool and wet! Thankfully the heat in early June appears, which helped warm soils and got the crop growing robustly.

Recent IEM daily features have lamented the disparity between Des Moines precipitation and that of the rest of the state this month. The storms on Thursday attempted to make up that difference, but left a complex rainfall pattern over the Des Moines metro area. The featured map of MRMS estimates shows a range from a quarter inch over the airport to 4-6 inches over the northwestern suburbs. These totals were valid at 8 PM Thursday evening with more rain on the way.

The Storm Prediction Center has had Iowa in a moderate risk for severe weather for two days in a row now. A few tornadoes were reported in Iowa on Sunday and more are expected today. Heavy rainfall will be a problem again with expected over two inches for parts of eastern Iowa. A severe thunderstorm watch is already in effect this Monday morning with storms rolling across northern Iowa.