The image on the right hand side of this blog is the temperature outlook valid from May 21-27.  Notice how much of the country is highlighted in a probability of above normal temperatures, including right here in Iowa.  In our extended forecast, we have every single day at 5-10 degrees above our seasonal average.  There won’t be much humidity with this either, and with the dry air overhead, only a few clouds would be expected each day along with pleasant nights and mild afternoons.

The image on the left is the precipitation outlook for the same time period.  This large upper level ridge of high pressure will serve to block pretty much the southern 2/3′s of the country from much rainfall, including in our area.  Some dry conditions will likely persist going into next week, especially down to the southwest of us.  Even here in Iowa, I would think drier than average conditions would be likely for the rest of the month.  Not to say we wouldn’t get any rainfall, but when tallied, it appears we’ll have a decent chance at staying below average.  Of interesting note is all the rainfall from May 1-6 did allow southeast Iowa to get to average for the month, but it’s tough to call it that way, if it really doesn’t rain much for the next 1-2 weeks.  I have a feeling we’ll all be wanting a decent shower by the time this pattern breaks.

Last week we had complex after complex of storms, and this week – nothing.  Next week, we’ll also have very little to talk about as a big ridge of high pressure sits over the upper Midwest.  This ridge will create daily highs into the 70s and daily lows from 45-55 degrees.  In a word, comfortable.

The graphic you see above shows the model forecasts in graphic form for the next 7 days.  The different lines show either the differing model solutions, or some older data sets of the same models. The rule here though, really comes down to how much agreement there is between forecast models for highs and lows.  The general trend is for persistence, with an additional 1-2 degrees for highs and lows each day going through next week, hence our 70s out there.  It appears our chances for rain are nearly zero, once we get through the Friday night/Saturday isolated chance at showers.

It is really something how we went from super active to super boring just like that.  We’ll see how the rest of the month goes, but we’ll probably be in need of rain by next week…..as it stands now, we’ll be mainly dry through at least May 18th…perhaps longer.

The only system that will really bring us anything to think about as far as rain goes is set to arrive on Saturday. Even then, it’s looking like a very weak cold front, with very little

moisture or energy to work with. As a result, any rain that does fall on Saturday (and getting anything isn’t a guarantee) should be pretty light and spotty.

There’s a secondary cold front pushing into the state of Iowa later in the day on Tuesday.  While there isn’t much moisture to work with, there’s a very cold pocket of air aloft….roughly 20,000 feet high.  With this cold pocket of air (around -24C), and the combination of surface heating, the atmosphere will become unstable on its own, even without the front arriving until the night.  A few scattered showers will likely form by mid-afternoon over portions of the area.  Areas most favored for measurable rain would be along and north of I-80. Much of southeast Iowa will miss out on these showers.

After this, high pressure will build in through the week, giving us quieter weather with seasonal highs and lows.  The next chance of storms would be later Friday night into Saturday, but given low moisture levels and winds that aren’t too favorable for anything organized, it appears only a slight chance is warranted at this point.

We’re also watching for the potential for flash flooding. Thanks to saturated soils, it won’t take much rainfall to produce flash flooding. Our guidance on it suggests it will only take 1.5″-2.5″ of rain in three hours to cause flash flooding.

The weather will be changing a lot today in any one place, so be sure to stay weather-aware in case threatening weather approaches. Our severe weather page has all sorts of info: http://www.kcrg.com/weather/severe

3 Hour Flash flood guidance, from the National Weather Service, indicates rainfall totals of 1 to 3 inches will result in flooding.  A flash flood is defined as flooding caused by heavy or excessive rainfall in a short period of time, generally less than 6 hours.

Flash floods are usually characterized by raging torrents after heavy rains that rip through river beds, urban streets, or mountain canyons sweeping everything before them. They can occur within minutes or a few hours of excessive rainfall. They can also occur even if no rain has fallen, for instance after a levee or dam has failed, or after a sudden release of water by a debris or ice jam.

We’ve already had rain affecting southern parts of the TV9 viewing area today, and more disturbances will come through pretty much on a daily basis over the next several days. However, timing exactly when rounds of storms move through is very difficult, because the things that spark them are very subtle. Something to remember is that, even though we have lots of rain chances, there will be a lot of dry hours thrown in there as well.

The Storm Prediction Center has outlined us in a slight risk of severe weather both tonight into tomorrow and again on Thursday. As far as severe weather goes, it appears the greatest threats will be for hail and wind. The tornado threat isn’t zero, but at this time it doesn’t appear to be as much of a potential. The wind flow isn’t very supportive of tornadoes.

Something else we’ll be watching is for heavy rain. With a good amount of moisture coming in, storms will have no trouble gobbling it up and producing some hefty amounts of rain in localized areas. Any places that have moderate to heavy rainfall several times over the coming days will have saturated soil, so the potential for flash flooding will exist, too.

As is always the case, there are many details involved in the severe weather chances over the next couple of days. Keep updated with our latest forecasts as we pin down as many details as we can.

By the time we add up all the rainfall out of this week, it appears much of the area will see at least 1-2″ of rainfall, with some heavier amounts certainly possible.  This rainfall forecast does not include the weekend, which could bring another inch of rain to our area.  In general, it looks to be warmer than average, and wetter than average.

When we look at the severe risk, there certainly will be one across our area, but it’s tough to pin down the greatest threats.  A pattern like this would suggest hail and wind would be the main threats as opposed to tornadoes, but we’ll have to assess the small details every day.  The graphic above right shows the severe weather risk for later on Tuesday, and the graphic on the left shows the severe weather risk for Wednesday.  Iowa is involved in both, and likely will be added into future severe weather outlooks in the coming days.

The bottom line is to just pay attention to the forecasts over the next few days.  There will be plenty of breaks in the storm complexes, and during those breaks, that’s where we’ll experience our warm and muggy conditions.  The warmer we get, the better our heavy rain/severe weather risk gets.   Just a heads up for the week…it looks pretty active.

For Cedar Rapids, the average temperature so far this month has been 51.1°… which is 2.2° above normal! Going back to March, the average temperature was 51.3°, a whopping 14.7° above normal.

So, there are a couple of very unusual things happening here. The average temperature in April is cooler than the one in March, but April’s temperature has still been above normal. This is certainly an unusual circumstance, but since we have a couple days left in the month, we’ll have to see how it finally ends up compared to March.

Part of the reason this April has seemed so cool is the fact that March was so incredibly warm. There have also been fewer of the very warm days. Let’s compare the number of days in a given temperature range from March until April…

You can click the image for a bigger look. The most noticeable differences are on either end of the chart. April has had three more days than March did with highs in the 50s or cooler… and zero days in the 80s! March had four of them.