TURNING UP THE THERMOSTAT...
Who hasn't enjoyed the weather the past 5 days? I mean seriously, this is why we put up with winter...so we can bask in such splendid conditions. Here's the 5 day temperature departures going back to last Friday. Cool nights, mild days, and sunshine. That's what I'm talking about!
As amazing as its been, there are some people who depend on rain who are not so thrilled with the absence of it. I'm going to show you something that I think is quite remarkable to make my point. These are the 6 month rainfall totals. What's so remarkable is that around Burlington and Ft. Madison more than 31 inches of rain has fallen over the past 180 days. About 150 miles away to the NW amounts dwindle into that 10-14 inch range. It's that area around Cedar Rapids up to Waterloo and points west where farmers are praying for soaker.
Below are the departures which are quite dramatic from 9 inches above to 12 inches below. SE Iowa, central Illinois and northern Missouri are the hot spots for precipitation this year.
The soil moisture index reflects the extremes showing severe moisture deficiencies from about I-80 in Iowa off to the northwest.
Obviously, it's going to take a lot of rain over the next few weeks if we are going to put a dent in the dryness before the drier months of fall and winter limit that possibility. I do see some opportunity late week and perhaps again next week but as is often the case this time of year, amounts look scattered and much will depend on the timing of any forcing.
What will happen first is a return to southerly winds which will bring warmer temperatures and the moisture needed for rain. That also means substantially higher humidity levels. Notice water vapor has increased to 2 inches in parts of eastern Iowa by Saturday morning. That will be available for a front to work on as it enters the region Friday night or early Saturday. This is where timing becomes important as the best chances for heavier rain occurs towards Friday evening when instability is maximized. Those chances can extend into the overnight as the low level jet becomes a player. However, by morning both of those factors are substantially reduced and the rains tend to fall apart and diminish in intensity. If you want rain the best window is most likely between late evening and just before sunrise.
After the front passes Saturday, things look quiet through Sunday as a weak ridge of high pressure crosses the Midwest. Later Sunday night or Monday another opportunity presents itself as warm advection and southerly winds return to the pattern. I have turned to the ensembles of the EURO and GFS to give you and idea of what the two models are indicating for rain potential Friday through Monday morning. Ensembles are comprised of multiple solutions which are then averaged to get their output. Some amounts are likely going to be far higher than the average but considering how hard its been to get rain in the northern half of my area I think the ensembles are a good place to start. Here's what's shown.
Hopefully that split between the higher amounts NW and SE will fill in some where the rain is needed most in coming days.
One last thing I will touch upon is the potential for a day or two of significant heat next week. The 18Z GFS operational is very aggressive on that Monday and Tuesday. In fact the GFS shows highs around 100 next Tuesday in some of the drier parts of my area.
The EURO is more restrained with highs peaking more in the range of 91-94.
I feel quite confident that the GFS is too hot and in the end readings will be closer to what the EURO indicates. Even so its numbers are well above normal and may have some merit , especially in the areas where very little rain has fallen the past 6 weeks. Here top soil moisture is essentially non existent and evapotranspiration limited as well. Those two factors coupled in with a full day of sunshine and some strong compressional heating could at least give my driest counites a shot at 95. Plenty of time to unravel that thread.
Whatever happens, the heat should not last more than a few days. The MJO is moving in the direction of cooler phases and look what the day 10-15 temperature departures look like on the EURO. This model is notorious for not seeing cool air so if it sees it this strongly at this distance, it has a good chance to verify (probably even cooler). I'll no doubt have more on this in coming posts.
Alrighty then, I will wrap this up with a bow and wish you all a good day. Roll weather...TS