Main concerns through the short term are thunderstorm chances, the potential for severe storms and threat of locally heavy rain. the heavy rain threat appears to be highest Saturday night and then again from late Sunday afternoon into Sunday night.
For today, the general consensus from the available high resolution short range convection allowing models (CAMS) is that the bulk of storm activity should shift east of our area and be mainly over central iowa by around 7 am CDT. Then there may be an increase in activity from west to east across the forecast area from the late morning through the afternoon. Outside of possibly some outflow that could mess up the surface pattern, we generally expect south or southeast surface winds from 10 to 20 mph today. Temperatures should reach the mid to upper 80's in the northern parts of the forecast area. Highs in the southern parts of the area will likely reach around 90 to the lower and possibly mid 90's.
Storm Prediction Center - Day 1 Severe Weather Outlook
NWS Omaha Graphical Weather Outlook
HOUR BY HOUR FORECAST
I wanted to share a day by day precipitation forecast from the Weather Prediction Center. Each image covers the 24 period that you see in the caption below each image, and the grand total at the end.
Well folks, I wish I could say the entire event was going to be sunny and cool, but you'd find out pretty quick when the rain started falling that I was lying. Let's go ahead and first look at Friday into Saturday. This from the Omaha NWS office...
"There is a pretty decent front coming into the area Friday evening into Friday night. Various models have different depictions of the timing of the front, with the Nam a little quicker, and the GFS and little slower and the EC even slower still. Will have chance pops of storms along the front, and if storms could get going, there is a slight risk of severe storms Friday evening.
The front will remain in the area Saturday, perhaps just south of I-80, which will provide a continued chance of rain for the southern half of the area.
LONG TERM...(Saturday night through Wednesday)
Several rain chances exist during the extended period, and there is some potential for heavy rains both Saturday night and again Sunday night. The stalled frontal boundary, combined with a short wave ejecting out of the central/southern Rockies could lead to numerous showers/storms. PW values could be around 2" Saturday
night, and the GFS is suggesting rainfall could be excessive, although it's just outside our QPF window for this forecast, but it's certainly something we're watching closely. The boundary lifts north during the day Sunday, but remains in the area, thus rain chances continues. Additional heavy rain signals are in place Sunday night with more convection expected along the boundary, again with PW values near 2", which could lead to additional
excessive rainfall. While we can probably take one night of heavy rain without too much trouble, a second night in possibly some of the same areas could lead to flash or river flooding. Still 5 days out, but again, we'll continue to monitor it closely.
The previously mentioned front seems to wash out Monday, but the GFS remains the wetter model with rain chances continuing. Models do suggest another front could be moving into the area Tuesday afternoon into Wednesday, so rain chances continue those days as well.
Bottom line, the extended period, including the Labor Day holiday weekend is looking very active, with numerous rain chances, and the potential for heavy rain and flooding that linger into mid week."
Weather Prediction Center 24 Hour Rainfall Totals
I had a little too much to share on Facebook, time to use the blog. :-)
I wanted to give an update on the weather for the ProSolo and CAM Challenge coming up at the end of the week. If you were to look at the NWS forecast, it contradicts what they say in their Area Forecast Discussion, so we need to take a look at the discrepancies.
The image below is the current NWS forecast for Lincoln through Sunday. They do have thunderstorms in the picture for Friday, but for the moment, Saturday and Sunday are mostly sunny and mid 80's. You can always find that forecast here: http://www.daculaweather.com/4_track_lincoln.php
But if you read the AFD (those are posted automatically on the Facebook page), it says this...
"Medium range models indicate a more active period for later in the week and into Labor Day weekend as upper-level flow becomes southwesterly and subtle waves are forecast to move through the area."
My guess is that they are waiting to get a little closer in time before they modify the Saturday and Sunday forecast.
Here's a comparison between the GFS and Euro for the moment (both 12Z runs from today), and they are showing fairly similar things. There is one thing to note. Trying to pinpoint the exact locations where rain is going fall and when, when you are 4-5 days out is usually not very productive, and especially in this case. There are no major systems that will cause this rain, it's mainly from a warm moist flow around the backside of an area of high pressure with little waves of enhanced moisture rotating through, so the models really have no clue at the moment where those areas will end up. Click on any image to enlarge.
Lincoln stays on the edge of the heat and rain, but it's never too far away, and that is probably one reason why NWS Omaha is waiting to see how some of this evolves before updating the Sat-Sun forecast.
Here's a look at the temps from the Euro which I'm sticking with for now. I'm not showing the GFS because all summer it has had outrageously high temps that have not verified. It's now looking Friday will be the warmest day of the 7 day period, but notice how the upper 80's and 90's aren't too far away. These are all 1pm (central time) temps
So here is the summary of temps to this point. The top image is the deterministic model run, the bottom image are the ensembles, and you can see the differences between the two. Pretty close on Friday and Saturday, but they start to diverge a little after that. That diverging trend is the reason for using the ensembles to help average out the various ensemble members, and one of those ensemble members is the deterministic run in the 1st image below.
While we're looking, look at Wednesday on the top image... if that holds true, you might need a jacket. :-)