Difficult Weekend Forecast

I hope everyone enjoyed the splendid Friday across the area. Highs ranged from 69 in Milwaukee to 80 well inland. Plenty of sunshine. Nice start to Polish Fest, Lakefront Festival Of Arts, and many more festivals. This time of year it’s hard to keep track of all the festivals. Now everyone wants to know if the weather will cooperate this weekend.

Our forecast is quite complicated. There is no focal point in our immediate area for thunderstorms. Meaning no direct frontal passage, low pressure centers, troughs, etc. There is a low pressure center to our west, but for the most part it stays west of us on Saturday and then meanders to our south on Sunday. A stationary boundary (front) will hover to our south much of the weekend as well. So now we go to the models. This can be an adventure under this scenario. Here is what I mean. Let’s start with the GFS model for midday Saturday.

Note the lighter green in our area representing just scattered showers for Saturday afternoon. Now, on to the NAM. Same time period, midday Saturday.

The NAM has most of the precipitation staying to our west and keeps it there until Saturday night. Now, the RPM.

Note, the lack of any rainfall near us. I like the RPM for many reasons. We have used this model for almost 4 years at WISN and I have found it to be the most reliable for a 24 hour forecast. It is a higher resolution model than the NAM and GFS. This means it does a better job on picking up isolated showers and storms, lake snows, etc. Don’t get me wrong. It is still a model and is prone to mistakes, but I believe it is the most accurate 24 hour model I have ever used.

The easterly wind may actually help us keep the rain west on Saturday. Some dry air at the mid and low levels should hold off much of the rain. Now, let’s check out Sunday. I’ll start with the RPM for Sunday early afternoon.

If this verifies, Sunday afternoon is not looking too pretty. Now on to the NAM.

The NAM also brings us showers and storms around midday on Sunday. Finally, the GFS.

All three models have a chance of showers and storms on Sunday. I wanted to stay positive in my Father’s Day forecast, but Sunday is looking pretty iffy. Definitely have an alternate plan for a Sunday afternoon barbecue.

With all three models bringing at least a chance of storms on Sunday, I will have to amend my earlier forecast and put it a shot at storms. Hopefully, it won’t rain out any of your plans. Happy Father’s Day from Weather Watch 12.



7 Responses

  1. Friday, June 17, 2011

    Hi Mark,

    Mostly out of curiosity and because it was available, I decided to take a look at the ‘Futurecast’ from the Irad after reading your recent post. I figured that since it all seems so ‘iffy’, what’s one more opinion thrown into the mix! Anyway, according to it, looks like the rain chances are pretty slim from now through Sunday night. No doubt about it, from the little I know, it would seem that without a definite ‘weather making feature’ present, coming up with a forecast is quite a challenge. Appreciate your efforts to try and sort through it all and give your best ‘educated guess’.

    Tony (Pl. Prairie)

    • Tony,

      I hope the futurecast product is correct, but I’m doubting it. Certainly a challenging forecast for the next few days…actually pretty challenging into next week as well. Have a good weekend.


  2. Some hope for Sunday afternoon not being a washout… yesterday, the forecast for Saturday looked almost exactly like today’s forecast for Sunday. Yesterday was supposed to be pretty rainy too according to the models two days prior. They are definitely struggling as of recent.

    • Daniel,

      The joy of forecasting summer weather. Jet stream is weaker, systems don’t behave as nicely. Confidence not incredibly high with this forecast. Not fun for a Father’s Day weekend forecast.


  3. Mark – I generally agree with the lack of focus for Sat, but with the 500mb PVA/Vort nearby, I believe that is what is driving the GFS/NAM for convective. Looking aloft, you do have some general diffluence aloft aiding with lift. Looking at the backup RUC, it splits the difference with the GFS/NAM and RPM. Scattered seems plausible.

    • Timing the shortwaves and location certainly iffy for weekend. Baroclinicity on Sunday and boundaries left over from Saturday’s convection may be a focus. Have a good weekend.


      • ‘Tis the time of year of the MCS and plentiful outflow boundaries. I was watching this morning after our MCS and related wake low/heat burst that the surface obs looked like a salad. LOL I hate this time of year to the extent that the synoptic models really suffer and it takes more observation of surface obs/sat images to find the outflow boundaries that ultimately end up triggering much more than what gets modeled.

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