Thursday, September 25, 2014

Sunny and Clear Conditions Continue with the Uncertainty of Precipitation Early Next Week

Public weather briefing

Clear skies for the rest of the week into the weekend will persist. Light wind from the south/southeast will also continue until Monday where we will see a westerly shift in wind. Monday night will likely have mostly cloudy skies along with a chance of precipitation during the later hours.  The cloud cover is expected to dissipate early Tuesday with mostly sunny skies dominating for the rest of the day. Highs into the weekend and early next week will be in the upper 70’s with lows in the lower 50’s, giving a consistent stretch of weather through early next week.  


Tonight. Mostly clear skies with patches of fog. Calm wind. Low around 48.

Friday. Sunny with light wind.  High around 78.

Friday night. Clear with light wind. Low near 53.

Saturday. Sunny with light wind.  Highs in the upper 70s.  Lows in the lower 50s

Sunday. Continued clear and sunny with light wind. Highs in the upper 70s.  Lows in the lower 50s.

Outlook for Monday through Tuesday. Mostly sunny on Monday with light wind and a chance of light showers overnight. High in the mid 70’s and low in the lower 50’s.  Mostly sunny Tuesday with encroaching clouds overnight. Highs in the lower 70s and lows in the lower 50s. [CONFIDENCE: HIGH]

Forecast Discussion

The dry air in our region, along with the dissipating trough over Lake Superior, caused the clouds to break up much earlier than predicted during the day Thursday.  Clearing skies further promoted surface heating, which caused the daytime high to be slightly higher than originally forecasted for the day.

For the rest of the week and into the weekend our weather will be primarily dominated by the anticyclone over the eastern Great Lakes region, bringing southerly winds as well as warm air and clear skies. The GSF projects the formation of a weak area of low-pressure over northern Wisconsin early Monday.  This will bring weak westerly winds along with a slight chance of precipitation as an area of baroclinicity also moves down from the north. Northern Wisconsin is likely to receive light rain fall but there is some uncertainty as to the possibility of precipitation for southern Wisconsin as the dry air that will be covering the region for the next few days may be enough to impede any rainfall. The southern half of the state will likely experience mostly cloudy conditions Monday night along with a 20% chance of rain. 

Westerly winds will persist into Tuesday possibly bringing cloudy conditions in association with another cyclone projected to move east over the northern plains states bringing more moist air and an area of upper level divergence producing upward vertical motion in the Wisconsin/Iowa region.

Craig Oswald and Cody Kuchinski


  1. Pretty solid forecast overall, guys! Looks like temperatures ended up being warmer than expected over the weekend. It appears we had an upper-level low off to our west most of the weekend, which was well depicted by the models. But you'd think that being downstream of this feature we might have had a bit more cloud cover. As part of your reflection, could you speculate on why this may not have occurred?

  2. Great point Andrew, what appears to have occurred is that the area of divergence aloft, downstream of the upper level low, produced upward vertical as we would expect. Usually when this occurs we’d expect cloud production as parcels rise and condense. Atmospheric soundings from the weekend indicate that there was relatively dry and stable air over much of the region. Along with the dry air containing little moisture for condensation, the stability of the environment hampered upward vertical motion as rising parcels were forced back down as they cooled adiabatically in a relatively warm column. These conditions kept skies clear and sunny and promoted daytime surface heating which pushed high temps to around 82 degrees Fahrenheit, a few degrees warmer than forecasted.

    Even though the rest of our weekend forecast was pretty solid, there were areas of patchy fog that persisted during the early morning hours of Friday and Saturday that weren’t predicted. This was likely due to a strong surface inversion capping any vertical motion associated with the latent heat release of condensation and strong night time radiative cooling at the surface due to the clear skies, allowing surface temperatures to cool to the dew point producing areas of fog. The only other hiccup was that skies during the day Monday had scattered cloud cover. This likely occurred due to a shift from southerly to westerly wind bringing more moisture to the area, along with an increased forcing in upward motion as a weak cold front approached from the north in association with the weak surface cyclone over Lake Huron. This system is what also produced the few drops of rain that ended up falling in Madison Monday evening/night as predicted.

  3. Cody and Craig - Overall, I'm pleased to see that you were able to identify the primary features of interest throughout your forecast period and your reflection thoughtfully addresses some of the dynamical processes that may have contributed to the differences between verification and your forecast. You definitely want to bring more of this dynamical thinking into your forecast and public weather briefing above. For example, in the public weather briefing, if you mention precipitation or clearing skies, you definitely want to mention the dynamical structure responsible for that weather, be it a front or a high-pressure, etc. Furthermore, once you get into your forecast discussion, you do mention the presence of a front, which is great, but you want to also get into the processes that are driving the vertical motions along that front here as well. Also, definitely make sure to check that your forecast is free of errors (i.e. GSF should be GFS) and that your narrative is a bit more free flowing. I'm a huge fan of the discussion of uncertainty in your forecast discussion (don't be afraid to say you're uncertain if you are in the actual forecast section) and I can definitely tell you guys put some nice thought into these forecasts. Keep working on refining that more technical discussion of the dynamics and on your overall composition, and you'll have a nice product for Round 2.


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