NOTHING LIKE A COLD FRONT...
There's nothing like a cold front to change the game. Sunny skies went to stormy skies Tuesday night and by Wednesday the oppressive heat and humidity that scalded the region was broken, reduced to nothing more than a memory. One that's hard to forget though as highs Tuesday reached as high as 99 in Iowa City. As far north as Dubuque readings hit 96. In Lowden, Iowa...long time NWS coop observer Steve Gottschalk reported a high of 97, but with the extreme humidity the heat index reached 109 miserable degrees.
While the ensuing thunderstorms did produce some welcome rains, they were quite spotty. As you can see, the bulk of it fell in a 60 mile wide band between Iowa City and the NW side of the Quad Cities. In Iowa City no rain fell on the north side of town while further south at the airport .33" fell. At the NWS office in NW Davenport, .36" was measured but on the south end of town at the Moline airport, nothing at all. My point is that even in the areas where rain fell, it was very hit and miss.
The storms ushered in the cooler and drier air that made for a more comfortable day Wednesday. Similar weather is anticipated Thursday although temperatures will likely be a few degrees warmer. That implies highs in the upper 80s to perhaps low 90s in the south. Dew points will still be low and that will be our saving grace allowing no appreciable heat index.
Friday and Saturday the forecast gets more challenging regarding the impacts of clouds, precipitation, and temperatures. This is undoubtedly when the bulk of our active weather will occur. The first (low) chance of rain comes Friday as the remnants of an MCS (thunderstorm complex) approaches from the west. Some showers or storms may just clip my far southwestern counties but the bulk of the system now looks to remain just west and south, closer to the ring of fire. However, the blow off clouds could still reach us and have an impact on temperatures with the GFS only showing upper 70s and low 80s.
The EURO which had shown clouds and rain, especially in eastern Iowa has now reverted to a drier and warmer solution due to less clouds. Here's what it shows...highs well into the 80s.
Friday night and Saturday morning is the most likely window for storms in my area. That's when a ridge riding disturbance and warm air advection nudges a warm front into the area. As the low level jet intensifies Friday night thunderstorms should blossom out west and then move east into the region, especially after midnight. Some may produce gusty winds and heavy rain, particularly over my far western counties. The remains of these storms (a potential MCS) may linger into Saturday morning. Currently SPC shows only a marginal risk of severe weather Friday night but that is subject to change.
Saturday afternoon the focus will be on a fairly strong cold front that's due to arrive late in the day. The big question here is centered on the timing which will determine the amount of instability and thunderstorm potential. The GFS does show some healthy CAPE.
The EURO is not as robust but still shows healthy instability.
.However, negatives such as a cap and the effects of morning convection are issues that could hinder the overall storm environment. Models have trended a bit slower with the cold front the past 24 hours and that works in favor of storm development as it allows the atmosphere to recover and destabilize after the decay of morning convection. As it stands now, the best chances for storms Saturday afternoon or evening looks to be near and southeast of the Quad Cities. Even so, confidence has increased a bit that most areas will at least have a shot. Still some time to get that resolved. Here's what the EURO and GFS are suggesting for rainfall totals Friday night through Sunday morning.
Come early Sunday morning, our latest cold front is well to to the south allowing winds to switch to the north. That allows a pleasant air mass to settle in keeping temperatures and humidity at very comfortable levels through Tuesday. Here's what the NBM (national blend of models) shows for highs through July 3rd. Look at that 77 Sunday!
That's a wrap for now, enjoy what's destined to be another warm but nice summer day ahead. Roll weather...TS