Rain. It's something we've not seen a measurable amount of in Louisville for 16 straight days now. This is the driest stretch of weather we've had since 2008 and, should we not see any rain over the airport this afternoon, could surpass even that. We're still about a half inch ahead on rain for both the month and the year because of the nearly 3" deluge we had on September 11th. But your yard, plants, and crops need moderate amounts of rain at consistent intervals, not a deluge followed by 2 weeks of nothing.
A weak disturbance moving through this afternoon will allow for summer-like isolated showers and storms to develop this afternoon with summer-like highs in the low to mid 80s. The HRRR, NAM 4km, and RPM are pretty consistent with this happening after 2pm or so and the coverage of rainfall in our 29 counties should remain below 20% or so. Most folks will be staying dry today. Not good news if your yard (like mine) is turning brown.
After a few sunny and continued warm days to start the workweek thanks to high pressure, we'll be watching a well-advertised cold front move through. The timing of this has become more consistent and concrete on the models today so confidence is growing that late Thursday night into Friday morning will be the period we'll see a storm chance. At this distance out it's still possible that this will delay a little bit so we'll watch that. We'll also watch the strength of the storms associated with this since it will be a powerful cold front. Like yesterday, it's still looking like the storms will weaken considerably by the time they arrive overnight thanks to lessening instability and a siphoning off of moisture ahead of the front. The maximum upper-level wind strength will lag well behind the front but there may be enough ahead of it to add concern for some of our western counties. We'll keep tabs on that through the week.
Highs by Saturday will be in the upper 60s behind the front. The reinforcing shot of cool air in the form of a cut-off low that the models were advertising late last week for next Monday has disappeared for now since the trend has been to make the pattern in Canada a bit more held together and progressive. There's obviously still time to iron this out but the trend is to make next weekend's cool snap a short-lived one.
By the middle of next week something begins to happen to our north. Both the GFS and European models are showing cold air pooling up there, lots of it. The GFS is even cooler than the Euro you see to the right but at this distance out in time it's not that important. What's important to know is that the Arctic Oscillation (AO) trends down sharply during this time next week, further adding fuel to the fire that a collection of cool air will be allowed to plunge down into that area. But will it eventually make it down to the US, and more importantly, to Kentuckiana? That remains to be seen since the NAO and PNA are both fuzzy right now for that timeframe. Those two oscillations, especially the PNA though, will help us to determine whether this cold air can carve out a trough over the East US. The latest operational run of the GFS has the right blocking setup for this cool air to plunge toward us (no snow, too early) around the 10th of October. But that's just one run of one model. The Euro can't see that far out yet. Something to track indeed.