Current conditions show the slow-moving storm that brought heavy snow to the northern Rockies this past weekend now located over Ontario. A secondary low has developed along the cold front and is located over the Midwest. Two vorticity maxima can be seen in those same areas that are associated with the surface lows. The strong ridge over the SE has kept much of the eastern United States dry and well-above normal recently, but the approaching system should bring an end to the 80+ degree weather, for many cases until next spring.
Widely scattered showers and thunderstorms will overspread Kentucky starting this evening and continuing overnight. Aside from far western KY, severe weather is not expected across KY due to limited instability and the nocturnal frontal passage. Rainfall amounts will be less than 0.25 inches although higher amounts may occur in thunderstorms. Precipitation will end from west to east across the state on Thursday as high pressure builds into the state. High temperatures Thursday will remain in the 60s due to cold air advection bringing cP air into the state.
For Friday, a series of shortwaves will deepen the trough over the Great Lakes and bring a reinforcing shot of cold cP air to Kentucky for the first part of the weekend. Highs Friday and Saturday will be from 60-65 degrees and lows will dip below 40 in a few of the colder spots like Frankfort. The passage of the trough will be dry due to a lack of low-level moisture. Temperatures will rebound to near normal (70/50) Sunday and into early next week as the flow aloft becomes more zonal and the surface high moves to the east, putting KY in the return flow of the high. A weak and dry cold front is expected to cross the state early next week. The next chance of precipitation could occur later next week. Some of the GFS ensemble members show the possibility of a cut-off low over the central Plains later next week while others show a deep open-wave trough. However there is disagreement between the European model and GFS in the 8-10 day means. This is somewhat reminiscent of the recent weekend snowstorm in Montana which was originally modeled in the 8-10 day period as a cut-off storm in the central Plains. Instead, it remained far north of what was originally modeled and stayed in the northern Rockies. It will be interesting to see if the models once again move to a more progressive pattern in the coming days.
The CPC seems to agree that rain in the central U.S. is likely with this next system, as the 6-10 day forecast has above average precipitation in that region.
