Friday, May 3, 2013

Rainfall This Weekend Could Create Flooding Problems

If you we're singing the old song "Rain, rain, go away..." as this week's first post mentioned you know that the song also says "come back another day" and it looks like rain is most definitely ready to return to the area. After a warm and sunny first half of the week with high temperatures in the 70s and 80s a big change awaits us in the form of days of rainfall and temperatures in the 50s and 60s. This all moves in late this evening after a cloudy but warm day today; rain will stick around through Sunday night/Monday morning. Some indications suggest the weather not clearing up again until Wednesday. If you have plans outside this weekend, consider a back up plan because the weather will not be cooperating. Saturday and Sunday could will likely be considered "total washout" kind of days. Traveling north to Louisville for the Derby and associated festivities? Saturday should bring nearly continuous rainfall to that area as well so plan accordingly.

This major swing in the weather pattern for this weekend is all thanks to a rare May cold-core low in the mid-south. I say rare because of the amount of cold air in the upper-levels of the atmosphere that this system has with it this far south this time of year. As of this morning light snow was falling as far south as Arkansas, a state which has never had a location officially report measurable snow in May. That should give an indication of just how rare this system is. While we will not see any issues with very below normal cold or snow we will still have our fair share of problems with the system. This in the form of a lot of rainfall. This will set-up because this cold core low pressure system is becoming cut-off from the main flow (the jet stream) in the upper parts of the atmosphere thus leaving nothing to push the system along and move it out of our area. Thus the system will sit over the mid-south for 2-3 days pumping in a good deal of moisture and subsequent rainfall to south-central KY. Though there could be a few breaks in the rainfall Saturday night/Sunday morning is looks more likely that rainfall will be continuous from tonight until Sunday night!

The next question is how much rainfall? That is a good question that will likely vary to some degree across central Kentucky. A 2 inch rainfall will be widespread but some locations could see 2-4 and it is these locations that are currently just too difficult to pinpoint as the models have moved the axis of heaviest rain back and forth across the region. Moral of the story is that heavy amounts of rainfall are likely to occur of the south-central Kentucky region in the coming 3-4 days with 2-4 inches of rainfall a very real possibility. Some localized areas could see rainfall amounts greater than 4". The ground is still likely to be moderately saturated from last weeks heavy rainfall and thus flooding could become a real concern during the next week. A flood watch has already been posted to our south in central Tennessee.This system will spread the amount of rainfall over a couple of days and thus flash flooding is somewhat of a limited concern. River/stream flooding early to late week next week will likely be a larger concern especially in areas where rivers are still running relatively high from last weekends rainfall. Thus be aware of the flooding potential during the next week especially in low lying areas that often flood along rivers and creeks. Below is a map of the current forecast total precipitation from the National Weather Service: Weather Prediction Center which indicates 2.5 to 4 inches of rainfall across south-central Kentucky over the next 3 days.

Daily Forecasts:

Today: Cloudy to mostly cloudy with a high near 77.

Tonight: Rain will become likely after midnight with temperatures dropping to the low to mid 50s by morning.

Saturday: Rain, rain, and more rain. A steady rain will continue all day with one day rainfall totals in the 1-2 inch range. Temperatures will remain steady in the mid 50s.

Saturday Night: The rain will continue though some breaks will become more possible with temperatures overnight remaining in the low 50s to near 50.

Sunday: Rainfall is expected to continue though a few breaks will be possible. Total one day rainfall will be in the 1-2 inch range. Highs will struggle to climb with an expected high in the upper 50s to near 60.

Sunday Night: 50% chance of rainfall as it will become more scattered in nature. Low temperatures will remain in the low 50s.

Monday: Cloudy with a 40% chance of scattered rain showers. Highs should manage to return to the mid 60s.

Forecaster: Ryan Difani

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