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| FLASH FLOOD WATCH for South Central KY, Central/West TN, Central AR, Extreme East TX, and North LA thru Saturday 22 Dec |
Heavy Rain Likely Friday-Saturday, Flash Flooding Possible!
I should mention that even now there are several model inconsistencies regarding the timing of key features which means different model suggestions for the start of rainfall, the end of rainfall, how much rainfall we'll see, and even whether it will be rain the whole time or change to snow. As always, my forecast is based off of detailed analysis of observed conditions, both here and upstream, and constant scrutiny of many computer models/model runs in order to come up with the most accurate forecast possible. I always like to let you know how confident I am about different aspects of my forecasts and, unfortunately, confidence really drops after Saturday. Should conditions evolve unexpectedly then they will be acknowledged and addressed. Now, there are certainly a couple headlines to cover over the next few days so let's get to it:
Friday 22 December:
Temps when you wake up Friday morning temps will be in the low 50's, aided by southerly surface winds around 10-15mph (warm air advection). I think temps will make it to the upper 50's by the afternoon. As mentioned, the big story will be the heavy rain that's expected across the region. We may see a few showers during the early morning as a mid-level jet streak passes over the region but the "main event" will begin in the afternoon. Once it starts it will pretty much be here until Saturday afternoon. Rain will be heavy at times compounding its impact on holiday travelers so be careful and account for heavy rain and wet roads if you're out.
The risk of severe weather is low but I wouldn't be surprised to see a few embedded thunderstorms throughout the day since there is are indications of some instability across the region. This instability will be very weak most likely but strong moisture advection could aid destabilization somewhat. Wind shear values are actually quite impressive as well so that's another reason I think a few embedded cells will be capable of gusty winds and occasional thunder.
The main impacts however will be flash flooding and heavy rain leading to hazardous driving conditions. Current official forecast amounts have between 2"- 4"across much of Central KY, with 1"-2" North of the Western Kentucky Parkway, and higher totals South of it. I think some locations will see slightly higher totals approaching 5", especially near the TN/KY border up to Bowling Green. Rainfall totals like this may lead to flash flooding of streams, creeks, and perhaps roadways and parking lots with poor drainage so, again, be aware of these possibilities if you are traveling.
Temps Friday night thru the early AM Saturday should cool to the mid-upper 40's.
Saturday 23 December:
Rain will still be ongoing Saturday morning. High temperatures will range from the mid-40's in central/western KY to mid 50's along and East of I-75. This is one of those tricky scenarios as there is general model disagreement regarding the location of the cold front. Naturally, areas West of it will be cooler but the trick is determining how fast it passes through the region. Currently I think it will be draped across central KY by early Saturday afternoon allowing substantial heating in eastern parts of the State. Based on strong southerly flow ahead of the front I feel that mid-upper 50's are realistic temps east of the cold front Saturday (model data is suggesting 60's but rain/cloud cover should moderate that somewhat so I adjusted my forecast).
Some model data is suggesting a brief transition from rain to a snow/rain mix as the upper wave passes immediately behind the front and takes advantage of remaining moisture in the atmosphere but I personally think it will remain North of the Ohio River. Even if this were to occur there would be no impacts. Rain will end from West to East as an upper-low finally crosses the region.
Regardless of when the front passes one thing is clear, much colder air will pour in behind it. The coldest air will surge in from the North/Northwest on Sunday but temps overnight Saturday will still make it down to the 30's.
Sunday 24 December Christmas Eve
Sunday morning will be much colder than the previous few days and I think some locations will see temps drop into the 20's. Strong high-pressure will be off to our West and surface wind will be out of the North. This will limit high temperatures for our Christmas Eve to the upper 30's, maybe reaching 40 or so max. This high-pressure at the surface will reinforce the Arctic air moving into the region and will lead to very cold, perhaps sub 20's, temperatures to start the week.
The big thing to focus on for Sunday is a mid-level shortwave trough that is expected to pass over the Ohio Valley. This is where many of the model inconsistencies exist but the consensus for now is that when this wave swings through the area it will be enough to produce light snow showers Sunday afternoon. Indications are that less than a half inch of snow will accumulate, particularly in far eastern KY where terrain may enhance lift. Snow showers with little to no accumulation are also possible along and North of the WK Parkway.
Hopefully Santa reads this forecast because he, and you of course, will need to bundle up for Christmas Eve night/Christmas morning since lows Sunday night will quickly drop to near 20 degrees. Any roadways that managed to receive any moisture may develop slick spots.
Monday 25 December Christmas
Light snow flurries may still occur during the early AM. Temps will still be in the low-mid 20's when we wake up Christmas morning. Highs will eventually reach the low-mid 30's throughout the day under partly cloudy skies. Otherwise not too bad. Everyone enjoy your Christmas!
DKK
