Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 280937 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 437 AM EST Tue Feb 28 2017 .SHORT TERM...(Today through Wednesday) Issued at 254 AM EST TUE FEB 28 2017 Broad mid/upper level flow remains out of the southwest this morning. An embedded shortwave is noted on water vapor imagery, pushing east/northeast across the mid Mississippi region this morning. This is already helping to spark some shower and storm activity off to our west this morning across western Kentucky and western Tennessee. Hi-res models continue to have this activity expanding as it moves east this morning with showers a sure bet for the area by late morning into the early afternoon hours. For this reason, will continue with categorical pops. Instability will remain all elevated through the day, so no severe threat anticipated with this early activity. As the shortwave exits to the northeast this evening, it looks more likely we will see a lull in shower/storm activity through the evening hours. Southwest flow will continue into tonight with temperatures holding steady or even coming up a few degrees overnight. This will keep lows tonight near 60 or higher. A shortwave trough will push across the great lakes on Wednesday with a surface low tracking across the southern lakes. This low pressure will drag a strong cold front east across Kentucky during the day. Still lots of uncertainty with the speed of this front as it crosses the area on Wednesday with the 00z NAM maintaining its slower solution, while the 00z GFS maintains the faster solution. The other differences in the models stem around the surface instability available with this system. NAM continues to be plenty unstable during the afternoon, while the GFS remains very meager with its instability. ECMWF remains in between the two, but continues to lean towards the GFS solution. While instability is still in question, the amount of shear is certainly not. Strong/deep layer unidirectional flow remains in place through the day Wednesday. This would support a damaging wind threat if storms can get going. For this reason, SPC has expanded the enhanced risk of severe storms across eastern Kentucky this morning. Despite the expansion, confidence hasn`t increased all that much, as we will also have a good deal of cloud cover potentially limiting instability. With the shear being so strong, its possible it may overwhelm whatever instability is there also limiting storm organization. Either way, this is a tricky forecast surrounding the severe weather threat. Its best to stay updated on the latest changes as we head through the day today. At this point, it certainly looks like it could go either way with the severe threat on Wednesday. Despite the uncertainty in severe chances, measurable rain is a good bet with the frontal passage, so will maintain categorical pops again. PW`s will also be quite high across the area today through Wednesday and could lead to some heavy rain at times and potential for localized flooding. As mentioned in earlier discussions, the PW`s will be near the 99th percentile for this time of year, so certainly well above normal. Temperatures will spike around midday Wednesday before the frontal passage brings quickly falling temperatures through the late afternoon and evening hours. .LONG TERM...(Wednesday night through Monday) Issued at 437 AM EST TUE FEB 28 2017 A cold front will be exiting southeast of the area as the period starts. The GFS and ECMWF have it far enough away that precip is already finished. The NAM is slower, and still has some showers in southeast KY Wednesday evening. With the GFS and ECMWF in better agreement at a longer time range, prefer to give them more credence. Have used mainly 20-30% POP in the southeast part of the area to allow some minimal weighting for the NAM. Much colder air arriving behind the front will limit the diurnal temperatures rise on Thursday, even with clouds breaking up. Another cold front is expected late Thursday night as a weak, fast moving storm system sweeps by to our north. Moisture will be very limited, but forecast soundings in the NAM and GFS show some potential for snow showers with the arrival of the colder air, and a 20% POP was carried in our northern and eastern counties late Thursday night into Friday morning. Canadian high pressure with the cold air mass then builds in on Friday, and holds on with fair but cool weather into the weekend. The high shifts to our southeast by Saturday night, and warm air advection returns. This is followed by moisture advection Sunday night and Monday, well in advance of the next cold front, and along with it another potential for showers. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) ISSUED AT 1250 AM EST TUE FEB 28 2017 VFR conditions will be seen to start the period and will last through daybreak Tuesday morning. Clouds will be on the increase through the morning hours. A complex of showers and perhaps a few embedded storms will move across the area from late Tuesday morning through the afternoon hours. At this point, thunder chances are fairly low, so only planning to include some VCTS at KSYM, as instability is lesser to the south and east. Skies will lower to MVFR by this evening as the rain showers depart and that will likely carry into tonight. We will see a lull in rain shower activity through the evening hours. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...KAS LONG TERM...HAL AVIATION...KAS

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