Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 160052 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 752 PM EST Mon Jan 15 2018 .UPDATE...
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Issued at 752 PM EST MON JAN 15 2018 WSR-88D radar does show some returns across portions of the area. The first area is near the Bluegrass closer to the lagging 850mb front and you are probably seeing light snow in northern Fleming county at least. There is another area showing up across portions of the lake Cumberland region associated with the lower level front. These may or may not be reaching the ground depending on location. We have had one report tonight in Mt. Vernon of light snow and therefore made some adjustments to hourly POP grids to deal with this. Overall did trend the higher POPs slower to the southeast, as this is really a two part system with the initial front coming through right now into the early evening. Then as we get into the overnight and early Tuesday we will be better alignment with the upper level jet to produce better lift. The slower trend has also lead to far east valleys decoupling and have had to make adjustments to the hourly temperature grids to get a better handle on this situation. Grids have been updated with the current thinking and sent to NDFD.
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&& .SHORT TERM...(This evening through Tuesday night) Issued at 400 PM EST MON JAN 15 2018 The latest surface map features a broad area of low pressure centered across the southern Great Lakes region, with an occluded/cold front aligned south across western Indiana and Kentucky, and a more subtle warm front stemmed southeast into eastern Indiana and southern Ohio. Aloft, cyclonic flow reigns across the north central CONUS, with an upper level low centered across southeastern Minnesota. A sharper short wave, within the flow, is dropping south across the central Plains into portions of the front range of the Rockies. The models are in good agreement through the short term, with the upper level low and trough axis gradually shifting east across the Mississippi Valley through Tuesday night. This will escort the cold front through eastern Kentucky tonight, with much colder air moving in behind the boundary as it departs Tuesday. Light snow will break out across the area tonight, with the models continuing to show a slower trend with the onset. The bluegrass counties will see snow move in this evening, while locations across far southeastern Kentucky may not see any snow until closer to dawn. The weaker batch of forcing will be seen tonight. This is more associated with the passing surface front and perhaps a little mid-level support. Generally, around an inch of snow is expected. As we get closer to dawn and especially during the day on Tuesday, the right entrance region of an upper level jet streak will move in across the region aloft. This will provide more sustained and deeper lift for light snow, particularly along and south of the Hal Rogers Parkway and Highway 80 corridors, where 1 to 2 inches will fall. As such, will continue to advertise storm totals of 2 to 3 inches for southeastern Kentucky, with the Bluegrass seeing 2 inches or less. Any locally higher amounts will likely be in the favored higher terrain locations. There will only be a few degrees difference between lows tonight and highs on Tuesday, with ongoing cold air advection. Readings will range from the mid to upper teens in the west, to the lower to mid 20s in the east. Light snow will taper off from northwest to southeast on Tuesday, with snow showers hanging on the longest in the far southeast. Moisture will remain deep enough Tuesday night to allow for a continuation of flurries. Lows Tuesday night will be in the single digits, although lingering cloud cover will keep temperatures from really dipping despite the fresh snow pack. .LONG TERM...(Wednesday through Monday) Issued at 404 PM EST MON JAN 15 2018 A closed low will have dissipated as it moves eastward into the Ohio Valley during the short term, leaving Kentucky in a sharp positively tilted trough to start out the extended portion of the forecast. This trough will exit during the course of the day, with rising heights but nearly meridional flow expected across the state. This will essentially serve as a north to south highway for which cold air over Canada can transport itself into the state and even portions of the Deep South. By Thursday, the trough will have moved much farther east and we will transition to weaker and more zonal flow to round out the week. By Sunday, a closed low will develop across the southern Plains, quickly shifting eastward. This will lead to lowering heights once more for Sunday into Monday as the low quickly speeds northeast towards the Upper Great Lakes, though this time the pull of air will be from the south, much warmer and moist. At the surface, KY will find itself under high pressure to start the period after the passage of a cold front which will bring decent snow accumulations during the short term. However with the above mentioned upper level flow patten in place, northerly flow will extend from the surface all the way to the upper levels. I.e., cold air will have become entrenched across the state, leading to well below normal temperatures for Wednesday and Wednesday night. As clouds continue to clear out from the departing system in the short term, it is possible that flurries may occur throughout a portion of the day Wednesday, with any moisture from dissipating clouds being located in the dendritic growth zone. This area of high pressure should remain in control for the rest of the week and heading into the first part of the weekend. Models have it taking a southerly path, reaching the Southern Mississippi Valley by Thursday and then tracking east across the southeast states Friday into Saturday. Dry conditions will persist over the Ohio Valley during this time, but winds at the surface will become more S to SW and westerly in the mid and upper levels. This will help to moderate temperatures, with 30s expected on Thursday, and above normal temps in the mid 50s by Saturday. A low pressure system and associated cold front are expected to shift eastward from the Plains towards the Ohio Valley Sunday into Monday, following the greatest height falls and transitions of the upper level pattern. The cold front is expected to traverse the JKL CWA sometime during the day Monday, though timing this far out is still somewhat uncertain. Either way, strong southerly flow ahead of this approaching cold front will no doubt lead to an increase in moisture as well as continued temperature increases. Forecast includes clouds moving into the region as early as Saturday with chances of pops at times starting Saturday night and going into the day Sunday. Highs on Sunday are forecast to reach 60 despite ongoing cloud cover. The main area of precip will come along the frontal passage, overspreading the CWA as we head into the day Monday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) ISSUED AT 634 PM EST MON JAN 15 2018 The TAF sites are starting off VFR late this afternoon, but the sites will deteriorate through the night. This as an arctic cold front moves across the area bringing with it snow through the night into Tuesday. The hi-res models have trended slower and perhaps showing a bit less QPF in the Bluegrass region particularly. The latest radar does have returns in the Bluegrass region late this afternoon and we have started to get reports of light snow at some of the ob sites such as FFT and LEX. Given this started the TAF at SYM with VCSH and then bring more snow in later this evening and overnight. This will slowly spread southeast with the cold front, and then additional help comes later from an upper level jet. Did slow the timing from previous TAF at the eastern sites given some of the trends mentioned above. Thinking generally we will see anywhere from MVFR to IFR conditions with the snowfall. Some sites could go lower if you see a heavier band of snow setup. The conditions will improve by Tuesday afternoon, but did keep VCSH going given the potential for lingering flurries. The winds have slackened at TAF time, but we could see a uptick later this evening into tonight with the front. Winds are out of the southwest and west to start the period and will become west and northwest by the end of the period. && .JKL WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 10 AM EST Tuesday for KYZ044- 050>052. Winter Weather Advisory until 7 PM EST Tuesday for KYZ058>060- 068-069-079-080-083>088-104-106>120. && $$ UPDATE...DJ SHORT TERM...GEOGERIAN LONG TERM...JMW AVIATION...DJ is the U.S. government's official web portal to all federal, state and local government web resources and services.