Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 142057 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 357 PM EST Thu Dec 14 2017 .SHORT TERM...
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(This evening through Friday night) Issued at 357 PM EST THU DEC 14 2017 Low stratus has held strong across eastern Kentucky this afternoon in a post-frontal airmass. Temperatures have subsequently held steady with current readings spanning the 30s. Surface ridging building into the lower Ohio Valley and western reaches of the Appalachians will keep light upslope flow in place through much of the night as low-mid level moisture remains trapped beneath a subsidence inversion. Have therefore warmed overnight low temperatures a few degrees from the previous forecast given the greater amount of expected cloud cover. Readings should generally bottom out in the low-mid 20s, with perhaps a few valleys across portions of northeast Kentucky flirting with the 20 degree mark if any breaks in the clouds can occur nearer the core of the surface ridge. Yet another upper trough and associated surface low will rotate through the Great Lakes Friday, keeping below normal temperatures in the offing. Highs look to warm into the mid 30s, resulting in a similar overall feel to Thursday afternoon. The lack of any bonafide moisture recovery and northward displacement of the greatest forcing will negate the threat for precipitation throughout eastern Kentucky. Surface ridging nosing in from the southwest later in the day will keep winds southwesterly and preclude a significant change in airmass. Following what may be a quick valley dropoff in temperatures Friday evening/early night, an increasing pressure gradient downstream of a surface low pushing into the upper Midwest will promote warm air advection spilling into the Bluegrass and Lake Cumberland regions. Temperatures by daybreak Saturday should therefore bottom out a few degrees warmer than those seen Friday morning. .LONG TERM...(Saturday through Thursday) Issued at 322 PM EST THU DEC 14 2017 The extended portion of the forecast begins on Saturday with the upper level pattern transitioning to a more progressive and less amplified flow aloft. With a brief bout of ridging quickly passing through on Saturday. In fact, with southerly flow reengaging on Saturday, high temps will rebound into the 50s with clear skies in place thanks to the mentioned ridging in place. The pattern east of the Front Range displays a northern and southern portion of the jet stream and rather zonal. However, a strong wave over the southern stream develops over the southwest and moves into the lower MS Valley into Saturday night. This feature then lifts northeast into the OH Valley for Sunday morning and into the day on Sunday bringing a modest round of moisture. Another weaker wave tracks across the northern stream into the Great Lakes at this time as well. This will keep a decent round of precip over the area for Sunday and Monday. Concerning the Sunday morning onset, model profiles indicate the possibility of the lower profile wet bulbing due to evaporative cooling to freezing temperatures at the surface leading to a possibility of a sleet and or snow mix for a very brief period of time. However, latest trends have showed a later arrival time of precip, this combined with the time needed for the lower levels to saturate, will likely lead to an all rain event at this time with a few instances of snow mixed in. Rainfall, while still entering this event with dry conditions will accumulated roughly less than a quarter inch. After passage, another weaker wave along the northern stream will pass through the OH Valley on Monday with a slight chance of precip remaining into Monday night. Even so, temps will be above normal for this time with the lack of amplitude in the pattern and will only expect liquid precip. By Tuesday, another wave develops out of the southern stream and lifts northeast bringing another chance of precip into eastern Kentucky but with warmer air in place, this event too will be all rain. Despite some rain expected for Sunday through Tuesday, the lack of consistency in the models leaves more to be desired and the overall dry conditions across the area going into these events will be good chance pops at best. In fact, the super blend cam in dry for the last day of the extended on Wednesday so will go with that solution.
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&& .AVIATION...(For the 18Z TAFS through 18Z Friday afternoon) ISSUED AT 106 PM EST THU DEC 14 2017 Low clouds continue to hold strong in a post-frontal airmass this afternoon. These will gradually lift and scour out later this afternoon into this evening as high pressure builds into the Ohio Valley, but mid clouds will persist tonight before possibly lowering into Friday morning. VFR conditions are however expected to persist through the period at all sites. North/northwest winds of near 5 knots will further diminish this evening and tonight, while backing southwesterly Friday morning and increasing back to 5-10 knots later Friday morning. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...GUSEMAN LONG TERM...SHALLENBERGER AVIATION...GUSEMAN

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