Area Forecast Discussion
Issued by NWS Jackson, KY

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194 FXUS63 KJKL 150520 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1220 AM EST Sun Jan 15 2017 .UPDATE... Issued at 1030 PM EST SAT JAN 14 2017 Isolated to scattered light rain showers are continuing to linger across the east and southeast, as the cold front slowly sinks south. The last several runs of the HRRR also suggests a few showers lingering into the overnight in the south as the boundary drifts towards Tennessee. As such, have freshened up the POP trends through the overnight. Where showers are not occurring, still expecting patchy fog/drizzle to fill in overnight as plenty of low level moisture remains in the lower portion of the boundary layer, and gradual cooling occurs. Updates have been sent. UPDATE Issued at 639 PM EST SAT JAN 14 2017 Widespread rains will exit eastern Kentucky in the next hour or so. Have freshened up the hourly POPS to reflect the latest radar trends. Cooler air is making its push behind the departing wave, with northwest winds engaging once again. Current temperatures range from around 40 north of I-64, to around 60 in the valleys bordering Tennessee and Virginia. Forecast lows look on target, and will merely update the diurnal drop off through the night, based on the latest trends in observations. Once the widespread rain ends, expect some patchy drizzle/fog to take its place through the night. Updates will be sent shortly. && .SHORT TERM...(This evening through Sunday night) Issued at 335 PM EST SAT JAN 14 2017 A front which has been wavering across the forecast area today, will push off to the south tonight as a wave of low pressure moves off to the east. Rain will be widespread across the area into early evening, but with the front pushing into the TN valley tonight, rain chances will diminish. The front will stall and begin making its way back north on Sunday as surface high pressure moves from the eastern Great Lakes into New England. As the front shifts back north the threat for showers will return Sunday into Sunday night. Colder air will push into the area in the wake of the front tonight, with low temperatures in the 30s across the northern part of the area, and lower to middle 40s in the south. The temperature range will not be as great across the area on Sunday as it was today. Highs on Sunday will range from the lower 40s north, similar to today, but in the lower 50s south, or about 10 degrees cooler than today. With the front pushing back north Sunday night and cloudy skies temperatures will not fall much, with lows upper 30s north to middle 40s south. .LONG TERM...(Monday through Saturday) Issued at 335 PM EST SAT JAN 14 2017 The period is expected to begin with an upper ridge of high pressure centered over or near the Caribbean and extending into the Southeastern Conus, with another ridge extending into the west coast of the Conus with an upper level trough extending from Central Canada through the Northern Plains south to the Central Plains and Four Corners region and then southwest to Baja region. Within this trough, the model consensus is for a closed low over western OK or southern KS. At the surface, an area of low pressure is expected to be centered over the OK/KS area with a warm front extending east into the TN Valley region and the Southeastern states. With the axis of the upper level ridge extending into the OH Valley at the start of the period, a relative lull in shower chances should be featured at the start of the period. However, by Monday night the axis of the ridge moves east and the closed low/shortwave and sfc low initially over KS/OK should reach the mid MS Valley region. Meanwhile, the warm front and associated isentropic lift should increase as the ridge moves east, leading to increasing moisture and lift across the Commonwealth by Monday evening and into Monday night and good chances for showers. The surface low should track into the Western Great Lakes region while the weakening upper low/shortwave begins to interact with a northern stream shortwave. Models handle this differently as well as some of the individual shortwaves ejecting northeast from the Four Corners region by the Monday night period and timing uncertainties increase. The surface low should continue tracking across the Great Lakes on Tuesday as the upper level ridge axis and the cold front moves across the Commonwealth. The low level jet should increase by Tuesday ahead of this front and some limited generally elevated instability should also exist at some point. Since the boundary should also be moving through during the day, temperatures should generally reach the 60s with dewpoints in the 50s, slight chance of thunder has been included on Tuesday. With the uncertainty with the interaction of the northern stream and timing of individual waves in the southwest flow it is possible that chances for thunder might need to extend into Tuesday night for some of the southern or southeastern portions of the area. However, chances for thunder have been held at slight chance due to the timing uncertainties. Chances for showers will linger into Tuesday night and as late as early on Wednesday especially in the east as the boundary and upper level trough axis move through. Confidence decreases even more from mid to late week as a portion of the trough may hang up over the Four Corners and Baja region and the models generally have a lead shortwave ejecting northeast as well. Differences with a trough nearing the Pacific northwest likely are lading to different timing of the shortwaves being ejected northeast. The ECMWF is quicker with the lead wave and would offer a wetter solution Wed night into Thu compared to the current dry forecast. The models then bring the last bit of this trough across the area on Thu night into Friday evening. Due to the timing uncertainties, pops were carried most of the time from mid to late week other than on Wed night and Thu. At this time, systems are rather progressive and individual rounds of rain appear to be on the moderate to possibly heavy side. This pattern will still need to be monitored as even the current forecast rainfall would probably lead to at least elevated water levels on downstream river points sometime during the period. What is more certain is that temperatures through the period will remain above normal and at times well above normal as 850 mb temps are forecast to remain well above 0C for the period. Highs during the period are expected to average in the 15 to 20 degree range above normal, if not more on a couple of days, with overnight lows averaging about 10 to 20 degrees above normal. Some of these days could also flirt with record high temperatures, mainly Tue and perhaps at the end of the period. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) ISSUED AT 1220 PM EST SAT JAN 14 2017 The surface cold front has likely made it south of the region with winds out of the NW this hour. There are still a few showers along the VA border otherwise fog, low CIGS and drizzle remain the concern overnight. Right now most TAF sites are close or exceeding airport mins and would suspect that to remain the case through mid morning to early afternoon. After this would suspect some improvements to MVFR CIGS based on much of the sounding guidance before dropping again in the evening hours. Also rain showers will be on the increase particularly across the northern TAF sites. The winds will remain light through the TAF period, and will start off out of the NW and come around to the NE to round out the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GEOGERIAN SHORT TERM...SBH LONG TERM...JP AVIATION...DJ

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