Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 272043 AFDJKL Area Forecast Discussion National Weather Service Jackson KY 443 PM EDT FRI MAY 27 2016 .SHORT TERM...(This evening through Saturday night) Issued at 349 PM EDT FRI MAY 27 2016 Afternoon showers and storms have developed as expected mainly near the VA/TN border this afternoon. So far these showers have struggled to become thunderstorms, and thus far little to no lightning has been detected on the NLDN/ENTLN networks. That said the MRMS VII product suggest only hints of ice in the far east showers and that has been the area with the only cloud to cloud strike so far. Either way will keep wx grids going with isolated to scattered thunderstorms given the decent CAPE and steep lapse rates. However given the fact that there is such weak steering flow and no shear these storms will have a up hill battle becoming organized. These showers and storms will be mostly diurnally driven and are expected to subside through the evening hours. After this did keep some valley fog in the forecast and this would be enhanced in areas that do manage to see a storm For Saturday the focus shifts to the west where a 500mb wave across the lower Mississippi River Valley that will eject NE into western KY. This will bring PVA across western and central KY by Saturday afternoon. This wave is also translating to the 700mb level as well and will advect reasonable vertical velocities across central KY. Right now will keep shower and storm chances isolated to scattered through the day on Saturday with better chances overall residing in the NW portions of the CWA. While the weakly sheared environment and 700mb cap will be the caveat; steep low level lapse rates, decent mid level dry layer, and MUCAPE around 2000 to 2500 J/kg could be enough to get a isolated marginally severe storm. The main risk would be gusty winds and small hail Saturday night we should see most of the storms subside as we loose the heating. That said areas that see storms and deeper valleys will have another opportunity to see patchy fog. After this the GFS remains more robust with bringing weak PVA/western wave influence and moisture from the potential tropical disturbance. Meanwhile the NAM/ECMWF seem a bit more reserved with this thought. Therefore toward dawn kept pops isolated coverage and mainly in the far east Temperatures in the short term remain above normal with highest temps forecast in the far east. .LONG TERM...(Sunday through Friday) Issued at 400 PM EDT FRI MAY 27 2016 The period is expected to begin with a tropical disturbance along the South Carolina or Southeast US coast with a ridge extending west toward the Mid Atlantic from the Atlantic. Meanwhile a shortwave trough is expected to be moving across the lower Ohio Valley region at that point. Early in the period, the tropical disturbance is expected to meander a bit inland. The strength of the ridge to its north and northeast determining how far west the disturbance gets and how closely it approaches the area before being drawn north and then northeast by the shortwave trough moving through the Ohio Valley and Great Lakes region. This track would take the disturbance toward the mid Atlantic and Northeast states from Sunday night into Monday night. Model uncertainty remains in how close the tropical disturbance would get to the region at the start of the period and if it gets as far west as the 12Z GFS operational run it might bring a bit better coverage of convection than is currently forecast for Sunday into Sunday evening. At this point, the main forcing on Sunday will be the approaching shortwave and scattered coverage is expected at this time. Rather weak ridging should move across the area from Monday night into Tuesday night. The atmosphere though may not be completely capped and convection may be able to break the cap over the Cumberland Plateau or mountains near the VA border and or nearby portions of East TN or SW VA and outflow into the VA and TN border counties and lead to some isolated convection for Tuesday afternoon and evening. Height rises are anticipated from Tuesday night into Wednesday so Tuesday night should remain dry and Wednesday could also possibly end up dry. However, models bring a weak disturbance across the region and convection is progged by both the GFS and ECMWF 12Z and prior runs. A trough will approach the area from the west to end the period. An associated cold front should then approach the area from the west Wed night, with the front possibly crossing the area by Friday. More organized convection is expected along and in advance of the cold front. Convection will remain a possibility through the end of the period as the 500 mb trough axis may not cross the area before the end of the period. High and low temperatures should average above normal through the period, although highs on Friday might be near average depending on the timing of the cold front. Overall, temperatures should not be out of the ordinary for late May into early June. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) ISSUED AT 138 PM EDT FRI MAY 27 2016 All sites this early afternoon hour are remaining VFR with some scattered CU across the eastern KY. We are seeing some isolated showers developing along and near the VA border this afternoon and this will become the aviation concern this afternoon. Right now the issue is the isolated to scattered nature leads to VCTS confidence at best. Most sites are not expected to get nearby storms till generally after 20Z to 21Z. This could lead to brief lowering in CIGS and VIS under heavier storms. Overnight the concern becomes patchy valley fog and any location that gets enhanced moisture from storms. Right now kept most sites VFR but southern sites of SME/LOZ did add MVFR VIS. Given no steering flow and high pressure no issues with winds are expected. && .JKL Watches/Warnings/Advisories... None. && $$ SHORT TERM...DJ LONG TERM...JP AVIATION...DJ

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