132 FXUS63 KLMK 101540 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 1140 AM EDT Wed Oct 10 2018 .Forecast Update... Issued at 1140 AM EDT Wed Oct 10 2018 Light showers associated with a warm advection wing are slowly lifting north of the area late this morning. As we move into the early afternoon, expect a relative lull in precipitation. This will be short-lived however as some weak destabilization couples with the approaching strong cold front. Expect a scattered to broken line of showers and storms to develop to our west and move into our area from mid/late afternoon into the evening hours. The best deep layer shear for organization should be along and north of the Ohio River, which is where the SPC Marginal Risk is located. So, could see a few organized storms with a localized bowing segment/severe threat. Overall, instability should be pretty weak given the cloud cover however some peaks at the sun and a steady warm advection component should contribute to destabilization. Will keep an eye on afternoon/evening development, but expect mainly SPS worthy threats with a few localized warnings possible. Otherwise, temps are currently in the mid 70s. Would be inclined to back off the forecast highs of upper 70s low 80s given the cloud cover, but latest satellite imagery shows a few breaks. These breaks combined with a steady warm advection component make the ongoing forecast still reasonable. No changes planned at this time. && .Short Term...(Today and tonight) Issued at 300 AM EDT Wed Oct 10 2018 Regional radars are beginning to pick up on some light echoes across parts of western Kentucky and the Tennessee Valley early this morning. Shower activity is expected to grow in coverage and eventually impact central KY and southern Indiana through much of the morning hours. Should see that activity push out of the region by early afternoon, with some partial clearing possible. Models indicate the atmosphere developing some weak instability in the afternoon, which could help contribute to some isolated to scattered showers/storms. The greater chance/coverage of precipitation will occur during the late afternoon to overnight timeframe ahead of a strong cold front moving in from the west. Instability ahead of the front continues to look weak, generally under 1000J/Kg, due to widespread cloud cover. Deep layer shear will be modest though (0-6km bulk shear 30-40kts), and could contribute to some organized storm structures should enough instability be realized. The current 06z Day 1 SPC Outlook highlights parts of southern Indiana and northern Kentucky in a marginal risk, which is where the best shear/instability will be co-located ahead of the front. Main threats with any strong to marginally severe storms will be gusty winds and small hail. Heavy rainfall will also be a threat in the stronger showers/storms, as PWATs remain high (~2") ahead of the cold front. Winds will switch quickly to the northwest behind the front tonight, and could be gusty at times. Much, much drier and cooler air will advect in from the northwest, ending the long streak of above normal temperatures we've experienced over the past couple of weeks. .Long Term...(Thursday through Tuesday) Issued at 254 AM EDT Wed Oct 10 2018 After some lingering showers in the Blue Grass and Lake Cumberland regions Thursday morning, Canadian surface high pressure will build into the region and provide us with mostly dry weather through Saturday. The possible fly in the ointment will be a fairly sharp upper trough that will swing overhead Friday evening. The trough will primarily produce mid and high clouds with dry air in the low levels thanks to the surface high. However, some rain could make it to the ground so after coordinating with surrounding offices will include a slight chance of precipitation in conjunction with the upper disturbance. Friday morning low temperatures may dip briefly into the upper 30s north of I-64, and a few low, rural cold sinks in southern Indiana could see a bit of patchy light frost. Some very patchy, very light frost could form in southern Indiana on Saturday morning as well if the upper shortwave trough's mid/hi clouds can clear out enough by dawn. The Saturday night through Monday period is not being handled well by the models at all, and there is great uncertainty in the forecast. Generally speaking, though, an upper trough will sweep eastward from the upper Plains through the Great Lakes to the Northeast. Surface low pressure will cross Ontario and Quebec with a cold front trailing southwestward to another low crossing the southern U.S. This southern low may be remnants of former Pacific Hurricane Sergio, and will bring moisture along with it as it interacts with the front and moves through the mid-Mississippi and Ohio Valleys. The end result will be rain chances in the forecast for this time frame, with future forecasts hopefully being able to refine the timing. No thunder is expected. We should then dry out on Tuesday as the upper flow goes zonal and high pressure moves in at the surface. Patchy frost will again be possible Tuesday morning. && .Aviation...(12Z TAF Issuance) Issued at 636 AM EDT Wed Oct 10 2018 Light rain is beginning to spread into central KY and southern Indiana this morning, but is not anticipated to cause any visibility issues this morning at TAF sites. Could see some isolated spots dip down to MVFR cigs as stratus moves in from the south this morning, though the lowest ceilings will generally be west of I-65. Models indicate some clearing behind the ongoing showers by this afternoon, though it will be short lived as a cold front approaches from the west and results in another round of showers and storms. IFR to MVFR cigs/vis will be possible with the stronger showers/storms this afternoon and evening. Winds will also be gusty at times out of the south through much of the day, and will quickly shift to the northwest behind the cold front tonight. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...BJS Short Term...DM Long Term...13 Aviation...DM