301 FXUS63 KLMK 091615 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 1115 AM EST Sat Mar 9 2019 .Forecast Update... Issued 1100 AM EST Sat Mar 9 2019 Elevated convection developing along and ahead of the warm front is now in play for a few locations west of I-65. Leading band runs from near Jasper to Elizabethtown to Lake Cumberland, with another band just getting into the Bowling Green area and seemingly aligned with the warm front itself. POPs really ramping up for most of the area in the next hour or two, pretty much on schedule with the previous forecast. Thunder potential seems to be well handled, but we will push an update to legacy forecasts soon, mainly to clean up wording. Hourly temp curves have been adjusted in the hi-res products to show a sharper and slower warm front. Late afternoon SVR potential is largely unchanged, as it remains conditional on getting sfc-based instability. still seems like we can do that mainly south of I-64 and west of I-65, with a little wiggle room in line with SPC slight risk. && .Short Term...(Today and tonight) Issued at 308 AM EST Sat Mar 9 2019 Currently, a solid stratus deck resides over the region with temps sitting in the 30s to low 40s. Seeing some patchy fog mainly across our southern half of the CWA. For the most part, it seems transient on webcams and obs are mostly ranging between 1 and 5 SM. A few spots have gone below a mile, but not planning any special mention at this time. Will continue to monitor. ...Breezy with Strong to Severe Storms Possible Today... A strong and negatively tilted shortwave trough is expected to eject out of the Plains and into the Great Lakes region later this afternoon into this evening. The associated ~990mb surface low will follow the same trajectory. As this occurs, a warm front currently situated over southern TN will lift north through our CWA by this evening, establishing a weak but notable warm sector over the region. Although the warm sector will be short-lived, it will be accompanied by a very impressive kinematic setup. The exit region of strong mid/upper level jetting will overspread the region later this afternoon into the evening, creating strong forcing and low level jet response around 70 knots! The overall setup will create a situation where several rounds of convection will move through the region from later this morning through late this evening. Initial convection this morning into the early afternoon will likely be elevated in nature given a strong inversion near the surface, however as we move into the afternoon and especially the early evening hours, storms will likely be able to become more surface based. Bottom line, the severe threat gradually increases through the day. Instability remains the big question mark, and there are several initial obstacles to overcome to even get to the point where meager surface based values will be possible. 1.) Getting the warm front north this afternoon. 2.) Overcoming late morning and early afternoon elevated convection, including heavy sky cover. Do think we'll be able to overcome these as models agree that strong advection should win out by afternoon and evening. The latest data continues to hint at a weak and narrow instability axis developing by late afternoon/early evening and moving into area mainly along and west of the I-65 corridor. This instability axis will generally be around 500 J/KG of SB CAPE or less, but there could be a few pockets greater than 500 J/KG, especially down toward the Bowling Green region. Generally, the warm sector will be characterized by peak temps reaching the low to mid 60s, with peak dew points mostly in the 55 to 60 degree range later this afternoon into the evening. The intense low level jet combined with the strong and veered mid levels produces some long and looping hodographs. The resulting SRH values (both 0-1 and 0-3km) will grab your attention, with values that would easily support rotating discrete cells in the presence of strong enough updrafts. In addition, any linear segments will likely bow out along with potential for mesovortices. Bottom line, shear isn't in question, and really hasn't been all cool season as you might expect. Hi res models seem to depict mostly a combination of discrete cells and linear segments for storm modes, which seems to fit the shear profile and weak instability. In a nutshell, here's what we're thinking for specifics of the potential severe setup: * Timing: 2pm - 10pm * Storm mode: Mix of linear/bowing segments and discrete storms * Threats: Straight-line damaging winds, heavy rainfall, and hail, with an isolated tornado threat, mainly west of I-65 and across southern KY. * Confidence: High if we are able to destabilize Given multiple rounds of showers and storms, can't rule out some isolated flooding problems in addition to the other threats. Any heavy rainfall will be brief as storm motion will be quite fast which should be the main limiting factor. Will message as a threat, but overall have most spots around 1 inch of QPF with locally higher amounts. As far as the ongoing Wind Advisory headline goes, confidence is fairly low. It seems that by the time we get our warm sector established to the point where some of the stronger winds aloft can be mixed down, we'll be under the threat for convective winds. So, not really sure whether the Wind Advisory helps messaging at that point or is just confusing. The bigger gradient wind issue may be with post cold frontal winds as lapse rates steepen and strong low level jetting is still around through the overnight. Will likely leave the afternoon/evening Wind Advisory as is for now, but not sure the gradient winds out ahead of storms will be strong enough given the initial low level inversion. .Long Term...(Sunday through Friday) Issued at 250 AM EST Sat Mar 9 2019 ...STRONG STORMS POSSIBLE MID-LATE NEXT WEEK WITH POTENTIAL FOR MORE HEAVY RAINFALL... Sunday through Tuesday Night... Quiet period of weather is expected in the Sunday through Tuesday time frame. Surface high pressure is expected to dominate the weather pattern over the Ohio Valley with a general quasi-zonal flow aloft. Highs during the period will warm into the lower to middle 50s with overnight lows in the upper 20s to the lower 30s. Lows Tuesday night should average a little milder with mid-upper 30s expected. Wednesday through Friday... By mid week, the upper pattern is forecast to become amplified once again with a sharp upper trough axis moving out of the western US. Downstream ridge is expected to expand a bit which should result in much warmer conditions for Wednesday. We may see a few light showers early Wednesday as the ridge builds, but by and large Wednesday looks to be dry, but breezy. Highs look to warm into the mid-upper 60s west of I-65, with lower-mid 60s over our Bluegrass region. By late Wednesday, sharp upper trough looks to take on a negative tilt over the Plains. This will result in lee side cyclogenesis east of the Rockies with a low pressure center rapidly moving from the southern Plains up into the Midwest. The overall track of this particular system is a bit more west than this weekends system. Arcing cold front will push into the region early Thursday. However, as this front heads east, it looks to become aligned with the flow aloft which would allow it to slow down considerably and perhaps stall a bit over the Ohio Valley. Showers and thunderstorms (some strong) are likely across the region on Thursday and continuing into Thursday night. The front does look to make some eastward progress by Friday resulting in a nice drying trend to end the week. Main concern with the Thursday system is the potential for heavy rainfall. We'll have a deep moisture plume directed off the Gulf and multiple perturbations will likely bring waves of precipitation to the region. An inch or two of rainfall looks likely with this system and that could result in some hydro issues across the region. Highs Thursday should warm into the mid-upper 60s. Cooler air will push in late Thursday and early Friday behind the front with readings falling into the 40s by Friday morning. Highs Friday will likely top out in the upper 40s to the lower 50s. && .Aviation...(12Z TAF Issuance) Updated at 627 AM EST Sat Mar 9 2019 A warm front remains south of the TAF sites at this hour, and seeing widespread IFR as a result. In addition to the ceilings, visibilities will likely vary between IFR/MVFR through much of the morning, but will improve as the warm front begins to lift north. Further north at HNB/SDF, it should be mainly ceiling restrictions with less in the way of vis restriction. The warm front will lift north over the region later this morning through the afternoon with steady E winds becoming SE and S through the day. Magnitudes will increase and become strong by afternoon with sustained 15 to 25 mph, gusting between 30 and 40 mph. Ceilings should rise back to low MVFR by late morning or early afternoon, along with widespread rain and scattered storms overspreading the area. Expect MVFR ceilings/vis to prevail for much of this time, but will also likely go back to IFR periodically in stronger showers and storms. A few severe storms are possible later this afternoon into the evening. A strong cold front moves through by late evening with surface winds veering to a SW component and still gusting. Winds won't be quite as strong but could still see some 25-35 mph gusts through the end of the TAF cycle. MVFR ceilings will quickly clear out overnight behind the strong cold frontal passage. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...Wind Advisory until 10 PM EST /9 PM CST/ this evening for KYZ023- 024-026>028-053-061>064-070>076. && $$ Update...RAS Short Term...BJS Long Term...MJ Aviation...BJS