880 FXUS63 KLMK 240546 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 1246 AM EST Wed Jan 24 2024 ...Updated Aviation Discussion... .Forecast Update... Issued at 751 PM EST Tue Jan 23 2024 Main concern early this evening is with some patchy dense fog we are seeing along and north of the I-64 corridor. Visibilities have been bouncing around between 1/4 and 1 mile across our northern tier, and between 1 and 2 miles down to the I-64 corridor early this evening. These reduced visibilities are an advection type of fog given the cold ground temps, with milder airmass overspreading. Expecting some slow improvement over the next few hours, however confidence is fairly low on just how much, if any, improvement will occur. We aren't far from needing a Dense Fog Advisory across our NW, but the bouncing visibilities are mitigating that at the moment. For now, have issued a Special Weather Statement, and will continue to monitor through the evening. && .Short Term...(This evening through Wednesday) Issued at 255 PM EST Tue Jan 23 2024 ================================================================= Key Messages: * Periods of rain through Wednesday * Chances for embedded non-severe thunderstorms late Wednesday ================================================================= First wave of showers weakening over the Ohio Valley under shortwave ridging aloft. Plenty of pooled low-level moisture near a quasi- stationary front will leave persistent low clouds and even a bit of drizzle or light rain into the evening. Overnight the next shortwave, currently over Texas, will lift NE and a 50 kt low-level jet will bring another slug of moisture into the Ohio Valley before dawn on Wednesday. Look for widespread rain for much of Wed morning, with additional QPF approaching 1 inch west of I-65. Heaviest rain axis will be to our west, so this rainfall will mainly prime the soil for the later waves yet to come. That wave will lift out around midday, and another break in the action is possible especially over southern Indiana and west-central Kentucky. By late afternoon/early evening, another impulse lifting out of the ArkLaMiss region will bring another batch of rain. Model soundings show a fairly deep saturated and moist adiabatic environment, but just enough instability to support some embedded thunder. However the lack of sfc-based instability and modest wind fields will keep any svr potential at bay. Temperatures will run solidly above normal through the period, with steady or slowly rising temps after midnight tonight, and highs pushing 60 on Wed afternoon. .Long Term...(Wednesday night through Tuesday) Issued at 300 PM EST Tue Jan 23 2024 ================================================================== Key Messages: * Temperatures in the low 60s for Thursday, 50s for Fri-Sat * Warm with widespread soaking rains Wednesday night and Thursday. Minor areal and river flooding could occur. * Dry weather briefly returns Friday * More rain, breezy conditions, and possible isolated storms expected Saturday into early Sunday. ================================================================== Another shortwave trough will be ejecting out of Texas by Wednesday night and early Thursday. Deep southerly flow will continue to advect rich Gulf moisture into the Ohio Valley, and we should see PW values surge even high on Thursday as the magnitude of low level moisture transport enhances with low level jetting. PW values could exceed 1.4-1.5 inches, which would be above the daily max of sounding climatology of BNA. The shortwave will pivot several strong vort lobes over the region Wednesday night and into Thursday, providing large scale forcing to promote additional moderate rain showers across the region. Instability continues to look rather weak for Thursday, but perhaps some sfc based instability could develop given that sfc dewpoints could reach the lower 60s. EPS is a bit more generous with SBCAPE than the GEFS, with the EPS having a mean ensemble of around 100 J/kg for several hours of the day. Best chances for any instability will be across south-central Kentucky. While it still appears that instability will be weak enough to limit concerns for even scattered convection, isolated higher rainfall rates will be possible across our south and southeast. Guidance continues to hint at potential for training rain showers across our southeast through Thursday, which will pose a greater risk for flash flooding. The cool ground should also boost runoff to some degree, which may result in minor areal and river flooding. See the Hydro section for more details. Precip will taper off Thursday night with the passage of the associated cold front, leading to a drier period for Thursday night and into Friday. Total rainfall amounts when it's all said and done will be ranging between 1.5-2.5 inches, though some isolated amounts closer to 3 inches is possible too across southern KY. Friday remains the only dry day of the long term period, with temperatures in the low to mid 50s. After Friday's quiet wx day, the parade of shortwaves will continue for Saturday as another shortwave ejects out of the southern Plains. However, this weekend's system appears to be much stronger, which will bring a high shear, low CAPE environment to the region. Confidence for this weekend is low given that the forecast will depend on the storm track. Cold air will wrap around the low as it departs on Sunday, which could result in some wintry precip somewhere across the region. Again, confidence remains low, and will continue to monitor in the coming days. && .Aviation...(06Z TAF Issuance) Issued at 1245 AM EST Wed Jan 24 2024 It is a messy, complicated forecast over the next 24 hours. Rain showers, low-level wind shear, low ceilings and visibility will all cause impacts to aviation. Ceilings are actually VFR to begin the period at SDF/BWG/LEX with high-end MVFR at HNB. Ceilings will be at their highest for the first 3-6 hours of the forecast period before they deteriorate from west to east mid-morning into early afternoon. Widespread IFR/LIFR with a combination of low stratus and then fog is expected this afternoon into early Thursday morning. The worst conditions are expected late tonight into early Thu morning, when very low ceilings and dense fog are likely. Also expect LLWS to become more of an issue by 09-12z this morning as a strong southerly LLJ punches up from the south. LLWS conditions will linger into early afternoon with 40+ kts as low as 2 kft. This low-level jet also signals the arrival of a slug of moisture and enhanced lift that will contribute to moderate to occasionally heavy rainfall after 10-11z. && .Hydrology... Updated at 305 PM EDT Tue Jan 23 2024 Key Messages... * Widespread rain and possible isolated storms will bring up to 2-3 inches of rainfall through Thursday, resulting in an increased likelihood for minor river flooding. Ample moisture transport into the region over multiple days and anomalous precipitable water of 1.2-1.5 inches will lead to efficient rainfall accumulation. Expect 2-3 inches of rain over the region through Thursday night. This amount of rainfall coupled with cold ground temperatures and snow melt increases the potential for runoff and minor flooding (both areal and river flooding). The highest potential for minor flooding is in central and southern Kentucky. Looking at some ensemble guidance, the NAEFS shows a 65% chance of reaching bankfull/action stage and a 25% chance of minor flooding along Elkhorn Creak at Peaks Mill. Along the Green River at Woodbury/Rochester Ferry, there is a 60-80% chance of reaching action stage and a 40-45% chance of minor flooding. Rivers will begin to rise with the onset of precipitation on Wednesday, and flooding concerns to increase on Thursday. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...BJS Short Term...RAS Long Term...CJP Aviation...EBW Hydrology...SRM