Area Forecast Discussion
Issued by NWS Louisville, KY

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000 FXUS63 KLMK 190004 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 804 PM EDT Sun Apr 18 2021 ...Updated Aviation Discussion... .Short Term...(This evening through Monday) Issued at 245 PM EDT Sun Apr 18 2021 Afternoon satellite imagery reveals partly cloudy skies across the region. Cu field has a bit more coverage than expected which has kept temperatures down slightly. KY Mesonet readings show current temps around 60 degrees in most places. Area radars show a few scattered showers, mainly north of the Ohio River. In the near term, expect temperatures to top out in the 59-64 degree range with a few scattered showers mainly north of the Ohio River and west of I- 65. Main weather feature of note is a mid level vorticity maximum over western MO. This feature is forecast to move eastward this afternoon and evening. Rain showers continue to develop over central and SE MO this afternoon. This activity should continue to expand in coverage as the vorticity max moves closer to our area. As this feature rolls eastward, a cluster of mainly rain showers will move through western KY this evening and then through mainly south-central Kentucky late this evening and into the overnight hours. Best chances for rainfall look to be south of a line from roughly Jasper, IN to around Richmond Kentucky. The Bluegrass region may escape this system and remain dry, but cloudy overnight, however, a few showers may get as far north as the Lexington area. Overall threat of thunderstorms looks to be fairly low this evening and into the overnight period. This is mainly due to weak environmental wind fields, meager moisture profiles, and lack of surface based instability. While model soundings do show some elevated instability, still can`t rule out a rumble or two of thunder or a couple of lightning strikes from any stronger cores that develop. The best chances of any thunderstorms would be west of the I-65 corridor. Temps this evening will be in the upper 50s to the lower 60s before falling off into lower 40s overnight. Clouds should start to mix out late tonight across the west. Should this occur, combination of clear skies, light winds, and some wet ground may result in an area of fog formation. As of this writing, I think the best chances of fog would be along and west of the I-65 corridor. For Monday, the mid-level vorticity maximum will continue off to the east and some mid-level ridging will build into the area. Partly to mostly sunny skies are expected. Highs on the day should top out in the 63 to 68 degree range. A few of the typically warmer urban spots could hit 69 or 70. .Long Term...(Monday night through Sunday) Issued at 256 PM EDT Sun Apr 18 2021 Tuesday afternoon, a southwest to northeast oriented cold front will begin to push cloud cover into the CWA from the northwest, and by Tuesday night, precipitation will begin to work its way across the CWA. It`s this precipitation that is going to be the main focus over the next couple of days because it will likely bring snowfall to the region. This front is strong and will bring a significant temperature drop with it. Highs on Tuesday that range from the mid 60s to low 70s will drop into the 30s by Wednesday morning. This system also carries a decent amount of moisture that will converge Gulf moisture from the south and Pacific moisture from the northwest. Precipitation will remain behind the front. This is the cool side of the front, and it will help precipitation remain frozen before hitting the ground. Any precipitation that begins as rain will quickly change to snow without a warm nose giving the chance for sleet. The question still remains how much will fall as rain, and how much as snow. Looking across model guidance, the GFS is bullish on total precipitation amounts (0.50 to 0.75"). the NAM has streaks of these higher amounts across the region, but I used blended amounts in the forecast with slightly over 0.25" in southwest Indiana, and tapered amounts off to the southeast with less than 0.10" in the Lake Cumberland region of Kentucky. Believe most of this will fall as rain, but have around 0.25" of snow in parts of Crawford and Harrison Counties (IN) and areas to their north. Snow amounts will fall off quickly, leaving only trace amounts southeast of the Ohio River in Kentucky. Warm ground temperatures will limit impacts across the area. Behind the front, surface high pressure and a more zonal pattern move into the Lower Ohio Valley. This brings more sunshine but cool temperatures remain. Highs on Thursday range from the mid 50s in the Bluegrass to near 60 in Bowling Green. Then, highs in the 60s stick around from Friday through Sunday. That`s around 10 degrees below normal. Low temperatures near freezing will likely bring frost to many areas Thursday and Friday mornings. These cold temperatures are around 20 degrees cooler than normal. Friday night into Saturday, another cold front is expected to bring the next round of rainfall to the region. && .Aviation...(00Z TAF Issuance) Issued at 803 PM EDT Sun Apr 18 2021 A fairly potent upper disturbance will rotate through our region this evening and tonight, bringing some light showers most notably at HNB/BWG. Will only mention VCSH at SDF/LEX. Bkn-Ovc ceilings around 5-8 K feet should remain VFR, but some brief lower ceilings down near 4 K feet also can`t be ruled out overnight. Toward dawn, some patchy fog could briefly develop if we clear out quick enough, however most indications that cloud cover will hang on long enough to mitigate larger fog concerns. Did hint at some 6sm BR at HNB/LEX/BWG for a few hours around sunrise. Otherwise, Monday will be nice with mostly sunny skies and a steady WSW surface wind. CONFIDENCE: Medium-high confidence on shower activity for this afternoon and evening. Low confidence on fog development overnight. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Short Term...MJ Long Term....KDW Aviation...BJS is the U.S. government's official web portal to all federal, state and local government web resources and services.