Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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895 FXUS63 KLMK 291112 AAA AFDLMK Area Forecast Discussion...UPDATED National Weather Service Louisville KY 712 AM EDT Mon Apr 29 2024 .KEY MESSAGES... * Showers and scattered thunderstorms will be possible late this afternoon and into the evening and overnight period. Gusty winds and heavy rainfall will be the main threats with this activity. * Additional showers and thunderstorms possible late in the week, though confidence in exact timing remains low. && .SHORT TERM /THROUGH TONIGHT/... Issued at 332 AM EDT Mon Apr 29 2024 Early morning satellite imagery and observations reveal mostly clear skies across much of central and eastern Kentucky. Some high level cirrus was starting to invade western KY ahead of a line of storms out near the St. Louis area. Temperatures across the area were generally in the low-mid 60s. A few of our typical radiational cooling spots (mainly valley locations) were down in the mid 50s. For the remainder of the overnight period, dry weather is expected with a gradual increase in upper level cloud cover coming in from the west. Convective line out near St. Louis will continue to move eastward and gradually weaken as it moves toward the IL/IN border region toward sunrise. For today, an upper level trough axis over the Plains which has been responsible for the wave of severe weather out that way will move northeastward into the Great Lakes. As this occurs, the flow pattern aloft will deamplify a bit while a surface cold front pushes through the Ohio Valley. With the deamplification of the pattern, synoptic scale forcing will become weaker with increasing time. Ongoing convection out to our west is forecast to weaken as it move eastward this morning. However, we may see some convective outflows that may generate some weak convection over southern IN as early as lunchtime or shortly thereafter. Much of the day looks to be dry across central KY, though convection is likely to increase in coverage by late afternoon in areas west of I-65. Highs on the day will range from the upper 70s to around 80 west of I-65, with readings mainly in the lower 80s east of I-65. Toward evening, we should see scattered convection move into SW IN and western KY and impinging into our western CWA. Model soundings do show somewhat steep low-level lapse rates with about 300-800 J/kg of MLCAPE available. The wind profile remains uni-directional with less than 30kts of bulk shear. Multi-cellular convection and perhaps some small linear segments look likely by late evening. Overall severe threat looks to be quite low given the limited shear/instability. However, a few storms may produce some small hail and gusty winds within the strongest cores. For tonight, convection should be in progress this evening, mainly west of the I-65 corridor. This convection will spread eastward through the I-65 corridor during the evening and into areas east of I-65 overnight. The storms this evening may be strong in spots with gusty winds and small hail being the main threats. As we get into the mid-late evening and overnight, instability will fall off and storms will weaken. PWAT values will be above an inch in many spots tonight, so periods of heavy rainfall will be possible as this activity moves east overnight. Total rainfall amounts for today and tonight will be 0.75-1.50 inches with some isolated higher amounts in spots that see repeated rainfall. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 332 AM EDT Mon Apr 29 2024 An upper level shortwave trough and weak sfc low are forecast to be over central Kentucky Tuesday morning. This weak sfc reflection will ride northeast along a cold front passing through the region. Showery weather will be ongoing Tuesday morning, mainly east of I- 65. Any convective activity will be much weaker by this point, so rainfall totals will be much lower than from Monday night convection. Isolated embedded storms will still be possible into early Tuesday afternoon, mainly from the southern Bluegrass Region south into the Lake Cumberland region. Rain chances will taper off from west to east during the day as drier air filters in behind the cold front. Shortwave ridging builds in from the west Tuesday afternoon and evening in the wake of the departing wave. Clouds are forecast to clear out from west to east during this time frame. Tuesday highs will be in the 70s, with low/mid 70s more likely in the Bluegrass Region and mid/upper 70s along and west of I-65. Ridging amplifies over the Southeast and Ohio Valley Tuesday night through Thursday, and confidence continues to increase in a period of dry, warm weather. Low to mid 80s will be common for highs Wednesday afternoon. Temperatures are likely to soar into the mid to upper 80s Thursday afternoon. As upper level ridging amplifies over eastern portions of the country heading into Thursday, a notable trough is forecast to swing from the Rockies across the northern and central Plains. In the lower levels, low pressure develops quickly northeastward from the Plains to Upper Midwest. Meridional flow will help keep an axis of deeper moisture and unstable air off to our west in the Plains and MS Valley through Thursday. However, that changes Thursday night into Friday as the low pressure system drags a cold front toward the Lower Ohio Valley. Showers and thunderstorm chances are maximized Friday into Friday night along and just ahead of the cold front. While confidence in timing has increased a bit, forecast confidence remains low on rainfall amounts and the strength of potential convection/severe risk. Rainfall chances decrease behind the cold front, but low rain chances linger into the weekend due to increased model spread and timing differences. 70% of ensemble members are dry by Saturday afternoon. Current thinking is optimistic the drier trend continues for Saturday, but model spread should narrow (thus increasing forecast confidence) quite a bit over the next 48 hours. && .AVIATION /12Z TAFS THROUGH 18Z TUESDAY/... Issued at 712 AM EDT Mon Apr 29 2024 For the upcoming period, VFR conditions are expected to prevail for much of first half of the period. A weakening ling of convection out east of KSTL will continue to work east this morning and continue to weaken as it approaches the IL/IN border. Some scattered showers may hold on and affect KHNB for a few hours later this morning. Elsewhere, mainly breezy conditions are expected from mid-morning through the afternoon. Southwest winds of 10-15kts with gusts to 20kts will be possible. Winds will likely loose some of their gusts this afternoon as thicker cloud cover moves into the region. More widespread convection looks to develop ahead of an approaching cold front after 29/21Z or so affecting mainly KSDF/KHNB. Will continue to mention VCTS at KSDF after 29/22Z, though best thunder chances may hold off until 30/00Z or shortly there after. Cold frontal boundary will move through the region later tonight bringing widespread showers and a few storms to all the terminals. MVFR cigs are expected to become common with the rain showers and cigs may drop to IFR at times later tonight. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ SHORT TERM...MJ LONG TERM...EBW AVIATION...MJ