Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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099 FXUS63 KLMK 290144 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 944 PM EDT Sun Apr 28 2024 .KEY MESSAGES... * Showers and thunderstorms likely late Monday afternoon through Tuesday morning. A few stronger storms capable of gusty winds and heavy rainfall will be possible. * Additional showers and thunderstorms possible late in the week, though confidence in exact timing remains low. && .UPDATE... Issued at 943 PM EDT Sun Apr 28 2024 Nighttime microphysics satellite imagery shows that the cu field present across much of the Ohio and Tennessee valleys this afternoon has dissipated with the loss of daytime heating. As a result, we have mostly clear skies across the region at this hour, which should continue over the next several hours before high clouds begin to increase from the west. Winds have dropped off considerably since sunset as an inversion within the PBL takes hold. Small downward adjustments were made to winds in the near term to account for this, though 5-10 mph southerly winds are still expected overnight. The only other change to the forecast was a slight delay in the onset of precip chances across Dubois/Perry/Orange County IN tomorrow morning, in accordance with preliminary 00Z hi-res trends. In general, the forecast is on track at this time. Updated products were sent with the latest changes. && .SHORT TERM /THROUGH MONDAY/... Issued at 319 PM EDT Sun Apr 28 2024 Visible satellite imagery shows a mix of sun and clouds across central KY and southern IN this afternoon, with a relative maximum in cloud cover along the I-65 corridor. Current KY mesonet obs show temperatures a few degrees cooler in this zone, with temperatures generally in the upper 70s and lower 80s at this hour. Breezy S/SW winds are continuing in the presence of a tight pressure gradient; sustained winds of 10-15 mph with gusts of 20-25 mph are noted in latest obs. Warm and breezy conditions will continue through the afternoon and evening hours, with winds gradually weakening around and after sunset. Tonight, dry weather is expected to continue in our neck of the woods, with diurnal cu expected to dissipate and mostly clear skies returning for the nighttime hours. A large convective complex is expected to develop across the southern Plains and into the Ozarks later this afternoon; while it is expected to push east toward the Mississippi Valley later tonight, it should outrun the best instability and weaken considerably before it approaches the western CWA in the immediate pre-dawn hours tomorrow. Still, there is a 20- 30% chance for residual rain showers to reach our western border communities by around sunrise Monday, with most areas across central KY and southern IN remaining dry at least through sunrise tomorrow. Temperatures will be unseasonably mild tonight as warm SSW flow continues. Lows should range from 60-65 across most areas Monday morning. Tomorrow, the upper-level trough which has been responsible for active weather to our west over the past few days will eject northeastward into the upper Great Lakes and central Canada, bringing an associated cold front into our region by tomorrow afternoon. The trajectory of the upper-level trough is such that large-scale forcing will be modest at best, with the weakening front serving as the primary initiation zone for convection tomorrow afternoon and evening. A tongue of higher boundary layer moisture along the front will allow for modest amounts of instability, with 12Z HREF mean MLCAPE generally ranging from 200-600 J/kg. With that being said, the lack of height falls and dry air surging in aloft will limit overall instability, and wind profiles show fairly unidirectional deep-layer flow. As a result, while scattered showers and thunderstorms are expected tomorrow afternoon and evening, the severe potential is fairly limited, though a gusty shower or storm would still be possible. The main timing for showers and storms looks to be after 21Z along the I-65 corridor, with much of the day remaining dry. Temperature forecasts are somewhat tricky tomorrow -- while it will certainly still be warm across the region, exactly how warm it gets will be determined by how quickly clouds along the front make it into the region. As such, have bumped temperatures slightly above NBM guidance east of I-65, where there is greater confidence in mostly sunny skies through the early afternoon hours on Monday. If clouds are slower to arrive, temperatures would likely end up a few degrees warmer than currently advertised. Last but not least, it will still be breezy tomorrow, with S/SW winds picking up during the mid-morning hours. Sustained winds will range from 10-15 mph, with gusts up to 25 mph expected. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... Issued at 319 PM EDT Sun Apr 28 2024 Upper trof will cross the region Monday night, dragging a weak cold front through the Ohio Valley with it. Convection developing over the mid Mississippi Valley on Monday afternoon will push eastward across Kentucky and Indiana Monday night, with enough convective character to support embedded thunder, locally gusty winds and at least brief heavy rainfall. Rainfall totals could exceed 1 inch in the areas that see the strongest showers and storms. After the precip slowly departs Tuesday, the middle of the week looks dry as ridging amplifies over the Deep South and the Ohio Valley. Unseasonably warm temps will continue with highs pushing well into the 80s on Thursday, as it looks like showers associated with the next system could hold off into Thursday night. A series of upper waves will bring increasing rain chances, possibly starting as early as Thursday afternoon and continuing through at least Friday night. Details remain uncertain at this time, but better model agreement should shed more light in the coming days. Sfc cold front pushes through Friday night, but can`t rule out post- frontal precip lingering into Saturday. We`ll carry a 30-40% chance of precip on Saturday for now, but confidence is low. We can say with better certainty that temps should continue to run on the high side of normal for early May. && .AVIATION /00Z TAFS THROUGH 06Z TUESDAY/... Issued at 739 PM EDT Sun Apr 28 2024 There is high confidence in VFR ceilings and visibilities at all sites tonight into the pre-dawn hours tomorrow. Most lingering low- mid level cu should dissipate over the next 1-2 hours as we lose daytime heating, while the nighttime low-level inversion should also help to reduce wind gusts. The main forecast concern overnight is LLWS as a 45+ kt LLJ moves across western KY and southwest IN after 06Z. Have included LLWS mention for SDF/HNB/BWG, which will be closest to the jet core, but marginal WS is also possible at LEX/RGA between 08-13Z tomorrow. Just before sunrise tomorrow morning, a decaying band of showers will approach HNB. There is low-medium confidence that this band of showers will hold together to make it to HNB, and any impacts from this area of showers should be minimal. Ceilings will begin to decrease from west to east during the day on Monday, although daytime heating should help keep things VFR through sunset tomorrow night. Winds should also become gusty out of the S/SW during the mid- morning hours as a cold front continues to slowly move closer to the region. A secondary band of showers and storms is expected to develop tomorrow afternoon and move west to east across local terminals through the evening and nighttime hours Monday into Tuesday. This area of showers and storms may bring reduced CIGs and VIS, as well as gusty winds; however, confidence in TS is too low at this time to carry anything more than vicinity mention. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ UPDATE...CSG SHORT TERM...CSG LONG TERM...RAS AVIATION...CSG