Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
446 FXUS63 KLMK 161733 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 133 PM EDT Tue Jul 16 2024 ...Updated Aviation Discussion... .KEY MESSAGES... * Triple-digit heat index values possible today. Heat advisory remains in effect. * Storm chances increase tonight into tomorrow as a frontal boundary sinks into the region. Flash flooding possible in areas that see repeated storms. Isolated strong storms with gusty winds possible as well. * Cooler temps in the 80s for Thursday into the end of the week. && .UPDATE... Issued at 1044 AM EDT Tue Jul 16 2024 Remnants of the early morning MCS have struggled to make it south of the Ohio River this morning, but the outflow boundary has surged all the way to the Kentucky/Tennessee state line. A few showers fired off along the outflow across central Kentucky, but meager lapse rates and low level stability kept those showers from really ever becoming organized. We`ll continue to see the showers across southern Indiana dissipate, and may end up with a lull in activity for the early afternoon. Beyond that, confidence does remain somewhat limited. SPC extended the Slight risk further east, and now encompasses the western half of our CWA. While the best severe chances still remains to our west, strong heating combined with a moisture-rich airmass will aid in minimizing any morning CIN and realize some destabilization over 2000 J/kg. Depending on where remnant outflow boundaries are located, some isolated storms could fire up along those boundaries later this afternoon and evening. Model soundings show weak shear, but steep low level lapse rates and high DCAPE to support a damaging wind threat. As for the Heat Advisory, there remains uncertainty whether the northern parts of the forecast area will reach criteria later this afternoon after the morning precip and lingering cloud cover. However, after chatting with PAH, will keep the headline going and see how temperatures recover this afternoon before making any changes. Some tweaking may be needed, but that will be later. The general forecast is in good shape without any major changes. Will send updated forecast products. && .SHORT TERM /THROUGH TONIGHT/... Issued at 331 AM EDT Tue Jul 16 2024 A decaying line of showers and storms are steadily pushing southeastward this morning from Illinois and Indiana. While this activity is moving into a more stable environment, an outflow boundary ahead of the main activity has helped to spark off some precipitation across our southern Indiana counties this morning. Additional showers/storms may filter in from the north/west later in the AM, though it is expected to generally be weak. Confidence in the forecast details remain low today given the difficulty in forecasting evolving mesoscale features and details that are often poorly captured by models. One particular aspect of the forecast that remains uncertain is how warm we`ll get this afternoon. The clouds and spotty precipitation will slow the rise of temperatures this morning after dawn, though some clearing is anticipated by the late morning or early afternoon hours. How long the clouds linger will certainly have an impact on the overall highs today, and it`s possible that we may not hit heat advisory criteria across the region. With the advisory already in place, though, and the potential to still see some +100 heat indices should we clear out, plan to let the advisory ride out for time being. A slow moving frontal boundary will begin approaching the region tonight. Showers and storms are expected to develop along and ahead of it, all of which will be capable of heavy rainfall given the moist environment. SPC HREF guidance has honed in on southern IN and portions of northern KY for heavy rainfall potential via the Localized Probability Matched Mean (LPMM) product over the last couple of runs, which seems feasible given that storm motions could be nearly parallel to the frontal boundary as it comes sliding in from the north, supporting a storm training threat. After coordinating with neighboring offices, a flood watch has been issued for the aforementioned areas starting this evening and continuing into tomorrow afternoon. Outside of the flood threat, a low-end severe threat of gusty winds in the strongest storms remains possible from water-loaded downbursts. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Issued at 331 AM EDT Tue Jul 16 2024 On Wednesday, a upper trough centered near the Great Lakes will push a surface low through the Midwest towards the Lower Ohio Valley behind a weakly defined cold front. Moisture from the Gulf of Mexico will keep precipitable water values ahead of the front in the 1.5 to just over 2" range. Current model projections still lack agreement on the exact placement and timing of precipitation, but early in the day, there is a good chance that remaining precipitation from the night before could remain in the area. Given the time of day, severe weather wouldn`t be expected as instability would be limited. Believe the day would begin as showers with some garden variety thunderstorms being possible. Given the juicy air mass, any convection would likely produce heavy rain. Behind any remaining morning activity, the day could be mostly dry for most people with showers and storms not increasing again until the front begins to drop south through southern Indiana later Wednesday afternoon/ evening. By this time, the environment could recover from the earlier convection. MLCAPE values could recover to 1,000-1,500 J/kg with fairly steep low level lapse rates and DCAPE values nearing 1,000 J/kg, so some gusty winds will be possible with any convection that forms ahead of the sinking front. If the front pushes through a little earlier in the day, there will be less time for the environment to recover which would lower instability and thunderstorm strength. Showers and thunderstorms will work their way south through central Kentucky and are expected to exit by early Thursday. The rain and cloud cover will help to limit high temperatures as the front begins to work through the region on Wednesday. Highs in the low 80s are expected in parts of southeastern Indiana with temperatures closer to 90 along the Tennessee border in Kentucky. Everyone else is expected to see the mid 80s. Behind the front on Thursday, temperatures dip to the low 80s across the CWA before clearer skies and sunshine bring the mid 80s back for the rest of the week. && .AVIATION /18Z TAFS THROUGH 00Z THURSDAY/... Issued at 133 PM EDT Tue Jul 16 2024 VFR conditions are across the region, with plenty of high cirrus clouds spreading out overhead. While VFR will continue for this afternoon and evening, conditions will deteriorate later tonight as showers and storms fire up again along an approaching cold front. Ceilings will lower through the night as shower and storm chances ramp up. Highlighted the best potential with PROB30 groups for now, which included vis restrictions and lower ceilings. Ceilings could drop to MVFR by tomorrow morning before once again improving to VFR by the afternoon hours. Winds during this period will mostly be from the southwest. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for KYZ023>043-045>049-053>057-061>067-070>078-081-082. Flood Watch from 8 PM EDT /7 PM CDT/ this evening through Wednesday afternoon for KYZ023>025-030>037. IN...Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for INZ076>079-083-084-089>092. Flood Watch from 8 PM EDT /7 PM CDT/ this evening through Wednesday afternoon for INZ076>079-083-084-089>092. && $$ UPDATE...CJP SHORT TERM...DM LONG TERM...KDW AVIATION...CJP