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Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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174 FXUS63 KLMK 121351 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 951 AM EDT Mon Aug 12 2024 .KEY MESSAGES... * Below normal temperatures and low humidity will continue Monday. A few sprinkles possible by tonight. * Mostly dry weather through the first half of this week with precipitation chances increasing mid-to-late week. * Temperatures will gradually warm this week. && .UPDATE... Issued at 950 AM EDT Mon Aug 12 2024 Another fall-like morning with temperatures in the upper 60s. Surface high pressure is over the region is allowing for calm winds. Looking at satellite some high clouds streaming along I-64 are beginning to thin. By this afternoon, mid-high level clouds will begin to build into the region from the west and temperatures will warm into the low-mid 80s. Current forecast remains on track. && .SHORT TERM /THROUGH TONIGHT/... Issued at 321 AM EDT Mon Aug 12 2024 Pretty quiet weather in the short term as surface high pressure continues to control the region beneath fairly quiet zonal flow aloft. Looking for the first part of the day to be mostly sunny with a very light NE surface wind, and some occasional upper clouds. As we move into the evening and overnight a weak shortwave will approach within the low amplitude NW flow aloft. Mid and upper level sky cover will increase with this feature, especially across the western CWA. Models have been fairly consistent showing just enough moisture between 850-700 mb to squeeze out some very light rain and/or sprinkles. Have kept the very small chances for measurable QPF (15-20%) across our far western CWA, however have taken a bit more broad approach to mention of some sprinkle chances across much of the northern two-thirds of the CWA. Overall, forecast soundings show some pretty dry air below 850 mb, so a good bit precipitation falling out of the mid deck will likely evaporate. Outside of that, look for continued pleasant temperatures in the low to mid 80s (a little below normal) for this afternoon. Overnight, temps will be a bit milder thanks to some upper sky cover. Values mostly in the low to mid 60s should be common. Leaned on the high side of guidance here given the mid/upper sky cover. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 321 AM EDT Mon Aug 12 2024 Tuesday through Wednesday Night... At the beginning of the extended forecast period, broad mid- and upper-level ridging is expected across the middle of the CONUS, with upper troughs located along both coasts. At the surface, a broad area of high pressure is expected from the Great Lakes region down toward the central Appalachians, with low pressure located along the lee of the Rockies. The dry air mass which has been in place over the region this weekend should still be hanging on across the Ohio Valley Tuesday into early Wednesday, though low level moisture return on the west side of the 850 mb ridge will bring anomalously high PWATs toward the Ozarks and mid-Mississippi Valley. This should create a fairly tight moisture and instability gradient along and west of the Mississippi River, with occasional convective systems riding along this gradient during the mid-week period. Since the air mass over our area should still be fairly dry and stable Tuesday into Wednesday, precipitation will struggle to make it east of the Mississippi Valley. As a result, will keep a largely dry forecast going through Wednesday night, with a very slight (10- 15%) chance for a few showers existing along and west of the Natcher Parkway. Later during the mid-week period, an approaching upper trough coming down from central Canada should help to increase heights over the Ohio Valley as the ridge gets squeezed eastward. This should help temperatures to warm over the mid-week period, with highs and lows returning to near climatological norms by the end of the week. Thursday through Next Weekend... The aforementioned shortwave will help to bring better low-level moisture into the region by Thursday, also contributing to increasing instability. This will allow subsequent convective systems to progress farther eastward, increasing chances for showers and storms. While CSU ML severe probabilities remain low and are not particularly focused on any one area, the general pattern of shortwave disturbances descending in NW flow would be supportive of MCS-type systems which would carry an associated severe wind threat. To reiterate, severe probabilities continue to look low, as the moisture/instability gradient is expected to become more diffuse later in the week; however, it will be worth monitoring later in the week. The primary window for stronger storms is expected to be Thursday night through Friday night, as faster flow aloft from the approaching shortwave helps to bring additional wind shear. Outside of storm chances, temperatures and humidity values should be more typical for mid-August during the late week period, with afternoon highs ranging from the mid-80s to around 90 and nighttime lows falling into the upper 60s and lower 70s. Next weekend, ensemble guidance continues to show a bit of spread in solutions; however, there seems to be some convergence toward a solution which evolves the late week shortwave into a closed low over the Great Lakes and Ohio Valley. With moisture pooling in the vicinity of the upper low, a continuation of active weather and increased precipitation chances would be expected. This should also help to bring temperatures back down a few degrees given extra clouds/moisture, though forecast confidence remains modest at this lead time. && .AVIATION /12Z TAFS THROUGH 18Z TUESDAY/... Issued at 641 AM EDT Mon Aug 12 2024 VFR conditions will persist through the valid TAF period. Look for some transient upper clouds early this morning with calm or light and variable winds. A light NE surface wind should develop by late morning into the afternoon, along with some high clouds overspreading the region. By this evening, looking for a mid deck of clouds around 8-12 K feet, mainly for HNB/SDF/LEX. Perhaps a few sprinkles could develop for HNB, but not impactful enough to mention at this time. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ UPDATE...SRM SHORT TERM...BJS LONG TERM...CSG AVIATION...BJS