Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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689 FXUS63 KLMK 271900 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 300 PM EDT Thu Jun 27 2024 .KEY MESSAGES... * Shower and storm chances return Saturday through early Sunday. Locally heavy rain and gusty winds will be the main threats. Above normal temperatures return by early/mid next week. * Another period of unsettled weather returns to the region by late Wednesday and Thursday. && .SHORT TERM /THROUGH TONIGHT/... Issued at 259 PM EDT Thu Jun 27 2024 Synopsis...Positive upper height anomalies will continue rising across the Lower Ohio Valley and Mid Atlantic as a broad ridge expands over the southern half of the CONUS. Meanwhile, a northern- stream, shortwave trough will proceed through the Northern Plains as it slowly weakens. At the surface, high pressure over the Great Lakes will eject to the east with low pressure and attendant cold front approaching the Upper Midwest. This Afternoon & Tonight...Mid-level subsidence and dry airmass have kept mostly sunny conditions across the area this afternoon. Satellite imagery shows a fair weather cumulus field developing northeast to southwest as convective temperatures are met. Highs this afternoon should top out in the mid to upper 80s with dewpoints in the 60s, a momentary respite from the intense heat. For tonight, expect low level clouds to dissipate after sunset, although a steady increase of high clouds is anticipated based on upper-level saturation depicted in GFS forecast soundings. As for fog chances, confidence is low in coverage or intensity of dense fog as upper clouds would most likely limit radiational cooling. Friday...Winds will shift from the east-northeast to south-southeast during the day in response to the ejection of the surface high pressure and influence of lower pressures associated with the approaching low and cold front. As a result, theta-e advection will overspread the area with highs increasing to the upper 80s and low 90s. At the same time, precipitable water values will ascend slightly over 1.5 inches in the afternoon providing an opportunity of a low chance of brief showers along the Lake Cumberland region where shallow moist convergence should be maximized. Nonetheless, probability of thunder will be rather low as a capping inversion will exist in the 700-600 mb layer and sufficient dry air lingers in the mid-levels. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Issued at 259 PM EDT Thu Jun 27 2024 Friday Night through Sunday Night.. Could see a few showers/storms Friday evening ahead of weak warm frontal boundary lifting north of the region. Silent PoPs still look good here and a few spots could pick up a little QPF. Lows will be warm with readings in the low-mid 70s. For Saturday, pretty decent shortwave trough axis is forecast to track from the Midwest through the Great Lakes during the day on Saturday while pushing into New England by Sunday. Associated surface cyclone and southward extending cold front will approach and slowly move through the region late Saturday and Sunday. Ahead of the front, we should still get decently warm on Saturday with highs warming into the upper 80s to the lower 90s. With dewpoints in the upper 60s to lower 70s, this will result in heat indices rising into the upper 90s and lower 100s. We`ll have plentiful moisture in the column Saturday afternoon. Forecast soundings still show fairly marginal lapse rates with tall/skinny CAPE profiles along with high freezing levels. PWATs from the models still rise to above 2 inches on Saturday, but overall bulk shear values remain friarly marginal with 20-25kts expected. The overall profile would support convection that would feature warm cloud depths and good precipitation efficiencies. Given the weak shear and steering flow, these storms could be slow moving and lead to a localized flash flood threat in some areas. The tall CAPE profile and weak shear could support a wet microburst threat as well. SPC has a marginal risk out for the area which seems appropriate. Somewhat stronger shear will be available to our northeast which agrees well with current Slight risk area. While overall coverage here may be a bit sparse, if more convective coverage ends up occurring, the marginal risk could see an upgrade to a slight at some point. Frontal boundary looks to push through the region Saturday night with convection continuing but diminishing in strength as we lose heating and the PBL stabilizes. By Sunday morning, the cold front should be bisecting the region and continuing to push southward, so precipitation chances will decrease steadily through the day across southern IN and the northern half of KY. A few scattered showers/storms may continue across the south until the front clears. Most locations should be dry by Sunday evening. Highs on Sunday will be cooler with readings in the 85-90 degree range. Lows Sunday night will drop back into the low-mid 60s, with some of the valley and typical good radiational cooling spots dropping back into the 50s. Not bad for late June/early July. Monday through Tuesday Night... A dry period of weather is expected for Monday and Tuesday as the upper trough axis heads off to the east and upper level ridging builds back into the area. Monday will feature below normal temperatures for much of the region with highs in the low-mid 80s. The Bluegrass region of central KY may stay a bit cooler here with upper 70s. Lows Monday night will be cool as well with most locations dropping into the upper 50s to around 60 with the cooler valley locations dropping as low as the lower 50s. Temps will rapidly warm back up by Tuesday with highs in the upper 80s to the lower 90s with overnight lows in the 70s. Wednesday and Thursday... Upper ridge axis looks to get a bit more flattened by Wednesday as a series of waves moves through in the westerly flow pattern across the northern tier of states. A cold front will drop into the region around Wednesday evening bringing a round of showers/storms to the region. This front looks to stall out across the Ohio/Tennessee Valleys by Thursday and could serve as a focus for additional convective development. Some strong/severe storms could occur in the Wed/Thu time frame given that we should have decent instability. Overall shear still looks to remain marginal with the faster flow displaced to our north. However, we still have several days to watch the overall scenario play out. Highs during the period will be in the upper 80s to the lower 90s with overnight lows in the upper 60s/lower 70s. && .AVIATION /18Z TAFS THROUGH 00Z SATURDAY/... Issued at 116 PM EDT Thu Jun 27 2024 Discussion...VFR conditions will continue through this TAF period as surface high pressure and dry air remain in control. On the other hand, winds will stay light with a gradual shift from the northeast this afternoon to the south-southeast tomorrow afternoon. Finally, today`s mixing and increasing upper cloud cover tonight will limit radiational cooling and potentially fog formation at the terminals. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ SHORT TERM...ALL LONG TERM...MJ AVIATION...ALL