Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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302 FXUS63 KLMK 122344 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 744 PM EDT Wed Jun 12 2024 ...Updated Aviation Discussion... .KEY MESSAGES... * Above normal temperatures expected Sunday into next week. Rain chances return early next week as southerly flow draws moisture northward from the Gulf. && .SHORT TERM /THROUGH THURSDAY/... Issued at 254 PM EDT Wed Jun 12 2024 High pressure continues to dominate over the Ohio and Tennessee valleys this afternoon, with light winds, mostly sunny skies, and seasonably warm temperatures present across southern Indiana and central Kentucky. Low humidity values continue across the region as anticyclonic flow in the low-to-mid levels carries most of the returning moisture up into the upper Midwest. The upper level pattern across North America is characterized by quasi-zonal flow atop a broad ridge which will gradually spread eastward over the next few days. As the ridge axis spreads to the east, increasing heights and temperatures aloft will translate down to the surface, with a warming trend continuing into the day on Thursday. With the dry air mass remaining in place tonight, temperatures should once again be able to cool efficiently in the presence of light winds and mostly clear skies. While low-level atmospheric moisture should be fairly mixed out by now and ground surface moisture continues to decrease, short range model guidance continues to suggest a low-medium probability of some valley fog just before sunrise Thursday. Low temperatures will once again exhibit a relatively wide range, from low-to-mid 50s in the coolest valleys to just above 60 degrees in the urban heat centers. Tomorrow, we`ll see another step upward in temperatures by around 5 degrees across the board. As lower sfc pressures along a frontal boundary approach from the upper Midwest tomorrow afternoon, light SW winds should pick up at around 5-10 mph. While there may be scattered high convective debris clouds in the morning hours from storms tonight over MN/WI/IA, continued abnormally dry air in the low-mid levels should allow for another day with mostly sunny skies and highs ranging from the mid 80s to around 90 degrees. . && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... Issued at 254 PM EDT Wed Jun 12 2024 Overview Not much has changed in the forecast thinking, as long-term models continue to show excellent agreement in the large-scale features. The finer details are coming into focus with more CAM`s available for the Friday cold front and subsequent rain chances. Beyond that, ridging across the region brings our warmest days Sun/Mon, but Monday still is in question with moisture return and rain chances short-circuiting the heat. The rest of the work week looks to be a push/pull for whether it`ll be heat on any given day or whether afternoon pulse storms will bring relief. Thursday Night and Friday Still seeing indication of rain chances in larger-scale models, but now we have CAM guidance showing a decaying line of showers/storms pushing in from the NW late Thursday night and into Friday morning. Specifically, the 12Z FV3/HRRR show this with the NAM3k going for the weakening even earlier in the evening Thursday. All three keep a weak convergent boundary over our area Friday, that may serve to spark off isolated storm development in the late morning and afternoon hours. Will go a little above NBM guidance for this period, keeping in at least isolated mention for rain chances. One other thing, with afternoon development, it`s worth noting that DCAPE`s are fairly high, though shear for organized storms is low. Wouldn`t be surprised to see an isolated stronger wind gust come out of these storms. Friday Night through Saturday Night This period will be a transition. We`ll start off with a little cooler night Friday night, in the wake of that decaying frontal boundary. Any showers/storms should quickly end with loss of daytime heating. By Saturday night, high pressure at the surface will shift northeast of the region, allowing for a return southerly flow to being. Sunday through Wednesday That return flow will bring in warmer thicknesses as well as steadily increasing moisture. The first will bring a quick shot upwards in high temperatures for Sunday. 24-hour thickness change progs still argue for readings some 10-15 degrees warmer than Saturday. Mitigating factors though will be the humidity as well still very green surface vegetation. NBM went with changes of 6-8 degrees over that span, and MEX guidance is in line with this change as well. As we shift over to Monday and the work week, our precipitable waters get into the 75th-90th percentile and hover at those levels. Thus the reason for the push and pull between heat from the ridge expected to be centered over the Mid-Atlantic states, potentially capping convection, and storms firing off in that moist environment. Grand Ensemble guidance from the CMCE/GEFS/ENS show chances for measurable rains each day in the 35-45% range. Bottom line for now, we`ll continue to advertise the first heat wave of the season and perhaps the first time getting into summer pulse thunderstorm season as well. && .AVIATION /00Z TAFS THROUGH 06Z SATURDAY/... Issued at 744 PM EDT Wed Jun 12 2024 High pressure continues to dominate the region, with VFR conditions expected to prevail. Surface winds will either be light out of the S or calm overnight, and then take on a 5 to 10 mph SSW component on Thursday afternoon. Can`t rule out a brief period of fog early Thursday morning but crossover Ts don`t support fog at any of the TAF sites. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...Air Quality Alert until midnight EDT tonight for KYZ029>031. IN...Air Quality Alert until midnight EDT /11 PM CDT/ tonight for INZ076>079-083-084-089>092. && $$ SHORT TERM...CSG LONG TERM...RJS AVIATION...BJS