


Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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483 FXUS63 KLMK 171722 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 1222 PM EST Mon Feb 17 2025 ...Updated Aviation Discussion... .KEY MESSAGES... * Cold temperatures early this morning have frozen lingering wet surfaces. Areas of black ice are possible for the morning commute. * A skiff of light snow is expected Tuesday morning. A dusting to a half an inch of accumulation is most likely in a triangle between Jasper, IN, the Louisville Metro, and Hartford, KY. Flurries expected elsewhere. * An impactful winter storm is forecast to bring snow accumulations for Tuesday night through Wednesday afternoon. A Winter Storm WATCH remains in effect for all of southern Indiana and central Kentucky. * Very cold temperatures are expected after the mid-week winter storm. && .UPDATE... Issued at 1053 AM EST Mon Feb 17 2025 Morning satellite and observations show partly cloudy skies across the region. Morning temperatures were in the upper teens to the lower 20s along and north of the WK/BG Parkways. Across the south where low clouds hung in overnight, temps were generally in the mid 20s. Should continue to see this low cloud layer break up a bit and scour out later this morning and into the afternoon. Afternoon highs in the lower-mid 20s across southern IN and the northern half of KY look good, with upper 20s/lower 30s across southern KY. On the hydrology side, after coordinating with WFO JKL, we have gone ahead and dropped our areal flood warnings across the CWA. Water continues to recede in our counties with flooding largely confined to the river basins, though some roads in low spots may continue to be flooded for a little while longer. && .SHORT TERM /THROUGH TONIGHT/... Issued at 336 AM EST Mon Feb 17 2025 Things are fairly quiet early this morning, although a couple of things worth noting off the bat. The lingering stratus deck, mostly along and south of the Ohio River now, is continuing to make slow progress. Still seeing some flurries with these clouds, so have extended the residence time of that over much of the eastern half of the CWA to account for that. Still expect overall improvement by mid to late morning with some partial sunshine mid to late morning through early to mid afternoon. The sunshine will help a little, but temperatures are still going to struggle under a steady cold advection component and a fairly fresh snowpack. Looking for highs only in the upper 20s to around 30 across southern IN and northern KY, and may squeeze into the low and mid 30s across southern KY. We`ll see increasing upper sky cover by late afternoon through the evening, and cloud ceilings should steadily lower into tonight. There has been a consistent signal for a skiff of snow starting in the pre-dawn hours across our west central to NW CWA, and lasting into Tuesday morning. We`ll see a period of some weak low to mid level frontogenesis beneath the favorable right entrance region of an upper jet. Saturation is co-located with temps at least to -10C, and given our surface temps in the teens to around 20, snow ratios are expected to be quite high. Looking for them to be in the 15 to 18:1 ratio, and with roughly .02" to .03" of forecast QPF think that a dusting to a half an inch of snow seems pretty reasonable. That range should apply to a triangle between Jasper, IN to Louisville, KY to Hartford, KY. Outside of that area, will carry just flurry mention for a good chunk of southern IN and northern KY. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 336 AM EST Mon Feb 17 2025 ===== Tuesday ===== Upper level flow will be mostly zonal for the start of the long term period, though a weak disturbance riding in the flow, combined with right entrance region jet dynamics, could produce some light snow across portions of southern Indiana and north-central Kentucky during the morning hours. Temperatures will start out in the teens and low 20s, which will help keep any precip as snow. Snow amounts up to half an inch are expected Tuesday morning with this weak disturbance. High temps for the day will vary quite a bit from north to south across the forecast area, with north-central Kentucky and southern Indiana counties staying in the 20s, but south-central Kentucky likely getting above freezing and in the mid-30s. Tuesday Night through Sunday... * IMPACTFUL WINTER STORM EXPECTED TUESDAY NIGHT * * WINTER STORM WATCH REMAINS IN EFFECT * The primary focus of the long term period continues to be on the storm system set to bring impactful snow amounts to the area for Tuesday night and into Wednesday. An amplifying mid-level trough over the Great Plains will sweep across the central US, leading to an increase in synoptic scale forcing over the region. We`ll see an increase in 850-700 mb WAA and isentropic lift spread over the area Tuesday night as a sfc low develops along the Gulf Coast. Combined with upper level divergence within the favored right entrance region of a 120kt upper level jet streak, low level convergence and strengthening FGEN and vertical velocities will support widespread moderate to locally heavy snowfall in the forecast area. Despite the low-mid level WAA, our column is expected to be cold enough for this event to support all snow p-type. Snowfall amounts have decreased slightly with this Monday morning forecast package, but there remains some considerable spread in ensembles, as evident in the box and whisker plots. The NBM, for example, has a 24-hour snowfall spread between 1-10 inches, with a mean of around 3-4 inches for the area. With such spread, confidence in snowfall amounts remains somewhat limited at this time. The GEFS and EPS ensembles have come down in snow amounts since the 12z suite, which has lowered LREF snow probabilities. What is consistent is the axis of expected heaviest snow, which is expected to set up across southern Missouri and extend eastward into portions of southern Illinois and western Kentucky. This corresponds well with the WPC WSSI-P for highest probabilities of moderate winter impacts. While a mix of minor and moderate impacts are possible across our area, the greater impacts are most likely in the western half of the Commonwealth. Snow to liquid ratios are expected to be fairly high, with 13:1 to 17:1 north of the parkways, and a more modest 10:1 to 13:1 across south-central Kentucky. WPC 24-hour snow prob guidance gives good indications of the snow amounts possible. The high snow chances appear to focus on central Kentucky, between I-64 and the Cumberland Parkway. This still agrees quite well with the previous forecast, which mentioned Elizabethtown to Richmond. In this specific area, there is an 82% chance of exceeding 2 inches in 24 hours. Additionally, there is a roughly 40% chance of exceeding 4 inches, and 5-10% of exceeding 6 inches of snow. While confidence is not high enough to upgrade to a Winter Storm Warning with this forecast package, will continue with the Winter Storm Watch at this time. An upgrade to at least a Winter Weather Advisory will be needed in a future forecast package. Much of this snow will fall from mid-late evening Tuesday through Wednesday afternoon with things diminishing Wednesday evening. Continue to monitor for forecast updates, and have plans in place to prepare for impacts to daily life. * VERY COLD WEATHER LATER THIS WEEK * In the wake of snow, very cold air will take hold across the area for the rest of the week. Temps for Wednesday night into Thursday morning are forecast to drop to single digits, with wind chills near or just below zero. With such a cold start to Thursday, temps will have a difficult time recovering. Highs for the day will struggle get out of the teens and low 20s. Highs Friday may struggle again to get into the mid-upper teens, with lows Saturday morning dropping back into the low single digits. Some moderation in temps is possible this weekend. && .AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 1221 PM EST Mon Feb 17 2025 MVFR stratus deck continues to scour out across the region. KBWG may hold on to MVFR cigs for another couple of hours or so. Elsewhere, VFR conditions with mainly west-northwest winds of 5-8kts will be seen this afternoon with upper level cloud cover increasing late in the day. Later tonight, cigs will gradually lower after midnight with some light snow developing at KHNB/KSDF. Some flurries will be possible over at KLEX/KRGA. Winds will shift to the north tonight and then veer to the northeast late tonight into Tuesday morning. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...Winter Storm Watch from Tuesday evening through Wednesday evening for KYZ023>043-045>049-053>057-061>067-070>078- 081-082. IN...Winter Storm Watch from Tuesday evening through Wednesday evening for INZ076>079-083-084-089>092. && $$ UPDATE.......MJ SHORT TERM...BJS LONG TERM....CJP AVIATION.....MJ