Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 12/08/21

Area Forecast Discussion
National Weather Service Louisville KY
800 PM EST Tue Dec 7 2021 .Forecast Update... Issued at 800 PM EST Tue Dec 7 2021 Forecast remains on track this evening. Have gotten several reports of dustings to very light snow accumulations across a corridor of southern Indiana counties stretching from Dubois County into Scott County. While regional radars reveal fairly light reflectivity returns, surface obs in these areas have seen visibilities drop as low as 2 1/2 miles in some of the more moderate pockets of snow. Overall accumulations across southern Indiana will likely range from a light dusting to as much as a half inch once all is said and done. We may see some light snow showers or flurries across portions of central Kentucky later tonight, but the best chance for any sort of light accumulations will be north of the Ohio River. && .Short Term...(This evening through Wednesday) Issued at 318 PM EST Tue Dec 7 2021 ...A Dusting Of Snow Possible For Some Tonight... Afternoon satellite and observational data reveal mostly cloudy skies across southern Indiana and the northern third of Kentucky. Under the clouds, temperatures were in the upper 20s to the lower 30s. Some clearing made it as far north as the WK/BG Parkways and in areas along and south of there, temperatures were generally in the low-mid 30s. Across southern KY where more sunshine has been observed, temperatures had warmed into the upper 30s and lower 40s. KLVX shows a bit of reflectivity aloft over southern Indiana. ACARS soundings out KSDF match up pretty well with the NAM profiles showing an fairly extensive dry layer below 700 hPa. While there has been some higher reflectivity over towards Evansville, recent surface obs do not show any precipitation reaching the ground, with the closest report being out across Missouri out near St. Louis. So, in the near term, we`re not expecting any significant weather. Surface temperatures are near their highs for the day and will drop after sunset. A few snow flurries may develop over our southern Indiana counties toward sunset. For this evening and overnight, a fast moving short wave trough axis is forecast to swing through the region. The models show a bit of moistening in the 700-500 hPa layer which should saturate the DGZ sufficiently to get some good dendritic growth. The short range, high resolution NAM/WRF family of models continue to suggest best chances of light snow with minor accumulations across southern Indiana and into southeast Ohio and into far northern Kentucky. This is likely due to the models showing the best QG/Omega forcing here to get parcels up into the DGZ and get the dry layer near the ground to moisten from top-down. QPF amounts are rather scant, but if the forcing is indeed strong enough and we can saturate down, it appears that some minor accumulations (quarter-half inch) will be possible across our southern Indiana and far northern KY counties. Further south, while the models do show moistening aloft into the DGZ, the dry layer below 700 hPa looks to remain in place. So while a brief period of lift passes through the region, we`ll probably get a bit of snow falling aloft, but it evaporates into the dry air and may not sufficiently moisten it enough to get light snows down to the surface. Generally speaking, we believe snow flurries will generally be the pre-dominant weather type tonight in areas south of the Ohio River and down to the Parkways. Late tonight, as the forcing moves off to the east, a secondary slot of forcing may pass across southern KY generating some very light snow flurries for a time across our southeast/Lake Cumberland region. Temperatures tonight will be below freezing with lows in the upper 20s. While the snow flurries across north-central KY will likely not result in any impacts, the lighter snow expected across southern Indiana may cause some negative travel issues late tonight with icy spots developing along bridges/overpasses and untreated road surfaces. Will continue to mention these negative impacts with an Special Weather Statement. For Wednesday, with the upper wave moving east of the region, drier air will push into the region and we should see skies scour out during the morning hours. By the afternoon, we`ll get back into a southerly wind flow pattern with temperatures warming up. Highs will range from the lower 40s over southern Indiana and into the northern Bluegrass with mainly mid-upper 40s being found along the WK/BG Parkway corridor. South of the Cumberland Parkway, temperatures may warm into the upper 40s to the very low 50s. .Long Term...(Wednesday night through Tuesday) Issued at 310 PM EST Tue Dec 7 2021 ...STRONG TO POSSIBLY SEVERE STORMS POSSIBLE LATE FRIDAY INTO SATURDAY WITH HEAVY RAINFALL AND POSSIBLE FLOODING CONCERNS... Wednesday Night through Thursday...The long term period starts off quiet as upper level ridging and surface high pressure move through the region. By mid morning, surface high pressure will move toward the east coast as deepening low pressure across the Central Plains creates a tight pressure gradient over the OH Valley resulting in breezy southerly winds with gusts up to 25-30mph possible. This southerly fetch will pull warm, moist air into the region with afternoon highs reaching roughly 10 degrees warmer than Wednesday. Clouds will increase throughout the day with possible light rain/drizzle occurring overnight. Friday and Saturday...A phased upper level pattern will set up another high shear / low CAPE environment with abundant moisture in place across the region as southerly flow pushes PWATS well above climatological norms. An H85 stable layer appears to remain in place throughout much of Friday afternoon along with low stratus in place, which may reduce chances and coverage of convection. Still expect some warm sector showers to occur throughout the day Friday with temperatures reaching into the mid to upper 60s with some 70s possible. Dew points will also experience a notable increase into the lower 60s. Most of the forcing and instability occurs Friday night into Saturday morning when the strongest activity is expected to occur. This is also when the highest rain rates are expected. Total QPF expected to be 1 to 3 inches with the higher amounts expected east of a line from Lexington to Bowling Green. With that said, flooding concerns are on the table. Rain begins to taper down by Saturday night with chances of light rain/snow mix possible on the backside of the system as cold air catches up to the rain. Sunday and beyond...Upper level high pressure builds in across the Gulf with low amplitude ridging extending across the OH Valley as surface high pressure tracks east across the region. Expect dry conditions to end the weekend and for the beginning of the next work week. Temperatures will start off cool on Sunday with highs only reaching into the 45-50F range, but the days will gradually warm into next week with highs pushing back into the mid to upper 50s by Tuesday. && .Aviation...(00Z TAF Issuance) Issued at 601 PM EST Tue Dec 7 2021 Recent radar trends have shown some `higher` reflectivities (20- 25dBZ) across portions of southern IN, and moisture has started to saturate the lower levels of the atmosphere to allow some snow to reach the surface. Cigs/Vis will remain generally in the low-end VFR range with this snow, but can`t rule out some periods of MVFR in any `heavier` bands that develop. Snow will gradually overspread the northern half of the region and end from west to east. Cloud decks will remain between 5-10kft through the first half of the night, and then lift to +20kft toward sunrise. Skies will eventually clear out from west to east, and winds will shift to the west by the afternoon. && .Climate... Updated at 320 PM EST Tue Dec 7 2021 Strong warm air advection Friday will push temperatures into the upper 60s to low 70s. It is possible that a record or two could be tied or potentially broken. Below is a summary of forecast temperatures, climatological normal values, and the daily record max temps for December 10. ====== Friday Maximum Temperatures ====== Forecast / Normal / Record (Year) SDF: 70 / 49 / 71 (1971) BWG: 70 / 51 / 74 (1971) LEX: 66 / 47 / 72 (1971) FFT: 67 / 48 / 76 (1952) && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...DM Short Term...MJ Long Term....CG Aviation...DM Climate......CG