Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 01/17/22

Area Forecast Discussion
National Weather Service Louisville KY
1100 PM EST Sun Jan 16 2022 .Forecast Update... Issued at 1100 PM EST Sun Jan 16 2022 Winter storm continues to wind down across the region. Earlier deformation band has weakened and continues to move eastward through the Bluegrass region. Light snow will continue for the next few hours with a break before the next system swings through. Given that significant snows are no longer likely, we`ve gone ahead and dropped the Winter Storm Warning. For the overnight, the next disturbance is coming down the pike through east-central MO and central Illinois. Based on upstream reports, a dusting on untreated road surfaces has been reported in the St. Louis area. While the models are still putting out some slightly higher accumulations than that, we`ll probably have some slick spots develop in areas that hadn`t seen snow with the previous system and we`ll probably see a redevelopment of additional issues in areas that saw snow earlier but have improved. For that reason and in the interest of safety and impacts, have gone ahead and issued a Winter Weather Advisory for the overnight period. If this system doesn`t amount to much, this advisory could be dropped earlier than the current expiration. Will make some minor adjustments to the ongoing forecast and have updates out shortly. In the interest of newscasts, we have continued to put out local storm reports on the accumulation amounts we have received from our media partners and from social media reports. Issued at 920 PM EST Sun Jan 16 2022 Deformation band has exited the I-65 corridor and is currently located from just west of Frankfort and extends southward to near Campbellsville. This band is heading east and will affect those area along I-64 and the Bluegrass Parkway. Based on its movement, it should impact the Lexington area over the next couple of hours. Temps across the region are in the upper 20s to the lower 30s and temperatures will continue to drop into the mid-upper 20s overnight. So slick spots will be possible in areas along the I-65 corridor but much of the more widespread hazardous travel will be out in areas mainly east of I-65 this evening and into the overnight. We`re going to look over the headlines here over the next hour or so. There is still a chance that we can some additional snows that will push us over warning criteria, most likely in areas along and north of the Bluegrass Parkway. However, am concerned about upstream disturbance that will bring additional light snows into the region after 06Z. Latest guidance suggests another half to perhaps 1 inch of snow could fall between 07-13Z which will probably lead to additional hazardous travel conditions. Current thinking is that we may hoist a new Winter Weather Advisory to cover the impacts of that additional snow, while also covering the ongoing hazardous conditions out east of I-65. Just as a heads up, we`re working on sending out local storm reports with the snowfall amounts we`ve collected from social media and our media partners. Issued at 740 PM EST Sun Jan 16 2022 Western edge of the snow is working its way across the I-65 corridor at this hour. We`ve seen the intensity of this band oscillate over the last few hours. It seems to be picking up again in the I-65 corridor over southern Jefferson and down into Bullitt county. We expect this activity to continue to move off to the east over the next few hours. Other stronger snow band extended from near Covington southwestward through Owen, Henry, Franklin, Shelby, Spencer, Anderson, Washington, Marion, and down into Taylor and portions of Adair county. This band may intensify a bit over the next hour as it slowly pivots to the east. Most likely 0.5-1.0in/hr rates will be possible in this band as it translates through the US 27/127 corridor and eventually into the Lexington Metro this evening. With this update, we are going to clear Warren, Logan, Simpson, and Allen counties out of their respective advisories and warnings as the activity in this area has diminished significantly. All other advisories and warnings will continue unchanged for now. Issued at 552 PM EST Sun Jan 16 2022 Moderate to heavy snow continues across our east-central sections of the forecast area. The earlier mix has changed to snow from the Lexington metro area southward and we expected areas of the northern Bluegrass to go to snow momentarily. Main issue is further west out near the I-65 corridor where the very back edge of precipitation band has intensified a bit over the last 30-45 minutes. This band started off as mainly sleet, but has changed over to snow now. With darkness setting in and temps at or below freezing, we expect some accumulation of snow that is impactful enough to warrant an expansion of the Winter Weather Advisory westward to cover Oldham, Henry, Jefferson, Bullitt, Hardin and Grayson counties. This band will continue to move eastward over the next 1-2 hours and may produce a quick inch to maybe two inches in spots before the precipitation diminishes by mid-evening. This update was mainly to expand the Winter Weather Advisory westward, but other segments of the winter weather advisory and winter storm warning have not been changed. && .Short Term...(This evening through Monday) Issued at 330 PM EST Sun Jan 16 2022 ...Significant Wintry Accumulations For Portions of Central and Eastern Kentucky This Afternoon & Evening... The upper low is now quickly moving through NE Georgia and will head through the mid Atlantic tonight. As a result of the NE movement, the broad precipitation shield has made its pivot to a SW to NE orientation and will persist over our area through the evening hours. We`ve seen a lot of locations start to change over to more sleet and snow, and with evidence of the warm nose collapsing on dual pol and some AMDAR soundings, we expect to see the hard changeover everywhere soon. So far, we`ve observed a change over to all snow in heavier rates, with a mix showing up outside of the heavy rates. Starting to see some light accums on webcams across our southeast where it has changed to all snow, and from here expect steady accumulations in the Advisory and Warning areas until the precipitation shield lifts NE later tonight. Have some concerns that we may underachieve in the Warning areas due to marginal surface temps and some of the latest data, but have no plans to change anything as we will still see impactful wintry weather in these areas through the evening. Plus, we are just now reaching the heart of the event and more organized banding is just starting to try and set up. Will probably be able to let some of the SW Advisory counties go sooner than later as the western edge of the precipitation shield starts to dry up and shift east. However, there are still some light returns down there so will hold off until the threat is completely over. Also decided to issue a Special Weather Statement for the counties NW of the Advisory as we are getting some light accums on elevated surfaces. We`ll see a brief lull in precipitation after Midnight as the main storm system lifts off to the NE, however a quick hitting Clipper is expected to quickly come in on the heels of this system in time for the morning commute. Given steepening low level lapse rates and favorable temps, some quick burst scattered to numerous snow showers may cause a dusting to a half an inch for some. Given that this will be during the morning commute (even though it is a holiday) there will probably be enough traffic concerns to warrant a Special Weather Statement. We`ll hold off on that until this event ends, however messaging is encouraged as most folks were focused on today`s storms. These quick hitting snow shower events can be a bit sneaky with impacts, and this one kind of has that look. .Long Term...(Monday night through Sunday) Issued at 330 PM EST Sun Jan 16 2022 By Monday evening, the large upper level low will be well off to our east, and mid-level NW flow brings drier air into the region. Low temps for Tuesday morning will drop into the 20s and possibly the teens for a few spots as well. In the low levels, weak ridging and a sfc high over the Gulf States will be spreading northward Monday night. The expansive dome of sfc high will remain across the Gulf on Tuesday, but southerly low level winds and a brief period of zonal flow aloft will contribute to temps reaching the 40s on Tuesday. On Wednesday, an upper shortwave and associated sfc low will track across the US/Canadian border, trailing a cold front through the Midwest. Deep southwesterly flow and low level jetting ahead of the front will help keep temps above freezing and support liquid precip. Soundings suggest the moisture advection could be strong enough to raise PW values near the 90th percentile. Best chance for rain showers will be from Wednesday morning through Wednesday night, with cooler NW post-frontal flow filling in by early Thursday morning. Colder air may catch up with any precip lagging behind the frontal boundary, resulting in a chance for a brief change over to light wintry precip Wednesday night. As we head into the back half of the long term, model solutions appear to have come into better alignment for the Thursday/Friday time frame. Expect to see a Canadian high dive southward by Thursday morning, bringing much colder air to the Ohio Valley. We could see temps struggle to get out of the 20s for Thursday and Friday in addition to morning lows in the teens. The sfc high will slide towards the Northeast on Saturday and southerly return flow returns. && .Aviation...(00Z TAF Issuance) Issued at 628 PM EST Sun Jan 16 2022 IMPACTS: - Light/moderate snow to impact KSDF early this evening - Light/moderate snow expected this evening at KLEX - Additional light snows expected later tonight and Mon Morning DISCUSSION: Winter storm continues mainly east of the I-65 corridor. Decent deformation band developed near/just west of I-65 corridor and continues to move east. This will result in light snows at KSDF through about 01Z or so. Bands of light snow will affect KLEX this evening with IFR and possibly dips into LIFR at times. KHNB and KBWG should remain mostly dry with VFR conditions at KHNB and MVFR conditions giving way to VFR at KBWG. Winds will be out of the northwest at 10-12kts with occasional gusts to 15-20kt at times. Later tonight, secondary disturbance is forecast to drop in from the northwest late tonight and bring a round of snow showers to the region from about 09Z through 16-17Z Monday. We expect mainly MVFR conditions with that activity with improving conditions after 17Z. CONFIDENCE: Medium confidence on all elements. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...Winter Weather Advisory until 8 AM EST /7 AM CST/ Monday for INZ076>079-083-084-089>092. KY...Winter Weather Advisory until 8 AM EST /7 AM CST/ Monday for KYZ023>043-045>049-053>057-061>067-070>078-081-082. && $$ Update...MJ Short Term...BJS Long Term....CJP Aviation.....MJ
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
725 PM CST Sun Jan 16 2022 .UPDATE... Issued at 725 PM CST Sun Jan 16 2022 A narrow ribbon of light snow continues to move across the area early this evening, briefly lowering vis into the 2 mile range with a light coating of snow. RFD measured a tenth of an inch at 00z and a dusting will be possible with this band. The low levels were quite dry ahead of this light snow, but are quickly becoming saturated. The HRRR/RAP continue to show some redevelopment or enhancement of the light snow over the metro area in the next few hours. Opted to bump pops to likely for a few hours this evening and added a tenth of inch of snow accumulation to the grids. Some flurries may continue into the overnight hours. cms && .SHORT TERM... Issued at 221 PM CST Sun Jan 16 2022 Through Monday night... Upper-level satellite imagery depicts a sharp shortwave screaming southeast across the Upper Great Lakes on an approach to phase with the sprawling low pressure system across the southeastern United States. A narrow band of snow is evident along the leading edge of the shortwave, though ground observations reveal that hardly anything is surviving through a parched low-level airmass. While not sampled where snow is attempting to fall, recent AMDAR soundings from aircraft arriving and departing ORD, MDW, and MKE reveal the the mean 900 to 600 mb relative humidity across northeastern Illinois and southeastern Wisconsin ranges anywhere from 5 to 25%. Even with impressive upper-level lift / DCVA as well as steepening lapse rates in the heart of the DGZ, the prospects of snowflakes surviving the trip to the ground as the band sweeps across our area this evening seems to be lowering even as precipitation rates increase above the dry layer. We thus opted to cut back on the mention of snow in our official forecast, with a 20% chance of a flurry/light snow shower seeming appropriate (if not still a tad aggressive). Snow or no snow, clouds will become overcast this evening and hold overnight lows close to 20 degrees. After midnight, a cold front will sweep across the area leading to blustery northwest winds. Depending on the eventual depth of the clouds after midnight (which partly hinges on how much saturation can be archived through virga this evening), a few snow grains cannot be ruled out through about daybreak. The best chances for snow overnight will be in far northeastern Porter County where the increasingly unstable waters of Lake Michigan and northwesterly fetch will afford the development of snow showers. With inversion heights expected to top off near 5000 feet (and entirely below the DGZ), a low-quality snow grain is preferred which will limit snow rates and accumulations. Snow should taper toward noon on Monday as inversion heights lower and moisture quality decreases, leaving behind perhaps as much as in inch or two in total snow accumulation (particularly northeast of a line from Portage to Malden). Elsewhere, tomorrow will start cloudy before mixing allows for at least pockets of mixing and clearing. Highs should top off in the upper 20s, but the blustery northwest wind will make it feel more like the teens. Borchardt && .LONG TERM... Issued at 221 PM CST Sun Jan 16 2022 Monday night through Saturday... The long term period begins with slightly above normal temperatures for this time of year due to southerly winds advecting warm air into northeastern Illinois and northwest Indiana. Highs on Tuesday are forecasted to reach the mid to upper 30s with some locations possibly reaching 40 degrees. Lows on Tuesday night look to stay mild and in the low to mid 30s before a cold front pushes through the area. Temperatures will be dropping throughout the day on Wednesday behind the front with blustery northwesterly winds around 25 mph. The arctic airmass behind the front will create a cold conclusion to the work week with highs struggling to make it into the 20s and overnight lows in the low single digits and even sub-zero in places. Wind chills may drop to be well below zero in the negative teens through weeks end. Precipitation chances with the aforementioned cold front look to be low due to a lack of moisture in the mid and upper-levels of the atmosphere. Current model guidance shows relative humidities struggling to reach 50% as the front moves through which should suppress any precipitation development. However, a band of moisture does look to develop and move down lake Michigan on the backside of the system Wednesday night into Thursday which would allow some lake-effect snow showers to develop across portions of northwest Indiana. Given the northwest flow in place, precipitation chances are expected to be higher towards northern Indiana and southwestern Michigan with lower chances further to the west. I have opted to keep slight chances of precipitation mentioned for the Indiana lakeshore and northeastern Porter county at this time to account for this potential. The next chance for more widespread precipitation doesn`t look to be until the weekend where models are showing another clipper system diving across the Great Lakes region. Forecast guidance is still uncertain on the timing of this system and the extent of the precipitation with it so I have opted to leave precipitation chances as they were from the NBM forecast. Yack && .AVIATION... For the 00Z TAFs... 525 PM...Forecast concerns include... Chance of light snow this evening. Mvfr cigs overnight/Monday morning. Gusty northwest winds overnight thru Monday afternoon. An area of light snow is moving across northwest IL and south/ central WI early this evening, dropping visibilities into the 2-3sm range for a short period of time. There is quite a bit of dry air in the low levels that this snow will need to saturate before reaching the ground across the Chicago terminals and as it saturates the low levels, it may begin to weaken/dissipate some, though confidence remains low. Much of the high res guidance then shows another area of light snow developing from the Chicago terminals south into central IL by mid evening. By that time, the low levels should be sufficiently moist that any snow that does develop should be able to reach the surface. For now, opted to carry tempo light snow with mvfr vis through 03z and monitor trends this evening. If snow does reach the Chicago terminals, possible vis briefly dips into the 2sm range. There will be a continued chance for flurries overnight. A large area of mvfr cigs across MN/IA and western WI will move southeast across the area overnight and prevailing mvfr cigs are expected through much of Monday morning, slowly scattering and lifting Monday afternoon. Westerly winds under 10kts will shift northwest later this evening with speeds/gusts increasing in the early morning hours. Gusts into the mid 20kt range are expected Monday morning. Gusts are expected to continue through sunset Monday evening, but should be slowly diminishing during the afternoon. cms && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory...LMZ744-LMZ745...midnight Monday to midnight Tuesday. Small Craft Advisory...LMZ740-LMZ741-LMZ742-LMZ743...midnight Monday to 3 PM Monday. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at: