073 FXUS64 KOHX 271102 AFDOHX Area Forecast Discussion National Weather Service Nashville TN 502 AM CST Sun Jan 27 2019 .DISCUSSION... An upper level disturbance will move across the mid state today. A weak sfc cold front will approach the mid state region from the Ohio River Valley as the morning hrs progress, and may actually enter northern portions of the mid state region during the early afternoon hrs, before pushing nwd as a warm front late afternoon. All in all, this wx pattern will bring variable cloudiness to our area, but the mid state region should remain dry. Afternoon high temps today will be around seasonal normal values, ranging from mid 40s north to lower 50s south. As this upper level disturbance pushes ewd, a more zonal flow pattern aloft is expected as the nighttime hrs progress, with sly sfc flow becoming increasingly established. Variable sky conditions will once again prevail across the mid state region. Overnight lows tonight, because of the establishment of sly sfc flow, will generally be in the lower 30s, around 30 Cumberland Plateau Region. Forecasted overnight lows will be a few degrees above seasonal normal values. As swly upper level flow develops ahead of next wx system to affect the mid state region, and the mid state is placed in the broad warm sector of a synoptic sfc frontal system with a sfc low centered across northern IL by Mon morning, ptcldy skies during the morning hrs will give way to mocldy skies during the afternoon hrs. A slight chance of light shwrs will be possible near the Land of the Lakes Region as the afternoon hrs progress. With a sfc pressure gradient becoming established also, this sets the stage for afternoon high temps on Mon on average to be 8 to 10 degrees above seasonal normal values. Mon afternoon high temps will be generally in the mid to upper 50s. The main wx event for the forecast period centers around the potential of rain shwrs Mon night transitioning to snow shwrs after midnight, with possible snowfall accumulations across the mid state region. Although some differences across the contiguous U.S. noted, a generally good run to run model consensus solutions across the mid state region with this developing wx system. The colder air that will allow for this transition from rain to snow will originate from a sfc high pressure center established across British Columbia by the morning hrs on Mon. It will then move sewd into the nrn Rockies by Mon night, and continue its sewd plunge into the western half of the contiguous U.S. by Tue morning. This will set up also an enhanced sfc pressure gradient behind this frontal system on Tue morning also, as influences of this colder air mass rush into the mid state region. As a result, some gusts around 35 mph possible across the Cumberland Plateau Region on Tue afternoon. Look for above mentioned sfc front to push quite quickly swd as Mon into Mon night progresses, with the front entering nw portions of the mid state by the early evening hrs on Mon night and push thru the entire mid state and well south and east by just shortly after sunrise on Tue. Model consensus showing shwrs spreading from nw to se during early evening hrs, and enough post frontal atm lift to support a rain/snow shwr transition zone entering ern parts of the Nashville Metro area by around midnight. Light snow shwrs will be to the nw of this area as cold air begins to work into the mid state region. As the overnight hrs progress, and colder air works across entire mid state region, with light, and embedded moderate snow shwrs, expected for all locations as the early morning hrs progress. Along with the above mentioned sfc features, upper level flow will become increasingly swly behind this sfc frontal passage as a pronounced upper level trough approaches the mid state region from the MS River Valley. As this upper level troughing moves ewd across the mid state region on Tue, locations generally around and east of I-65 will experience light snow shwrs during the morning hrs, with snow shwrs finally tapering off across the Cumberland Plateau Region by the mid afternoon hrs on Tue. The above mentioned is a consensus solution, with individual models either being a little quicker or a little slower in moving post frontal moisture with this system out of the mid state region. Some uncertainly still remains about actual accumulation amounts, but it is looking more and more likely that significant snowfall accumulation amounts will occur across mid state region. From the consensus of the model runs this morning, total accumulations from Mon night thru Tue afternoon looks to be around one half of an inch across nw portions of mid state region, to one to two inches cntrl, to 2 to 3 inches east and Cumberland Plateau Region, where higher elevations and orographic lifting influences could play a role in additional snowfall accumulation. Overnight lows on Mon night, as the colder air moves in behind this frontal passage, will be around 20 in the Land Between the Lakes Region to mid 20s srn portions Cumberland Plateau Region. Afternoon highs on Tue will generally be in the mid to upper 20s. Will be issuing a special weather statement, SPS, later this morning to provide heads up information and additional details. Like most potential winter wx systems that could effect the mid state region, there continues to be some uncertainty here, and thus later model runs with forecasters meteorological interpretation will be needed as the time of this potential winter wx event approaches for most accurate expected snowfall accumulation amounts. A dry cold front will move into the mid state from the Upper MS River Valley/Great Lakes Region by Wed morning accompanied by a weak upper level distrubance around base of broad upper level troughing influences across cntrl and ern contiguous U.S. Although the remaining influences of the once British Columbia high pressure air mass will now be south of the mid state region, a reinforcing shot of colder air will now be provided by and artic airmass moving out of srn Canada, ushering likely the coldest temps of the winter season to the mid state region, is expected. Although dry conditions are expected Tue night thru Thu under generally ptcldy skies, lows Tue night will span the teens, with some locations experiencing single digit wind chills. Except for locations near the TN/AL border, temps will once again not get above freezing on Wed afternoon. Afternoon high temps on Wed will range from low 20s north to lower 30s south. As brunt of these strong sfc high pressure influences build into the mid state region on Thu night, overnight lows will be in the single digits north and Cumberland Plateau Region to lower teens near the TN/AL border. Most locations will experience single digit wind chills Thu night also, with some locations generally around and east of I-65 experiencing wind chills zero to a few degrees below zero, especially Cumberland Plateau Region. This high pressure area will begin to shift ewd as Thu progresses, with afternoon highs on Thu slightly warmer. Temps will be at or above freezing mainly for locations south of I-40 with those locations around and north of I-40 remaining in the upper 20s to lower 30s. A slight chance of light snow shwrs will be possible Thu night into Fri morning. Then a transition to all rainfall by the afternoon hrs is expected as another upper level system moves across the mid state region in nwly upper level flow. Lows Thu night will mainly be in the lower 20s with afternoon highs on Fri upper 30s north to lower 40s south, upper 30s Cumberland Plateau Region. Discrepancies in model solutions become more apparent from Fri night onward. However, at this time will go with generally ptcldy skies Fri night into next Sat with a warming trend. Temps are expected to be closer to seasonal normal values. Another potential wx system looks like it will move into the mid state region providing some rainfall next Sun. && .AVIATION... 06Z TAF DISCUSSION. Mainly VFR flight conditions for mid-state terminals. Only exception may be KCSV as a weak wave bring more clouds in tonight and possibly some MVFR cigs. Winds will be light out of the SSW, then shift to the northwest late Sunday morning. && .PRELIMINARY POINT TEMPS/POPS... Nashville 49 32 58 23 29 / 0 0 10 80 20 Clarksville 44 32 56 19 28 / 10 0 20 80 10 Crossville 45 30 53 25 26 / 0 0 0 80 80 Columbia 50 31 58 23 30 / 0 0 0 80 20 Lawrenceburg 50 31 58 24 30 / 0 0 0 80 30 Waverly 48 33 57 20 29 / 0 0 10 80 10 && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......31 AVIATION........Unger