Scientific Forecaster Discussion
000 FXUS63 KPAH 092316 AFDPAH Area Forecast Discussion National Weather Service Paducah KY 516 PM CST Mon Dec 9 2019 .SHORT TERM...(Tonight through Wednesday night) Issued at 200 PM CST Mon Dec 9 2019 A cold front's passage later today into this evening will lead to a big change in airmass, as highs today near or in the 60s plummet a good 30 degrees tomorrow. During this transition, overrunning moisture will create a window of opportunity for wintry pcpn, changing light rain to light snow late tonight-early tmrw. WPC and the blend/GEFS is consistently keeping only trace to a few tenths of an inch (less than a half inch) across our extreme southeast, despite some hints at deterministic 06z and 12z GFS amounts slightly higher. But even looking more closely at the GFS, both the gridded time/height cross section and sounding data for that area around HOP reveals a large dry nose, in fact the 12z run increased its strength from 06z, coming in late tonight between the boundary layer and about 600 mb. This should really impede accumulating potential, even with a wetter overall qpf/solution, so we like the blended/ensemble approach this time with minimal impact snows affecting mainly our western Kentucky counties around the Lakes eastward, bordering the Tennessee border. Surface temps there during the best time for snow will range from the mid to upper 30s, and ground temps may be higher than that, two more factors supporting minimal impact forecast. .LONG TERM...(Thursday through Monday) Issued at 200 PM CST Mon Dec 9 2019 In the long term, collaborative efforts yielded an agreement to utilize WPC qpf when the next moderating warmup/return chance of pcpn enters the forecast late in the week/into the weekend. Little change off the blend occurs otherwise, as the models are fairly straightforward with the development of a Gulf Coastal trof that places us to the north of the main impact/pcpn field heading into the weekend. This is followed by a more zonal pattern in its wake, with a clipper like wave of energy racing quickly across the Great Lakes Saturday, continuing our smallish pops thru the bulk of the days 5-7 period, even though much of that time period will actually be dry. Temps should be at/near climo norms, varying a few degrees on either side of the means. && .AVIATION... Issued at 515 PM CST Mon Dec 9 2019 After discussion with the dayshift aviation forecaster, decided to continue the trend of a slower rise of ceilings from IFR/MVFR to VFR tonight and Tuesday and maintaining a lower scattered cloud deck for moisture trapped within the post-frontal inversion. The GFS numerical guidance seems to be closest with this solution. Lowest ceilings will likely remain associated with the passage of the cold front into the area through at least 06z, as some post frontal boundary layer cooling and higher relative humidity is anticipated versus drier air intrusion aloft later in the night. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. &&