765 FXUS63 KPAH 180939 AFDPAH Area Forecast Discussion National Weather Service Paducah KY 339 AM CST Fri Jan 18 2019 .SHORT TERM...(Today through Sunday night) Issued at 338 AM CST Fri Jan 18 2019 Main forecast challenges/concerns in the short term continues to lie with the storm system expected to affect much of the region tonight through Saturday evening. Important note: There is still a considerable amount of model uncertainty in regards to the winter aspect of this system Saturday afternoon and evening. Confidence remains low at this time, especially in locations along and south of the Ohio River. Widespread moderate to occasionally heavy rains, and even a few isolated thunderstorms (south areas), will spread east across the forecast area tonight as strong mid level forcing gets underway ahead of a potent mid level trof moving east through the southern Plains/AR region. General rainfall amounts close to an inch to an inch and a half are expected through Saturday, highest numbers over wrn KY. With the ground already quite wet, we could see some minor flooding impacts to creeks, streams and clogged drainages, especially where the rain comes down hard at times. However, widespread flooding is not expected to pose an issue, so will hold off on any headlines at this time. Bigger questions and uncertainty come into play Saturday afternoon and Saturday night as the associated surface low moves east through the mid MS River Valley. Though most models have come into agreement now on a surface low track through wrn KY on Sat, there are still differences on how they handle the mid/upper level dynamics as northern and southern branch trofs interact and try to possibly phase. For now, it looks as through there is decent consensus that at least some type of deformation zone will set up for a few hours as much colder air sweeps southeast into the region Saturday afternoon and early evening. If this scenario indeed occurs, we would have the potential for a couple inches of snow across about the northern half of the forecast area. Generally less than an inch would be possible farther south over southern portions of western KY and MO. However, with rapidly falling temperatures into the 20s and blustery north winds howling over 30 mph, even small amounts of accumulating snow could cause some travel impacts. Given existing uncertainty and the fact that the main winter impacts are not anticipated until later in the 3rd period of the forecast, will hold off on headlines with this package and let the day shift take another look and hone it a bit better. It is still a somewhat fluid situation given the complexity of the mid/upper level dynamics. Will issue a strongly worded special weather statement with this forecast package. Conditions will become quite blustery and cold Saturday night as the low pulls off to the east, with temps tumbling into the mid teens to near 20. Wind chills will likely dip into the single digits at most locations by sunrise Sunday. As the bulk of the cold air arrives in force Sunday, high temps at most locations will not get out of the 20s. It could even stay in the teens to near 20 up along the I-64 corridor if there is a decent coating of snow on the ground. Sunday night appears it will be the coldest night with this outbreak as the surface high moves east over the Great Lakes region. Most locations will fall well into the teens by sunrise Monday. .LONG TERM...(Monday through Thursday) Issued at 338 AM CST Fri Jan 18 2019 Confidence in the long term portion of the forecast starts off higher than average with good overall model agreement at the start of next week. However, confidence drops off by mid week with greater model variability over the timing of the next weather system. The core of Arctic high pressure will shift to the east by Monday as our next storm system approaches from the Central Plains. Flattening flow aloft and low level southerlies should bring about a decent moderating trend, with highs on Monday forecast back into the 30s. The chance for precipitation will increase late Monday night into Tuesday as the Plains system approaches and makes passage. The bulk of available guidance indicates a thermal profile warm enough to support mainly rain during this time. Enough cold air may work in on the back edge of the precipitation shield to result in a transition to a period of snow or a mix before ending sometime mid week. The forecast from Wednesday on is really subject to change at this point. The model blend hangs on to a small chance of snow through Wednesday night and Thursday morning. Of the 00Z runs, the CMC is the only model that supports this, as was the case with its 12Z predecessor, primarily due to its slower/further west progression of a secondary southern stream wave. Prior to that, the ECMWF had been the slow outlier. Within the 00Z GEFS, a quarter of the ensemble members support a secondary round of wintry precipitation Wednesday into early Thursday. So while prolonging precipitation chances is not necessarily the favored solution at this time, it cannot be completely ruled out. Thus, will maintain the low chances in the initialized blend for the time being until confidence improves. && .AVIATION... Issued at 1043 PM CST Thu Jan 17 2019 Little functional change from the 00z Friday WFO PAH TAF issuance. Even as a surface low moves into and slightly deepens over southern Oklahoma near 00z Saturday, the pressure gradient that would enhance mixing remains generally west of the WFO PAH TAF sites. The exception would be KCGI, but scattered rain will serve to keep ceilings near or below 1000 feet agl toward the end of the period. For the most part, with light winds in place, fog potential will be limited through the forecast period. With limited mixing through the 06z forecast, plan to keep with the status quo for ceilings with this issuance. Low end mvfr and upper end IFR ceilings will be the rule. Should the system over OK speed up, we may see more improvement into the MVFR category of ceilings for KCGI and possibly KPAH. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ SHORT TERM...GM LONG TERM...RJP AVIATION...Smith