067 FXUS63 KLSX 110454 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1154 PM CDT Wed Oct 10 2018 .SHORT TERM... (Through Late Thursday Afternoon) Issued at 337 PM CDT Wed Oct 10 2018 The cold front was located from western IL into far southeast MO late this afternoon, and moving east at a decent clip. Instability is diminishing along and ahead of the front, and spotty showers will remain possible with the front during the remainder of the afternoon as it progresses through southwest/south central IL. The the main story tonight will be chilly temperatures and slowly decreasing cloud cover. West northwest winds will diminish by early evening but will continue to usher much colder air into the area. Tonight will be the coldest thus far this fall. I am a bit pessimistic on the clouds clearing given the upstream extent and have slowed the trend from the previous forecast. Weak CAA will persist in the morning and I think any remaining clouds will decrease and/or we will see just some scattered diurnal cu develop. Highs will be significantly colder than today and all but far southeast MO and southwest IL will remain in the 50s. Glass .LONG TERM... (Thursday Night through Next Wednesday) Issued at 337 PM CDT Wed Oct 10 2018 High pressure will dominate the area Thursday night and the main question for this period is the potential for any frost. The evening and first part of the overnight period will be relatively void of clouds. With light winds we should temperatures fall rather quick and I have mentioned some frost across northern portions of the CWA, roughly north of I-70. Clouds will begin to overspread the area before daybreak on Friday ahead of the next system. An upper trof will move southeastward from the northern Plains into the mid-upper MS Valley on Friday. Large scale forcing associated with the trof along with low level WAA and low-mid level frontogenetic forcing will result in a large rain area of rain overspreading across the region from the west. The combination of clouds and diabatic cooling will make for a cold day/rain and well below average temperatures, especially across northeast MO and west central IL. The rain shield should exit to the east of the area by late evening in association with the progression of the upper trof and forcing. Temperatures will fall into the 30s overnight and surface winds will be light. Normally this would suggest frost potential, however the wet ground from the rain and likelihood of lingering clouds are negative factors and will not mention any frost at this time. Another upper trof moves into the Plains late Sunday and advances into the Mid Mississippi Valley in the Monday-Monday night time frame. The ECMWF and GFS differ a bit handling this trof and the associated rain shield which is largely driven by frontogenetic forcing. At this time we have favored the wetter ECMWF solution which spreads rain across the southern 2/3rds of the area Sunday into Sunday night. Little or no precipitation is expected Tuesday into Wednesday with temperatures at or below average. Glass && .AVIATION... (For the 06z TAFs through 06z Thursday Night) Issued at 1137 PM CDT Wed Oct 10 2018 Main changes are to keep gusts to around 20 kts going thru the overnight hours and Thurs. MVFR cigs are also expected to linger into Thurs morning. Have increased clouds on Thurs, but expect more breaks in the clouds compared to Wed and therefore also expect higher bases. Winds are expected to diminish during the afternoon hours as the sfc ridge builds into the region. There shud be a brief window as clouds dissipate and move out of the region before a mid deck is progd to move back into the region. SPECIFICS FOR KSTL: Expect MVFR cigs and gusts to remain overnight and into Thurs morning. The gusts shud diminish during the afternoon hours. The lingering CU shud also diminish during the late afternoon into the early evening hours before a mid deck moves back into the area. Tilly && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX