910 FXUS63 KLSX 102115 AFDLSX Area Forecast Discussion National Weather Service Saint Louis MO 415 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 progesses 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 exent 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 comination 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 liklihood 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 18z TAFs through 18z Thursday Afternoon) Issued at 1228 PM CDT Wed Oct 10 2018 The cold front stretched from near KUIN southward across far eastern MO at midday. The cold front will continue to push east through the remainder of the afternoon. Thus far it has only been accompanied by spotty showers, and I think that will be the trend until it pushes into southwest IL this afternoon when there will be an opportunity for a few thunderstorms. Post-frontal clouds dominated by MVFR CIGS/flight conditions will remain extensive this afternoon through tonight, and I may be a bit optimistic with the trend to scattered in the TAFS near 12z. Gusty west winds are expected to persist through sunset and then resume some gustiness from the northwest on Thursday morning. SPECIFICS FOR KSTL: The cold front will move through the terminal around 19z and will be accompanied by a brief chance for showers. In the wake of the cold front, gusty west winds and MVFR CIGS/flight conditions will persist through sunset. Post-frontal clouds dominated by MVFR CIGS/flight conditions will remain extensive tonight, and I may be a bit optimistic with the trend to scattered in the TAFS near 12z. Gusty northwest winds will resume on Thursday morning. Glass && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX