317 FXUS63 KLSX 101745 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1245 PM CDT Wed Oct 10 2018 .SHORT TERM... (Through Late Tonight) Issued at 310 AM CDT Wed Oct 10 2018 Cold front extending from a surface low over west central IA south through northwest MO and southeast KS will move eastward today as a negatively tilted shortwave moves the region. A north to south band of showers and a few embedded thunderstorms was moving into the St Louis metro area early this morning, and will continue to translate slowly eastward. This activity was ahead of the cold front and in a region of low level moisture convergence associated with a southerly low level jet. There will be the potential for isolated strong to severe thunderstorms containing locally heavy rainfall and damaging winds today, mainly across southwest IL due to favorable low-mid level wind shear as a mid level wind max moves over the area, along with sufficient CAPE. By afternoon most of the showers and storms will be across southwest IL into parts of southeast MO. Temperatures will fall today due to strong low level cold air advection behind the cold front. Tonight's lows will be much colder as a large and strong surface ridge over the northern Plains builds southeastward into MO, ending the chance for rain by early evening. Lows tonight will only be 5 to 10 degrees below normal, but it will feel quite cold due to the unseasonably warm conditions experienced for much of October so far. GKS .LONG TERM... (Thursday through Tuesday) Issued at 310 AM CDT Wed Oct 10 2018 Dry and much colder conditions can be expected Thursday and Thursday night. It may be cold enough across northeast MO and west central IL for patchy frost late Thursday night and early Friday morning, although increasing cloudiness will hinder frost formation. The models are now stronger with an upper level trough moving eastward through our region on Friday and hence have more QPF for the forecast area Friday into Friday evening despite the relatively dry surface/boundary layer with the surface ridge over our area on Friday. With cloud cover hindering diurnal solar insolation on Friday high temperatures should be 15 to 20 degrees below normal. Will see slightly warmer temperatures on Saturday with surface winds becoming southerly on the backside of the retreating surface high. Another round of precipitation can be expected Saturday night and Sunday, and possibly lingering into Monday morning. A southern stream shortwave and associated surface low will pass south of our area and lead to showers, particularly across southeast MO and southwest IL. A northern stream shortwave and associated cold front will drop southeastward through our forecast area Sunday and Sunday night behind the surface low. The operational GFS is a little more progressive than the ECMWF model and shifts the precipitation southeast of our forecast area Sunday afternoon, while the ECMWF does not shift the rain southeast of our area until Monday afternoon. For now will lean toward the slower solution. The cold front will bring another shot of cold air into the region Sunday night and Monday. Both the GFS and ECMWF bring the zero degree C 850 mb isotherm south of our forecast area on Monday. GKS && .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