604 FXUS63 KLSX 100912 AFDLSX Area Forecast Discussion National Weather Service Saint Louis MO 412 AM 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 embededed 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. Tonights 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 slighty 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 06z TAFs through 06z Wednesday Night) Issued at 1211 AM CDT Wed Oct 10 2018 A line of showers with a few embedded thunderstorms continues to move slowly east through central and northeast Missouri into east central Missouri and west central Illinois. This slow progression eastward is expected to continue through the rest of the night and into Wednesday. Heavy showers embedded in the line will be capable of intermittently dropping visibility and ceilings to IFR. However, think flight conditions will generally stay MVFR with the line of showers. Most guidance fills in low ceilings after 12Z ahead of the cold front with heights down below 2000 feet. The front will move through from east to west from around 15Z in central Missouri to around 20-22Z. There should be a general improvement to VFR during the afternoon after FROPA. Southerly flow ahead of the front will turn sharply to the west after the front passes. SPECIFICS FOR KSTL: The line of showers moving into east central Missouri will likely be to the terminal by 08-09Z. There are a few embedded thunderstorms which will be capable of reducing visibilities to IFR levels, and ceilings could drop below 2000 feet in these storms as well. More shower activity is expected in the morning with ceilings dropping below 2000 feet ahead of the front. Latest guidance has the cold front moving through the terminal between 18-19Z, and other than a stray shower that should be the end of the precip. Ceilings should begin rising behind the front as well and I expect VFR flight conditions by late afternoon or early evening. Carney && .PRELIMINARY POINT TEMPS/POPS... Saint Louis 76 44 60 40 / 90 5 0 0 Quincy 70 39 53 36 / 90 5 0 0 Columbia 68 39 55 38 / 80 0 0 5 Jefferson City 70 41 57 39 / 80 0 0 5 Salem 79 45 59 39 / 90 10 0 0 Farmington 76 44 60 40 / 90 5 0 0 && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX