411 FXUS63 KLSX 161747 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1247 PM CDT Sun Oct 16 2022 .SHORT TERM... (Through Late Monday Afternoon) Issued at 304 AM CDT Sun Oct 16 2022 Aloft we remain in northwesterly flow on the southwest side of a robust trough centered over Ontario, while a weak ridge is stretched across the western CONUS. At the surface a dry cold front is moving through the region early this morning, currently stretching from west-central Missouri to west-central and north-central Illinois, behind which a surface high will move into the region. The passage of the front will usher in Arctic air and bring near record breaking temperatures for the first half of the work week. While 850 mb temperatures will begin to cool today, conditions will still be similar to yesterday across the region, dry with near to slightly below normal temperatures under a mostly clear sky. Cooling will continue tonight into Monday, CAA along the northerly flow will cool 850 mb temperatures into the single negative digits. Under a clear sky overnight lows will cool into the 30s, 10 degrees cooler than last night. Mixing during the day Monday will bring cooler temperatures aloft down to the surface, and high temperatures will peak in the mid 40s to mid 50s across the area, 15 to 20 degrees below normal. Temperatures will come close to breaking the low maximum temperature records at all climate sites (see Climate section below). In addition, mixing and a tighter surface pressure gradient will keep winds elevated between 15 and 20 mph and gusting into the upper 20s, resulting in a cold and blustery day. Winds will diminish with sunset, and a clear sky and continued CAA will allow temperatures to drop into the 20s or even teens across the valleys and cooler spots of the forecast area. The spread of solutions for the overnight lows continues to be small, increasing confidence that these sub-freezing temperatures will be realized. A Freeze Watch has been issued for the forecast area accordingly. Most of the area is expected to drop below 28, which will result in a killing freeze for these areas and an end to the growing season. Low temperature records for Tuesday morning at COU and UIN are in danger of breaking, while the urban heat island is expected to keep the temperature at STL above the record low. MRM .LONG TERM... (Monday Night through Saturday) Issued at 304 AM CDT Sun Oct 16 2022 CAA will continue in the low levels Tuesday along northerly flow. 850 mb temperatures will persist in the negative single digits, at the 0.5th percentile for this time of year. Despite the clear sky and ample sunshine, the cold start to the day and CAA will keep temperatures on Tuesday cold, about 20 degrees below normal. Even so, low maximum temperature records are safe for Tuesday. A clear sky overnight and light winds will push temperatures Tuesday night back into the 20s across the area, approaching record value. While northwesterly flow continues in the mid-levels, the center of the trough will shift southeastward through the Great Lakes region by Wednesday. This is mirrored in the lower levels, and flow will shift from northerly to northwesterly, and advect warmer air from the thermal ridge into the region. This will bring an end to our near record cold snap and begin to moderate temperatures across the region. Through the end of the work week and into the weekend the mid-level trough lifts out of southeastern Canada, and the weak ridge across the western CONUS begins to break down. This signals a pattern shift for the weekend and beyond. Another trough will come onshore over the weekend, and throw the mid-Mississippi Valley into southwest flow aloft. Likewise in the lower levels southwesterly flow will become established by the weekend, continuing the warming trend. The southwesterly flow may also open the region back up to Gulf moisture, and could bring precipitation back to the region. Some ensemble members are indicating light precipitation next weekend, but a majority of them keep the area dry. At this point, will stick with the NBM, which keeps the weekend dry. MRM && .AVIATION... (For the 18z TAFs through 18z Monday Afternoon) Issued at 1240 PM CDT Sun Oct 16 2022 VFR conditions are expected to extend through the end of this TAF cycle. Thicker mid to high clouds run along a stationary boundary well to the south (AR/TN/KY) of all terminals. A few mid-level clouds over northern MO continue to erode as they encounter dry air. Provided the sunshine between the two, deeper mixing will result in an occasional afternoon gusts. Northwesterly winds will be sustained between 5 and 10 knots tonight with a better potential for gusts from mid-morning Monday through the afternoon period. Maples && .CLIMATE... Issued at 215 PM CDT Sat Oct 15 2022 MON TUE WED 17 18 19 STL-- LOW MAX 49(1976) 42(1880) 42(1989) LOW MIN 29(1943) 27(1976) 25(1972) COU-- LOW MAX 48(1976) 38(1898) 41(1930) LOW MIN 26(1976) 25(1952) 22(1972) UIN-- LOW MAX 46(1989) 45(1989) 41(1989) LOW MIN 27(1943) 24(1948) 20(1972) && .LSX WATCHES/WARNINGS/ADVISORIES... MO...Freeze Watch from Monday evening through Tuesday morning for Audrain MO-Boone MO-Callaway MO-Cole MO-Crawford MO- Franklin MO-Gasconade MO-Iron MO-Jefferson MO-Knox MO-Lewis MO-Lincoln MO-Madison MO-Marion MO-Moniteau MO-Monroe MO- Montgomery MO-Osage MO-Pike MO-Ralls MO-Reynolds MO-Saint Charles MO-Saint Francois MO-Saint Louis City MO-Saint Louis MO-Sainte Genevieve MO-Shelby MO-Warren MO-Washington MO. IL...Freeze Watch from Monday evening through Tuesday morning for Adams IL-Bond IL-Brown IL-Calhoun IL-Clinton IL-Fayette IL- Greene IL-Jersey IL-Macoupin IL-Madison IL-Marion IL-Monroe IL-Montgomery IL-Pike IL-Randolph IL-Saint Clair-Washington IL. && $$ WFO LSX