Scientific Forecaster Discussion
000 FXUS63 KLSX 060452 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 1052 PM CST Thu Dec 5 2019 .SHORT TERM... (Through Late Friday Night) Issued at 324 PM CST Thu Dec 5 2019 The approaching surface cold front, driven by the mid level shortwave, will drive light rain into the region late tonight into early Friday morning. The majority of this rain will stay south of I- 70, though brief periods of light rain cannot be ruled out along the Columbia-St. Louis-Salem, IL line. Both the front and light rain exit the area Friday morning, leaving the remainder of Friday dry. Behind the front, northerly winds will advect cold air into the region. This cold air advection combined with lingering low stratus will help keep temperatures much cooler than recent days, with highs mostly in the 40s. Temperatures on Friday will peak in the around sunrise before slowly falling through the morning hours, then remaining steady during the afternoon. MRM .LONG TERM... (Saturday through Next Thursday) Issued at 324 PM CST Thu Dec 5 2019 A rapidly moving surface high builds into the region in the wake of Friday's system and keeps the weekend largely precipitation free. As it moves out of our area Saturday winds will veer to the south and we will return to above normal temperatures in the 50s Sunday through Monday. As the weekend surface high continues eastward out of the Midwest another surface low, attached to a deepening mid level trough, edges into the region Sunday night. This system will provide our next round of precipitation starting Sunday night into Monday night. The mid level trough deepens as it moves through the CWA on Monday, and steers the surface low out of the area to the northeast. As the surface low lifts out of the area Monday parallel to the slow moving cold front, guidance suggests a lingering chance of precipitation across the area through Monday night. Some of this precipitation may end as light snow before moving out of the area completely. A surface high building into the area in the wake of this strong surface low will keep the forecast precipitation free Tuesday through the end of the period. The passage of this cold front continues to mark a significant shift in temperatures as highs Tuesday through the end of the period will top out in the mid 20s to mid 30s. While this isn't particularly chilly for December, it is about 10 degrees below normal and will feel cool after the past several days of above normal temperatures. MRM && .AVIATION... (For the 06z TAFs through 06z Friday Night) Issued at 1035 PM CST Thu Dec 5 2019 Not a lot of changes from the prev TAFs. Still expect MVFR or low VFR cigs to develop as the cold front pushes south through the area. Winds will become northerly and increase. Winds will diminish late Fri afternoon and into the evening. Best chances for rain are at STL/SUS/CPS overnight, but do not anticipate visbys dropping below VFR. Tilly && .PRELIMINARY POINT TEMPS/POPS... Saint Louis 42 44 30 49 / 40 20 0 0 Quincy 33 38 25 46 / 5 5 0 0 Columbia 36 42 28 50 / 40 10 0 0 Jefferson City 38 43 28 52 / 60 10 0 0 Salem 44 48 29 47 / 50 40 0 0 Farmington 44 49 29 51 / 90 70 0 0 && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. &&