Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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051 FXUS63 KLSX 220904 AFDLSX Area Forecast Discussion National Weather Service Saint Louis MO 404 AM CDT Sun Sep 22 2024 .KEY MESSAGES... -There will continue to be chances for showers and thunderstorms through Tuesday. -Isolated severe storms are possible over southeast Missouri and southwest Illinois this afternoon and early this evening. The primary threat with the strongest storms will be damaging winds. -Temperatures will cool down behind a cold front today with below normal highs on Monday and Tuesday. && .SHORT TERM... (Through Late Monday Afternoon) Issued at 403 AM CDT Sun Sep 22 2024 Initial round of showers and thunderstorms is moving through the CWA this morning ahead of the cold front in a band of strong low level moisture convergence. This first round will eventually exit to the east by mid-morning as the low level jet veers and weakens. There will continue to be lesser chances (30-50%) for showers and thunderstorms this afternoon into this evening as the cold front that is currently over southeastern Iowa and northwest Missouri will move southeast across the CWA. There still remains the possibility for one or two storms to produce damaging microbursts over southeast Missouri into southern Illinois this afternoon and early this evening given MLCAPES around 1500 J/kg and deep layer shear around 30 knots. There will be some potential for locally heavy rainfall given that PWATS will be in the 1.6-2" range today, especially where any storms can train for very long. The chance for showers and thunderstorms will begin to increase again late tonight into Monday, particularly over the southern half of the CWA. Lift will increase across Missouri and Illinois as the HREF is showing an upper trough moving into the area from the west. Have kept higher PoPs (60-80%) over the southern half of the CWA where the stronger forcing and the best moisture transport will move into the area late tonight into tomorrow afternoon. There will be quite a range in highs today with the front and rain, ranging from near 70 over the north to the middle 80s in the south. Highs tomorrow will be below normal across the CWA with cold air advection behind the front, the clouds, and rain chances. Britt && .LONG TERM... (Monday Night through Saturday) Issued at 403 AM CDT Sun Sep 22 2024 There is decent agreement amongst the medium range models that upper trough will drop down into the Midwest behind Monday`s trough which will keep showers and thunderstorms going over the area Monday night into Tuesday. Some solutions show an upper low cutting off over the Midwest into late week which would keep a chance (20-30%) of showers going over the CWA Thursday into Saturday. Temperatures will still be below normal on Tuesday, but will climb back to near normal the rest of the week. Britt && .AVIATION... (For the 06z TAFs through 06z Sunday Night) Issued at 1044 PM CDT Sat Sep 21 2024 VFR conditions are expected for a few more hours with isolated showers moving through eastern sections of Missouri prior to 06z. Conditions deteriorate around 06z with showers and thunderstorms moving in from west to east. Just prior to 04z this evening, showers and thunderstorms spread from near the MO/IA border through west-central MO and into the southern Plains. This broad mass of activity will translate eastward overnight through into Sunday morning. MVFR ceiling/visibilities will be the primary impact with localize pockets of IFR possible at any terminals directly impacted by thunderstorms. This potential is greatest at KCOU/KJEF. While these conditions cannot be ruled out at KUIN and metro terminals, thunderstorms will likely weaken somewhat as they track east early Sunday morning. Though a bulk of the precipitation was originally expected to shift east through mid-morning Sunday, some of the latest trends in data show a slightly southward shift in the axis of heavier rainfall. If this trend continues, impact may extend slightly later into the morning. There is a brief lull behind this initial wave and the arrival of the cold front Sunday evening, when activity flares up again along and ahead of the front. The position of the front will determine exact placement of higher potential Sunday evening, but the general consensus if for rainfall to shift southeast of KUIN/KCOU/KJEF around 00z and metro terminal after 02z-03z. A few isolated showers may linger with MVFR ceilings along and behind the front. VFR could make a return at KUIN before the end of the TAF period. Maples && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX