Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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756 FXUS63 KLSX 062321 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 621 PM CDT Thu Jun 6 2024 .KEY MESSAGES... - Dry weather is expected to continue through tomorrow before a chance of showers and thunderstorms returns late Friday night into Sunday. The greatest chance (60-80%) is now late Friday night into Saturday morning across much of the area. - Temperatures will remain at or below normal through early next week. && .SHORT TERM... (Through Late Friday Night) Issued at 214 PM CDT Thu Jun 6 2024 We`re seeing another dry afternoon as we are in deep northwest flow between a deep low over Ontario and a large high over the southwestern CONUS. There is a area of showers and scattered thunderstorms over southwest Missouri, but it will continue to move to the southeast and away from the CWA. Our dry weather will continue through early Friday evening as the high currently over the Plains will move east across the area. There has been a consistent signal in the models the past two days that the MCS will develop over the Plains and move east into Missouri on Friday night. The HREF is showing a low level jet developing over eastern Kansas by Friday evening with MUCAPES over 1000 J/kg which will likely help initiate a MCS over eastern Kansas/southwest Nebraska/western Missouri late in the evening or overnight on Friday. Compared to past runs, this initiation is a bit farther north and will likely move into at least the western parts of the CWA after midnight on Friday night. There is some potential for a few strong storms given initial amounts instability and shear, but the airmass it will be moving into over eastern Missouri late Friday night will be increasingly stable. There may be some areas that may see locally heavy rainfall as PWATS will be near 1.8" per the LREF, but this system will also be fairly progressive which will cutback on the overall potential. Temperatures will drop below normal tonight with the dry air and good radiation cooling. Temperatures will climb back above normal on Friday with a sunny sky and 850mb temperatures climbing to around 15C. Britt && .LONG TERM... (Saturday through Next Thursday) Issued at 214 PM CDT Thu Jun 6 2024 The latest runs of the NAM/GFS/ECMWF has the MCS farther north across the heart of the CWA on Saturday morning. While there will be impressive deep layer shear, it will likely weaken as it will be encountering less instability and a veering low level jet as it moves east southeast. How quickly this MCS exits the area will determine how quickly we will be able to destabilize ahead of an afternoon front that both the NAM/GFS are bringing southeast through the area. If the MCS is progressive, both the NAM/GFS are showing MLCAPES in the 1000-2000 J/kg range with deep layer shear near 40 knots, so couldn`t rule out a few strong to severe storms with this front. The front will then become elongated under the west- northwesterly flow aloft just to the south of the CWA on Saturday night and another MCS will develop and move along it late Saturday night into Sunday morning. Will keep high chance or likely PoPs for the scenario. The LREF is then showing the upper ridge and a surface high moving across the area early next week which will bring drier weather to the area early next week followed by an upper trough and an attendant cold front dropping down out of the northern Plains by the middle of next week which will bring a low chance (20%) to parts of the area by Wednesday. Temperatures will be close to normal on Saturday, but then fall a bit below normal behind the cold front Sunday into Monday before starting a warming trend through the middle of next week that will approach 90 degrees by this time next week. Confidence in the warmup is trending higher as the deterministic NBM is siding toward the 75th percentile of the NBM IQR at STL, COU, and UIN on Wednesday and Thursday. Britt && .AVIATION... (For the 00z TAFs through 00z Friday Evening) Issued at 620 PM CDT Thu Jun 6 2024 Dry and VFR flight conditions will persist through the TAF period. Overnight, west-northwesterly winds will become light and continue through the day on Friday except at KCOU and KJEF where surface high pressure will trek across southern Missouri and allow winds to shift to southerly Friday afternoon. Mid-level clouds will increase Friday afternoon ahead of an incoming weather system that is beyond the current TAF period. MMG/Kimble && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX