677 FXUS63 KLSX 210324 AFDLSX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE ST LOUIS MO 924 PM CST WED JAN 20 2016 .UPDATE: Issued at 859 PM CST Wed Jan 20 2016 Mid-high level cloudiness will continue to spread eastward through our forecast area ahead of a strong shortwave moving slowly eastward through KS. There may also be some stratus clouds developing or retrograding from IL into parts of the area. The radar was depicting some light precipitation in eastern KS ahead of the shortwave. Looking at the latest HRRR and NAM model runs it appears that this precipitation will remain west of our forecast area tonight. With the cloud cover and lowering cloud ceilings expected the temperatures later tonight should be nearly steady or even rise slightly. GKS && .SHORT TERM: (Through Late Tonight) Issued at 330 PM CST Wed Jan 20 2016 Morning stratus has developed several holes in it during the course of the day and now only occupies areas in southern IL and northeast MO. Temps are in the upper 20s and lower 30s where the sun has broken out of the clouds, while still in the lower to mid 20s elsewhere. Another storm system has taken shape over western and central KS with an area of snow, while a much more significant system is moving thru UT and western CO at this time. The system over KS is expected to move slowly east tonight and weaken with time, only making it to the eastern part of the state by 12z/Thu. Any pcpn associated with this system should remain to the west of our region tonight. Of more significant note and challenge will be sky cover, its effects on temps, and potential for any fog. Sky cover should come from two main sources tonight: first from mid and hi clouds that will overspread our region later this evening from the KS system, and also from the low stratus that survives (mainly in southern IL) that will take advantage of veering cloud level winds from north to southeast to both advect westward into the heart of our region and expand in coverage as it does so. Ultimately, this will cloud up all areas again, but not before many areas will have the opportunity to have several hours of mostly clear skies with light easterly winds this evening with fresh snow cover. Have tried to compensate for this contingency in the min temp forecast, allowing for some areas in IL especially to drop into the single digits, and this will probably also allow for some fog development. As clouds increase later tonight, should see temps either steady out or even rise a few degrees. Biggest adjustments to MOS min temps are to the north and northeast of STL. TES .LONG TERM: (Thursday through Next Wednesday) Issued at 330 PM CST Wed Jan 20 2016 Focus continues to be system on Thurs into Fri. Latest mdl guidance has continued a more sly track. Mdls do continue to track a leading s/w lifting newd into the region late tonight into Thurs. Can not completely rule out light precip across portions of central MO, but based on forecast soundings, any precip will be light and sct. Of some concern is that while the NAM is the only mdl to suggest precip across this area, soundings also suggest that the available moisture may not be deep enuf for SN and FZDZ may be a threat. Otherwise, PoPs have been removed thru the weekend. Will need to continue to monitor the more nrn trof Thurs night into Fri as it drops swd into the area. Mdls suggest that any available moisture will precip out before it reaches the CWA. Regardless, will need to continue to monitor. Focus then turns to a system on Mon into Tues with a more amplified trof digging into the region. Mdls disagree regarding how this system will evolve and have therefore kept PoPs on the low end. Have also kept a RA vs. SN going for now. Will begin to fine tune p-types as the system approaches and mdls come into better agreement. Tilly && .AVIATION: (For the 00z TAFs through 00z Thursday Evening) Issued at 536 PM CST Wed Jan 20 2016 VFR flight conditions prevail across the region at this time, however MVFR cigs are not far removed and that is the forecast issue for this TAF package. Stratus with cig heights from 1500-2000 ft stretched from the OH Valley into far southern IL and was also located across south central MO. Current expectations are that the flow in the lowest 3kft of the atmosphere will gradually veer to more southeasterly this evening, and this should allow the stratus to advect northwest. If this in fact occurs the St. Louis region terminals and KCOU will be impacted and that is reflected in the latest TAFs, with cigs lowering to IFR on Thursday morning at KCOU. Will also have to be on the watch for some light snow in central MO but the probability is currently too low to mention. Some improvement expected by midday and into the afternoon on Thursday as the low level flow veers to more northeasterly. Specifics for KSTL: VFR flight conditions prevail across the region at this time, however MVFR cigs are not far removed as stratus with cig heights from 1500-2000 ft stretched from the OH Valley into far southern IL. Current expectations are that the flow in the lowest 3kft of the atmosphere will gradually veer to more southeasterly this evening, and this should allow the stratus to advect northwest and back into the terminal. Improvement expected by midday and into the afternoon on Thursday as the low level flow veers to more northeasterly. Glass && .LSX WATCHES/WARNINGS/ADVISORIES: MO...NONE. IL...NONE. && $$ WFO LSX