Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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257 FXUS63 KLSX 051109 AFDLSX Area Forecast Discussion...Updated Aviation National Weather Service Saint Louis MO 609 AM CDT Wed Jun 5 2024 .KEY MESSAGES... - This morning`s cold front will continue to produce the potential for showers and thunderstorms through this morning. There is a chance for isolated to widely scattered post-frontal showers and sub- severe thunderstorms early this afternoon generally south of I-70. - Dry, less humid weather will close out the work week before the slight chance (20 to 30%) of showers and thunderstorms returns on Saturday. - Near to below average temperatures will last through at least early next week. && .SHORT TERM... (Through Late Thursday Afternoon) Issued at 248 AM CDT Wed Jun 5 2024 Precipitation along this morning`s cold front is finally here as of 0730z. Convection along and ahead of the line has remained sub- severe in our forecast area, and this is expected to hold true through the morning. If a segment of the line does become severe, 60 mph winds will be the primary hazard. The current line of convection is expected to diminish with time before briefly resurging near sunrise due to a brief increase in DVPA aloft. Pulse type convection will re-fire along and just ahead of the cold front, but given a small amount of skinny instability (<500 J/kg MUCAPE), no severe is expected. The line will again diminish in coverage as it exits the forecast area. The arrival of the front is generally on time, teetering on slightly later than expected. The latest CAMs reflect this as well. The cold front still clears the CWA late this morning, but closer to noon than originally forecast. The largest implication from this are that the chance of showers and thunderstorms will linger a little longer into the day for some locations. Lingering low-level moisture and low-level cold air advection will create meager, shallow instability (<250 J/kg MUCAPE) until the low-levels dry out in the afternoon. Until then, isolated to scattered showers and non-severe thunderstorms are possible in areas generally south of I-70. There won`t be much change in temperatures today with highs landing in the low to mid-80s. The more noticeable change will be in tonight`s lows. A secondary cold front will pass through the forecast area from the north tonight. This front has become more robust in recent model runs, with most CAMs bringing sprinkles into northeast Missouri and west-central Illinois. Despite this, I decided to not to add PoPs tonight. Although moisture convergence will be strong along the front, atmospheric moisture will be quite shallow, sandwiched by very dry mid to upper level air and dry low- level air below. Even if we do see reflectivity echoes in our area, there`s no guarantee any rain will make it to the ground. What this cold front will do is usher in surface high pressure and cooler air. Radiational cooling is expected to take place amidst clear skies, dropping lows into the upper 50s and low 60s. Jaja && .LONG TERM... (Thursday Night through Tuesday) Issued at 248 AM CDT Wed Jun 5 2024 Temperatures from Thursday into early next week are expected to fall near average if not slightly below beginning this weekend. Lows will be almost (relatively) chilly, falling into the mid-50s and low 60s nearly every night. Our best chance at rain over the period will be on Saturday as a weak shortwave passes over the region. Although all deterministic guidance shows a flavor of warm sector or warm front showers and thunderstorms that day, there`s too much variance to confidently say that any one location will or won`t see precipitation that day. Confidence is greatest in southeast Missouri as the system has a consistent southward swing in guidance, but 60%+ of ensemble members still keep the area dry. Sunday now looks largely dry, which is expected to last through early next week as upper level ridging takes hold of our sensible weather. Jaja && .AVIATION... (For the 12z TAFs through 12z Thursday Morning) Issued at 609 AM CDT Wed Jun 5 2024 A cold front extends from K3LF south-southwest to KFAM as of 11z. Winds are quickly veering from generally southeasterly to northwesterly as the front passes. Ongoing convection ahead of the front is expected to weaken this morning, but stronger cells may still be able to produce flight restrictions if they impact a terminal directly. MVFR ceilings behind the front may briefly impact central Missouri through west-central Illinois this morning, but confidence in lower ceilings exists further southeast. These are expected to scatter out for most locations by noon. By mid- afternoon, dry and VFR conditions will take over and last through the end of the TAF period. Jaja && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX