textproduct: Springfield

KEY MESSAGES

- Thunderstorms are expected overnight tonight with the focus across central Missouri. A few storms could be severe with damaging winds the primary threat.

- Another round of thunderstorms is possible Wednesday evening, this time with the focus across southern Missouri. Damaging winds and heavy rainfall will be the primary threats.

- Hot and humid conditions continue to the south of a cold front on Wednesday with southwest Missouri having the best chance (50%) of seeing heat index values near 105 again.

SHORT TERM /THROUGH TONIGHT/

Issued at 200 PM CDT Tue Aug 18 2026

An upper level ridge is reorganizing over the Southwest US while a trough is passing through the Upper Midwest pushing east toward New England in the coming days. At the surface, high pressure currently over the lower Ohio Valley will push east toward the southern Appalachians, with a moist southerly flow through the Southern Plains and into the Ozarks. It's this southerly flow beneath the influence of the ridge that has led to another day of hot weather in southwest Missouri and eastern Kansas. Looking to the north, the remnants of a convective complex that moved into northwest Missouri this morning continues to dissipate as it heads east. However, redevelopment is expected this evening across northeast Kansas and northwest Missouri where the convective outflow intersects with an increasing low level jet. The developing storms would then track ESE primarily through central Missouri overnight. Initiation is expected around 9 or 10PM with storms not likely in our forecast area until between midnight and 6AM. With the warm, moist air mass feeding these storms and modest wind shear available, convective clusters capable of damaging winds will be possible. In addition, heavy rain rates of 1 to 2 inches per hour can be expected, though the focus for persistent rainfall at the moment remains just to our north closer to I-70.

Convection wanes Wednesday morning, though convective outflow pushes an effective cold front southward through the region. This will shove the hot and humid air mass further southwest for Wednesday, with the primary forecast uncertainty hinging on where that boundary lands. South of the front another hot and humid day is expected, with heat index values approaching 105, but north of the front it will be considerably cooler, potentially only in the 80s with cloud cover. NBM interquartile range for high temperatures on Wednesday is from 8 to 10 degrees, rather large for a Day 1 forecast this time of year. This reflects the uncertainty on that frontal position which will be determined by the track of convection tonight and the intensity of the push southward of the outflow. Southwest Missouri has the best chance (50%) of seeing another day of heat index values near 105, though confidence is not quite high enough to extend the Heat Advisory just yet.

Another round of convection is expected to fire in the vicinity of the boundary Wednesday evening. At this time the boundary is likely to be across far southern Missouri near the Arkansas border. Storms forming here will have access to the hot, humid, unstable air mass south of the front and moderately strong wind shear. Supercells and convective clusters will both be possible, with damaging winds and heavy rainfall the primary threats and hail or a tornado as secondary threats. These storms are expected to push south into Arkansas by around midnight Wednesday night as the front gets a better push southward behind the upper trough moving through the Great Lakes.

LONG TERM /WEDNESDAY THROUGH TUESDAY/

Issued at 200 PM CDT Tue Aug 18 2026

The story in the long range forecast will be the battle between cool air masses pouring out of Canada beneath a trough in the Eastern US and hot conditions building beneath the ridge over the Southwest US. Our forecast area will frequently be at the boundary of these two air masses, with heat building to the west while cooler air hangs on to the east beneath northwesterly flow aloft. There will also be occasional chances for thunderstorms as impulses rotate around the ridge, but limited moisture flowing north through the Plains will limit how frequent or widespread these convective complexes may be. Latest NBM PoP remains quite low (20 percent or less) through the extended forecast, but Low Resolution Ensemble guidance does show 30 to 50 percent probability of measurable rainfall in any 24 hour period through this weekend, indicating greater confidence that some storms will be around but timing and location uncertainty is keeping the PoP lower.

Confidence is greatest in cooler conditions Thursday into Friday, with NBM high temperature interquartile range of 5 degrees or less. However, uncertainty increases for the weekend with that same interquartile range rising to 10 degrees or more Sunday and Monday. If we stay more under the influence of the cooler air masses, temperatures will tend to top out in the 80s, but if the hotter air from the ridge noses in, then we will see temperatures approach 100 degrees again. Current NBM forecast is a blend which does reflect a rather large gradient, hotter in the west and cooler in the east.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 635 PM CDT Tue Aug 18 2026

For the most part, expect VFR conditions through this TAF period. There will be 20% chances for showers and storms late tonight and Wednesday, but expected coverage and confidence in details is too low to include any prevailing precipitation in the forecast. Look for LLWS at all sites tonight into early Wednesday.

SGF WATCHES/WARNINGS/ADVISORIES

KS...Heat Advisory until 8 PM CDT this evening for KSZ073-097-101. MO...Heat Advisory until 8 PM CDT this evening for MOZ066-077-088. Heat Advisory until 8 PM CDT Wednesday for MOZ093-101>105.