Area Forecast Discussion
Issued by NWS Springfield, MO
Issued by NWS Springfield, MO
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638 FXUS63 KSGF 201055 AFDSGF Area Forecast Discussion National Weather Service Springfield MO 555 AM CDT Fri Sep 20 2024 .KEY MESSAGES... - Hot again today. Heat Index values will reach the 95 to 105 F range. Some record highs may be challenged. - 10-30% chance for isolated showers and thunderstorms today in the eastern Ozarks and along the Missouri-Arkansas border. If storms develop, some may produce wind gusts up to 40-60 mph. - Numerous rounds of widespread showers and thunderstorms through the weekend (40-90% chance). Precipitation amounts will be highly variable across the region, but generally expect the highest amounts to be north of I-44. - A cold front will bring cooler temperatures next week with highs in the 70s and limited rain chances. && .SHORT TERM /THROUGH TONIGHT/... Issued at 400 AM CDT Fri Sep 20 2024 Current water vapor imagery depicts broad clockwise flow associated with a mid- and upper-level ridge over the Southern Plains. West of the ridge, a deep upper-level low is currently over California. The amplifying wave pattern is increasing jet stream wind speeds to 80-90 kts as they overspread the central Plains. At the surface, a slow-moving cold front is analyzed from north IA down through central KS and into north OK. Hot again today. Some record highs may be challenged: Yesterday was hot for mid-September standards. Observed highs exceeded the forecast highs by 4 degrees in many places. This led to Springfield having a high of 94 F and Joplin reaching a high of 99 F which beat the previous record of 98! With the ridge continuing to build into the region, the brunt of the cold front largely staying out of our area, and 21-23 C 850 mb temperatures advecting in, today is expected to be another hot one. Highs are forecast to be in the upper 80s in the eastern Ozarks, to the upper 90s along the MO/KS border. Given yesterday`s over-achievement, records may be challenged again today. Especially if skies remain mostly clear and deep vertical mixing occurs, as evidenced by RAP forecast soundings. See the Climate Section below for a summary of challenged records. With upper 60s to lower 70s dewpoints, Heat Index values will reach into the 95 to 105 F range with the higher values along the MO/KS and MO/AR borders. While a Heat Advisory is not anticipated, these Heat Index values are abnormal for mid- September (>0.8 on the Extreme Forecast Index with 1 shift of the statistical tail). This paired with the multiple day stretch of above 90 F highs brings possible "Major" (3 of 4) heat- related impacts to areas west of Hwy 65. Therefore, please make sure to still follow heat safety by staying hydrated and cool. If working outside, allow time for multiple breaks. This is especially true as lows tonight will provide little heat relief. Lows will be in the lower to middle 70s (76 F near Joplin!). These will be near record high minimums. 10-30% chance for isolated showers and thunderstorms today: A 25-35 kt W`ly low-level jet is currently overspreading the area. Modest warm air advection associated with this, along with convergence and uncapped 500-1000 J/kg MUCAPE at the nose of the LLJ, will allow isolated elevated showers and thunderstorms to develop across the eastern Ozarks (20-30% chance). These will generally develop around 5-7 AM and move out of our CWA by 10-11 AM. Severe weather is not expected with this round of rain. Later this afternoon, as the cold front becomes situated across central MO, 1000-2000 J/kg of MLCAPE will develop south of the boundary. Weak convergence along the boundary has a 10-20% chance to force isolated showers and thunderstorms south of I-44. The main uncertainty is the degree of capping. RAP forecast soundings not only depict weak low-level capping, but also a pronounced subsidence inversion associated with dry air in the mid-levels. Forecast parcel paths are just warmer than the environment at this level, however, model soundings usually underestimate these types of inversions. Additionally, the dry air aloft will effectively cool rising air more than parcel theory allows. For that reason, it will be difficult for many deep updrafts to develop, hence the 10-20% chance. Nevertheless, if storms do form, 25-35 kts of background 0-6 km bulk shear and inverted-V low-level profiles could support some downburst gusts up to 40-60 mph, especially along and SE of a line from Rolla to Branson where shear is higher and a Marginal (1 of 5) Risk is in place. First round of widespread rain chances late tonight (20-40%): As the potent trough traverses the Four Corners region tonight large-scale ascent on the downstream side of the wave--along with warm air advection within a strengthening nocturnal LLJ-- will create a strong surface mass response. The cold front will rapidly lift north as a warm front, spreading the warm and moist airmass back over our area. Ascent from strong positive vorticity advection and warm air advection looks to force a thunderstorm complex over east KS. CAMs then hint at this complex diving south into our region, bringing 20-40% chances for showers and thunderstorms north of I-44 between 1-7 AM Friday night into Saturday morning. Confidence is medium-high in thunderstorms impacting areas north of I-44 during this time, but chances are somewhat low due to disagreement in exact track and timing. Severe weather is not expected with this round. Widespread and more prolonged rain is more likely. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Issued at 400 AM CDT Fri Sep 20 2024 Numerous rounds of widespread showers and thunderstorms (40-90%): Details in exact location, timing, and amounts of the next rounds of precipitation become fuzzy through the weekend. Just as one example, outflow from the thunderstorm complex expected to drop through the area late Friday night will have an impact on the location of storms during the day Saturday. What is clear, though, is chances become high for multiple rounds of widespread showers and thunderstorms Saturday through Monday night as a widespread area of large-scale forcing from strong height falls and positive vorticity advection aloft and convergence from fronts and outflow boundaries near the surface spreads over the region. This leads to 35-65% chances Saturday and Saturday night with the greatest chances north of I-44 where the warm front will be situated. Severe weather is not expected Saturday and Saturday night. The best chances arrive Sunday and Sunday night as the potent shortwave lifts through the central Plains and the strong cold front progresses through our region. Chances Sunday and Sunday night increase to 40-90%. Once again, the greatest chances will lie along the warm front north of I-44. There is a Marginal (1 of 5) risk for severe thunderstorms for much of our area Sunday as strong cold front forcing pairs with 25-35 kts of 0-6 km bulk shear as evidenced by the 03Z SREF mean. Damaging winds look to be the main hazard, but confidence is low since instability will likely be limited due to copious cloud debris and ongoing thunderstorms through the weekend. Of additional note, flooding may be a hazard for localized areas north of I-44. Confidence is still low on this as well, since QPF spreads are still very high due to uncertainty in location, timing, and longevity of each round. For example, areas north of I-44 have a spread of 0.3-0.5 inches at the 25th percentile, to 2-2.5 inches at the 75th percentile for 48-hour rainfall (Saturday through Sunday). That being said, areas north of I-44 have the greatest chance of receiving at least an inch of rain over the length of the weekend (50-70%). The flooding threat will continue to be monitored and evaluated in the coming days. Cooler temperatures next week with limited rain chances: Ensemble cluster analysis is starting to come into more agreement with the large-scale pattern next week. While details about the location and intensity of shortwaves are still uncertain, the longwave pattern looks to have a deep trough settle over the eastern CONUS, allowing for a cooler and drier air mass to settle into place. As expected, PoPs have also then decreased next week as models hone in on this pattern. Before the cold front moves through, highs Saturday and Sunday range from the lower 80s to the middle 90s with lows around 70 F Saturday night and ranging from the middle 50s to the upper 60s Sunday night (cooler to the west). After the cold front clears the region, highs next week will be in the 70s with lows in the 50s. && .AVIATION /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 555 AM CDT Fri Sep 20 2024 Medium-high confidence that VFR conditions remain through the entire TAF period at all TAF sites. 8-12 kt winds will slowly shift from S`ly to WSW`ly between 12-18Z as a cold front slowly approaches the area from the N. This boundary will quickly retreat after 00Z, bringing back southerly winds through the end of the TAF period. Additionally, some models are hinting at isolated showers and thunderstorms developing near BBG sometime between 18-03Z. Confidence on this is currently low (10-20%), so have not put in the TAF for now. && .CLIMATE... Issued at 400 AM CDT Fri Sep 18 2024 Record High Temperatures (Springfield): September 20: 97 (1954)Forecast: 94 Record High Temperatures (Joplin): September 20: 99 (1954) Forecast: 97 September 21: 99 (2022) Forecast: 94 Record Highest Minimum Temperatures (Springfield): September 20: 74 (2018) Forecast: 72 September 21: 73 (1931) Forecast: 72 September 22: 70 (2017) Forecast: 71 Record Lowest Precipitation for Month of September: Springfield: 0.05" (1928) September 2024 Thusfar: 0.04" Joplin: 0.2" (2013) September 2024 Thusfar: T" && .SGF WATCHES/WARNINGS/ADVISORIES... KS...None. MO...None. && $$ SHORT TERM...Price LONG TERM...Price AVIATION...Price CLIMATE...Price