Area Forecast Discussion
Issued by NWS Springfield, MO
Issued by NWS Springfield, MO
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962 FXUS63 KSGF 241040 AFDSGF Area Forecast Discussion National Weather Service Springfield MO 540 AM CDT Tue Sep 24 2024 .KEY MESSAGES... - Dense Fog Advisory in effect from 4 to 10 AM for areas along the Missouri-Kansas border. Visibilities could be reduced to a half mile or less this morning. - 15-30% chances for isolated showers and perhaps a thunderstorm or two today and Wednesday. Many locations will remain dry. - Much cooler temperatures will occur this week with highs in the 60s and 70s. - Rainfall chances (50-80%) continue to increase for late in the week as confidence increases on track of the next system. There is the potential for widespread and prolonged rainfall with this system by Friday and Saturday, as well as breezy winds. && .SHORT TERM /THROUGH WEDNESDAY NIGHT/... Issued at 330 AM CDT Tue Sep 24 2024 Current water vapor imagery depicts a deep mid- and upper-level trough over the central CONUS. Associated with an upstream jet streak and a downstream jet streak of the trough, two cold fronts are set up. One that just moved through our area is draped across TX/AR and across the Ohio River Valley. The other is in NE and into the eastern Dakotas. Infrared satellite reveals thick low stratus moving through the region due to cooler temperatures and lingering moisture behind the front. These low clouds are starting to clear out of our western CWA, allowing greater radiational cooling in this area. Paired with weak winds, fog is developing along the MO/KS border. Current observations have visibilities around 2-5 miles and dropping. Dense Fog Advisory in effect from 4-10 AM along MO/KS border: Visibilities along the MO/KS border are expected to continue to drop as dense fog develops after 4 AM. Visibilities could be reduced to below half a mile at times. The fog should begin dissipating between the 7-10 AM timeframe as solar heating mixes out the fog. Elsewhere, visibilities may be modestly reduced due to drizzle and/or light fog as low-level RH is >85% and no cloud ice is present. RAP models suggest several waves of low-level lift, and with WNW`ly winds providing upslope lift along the Ozark Plateau, on and off drizzle looks possible through the morning, especially along the Plateau. Much cooler temperatures continue with highs in the 70s: The core of the aforementioned trough will sit over our region starting today. Along with modest surface high pressure, this will lock cooler air across our region the entire week. Highs today and Wednesday will be in the lower to middle 70s with lows in the lower to middle 50s. 15-30% chances for isolated showers today and Wednesday: The cold front in the Dakotas will drop to our region over the course of the day. Weak convergence along this front aided by synoptic ascent within the left-entrance region of the backside jet streak could force a few bands of light showers across the area today. With moisture limited within the core of the trough, showers will be light and scattered in nature (15-30% chance). Models depict the core of the upper-level cut-off low sitting over the Missouri bootheel during the day Wednesday. Some weak cold-core instability should develop within this region. Synoptic-scale ascent associated with a strengthening jet streak over the lower Mississippi River Valley could force some scattered showers in south-central Missouri Wednesday afternoon (and perhaps a thunderstorm or two given 500-750 J/kg MLCAPE). Once again, these will be more scattered in coverage as moisture will be more limited (15-30% chance). && .LONG TERM /THURSDAY THROUGH MONDAY/... Issued at 330 AM CDT Tue Sep 24 2024 Much cooler temperatures continue with highs in the 60s & 70s: As mentioned previously, the cut-off low will hover over our region with ensembles showing little signs of weakening. This will keep cooler temperatures in our area throughout the rest of the forecast period. Highs will consistently be in the lower to middle 70s with lows consistently in the 50s. Friday and Saturday look to be the coolest days where highs could only reach the middle 60s, especially along the Ozark Plateau. This is largely due to Friday and Saturday having the best chance for increased deep cloud cover and the potential for prolonged rainfall. Potential for widespread and prolonged rainfall late week: Ensemble members are in better agreement that the tropical system coming out of the Gulf will be entangled with the upper- level low in some good ol` Fujiwhara action. The absorption of a tropical system will certainly bring a boost of moisture to the upper-level low sitting across our region. Increased moisture and dynamical lift would force widespread and prolonged rainfall with high 72-hour rain totals somewhere in and around Missouri. The main uncertainty now, is how far west and south the upper-level low gets slingshot by the entanglement of the tropical system. Both the GEFS and EPS ensembles take the upper-level low south of our region, while the CMC ensembles notably have the mean track further east of our area. The GEFS/EPS scenario would bring higher coverage and amounts of rain while the CMC scenario would limit higher rainfall coverage to maybe our eastern counties. Details still need to be ironed out about the exact track of the system and subsequent impacts to our region. Nevertheless, current probabilistic model trends are increasing chances for widespread and prolonged rainfall somewhere in our CWA. The Extreme Forecast Index continues to highlight 1-2 shift of the statistical tail for QPF in the eastern Ozarks for Friday/Saturday. This is signaling a potentially abnormal rainfall event. Adding confidence, the WPC has a Day 4 Slight (2 of 4) risk for excessive rainfall along and east of Hwy 65. Additionally, the NBM is highlighting the eastern Ozarks as an area with a 1-in-40 year rainfall event should the mean outcome take place. The mean NBM QPF amounts is 1-4" for Friday through Sunday with the highest amounts east of Hwy 65. Do not get too hung up on amounts just yet, though. The mean is merely another sign of increasing confidence in widespread and prolonged rainfall across the region. There is still high ensemble spreads. For example, the 25th percentile has no rain at all west of Highway 65, while the 75th percentile gives widespread areas of 3-6". With all that being said, stay tuned to the forecast with updates to the track of the system, confidence in rainfall coverage and totals, and any new uncertainties and scenarios. Of additional note, given the strong dynamics of the system (and it being a post-tropical system of course), winds look to be moderately breezy Friday and Saturday. NBM mean sustained winds are at 15-20 mph with gusts up to 30 mph. The 75th percentile (should a stronger system scenario be in play) has sustained winds at 20-25 mph and wind gusts up to 40 mph. && .AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/... Issued at 540 AM CDT Tue Sep 24 2024 MVFR and IFR conditions will slowly clear away over the first 6 hours of the TAF period. Dense fog is currently struggling to fully develop at JLN, but there is still the possibility that visibilities there drop to around a mile before 14Z. After 18Z, cloud coverage will still be SCT to BKN with mid- and high- level clouds. Between 20-03Z, a band of light showers could impact all TAF sites (20-30% chance). While chances are low, model-to-model and run-to-runs have been consistent on this feature, so confidence on at least sprinkles impacting the TAF sites is medium-high. Otherwise, winds will be 5-10 kts out of the WNW, decreasing to below 5 kts after 00Z. && .SGF WATCHES/WARNINGS/ADVISORIES... KS...Dense Fog Advisory until 10 AM CDT this morning for KSZ073-097- 101. MO...Dense Fog Advisory until 10 AM CDT this morning for MOZ066-077- 088-093-101. && $$ SHORT TERM...Price LONG TERM...Price AVIATION...Price