Area Forecast Discussion
Issued by NWS Springfield, MO
Issued by NWS Springfield, MO
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959 FXUS63 KSGF 301025 AFDSGF Area Forecast Discussion National Weather Service Springfield MO 525 AM CDT Tue Apr 30 2024 .KEY MESSAGES... - Some flooding persists across the area from the several days of repeated heavy rain. - Dense Fog Advisory until 9 AM for the eastern Ozarks. - Thunderstorm chances (20-50%) move back into the area tonight into Wednesday morning, generally along and northwest of I-44. - The unsettled weather pattern will persist into the weekend with additional thunderstorm chances...the potential of severe weather...and more flooding. Most widespread chances are Thursday and Thursday night (70-90%). && .SHORT TERM /THROUGH WEDNESDAY/... Issued at 300 AM CDT Tue Apr 30 2024 Subtle upper-level ridging is filling in over the Plains states ahead of an approaching longwave trough and associated jet streak. A cold front at the surface--bringing lower 50 lows this morning--is just to the south, but is forecast to continue to dissipate as upper-level forcing lifts away from the area. Indeed, while much of our area has very calm and variable winds, observations in our western counties are already exhibiting SE`ly flow ahead of the next approaching system coming off the northern Rockies. Dense Fog Advisory until 9 AM for the eastern Ozarks: The light winds, clear skies, and saturated air along and behind the cold front is producing fog within the eastern Ozarks. GOES Nighttime Microphysics have shown this area of fog increasing in coverage and density as the night has gone on. West Plains has also been sitting below a quarter mile visibility for the past hour. As such, have issued a Dense Fog Advisory for the area until 9 AM when clear skies and surface heating will mix out any leftover fog. Some flooding persists across the area from recent heavy rain: While many rivers are starting to decline, several rivers, especially in west-central MO and east-central KS, are still in moderate to major flood stage. The Little Osage River - Horton point is the only river still in major and is expected to decline to moderate this morning. Despite the declining trend, impacts from the flooding are still ongoing within areas outlined by our flood products. Continue to pay attention to which areas are under warnings/advisories and as always, turn around, don`t drown! Thunderstorm chances return tonight into Wednesday night: Unfortunately, more rain chances are on the horizon, especially for the areas that have already received a lot of rain and are in the moderate/major flooding stages. The longwave pattern that`s setting up will exhibit a broad longwave trough axis over the northern Rockies. Several shortwaves are forecast to revolve around this axis, forcing multiple chances for showers/thunderstorms for the week ahead. The first shortwave is expected to traverse the northern Plains this afternoon. Synoptic ascent associated with the wave will force a surface low that will track across SD/MN. This will initiate S`ly flow across our region once again as warm, moist air streams northward into the surface low. This will warm high temperatures into the lower 80s today with dewpoints in the upper 50s. Storms are expected to form NW of our area along an associated cold front. Recent CAMs suggest an MCS to eventually develop and dive SSE, feeding off a moist 40-60 kt S`ly LLJ. The remnants of this MCS may reach into our NW counties after 9-11 PM tonight (20-50% chance). With MUCAPE values forecast to be in the 500-750 J/kg range, and the MCS becoming displaced from upper- level support, it should weaken as it enters our counties. HREF paintballs suggest the heaviest precipitation will stay NW of I-44, where the SPC has a Marginal (1/5; 5%) risk for an isolated damaging wind gust up to 60 mph and/or hail up to quarter size. Additionally, LPMMs only bring 0.25-0.5" of rain for our SE KS counties and <0.1" for other areas NW of I-44. However, springtime nocturnal MCSs are known to be silly little guys and last longer than models anticipate, so it would not be entirely unlikely for areas along and SE of I-44 to see remnant scattered showers/thunderstorms after 1-3 AM (15-30% chance). Nevertheless, increased cloud coverage from the MCS will keep lows near 60F tonight. Lingering stratiform rain/thunderstorms from the overnight MCS may be continuing across parts of the area Wednesday morning (15-40% chance). But generally, there will be lingering clouds and continued S`ly warm, moist flow ahead of the next shortwave trough to round the northern Rockies longwave. The southerly flow will bring highs Wednesday into the lower to mid-80s, especially for areas untouched by morning rainfall. The next wave will then slowly enter the northern Plains Wednesday afternoon. The chances for storms Wednesday looks near identical to Tuesday, with storms firing over KS/NE, congealing into an MCS, marching ESE into our CWA by the 9 PM to 3 AM timeframe, then slowly dissipating. As with Tuesdays chances, the areas most likely to be affected will be NW of I-44 (20-50% chance). And once again, lows will be in the mid-60s due to remnant cloud cover from the convection. If any or both of these rounds of convection occur, additional rainfall will bring further stress to our already saturated rivers along the MO/KS border. This is something that will need to be watched and monitored very closely. If CAMs continue to show a heavier rain signal, another Flood Watch may be needed for that area. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Issued at 300 AM CDT Tue Apr 30 2024 Unsettled weather pattern will persist into the weekend: The slow-moving wave that will have initiated Wednesday`s round of convection, will slowly traverse through NE/SD during the day Thursday. Positive vorticity advection along the eastern edge will orient the wave into a negative tilt and allow for the surface cold front to fully make its way through our area rather than stalling off to the west. This will bring widespread rain chances across our entire forecast area Thursday into Friday morning (70-90% chances). It will also cool Thursday`s highs into the upper 70s and lows in the 50s. While this wave of convection is expected to clear through our CWA, it will be slow-moving. Additionally, with the surface low and upper-level wave off to the north, mean flow will be largely parallel to the front, bringing another round of slow-moving and training thunderstorms across the area. The WPC has a Slight (2/5) risk for excessive rainfall for much of our area. This will once again bring a flooding threat to our area, especially in already rain-stressed zones/rivers. ESATs point to 99.5th percentile of low-level moisture surging through the area with PWATs around 1.25" which would indeed support any thunderstorm to be efficient rainfall producers. Additionally, the SPC has areas west of Hwy 65 in a Marginal (1/5; 5%) risk for severe weather as just enough MUCAPE and shear should be present. However, with the upper-level wave and surface low well to the north, only isolated marginally severe weather is forecast at this time (mainly damaging wind gusts up to 60 mph and hail up to quarter size). Lingering stratiform rain may be present during the day Friday, especially in the eastern Ozarks, as the system slowly exits the region. After of which, 20-40% chances of showers/thunderstorms stay persistent from Friday evening through Monday. The presence of chances during every time period highlights the ensemble uncertainty. The ensemble mean longwave pattern with a trough over the west CONUS and broad SW`ly flow across our area supports multiple rain chances, the uncertainty comes from disagreement in the location and timing of shortwaves that progress through the longwave pattern. This will become clearer with time, but for now, the average synoptic pattern does indeed support rain chances for much of the weekend period. Highs into the weekend will be in the middle to upper 70s with lows in the middle to upper 50s. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 521 AM CDT Tue Apr 30 2024 Clear skies producing VFR conditions will remain through at least 03-05Z for all TAF sites. Winds will be S`ly at 10-15 kts until the same time period. Confidence is increasing in remnants of a thunderstorm complex to stall over SE Kansas into SW Missouri in the 04-12Z timeframe. Greatest confidence for this occurring is in JLN (40-50%) with lower confidence in SGF (20-30%) and the lowest at BBG (10-20%). There is also a signal that these storms will stay over JLN for a long period of time (potentially from 04-12Z). During this time period, winds will be variable as a boundary fluctuates over the area. Lastly, there is a chance low-level wind shear could exceed 40 kts during the 00-06Z timeframe, but confidence is too low to include in TAFs at this time. && .SGF WATCHES/WARNINGS/ADVISORIES... KS...None. MO...Dense Fog Advisory until 9 AM CDT this morning for MOZ082-083- 096>098-105-106. && $$ SHORT TERM...Price LONG TERM...Price AVIATION...Price