Area Forecast Discussion
Issued by NWS Springfield, MO
Issued by NWS Springfield, MO
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377 FXUS63 KSGF 131743 AFDSGF Area Forecast Discussion National Weather Service Springfield MO 1243 PM CDT Thu Jun 13 2024 .KEY MESSAGES... - Heat and humidity will start ramping up today and continue into next week. - Low-end thunderstorm chances tonight and Friday (15-30%) as a front sags south into the area. && .SHORT TERM /THROUGH TONIGHT/... Issued at 133 AM CDT Thu Jun 13 2024 Large-scale mid- and upper-level ridging is beginning to inch into our region as evidenced by clockwise flow over OK/KS in current water vapor imagery. Mesoanalysis depicts the longwave ridge axis centered over NM where 850 mb temps are reaching into the 30-32 C range. At the surface and in the low levels, a high pressure system centered over the Mississippi River valley in AR/MO is slowly exiting to the east. In its wake, SW`ly low- level flow is ramping up, advecting into the region warm 850 mb temperatures from the west, and surface moisture from the Gulf. This sets the stage for the beginning of a hot and humid pattern for this time of year. Heat and humidity will start ramping up today: As mentioned above, height rises will continue to build into the region today, supporting the beginning of an influx of heat and humidity. A WSW`ly oriented low-level jet will bring in a nose of 20-24 C 850 mb temperatures. For reference, according to the SPC Sounding Climatology, the record high 850 mb temperature for today is 22.9 C. This will allow high temperatures to warm into the upper 80s and lower 90s. Additionally, SW`ly surface flow will advect in dewpoints around 70 F. This will begin our muggy pattern with Heat Indexes in the middle and upper 90s. Low temperatures tonight will also be mild in the upper 60s and lower 70s. Low-end thunderstorm chances tonight (15-30%): Meanwhile, a mid- and upper-level shortwave will traverse the upper Great Lakes with an associated E-W oriented surface cold front sagging southward through the northern Plains and Midwest states. With SW`ly flow ahead of this front advecting in warm, moist air, thunderstorms will develop ahead of the front in southern IA/northern MO. These storms are expected to evolve into an MCS thanks to generally stronger linear forcing along the cold front. The MCS will drop south into north-central MO during the late evening hours tonight. There is still the question of how far south the storms will survive and how much of our CWA will be impacted. In an ingredient-based approach, substantial capping will build over our region as night falls, thanks to very warm 850 mb temperatures. However, the 00Z HREF suite suggests at least 1000 J/kg of MUCAPE north of I-44 within 25-35 kts of 0-6 km bulk shear. HREF ensemble soundings depict this MUCAPE to be uncapped above 700 mb. Therefore, if the MCS can continue to be forced, elevated convection along the line could survive generally just north of I-44. The stout capping inversion could prove difficult to overcome, however. From a dynamics approach, the cold front is expected to continue to sag southward, providing persistent surface forcing on top of forcing already generated by the MCS`s cold pool. Though the cold front is not expected to be strong, convergence will be characterized by 180-degree vectors (S`ly winds against N`ly winds) which will aid surface forcing. However, the further the thunderstorm complex sags south, the more it gets positioned underneath synoptic-scale subsidence beneath the right exit region of a jet streak. This would act to weaken the MCS through the night. All that being said, there is currently a 15-30% chance that the MCS will make it to just north of I-44 before 1 AM. If anything, it may be residual stratiform rain at this time. These chances may increase as models come into better agreement. Some HREF CAMs dissipate the MCS along Highway 54, while others dissipate it over Springfield. Given the difficulty for most CAMs to correctly model cold pool driven MCSs, leftover scattered showers and thunderstorms reaching just north of I-44 seems the most reasonable outcome. Indeed, the MPAS models (which have refined microphysics schemes to generally better resolve cold pools) does show storms making it into the Springfield area between 10 PM and 1 AM. Given the aforementioned instability and modest shear, isolated marginally severe wind gusts (up to 60 mph) and hail (up to quarters) would be possible, especially along the Hwy 54 corridor where shear is expected to be more favorable && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Issued at 133 AM CDT Thu Jun 13 2024 Low-end thunderstorm chances Friday (15-30%): The cold front will continue its lollygag southward Friday, positioning itself somewhere along the MO/AR border. The air mass ahead of it will continue to be warm and moist (highs will be around 90 F), contributing to 2000-2500 J/kg of SBCAPE and 1250-1750 J/kg of MLCAPE. With the boundary forcing into this unstable air mass, thunderstorms are certainly possible, generally south of I-44 (15-30% chance). The uncertainty is in the amount of inhibition due to expected very warm 850/700 mb temperatures. HREF plumes are quite split on the amount of CIN, but the mean is progged at about -25 J/kg. While this is sufficient to inhibit convection, forcing along the surface boundary could be enough to promote a few isolated updrafts to break the cap. As such, there is a 15-30% chance of showers and thunderstorms south of I-44. Shear will be weak (<20 kts), so severe weather is not anticipated with any storms that do form. Heat and humidity continue into next week: The longwave ridge will continue to trudge eastward through the weekend with the axis being centered over MO Saturday night. Also during this period, high pressure will solidly be in place across the region. This will keep the hot and humid air mass locked into next week. Daily highs will be in the lower to middle 90s with nightly lows in the lower to middle 70s (approaching record high minimums every night from Friday through Tuesday). Dewpoints will hover around 70 F, producing Heat Indices in the middle to upper 90s and Wet Bulb Globe Temperatures in the lower to middle 80s, introducing some heat stress for outdoor workers and vulnerable populations. The hottest day looks to be Sunday with highs in the middle 90s. With this being the first prolonged period of abnormal heat, people should be cautious when being outdoors for extended periods of time. Taking multiple breaks, having functional cooling, and keeping adequately hydrated is highly recommended. There is some uncertainty Monday onwards in how hot each day will get. Cluster analysis shows that the EPS favors a much more amplified ridge pattern while the GEFS favors a flatter ridge. If the EPS scenario pans out, high temperatures could be higher than currently forecast. If the GEFS scenario pans out, temperatures could be slightly cooler. Trends will need to be monitored, but for now, the forecast advertises highs to continue to be in the lower 90s with lows in the lower 70s. Additional rain chances?: As the ridge exits to the east Saturday morning, a shortwave trough is forecast to approach the region from the west. This wave may provide enough forcing for additional rain chances Saturday morning through Sunday, though confidence is currently low on the development, coverage, and evolution of any precipitation associated with the wave due to warm 850/700 mb temperatures. Daily 15-20% chances of rain then exist next week as the synoptic pattern brings a belt of SW`ly mid-level flow over our region with an open Gulf to continue to provide moisture. Moderate Excessive Heat Risk (6/19-6/24): Both NAEFS and ECMWF ESATs are already beginning to max out on mid- and upper-level geopotential heights for next Wednesday (6/19) through Monday (6/24). This means the forecasted geopotential heights are higher than the 30-year climatology for this time of year. This is due to the longwave synoptic pattern depicting an amplified upper-level ridge to develop. This would force hotter high temperatures than what we are experiencing this week. The WPC has highlighted our region in a moderate (40%) risk for excessive heat during this time period. This is a heads-up call that temperatures could exceed 95 F during this time period. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1232 PM CDT Thu Jun 13 2024 High confidence that VFR conditions will prevail through most of the TAF period at all sites. A 15-30% chance of weak remnant showers, some of which may have thunder, may reach SGF and JLN. Model guidance remains divided as to how far south these storms will go, although most leave precipitation north of I-44. Thus, a PROB30 group was used for SGF and JLN. SW winds of 8-12 knots will begin to weaken around 2z, and begin to turn N from 14-18z. && .CLIMATE... Issued at 501 AM CDT Mon Jun 10 2024 Record High Temperatures: June 16: KSGF: 97/1952 KJLN: 95/2016 Record High Minimum Temperatures: June 15: KSGF: 74/2022 June 16: KSGF: 75/2022 June 17: KSGF: 76/2016 && .SGF WATCHES/WARNINGS/ADVISORIES... KS...None. MO...None. && $$ SHORT TERM...Price LONG TERM...Price AVIATION...Lindenberg/Kenny CLIMATE...Price