Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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229 FXUS63 KDVN 231913 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 213 PM CDT Thu May 23 2024 .KEY MESSAGES... - A line of thunderstorms is expected to move through the area late tonight, which could bring some strong to severe thunderstorms with it, with additional chances of showers and storms to redevelop Friday afternoon. - A quiet start to the Memorial Day weekend is expected for Saturday, with more chances of showers and storms on Sunday. Some storms Sunday could be strong to severe. - Active conditions will continue into Monday before drying out on Tuesday and Wednesday. && .SHORT TERM /THROUGH FRIDAY/... Issued at 207 PM CDT Thu May 23 2024 Another warm, quiet late Spring afternoon was unfolding across all of eastern Iowa, northwest Illinois and far northeast Missouri. 18z surface analysis depicted broad surface high pressure over the Midwest and Ohio River Valley, with a strong surface low just north of the Great Lakes. Another surface low was evident over northeast Wyoming ahead of a potent shortwave in the north central Rockies. This shortwave will be the driver of our weather through much of the short term period. Quiet, dry and warm conditions will prevail through this afternoon with PM highs approaching the upper 70s to low 80s. As we head into the evening, attention will turn to our west as a complex of showers and thunderstorms, some severe, develops across the north central Plains. This complex will be fueled by the aforementioned surface low and shortwave, with a cold front developing in tandem. In addition, a strong 40-55 kt LLJ will provide additional vertical shear and moisture to this complex, ensuring it continues its track east tonight. This complex should survive the trip and work its way into our western CWA around 09-12z (300a-600a). After this, there is a bit of uncertainty of what happens with this as it tracks across the region. So far, there are two scenarios: 1) The complex continues tracking into the area with additional redevelopment through the morning as it encounters diurnal heating and a decreasing cap (see 12z HRRR and NAMnest), or 2) the complex tracks more northeast that east along the CAPE gradient, impacting areas mainly along and north of Interstate 80 with scattered activity to the south that could break the cap (see 06z HRRR). As of this forecast discussion, I find myself leaning more towards Scenario #1 with latest HREF guidance favoring a decrease in SBCIN over areas along and south of Interstate 80. Should scenario #1 play out, we would need to watch for storms capable of producing damaging wind gusts and large hail thanks to the presence of high instability (MLCAPE around 2000 J/kg), very steep mid-level lapse rates around 7-8 C/km, favorable deep layer shear around 30-35 kts and a more linear storm mode favored. A tornado cannot be ruled out especially with any storm that interacts with remnant boundaries or that can become surface based. This complex should exit the area by late morning to midday, with potential for another line of showers and thunderstorms to move through the area during the afternoon/evening with the surface cold front. This threat will be heavily dictated by which scenario we see in the morning. If we see scenario #1 play out, much of our PM threat will be diminished with coverage more isolated to scattered due to more atmospheric stabilization. Should scenario #2 play out, storms during the afternoon could be stronger with more instability to work with. The Storm Prediction Center continues to highlight areas across east central and eastern Iowa in a Level 1 (marginal) risk of severe thunderstorms through 12z Friday, with a Level 2 (slight) risk along and east of a Manchester IA to Ottumwa IA line after 12z Friday. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Issued at 207 PM CDT Thu May 23 2024 Friday Night Through Daytime Saturday... High pressure will provide a dry start to the holiday weekend. Look for near normal highs in the low to mid 70s, and lows Saturday morning in the upper 40s to mid 50s. Saturday Night on... Active weather returns Saturday night as remnants from a complex of showers and thunderstorms moves into the area. This complex will dictate how things evolve for daytime Sunday, with potential for another round of showers and thunderstorms during the afternoon and evening. There is a chance these storms could be severe, with the latest SPC Day 4 outlook painting a 15% chance (slight) for areas along and south of Interstate 80. Higher chances remain to the south of the area near a upper jet poleward exit region, where there is enhanced upper level divergence in play. Other severe statistical guidance including CSU and CIPs are in agreement of severe potential, so please continue to monitor the latest forecasts if you have plans Sunday. Chances of showers and thunderstorms will persist into Memorial Day as another shortwave moves into the area. Coverage looks to be more isolated to scattered with this feature with lower levels of moisture and forcing at play. We quiet down by the middle of next week with high pressure moving across the area, though this will be short-lived with zonal flow and a renewed round of shortwaves moving into the area by late next week. Temperatures look to average near normal for the period. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1232 PM CDT Thu May 23 2024 VFR conditions are expected through midnight before a thunderstorm complex moves through the region late tonight and early Friday morning. PROB30 groups continue to be utilized to identify the time periods most favorable for storms, and have been added in this TAF for KMLI/KBRL where confidence is increasing for storms. Southerly winds around 5 to 10 knots are expected through this evening, with a few gusts up to 20 knots. && .HYDROLOGY... Issued at 1255 PM CDT Thu May 23 2024 Watch/Warnings: River Flood Warnings have been issued for the Cedar River at Cedar Rapids and at Conesville, both for minor flooding. Issued a Flood Watch for the Cedar River at Cedar Bluff for potential to reach into the minor flood category. Issued a Flood Watch for the Iowa River at Wapello and Oakville for the potential for minor flooding. Issued a Flood Watch for the Mississippi River at Gladstone, Burlington, and Gregory Landing for the potential for minor flooding. Flood Watch has been continued for the Wapsipinicon River at De Witt for the potential for Major flooding. Flood Warnings continue for the following: Iowa River at Marengo and North Skunk River at Sigourney for moderate flooding. Wapsipinicon River at Anamosa Shaw Rd. for minor flooding. See Flood Warning, Flood Watch, and Flood Statements for more information. Most of the river forecasts are starting to be based on routed flow. Some attenuation is still possible as the crest wave makes its way through the river systems over the next two to seven days. Because of this, confidence in some forecasts, especially those forecast to reach flood stage or a respective flood stage category beyond day 4, remain lower. Additional heavy rainfall is possible through the Memorial holiday weekend which may cause rivers to rise more than expected so stay tuned! && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...Speck LONG TERM...Speck AVIATION...Speck HYDROLOGY...Haase