Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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320 FXUS63 KDVN 272320 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 620 PM CDT Sat Apr 27 2024 .KEY MESSAGES... - Active period ahead by this evening through Sunday with several rounds of showers/storms. - Flash Flooding remains a concern for areas that receive repeated rounds of thunderstorms tonight/Sunday with the potential for areas of 2-4 inches of rain. A Flood Watch has been issued for southeast IA, west central IL and northeast MO where confidence in seeing these rainfall totals is highest. - Severe weather is also possible, particularly by this evening, but also into Sunday although prior convection may have an impact on the magnitude/timing/location of severe weather Sunday PM. - Unsettled weather continues through next week, with periodic rain chances. && .UPDATE... Issued at 613 PM CDT Sat Apr 27 2024 Frontal supercellular storms have been slowly moving east northeast in the north, but that process should shut down through 9 PM. The south 1/2 to 2/3rds will see a progressive QLCS move east northeast into the area, with wind and embedded possible QLCS tornadoes. Hail threats may be decreasing for now. This cluster of storms will push east more quickly than storms that were occurring earlier this evening, on the pace of 40-50 mph. Heavy rainfall remains expected from these storms, and any repeat/or bookend storm clusters. A tornado watch is in effect for most areas through Midnight. && .SHORT TERM /THROUGH SUNDAY/... Issued at 140 PM CDT Sat Apr 27 2024 Late morning surface analysis shows a surface low centered across eastern Minnesota and western Wisconsin, with a cold front draped to its south across east central Iowa and northwest Missouri. Off to our southwest, another surface low with a warm front and dry line was centered over the Oklahoma panhandle, with storms ongoing along this and ahead of a shortwave in the same location. This shortwave will progress northeast over the next few hours, and will be the driver of our weather over the next couple of hours. The overall forecast remains on track for the area, with shower and storm coverage expected to increase over the next few hours. The first round should be focused along the stalled cold front draped across east central Iowa as we destabilize and reach our convective temperature in the upper 70s. Latest CAMs focus the threat mainly along and northwest of the HWY 151 corridor. Ample 0-6km shear and steep mid-level lapse rates pushing CAPEs around 1000-2000 J/kg may lead to storms capable of large hail initially. The second round of storms will come this evening as the aforementioned shortwave rides the front and drives additional lift across the area. A renewed LLJ will also ensure ample lift and increased vertical shear. There remains some uncertainty as to where storms will initiate and track, which is likely tied to early PM convection and how much it stabilizes that warm sector air in eastern Iowa. Regardless, HREF ensembles continue to paint areas mainly south of Interstate 80 with high POPs. Severe storms will also be possible with mainly a large hail and damaging wind threat with near straight hodographs and cold pool dynamics in play. While low, can`t rule out a tornado threat in the QLCS and with any remnant boundaries from early PM storms. Look for this threat to wane by midnight, with concerns turning more towards a heavy rain/flash flood risk. Speaking of which, we will need to keep a close eye on flash flooding potential with these storms. LLJ will advect in a rather robust PWAT feed across the region with values approaching 1.75" by midnight. Where storms do train, latest CAMs show QPF by Sunday morning approaching 2-4 inches. This looks to be favored mainly in southeast Iowa, west central Illinois and northeast Missouri, where a Flood Watch is now in effect through Sunday morning. Heading into Sunday, scattered showers and storms will persist through the morning and early afternoon, with a renewed round of more widespread linear showers and storms expected by the evening ahead of another robust shortwave ejecting out of the Rockies. There is potential for this activity to become severe, with the Storm Predication Center advertising a Level 1 to 2 risk for the area. The primary threats with storms will be damaging winds and large hail, with a secondary tornado threat if low-level shear can materialize. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... Issued at 140 PM CDT Sat Apr 27 2024 Post cold front passage, we will be in for a dry start to the week with high pressure moving across the central Plains and mid-Mississippi River Valley. By mid to late week, a renewed round of showers and storms is expected for the area as a trough in the Rockies ejects several shortwaves across the Plains and Midwest. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 613 PM CDT Sat Apr 27 2024 A stormy period will be in place this evening, with thunderstorms widespread before 06Z in eastern Iowa and northwest Illinois. Winds will potentially exceed 40 kts along and south of Interstate 80 through 04z. Otherwise, thunder may become more sporadic overnight, with rain and mvfr cigs continuing. Sunday, a gradual improvement to higher MVFR to low VFR is expected, with another round of storms moving in during the afternoon from west to east. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...Flood Watch through Sunday morning for IAZ087>089-098-099. IL...Flood Watch through Sunday morning for ILZ025-026-034-035. MO...Flood Watch through Sunday morning for MOZ009-010. && $$ UPDATE...Ervin SHORT TERM...Speck LONG TERM...Speck AVIATION...Ervin