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Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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303 FXUS63 KDVN 140552 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 1252 AM CDT Wed Aug 14 2024 ...Aviation Update... .KEY MESSAGES... - Threat for severe weather and flash flooding from Wednesday night and through Thursday. Stay weather aware and have many ways to receive notifications, especially at night. - Temperatures near to above normal, with most in the low-mid 80s. Thursday will be the warmest day of the week, especially in the south, with heat indices near 90-95. - Precipitation amounts have trended down, quite substantially for some, over the last 12 hours. Will have to see if this trend continues, but still will advertise the potential for heavy rainfall and localized flash flooding. && .SHORT TERM /THROUGH THURSDAY/... Issued at 149 PM CDT Tue Aug 13 2024 Tonight, we are expecting a quiet night as high pressure continues to push off to our east. This will keep us in light southeasterly flow tonight. Similar to last night, we will remain mostly clear, with clouds diminishing in our south through the evening. Temperatures will largely be in the low-mid 60s. Tomorrow, we will start to see cloud cover increase through the day, as LLVL moisture return works into the area. The surface warm front is not expected to move in until later in the day and evening, which is where we will start to see those surface dewpoints start to increase. Thus, humidity-wise, much of tomorrow will be comfortable with temperatures in the low 80s. With this initial push of moisture in the area, we may see scattered and elevated showers develop through the afternoon, slowly pushing north. Confidence remains low on this, but have opted to include Slight-Chance PoPs to account for this potential. Although, we are expecting that much of the day remains dry for the area, with the severe threat being low until the evening and nighttime. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Issued at 149 PM CDT Tue Aug 13 2024 Wednesday Night...Organizing wave aloft with a short wave embedded in diffluent cyclonic flow aloft will provide the lift, combined with a re-invigorating SSW 35+ KT LLJ to induce another MCS somewhere acrs the northeast plains/MO RVR Valley/southern MN and acrs IA this period. Initial development will probably occur upstream acrs the MO RVR Valley, and then feed eastward acrs IA/southern MN into Thu morning. Some worry that it may be a mature squall line or linear type MCS as it pushes acrs the local area which would mean a possible damaging wind threat if it`s sfc/near sfc rooted or utilizing cold pool mechanics and projected effective shear of 45+ KTs. PWAT`s currently are still projected to be very high from 1.9 to 2.3+ inches, which would fuel intense rainfall rates. But if the system is progressive, that would limit a flash- flood threat but the line would still dump rain at high rates just for a shorter period. A more classic storm cluster MCS with some back-building potential would bring a high flooding threat and the chance for several inches of rain by Thu morning. This would bring about several hydro concerns such as rising rivers and streams besides the flash-flooding. General timing for the MCS will be anytime after midnight and to about sunrise on Thursday, give or take a couple of hours. Ahead of the line, some guidance is starting to hint at a warm advection band of precipitation at the nose of the LLJ. This will be an area to watch, as it can provide a focus for the MCS to follow and potentially surge along, as well as lead a an isolated elevated hail threat ahead of the impending MCS. Thursday...An uncertain scenario day, with what ever occurs and evolves out of Wed night and where it`s remnants lay out for additional lift and heating later in the day Thu to act upon for redevelopment. LLVL triple point/shear focus may occur acrs WI, with other fronts and outflow boundaries ringing the local area from northeast to the south. Thus the redevelopment may occur along these zones and largely out of our area of concern. We may just have secondary weaker re-development locally in the wake of a strong Wed night MCS. A lot of details still to be worked out for this day and can`t let the guard down yet. A Slight Risk (level 2/5) exists for areas along/east of the Mississippi River, highlighting that potential for strong/severe redevelopment that afternoon to evening. This is very conditional though, so stay tuned! Latest trends in guidance have been cutting back on precipitation totals, generally with a 1.00-2.00" range for the heavier hit areas when all is said and done. Although, areas that see multiple rounds of storms may see amounts above that range. Will have to continue monitoring these trends over the next 24 hours and hone in on a QPF forecast. Friday through Monday...Latest suite of medium range ensembles and upper jet progs suggest the upper wave to evolve into a closed upper low acrs the northwestern GRT LKS by week`s end, with the area suspect to diurnal afternoon sctrd pop-up showers on the system`s western flank through at least Friday. If this system can meander far enough to the east, it may leave a fair wx weekend with seasonable temps for the local area in it`s wake. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 1248 AM CDT Wed Aug 14 2024 Will go with a VFR TAF cycle again through Wed evening, with just decaying debris clouds and possible light rain/sprinkles out of the current NE activity coming acrs IA later today. Will also play the lower VFR to MVFR stratocu deck acrs MO into south central IA staying west or lifting to VFR levels later today. Light and variable sfc wind regime will go southeasterly and increase with tightening pressure gradient from upstream storm system as it moves in from the west...8-12 KTs with gusts up to 20 KTs Wed afternoon. The main precip action that will impact the TAFs will be more likely after 06z Thu. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...Gunkel LONG TERM...Gunkel AVIATION...12