Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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931 FXUS63 KDVN 301750 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 1250 PM CDT Tue Apr 30 2024 .KEY MESSAGES... - Active forecast remains through the long term, with near daily chances for precipitation beginning tonight. - Temperatures will remain above normal through midweek, trending towards normal for the end of the week. && .SHORT TERM /THROUGH WEDNESDAY/... Issued at 254 AM CDT Tue Apr 30 2024 A sprawling high pressure system at the surface was leading to a tranquil and cool early morning. An ideal radiational setup with light winds and generally clear skies has allowed temperatures to drop into the 40s across much of the area, with some areas down near 40 in the river valleys and drainage locations north. Far south areas were still around 50 or the lower 50s. Today should be largely quiet and very nice as it features a good recovery on temperatures aided by mixing and solar insolation leading to gusty southerly winds to 30 mph by afternoon. Mixing above 850 hPa and temps of 12C-14C brought to surface dry adiabatically yields highs from the mid 70s to lower 80s. Attention by this afternoon will shift to our west as a mid level wave ejects into the Northern Plains. Increasing forcing atop moisture advection in the low levels ahead of a deepening surface low and cold front will foster convection initially across parts of SD/MN/IA/NE, eventually zippering down the cold front into KS/MO while shifting east. Strong deep layer shear 40-50+ kts and very steep lapse rates of 8c/km will support Supercells with large/very large hail and damaging winds with this convection to our west. The challenge for our area is how far east does the instability axis translate and whether these severe storms can maintain some of their strength while entering eastern Iowa and northern Missouri this evening. In general the CAMs support a weakening trend as the convection enters the service area and likely begins to outpace the instability. 00z HREF ensemble paintball 4 hr max 2-5km UH >150 m2/s2 shows clustering to our west and brings it close to eastern Iowa before quickly waning 02z-05z. Latest few runs of the RAP however, show there is likely to be enough 0-1km instability (500-1000 j/kg) amidst strong 0-3km shear 40+ kts to maintain a severe threat into eastern Iowa with these cells. Proxy soundings show some low level CINH developing by the time the storms arrive, but lots of dry air sub-cloud and strong wind fields will still yield a concern for damaging wind gusts being the primary threat. Steep lapse rates around 7.5c/km and the strong shear will make hail also a threat. Agree with SPC expanding the Slight risk into portions of eastern Iowa and far northeast Missouri. The convection should further weaken approaching the Mississippi River heading into late evening and N Illinois through early overnight, but still have a gusty wind/small hail threat. Thereafter, the rest of the overnight looks to turn quiet once again. Wednesday looks to be largely quiet and beautiful with surface high pressure once again in control. Highs look to be in the 70s. Warm advection will kick in during the afternoon leading to increasing cloudiness. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Issued at 254 AM CDT Tue Apr 30 2024 The upper pattern becomes active once again with strengthening isentropic ascent by Wednesday evening/overnight fostering an increase in PoPs. A developing warm front well to our south will make this mainly a threat for locally heavy rainfall with any repetitive convection. After that system, we will start to see a potent wave deepen over the Rockies mid-late week. We will see a few leading impulses pass through the area, leading to persistent showers/storms for the remainder of the week. This will be a wet period, with the potential to see quite a bit of rain. With recent rains and more forecast, some rises along area rivers are expected. The parent wave developing is the one that has our attention though. Although, there is plenty of uncertainty with this, as well as major timing differences amongst guidance. Although, all long term guidance shows this system. If this wave deepens enough and we get that negative tilt upon arrival, this will bring the potential for strong to severe storms late in the week. Although, it is too soon to say for sure. WPC is highlighting our area in the risk for Excessive Rainfall from midweek through the end of the week, as they are currently forecasting between 1-3+ inches of rain by the week`s end for some. Thus, flash flooding will be possible, as well as rises along area rivers. So, just be mindful and stay up to date on our forecasts! && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1237 PM CDT Tue Apr 30 2024 Gusty south winds are forecast to develop quickly this afternoon behind a warm front that is lifting northward across the area. These gusty winds will continue into tonight until a cold front moves across the area overnight. Ahead of this cold front, a line of thunderstorms is forecast to develop in central Iowa and move across the eastern Iowa TAF sites between 00 to 06 UTC. MVFR ceilings and visibilities are possible at all TAF sites in the strongest storms. Included a prob30 group at MLI were confidence is lower that the line of storms will impact that site with a TEMPO at other locations. Gusty west winds are forecast to develop by mid morning on Wednesday with gusts up to 25 knots. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...McClure LONG TERM...Ervin/McClure AVIATION...Cousins