Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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108 FXUS63 KDVN 032339 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 639 PM CDT Wed Jul 3 2024 .KEY MESSAGES... - Showers and thunderstorms are possible on Independence Day as a warm front lifts north through the area followed by a cold front. There is a Slight Risk for severe storms for the far NW CWA with a Marginal Risk for most of the remainder of the CWA. - A rather active pattern still looks to be on tap through the longer range, with near daily chances for precipitation somewhere in or near our forecast area. Saturday may be the best chance at a dry day, with slight-chance PoPs daily from there. - Moderate to Major River Flooding continues, with further changes to river forecasts expected as we transition from predicted rainfall to observed rainfall over the next 36 hrs. && .SHORT TERM /THROUGH THURSDAY/... Issued at 250 PM CDT Wed Jul 3 2024 Tonight, dry conditions will prevail as high pressure drifts east and a low approaches from the plains lifting a boundary into the southern CWA. Slight POPs are in the southern part of the CWA for the overnight with chance POPs towards daybreak. Winds will be nearly calm and with any partial clearing, can`t rule out some patchy fog, but opted not to mention in grids. Lows will be in the mid 60s to near 70. On the Fourth, unfortunately, we will have to deal with chances of scattered showers and thunderstorms. Some of which could be strong to severe, as a low develops over southern MN with a cold front pushing into the western CWA during the late PM and evening. SPC has a Slight (level 2 of 5) Risk for primarily damaging winds and large hail for Buchanan and Delaware counties, with a Marginal Risk (1 of 5) for much of the rest of the CWA. Dew points will rise back into the upper 60s and lower 70s. With some partial sun, temperatures will rise into the low to mid 80s. MLCAPE will climb into the 1000- 1500 J/kg range with modest shear, so some organized cells will be possible. Moisture will be pooling ahead of the front with PWATs increasing to 1.5 to 2 inches. So, heavy rain will also be possible with any storm. Areas susceptible to flooding will need to monitor the situation closely. With many people outside on the holiday, remember that by definition a thunderstorm produces lightning and poses a risk as well. When thunder roars, go indoors! A key to the severe risk will be the degree of destabilization we see with any clearing. Stay tuned. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... Issued at 250 PM CDT Wed Jul 3 2024 Thursday night...Closed positively tilted upper low slated to dig down acrs MN into western WI through early Friday morning, with somewhat diffluent cyclonic flow sprawling acrs the upper MS RVR Valley. 40-50 KT effective shear levels and lingering MUCAPEs enough to continue isolated to sctrd showers and thunderstorms to move eastward acrs the area well into the night. More optimum support for stronger storms looks to occur acrs MN into WI, and especially to the south acrs central MO. But there may be enough locally to fuel a few strong to severe storms locally with large hail and gusty downburst winds as the main threats. But with the low coverage more areas will remain dry as opposed to get clipped by a passing storm. Pre-wave southwesterly LLVL flow/fetch will also draw higher THTA-E air back up acrs the area, noted by a PWAT increase to 1.5-1.8 inches. So localized heavy rainfall will continue to be a factor to keep in mind, but at very localized swaths. Low temps in the 60s Friday...Upper low/trof still on track to roll acrs the western GRT LKS into Sat morning. The associated cool pool aloft and any vort spokes should generate isolated to wdly sctrd instability showers possible acrs the area during the afternoon, especially north of I- 80. Ambient cumulus, the chance for a few showers and the cool pool itself may keep a lid on the temps at below normal levels mainly in the 70s. Saturday and Sunday...Broad upper troffiness still looks to reign acrs much of the upper CONUS this weekend, getting re-enforced acrs much of the upper midwest by additional northern stream upper waves propagating out of western Canada and into the mid/upper MS RVR Valley almost clipper-style. Long range timing these waves still suggest that Saturday will be dry ahead of this incoming process. Temps will still look to moderate back into the lower 80s. There may be a few showers and storms moving into the area Sat night with the first clipper, but as the upper trof axis slides overhead, late Sunday and especially Sunday night may be a better chance for sctrd showers and storms to occur. Seasonable temps in the low to mid 80s Sunday. Early next week...Upper jet and synoptic scale feature progs suggest the longer wave upper trof to linger and even deepen acrs much of the mid to upper MS RVR Valley this period. This would allow for wdly sctrd shower and storm development in the afternoon heating under this feature, with Monday looking prime. Trof axis migration a bit more off to the east may make for less coverage by Tuesday. Northwest flow and cooler core nature to the upper trof will continue to support near seasonable to somewhat below normal temps this period. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 640 PM CDT Wed Jul 3 2024 VFR conds for much of this taf cycle through Independence Day. The exeption is the potential for MVFR VIS late tonight into early Thursday with BR due to calm winds. Then scattered light showers may move across the taf sites in the morning and early afternoon. This was covered with a Prob30. Beyond this cycle, mainly Thursday evening, a cold front is expected to bring a sct-bkn line of thunderstorms. South winds 10-15 kts for much of Thursday. && .HYDROLOGY... Issued at 1211 PM CDT Wed Jul 3 2024 The forecasts along the Mississippi River havn`t changed much from the previous ones, with many forecast points cresting into the weekend. Locations from Dubuque to Keokuk are still expected to crest over their respective Major Flood Stage levels. At Gregory Landing, a crest in the Moderate category is forecast. The crest is forecast near Dubuque and Bellevue on July 4th and 5th, with sites from Fulton to Keokuk seeing a crest between July 6th and 8th. On the Maquoketa at Manchester, the heavy rains and training thunderstorms to produce them did not materialize and shifted to the south of that basin. Thus it is no longer expected to reach the minor flood stage and the warning has been cancelled. Also with the rainfall amounts not being quite as high or widespread as earlier anticipated in some of the more northern basins, several tributary forecasts have been toned down some. Ongoing river flood watches and warnings on the Cedar, Iowa, Wapsi, Skunk, and Maquoketa Rivers have been adjusted accordingly to the rainfall reports from this morning. But with a few other areas indeed receiving torrential rainfall a bit further south, the river flood watches for the North Skunk River near Sigourney and English River at Kalona have been upgraded to river flood warnings. Current projections for additional rainfall over the next few days through the end of the week look more spotty with widespread heavy rain not likely. This should help maintain the current forecasts from deviating too much from the most recent forecasts. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...14 LONG TERM...12 AVIATION...Haase HYDROLOGY...12