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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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514 FXUS63 KDVN 151625 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 1125 AM CDT Mon Jul 15 2024 .KEY MESSAGES... - The heat continues for today and Monday with peak heat indices between 100 to 110 F. A Heat Advisory is in effect area-wide today until 8 PM but afternoon relief is possible north if storms arrive. - An Enhanced Risk (Level 3 of 5) for severe storms across the outlook area. Damaging winds are the primary hazard, but tornadoes will also be possible today. - Moderate to major river flooding continues on the Mississippi River with most sites crested. The Rock River is now expected to see flooding due to the heavy rains upstream in the past 24 hours. && .SHORT TERM /THROUGH TONIGHT/... Issued at 316 AM CDT Mon Jul 15 2024 Today is another day to closely monitor forecasts and warnings! Our area is set to be impacted by a damaging line of storms this afternoon and evening, with an abundance of observational and model data supporting the apex of a severe bowing line, moving through eastern Iowa and northwest Illinois. SPC has our area in Enhanced, level 3 of 5, today, focusing primarily on damaging winds, but also noting a 5% tornado risk, and a low 2% hail risk. Today will be hot and humid, and while that will get handled by an advisory today (though some values may reach warning criteria in the south), the focus needs to be on severe weather during the afternoon and evening. This heat will be the pool of energy, CAPE we need to supply another round of severe storms. However, this time, we`re dealing with a strong trigger (mid level jet streak), focusing mechanism (front), and significant shear over 40 kts, and PWAT values over 2 inches and all those factors really add up to a potential high end event. The activity in eastern ND early today, will likely drop southeast into MN, but could trigger a few elevated cells into eastern Iowa and northern Illinois. Some CAMs do create a separate event from this activity, but that seems unlikely. Instead, it looks like air mass recovery will occur quickly today, with winds becoming southeast and increase to 10 to 15 mph. This is especially true over northern areas, where the mesohigh from last evening`s storms will be decaying. I expect storms to fire in central Iowa by mid afternoon, and will rapidly spread east and southeast. Damaging wind will be a threat from the onset, but with the backed winds in eastern Iowa and northern Illinois, STP values may exceed 2 in locations north of Interstate 80, supporting supercells and tornadoes during the afternoon and early evening. By early evening, an established bowing storm segment should be formed, moving east, with a comma head, and trailing line of cells. This will lay out a swath of heavy rainfall and wind, with guidance most supportive of this falling roughly along the Interstate 80 corridor, then sinking south during the evening. While the exact position is looking to go through our area, this event will fall into line once we know the position of backed winds and initial storms that trigger in central Iowa/northeast Iowa today. Once they are, the axis of most significant storms can be identified and communicated. After 9 PM, the mode of storms looks to become primarily heavy rain producing multicells storms, with the axis of heavy rain gradually sinking south through the late evening and overnight. Rainfall amounts of 1-2 inches will be common with this event, with some amounts in the late evening training supporting and additional 1" where training storms occur. Thus, this event could again impact rivers, especially with any amounts over northern Illinois, which is dealing with back to back heavy rainfall events in the past 36 hours. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 316 AM CDT Mon Jul 15 2024 Cooler and less humid air will move into the region behind a cold front by Tuesday and last through the end of the week. Overnight lows in the 50s are forecast on several nights, giving our air conditioning a bit of a break. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 650 AM CDT Mon Jul 15 2024 Patchy shallow fog will dissipate across the area by 13-1330Z. Southerly winds will increase with occasional gusts today, especially at airports along/south of I-80 where gusts as high as 25 kt may occur this afternoon. Isolated showers or storms (20-30 percent coverage) may sprout in the northeast quarter of Iowa, including near CID and DBQ between 16Z and 22Z, but confidence is low on this. The main story with the TAF is the high likelihood of growing storms into a quickly-moving storm complex expected late this afternoon through mid-evening over the area. These storms and especially the complex will be capable of severe winds, and likely will have temporary LIFR visibility in very heavy rainfall. Tried to incorporate that into two hour TEMPOs within the TAF, but naturally there is some uncertainty still with timing. Behind the storms later tonight, there could be again some fog/low cigs. && .HYDROLOGY... Issued at 1111 AM CDT Mon Jul 15 2024 The broad crest on the Mississippi River from Gladstone, IL (L/D 18) down through Gregory Landing, MO should be completed within the next 12 to 24 hours. A significant amount of water is working its way down the Rock River. This water will slow down and may briefly stop the rate of fall on the Mississippi River from Rock Island (L/D 15) down through Gregory Landing for the remainder of the week. By next weekend and into the following week, the Mississippi River from Rock Island on downstream will begin falling again. Tributary Rivers: The lower Wapsipinicon River near Dewitt, IA will fall below flood stage this afternoon. Water levels will remain high for the next several days before they start falling again. Backwater effects from the Mississippi River will keep the lower Iowa River just below flood stage for the remainder of the week. Based on water already in the Rock River basin and forecasted rainfall over the next 24 hours, the entire length of the lower Rock River will go into flood. The Joslin and Moline crest forecasts have jumped into the major flood category based on the predicted rainfall over the next 24 hours. If the rainfall is less than expected, then the crest forecasts on the lower Rock River would be lower. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...Heat Advisory until 8 PM CDT this evening for IAZ040>042- 051>054-063>068-076>078-087>089-098-099. IL...Heat Advisory until 8 PM CDT this evening for ILZ001-002-007- 009-015>018-024>026-034-035. MO...Heat Advisory until 8 PM CDT this evening for MOZ009-010. && $$ SHORT TERM...Ervin LONG TERM...Ervin AVIATION...Friedlein HYDROLOGY...08