Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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572 FXUS63 KDVN 152000 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 300 PM CDT Mon Jul 15 2024 .KEY MESSAGES... - A Heat Advisory is in effect area-wide today until 8 PM for peak heat indices between 100 to 100 degrees. - Today`s severe thunderstorm outlook has been upgraded to a Moderate Risk (level 4 of 5) for the northern two-thirds of the forecast area. The Enhanced Risk (level 3 of 5) remains to the south. Significant damaging winds are the primary hazard; several tornadoes are also possible. - A Flood Watch as been issued for counties east and northeast of the Quad Cities. Recent heavy rainfall has saturated the ground, making this area more susceptible to flash flooding. Rainfall rates could peak between 2 - 2.5" per hour. - 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 256 PM CDT Mon Jul 15 2024 There is a Moderate Risk (level 4 of 5) for severe weather this afternoon into tonight for much of the outlook area, with an Enhanced Risk (level 3 of 5) across the south. Please monitor the weather closely and heed any warnings issued for your location! SPC mesoanalysis early this afternoon showed a mid-level vorticity max across E South Dakota/SW Minnesota/NW Iowa, positioned to the south of a 80 kt 300mb jet over northern Minnesota and Wisconsin. A zone of low-level moisture convergence was noted (where surface dewpoints were between 75 to 80 degrees!), stretching from central Iowa to the Quad Cities and into central Illinois. As large-scale ascent associated with the mid-level impulse overspreads the area late this afternoon/evening, this quasi- stationary zone of low- level convergence may aid in focusing the convective initiation. With extreme instability in place (3500 - 4500 J/kg MLCAPE), anticipate explosive convective development and rapid upscale growth into one, or possible a few, bowing line segments. Forward-propagating Corfidi vectors and W to SE sloping theta-e and 1000-500mb thickness contours should help in eventually guiding the MCS to the ESE or SE later into the evening. CAMs have been consistent on showing significant severe wind gusts in the strongest bowing segments and the HREF max wind gust output shows several corridors with values of 60-70+ kts. Greatest uncertainty is on the exact placement/track of the dominant surging MCS, with a northern scenario focused across the NE forecast area (NW Illinois) and another camp further south which would bring significant winds to a larger portion of eastern Iowa and northwest Illinois. To reiterate, today is a favorable setup for a higher end wind event (scattered 75+ mph gusts) due to a very unstable air mass, sufficient deep layer shear, steep mid-level lapse rates near 8 C/km, and theta-e index values near 35. A few tornadoes are possible in association with any surging storm segments as 0-3 km shear of 30+ kts supports development of mesovortices. There is also potential for very heavy rainfall with PWATs near 2". There could be a zone of training convection that leads to heavy rainfall totals of 2-4"+. WPC has a Slight Risk for flash flooding across the outlook area. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 256 PM 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 /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 1252 PM CDT Mon Jul 15 2024 Main story continues to be on potential for severe storms late this afternoon through this evening/early tonight. Scattered storms will develop quickly by the late afternoon near or just northwest of the area and then grow upscale into one or more bowing segments. Severe wind gusts are the primary threat and a few tornadoes are possible. Any storms will bring potential for brief IFR/LIFR due to visibility reductions and low ceilings. Mentioned thunderstorm potential in TEMPO groups, but there remains uncertainty on the exact timing and on the severity of the wind gusts. Later updates to TEMPOs will likely be needed. && .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. Flood Watch from 6 PM CDT this evening through late tonight for ILZ001-002-007-009-016>018. MO...Heat Advisory until 8 PM CDT this evening for MOZ009-010. && $$ SHORT TERM...Uttech LONG TERM...Ervin/Uttech AVIATION...Uttech HYDROLOGY...08