233 FXUS63 KDVN 100318 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 1018 PM CDT Tue Oct 9 2018 ...HYDROLOGY UPDATE... .SYNOPSIS... Issued at 330 PM CDT Tue Oct 9 2018 Latest sfc analysis was indicating quasi-stationary front off to the north and west, bi-secting the state of IA from NE-to-SW. Some sign of a subtle sfc wave on this feature currently acrs central IA, but the main low is currently acrs east central KS. With lee side southeast LLVL flow, 0-3 KM SRH's, moist profiles(low LCL's) and CAPEs, this is what is driving the current tornado threat acrs areas mainly along and west of the MS RVR. The main front lifts out late tonight and Wed morning with more widespread rains and the prime flash flood threat, then the cool down will be on for the end of the week. Will have to watch for a cool season type lighter rain event sometime over the weekend, as well as some frost windows. && .SHORT TERM...(This Evening through Wednesday) ISSUED AT 330 PM CDT Tue Oct 9 2018 Tonight...As mentioned above, the area is prime for sctrd rather small individual supercells with rotation this evening, possibly east of the ongoing tornado watch area. Localized damaging wind possible too. As storms hit rain-sensitive areas, there may be the need for an evening flash flood warning. Then as a shortwave embedded in southwesterlies ejects out northeastward, and the main sfc low treks toward north central IA by midnight or 2 AM, expect an increase in shower/storm cluster coverage streaming up from the south/southwest up acrs the CWA, becoming more widespread after Midnight. Current indications suggest the heaviest rain may fall along a tier or two of counties along and west of the MS RVR, on eastward into IL late tonight and Wed morning. This activity fed by ongoing unseasonably high warm moist conveyor of 1.6 to 1.9 inch precipital waters by a SSW 30-40+ KT LLJ. Still see widespread 1-2 inch rainfall amounts by late Wed morning, with localized strips of higher amounts possibly up to 3-4 inches, if showers/storms can stream up acrs the same areas for a period. But late night frontal placement and convergent forcing suggests the higher rainfall amounts may fall out from south-to-north up the MS RVR valley. With such saturated grounds, see the scenario where several multi county flash flood warnings need to be issued later tonight into Wed morning. Although the flooding will become the primary concern after midnight and the evening severe threat, there may still be an isolated severe storm threat or even a isolated tornado threat well into the late night. Wednesday...Water and storm trouble should linger through late morning, then expected FROPA acrs the MS RVR by midday or early afternoon should lead to the end of the shower progression. Will still have to watch for strong storms to flare up along the front through at least midday as they exit the eastern border of the CWA. Post-frontal in-sweeping cool temp regime to make for falling afternoon temps west of the MS RVR. All in all, of course will keep the flash flood watches going through 18z Wed with expected flooding later tonight/Wed morning, with ongoing severe storm threat really aggravating the situation. .LONG TERM...(Wednesday Night through next Tuesday) ISSUED AT 330 PM CDT Tue Oct 9 2018 Sharp change to November-like weather is the main story for the long term. The season's first widespread first heavy frost appears to be setting up for Thu and possibly Fri night as well, when lows across the north may drop below freezing. Wednesday night...Brisk west to northwest winds and strong cold air advection will pull in temperatures in the 40s, then mid 30s to around 40 for lows by sunrise Thursday. The likelihood of lingering cloud cover and sufficient winds will prevent the threat for frost or near freezing temperatures as temperatures drop below zero celsius at 850 mb. Highs Thu will likely only reach the 40s north to lower 50s south. High pressure that follows will provide clearing skies and light winds for Thursday night. Have introduced widespread frost north and patchy frost in the south for late night/early Friday morning with lows in the 30s. Even colder temperatures spill in Friday into Friday night with daytime temperatures limited to the 40s, then overnight lows in the 30s and possibly around freezing north. Much of this is dependent on possible cloud cover and the timing/strength of an incoming shortwave. Will again mention frost, but confidence of frost formation is low, but there is a good potential for freezing temperatures in the north. Over the weekend, forecast confidence is low with a shortwave and cold frontal passage due to poor model agreement. For now, will maintain chances for a cold rain as temperatures only reach the 50s with lows in the 30s to lower 40s. Depending on the timing and how the system exits, conditions may even support snow flakes by late Sunday night into Monday morning. Cold and mainly dry weather lingers into early next week with temperatures sufficiently cold enough again for frost Monday night, then slightly warmer temperatures going into Tuesday as surface winds turn southerly ahead of the next cold front. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening) ISSUED AT 528 PM CDT Tue Oct 9 2018 Low pressure will pass north of the area tonight. Numerous showers and embedded thunderstorms will accompany the low. Expect ceilings to deteriorate to MVFR/IFR late tonight and for winds to shift the WSW mid to late Wednesday morning. Uttech && .HYDROLOGY... Issued at 953 PM CDT Tue Oct 9 2018 Main point...one more round of heavy rain is expected tonight into Wednesday. A broad swath of 1 to 2 inches of rain, with locally higher amounts, is expected from central Iowa into southeast Minnesota and Wisconsin. Soils generally north of I-80 and especially across Minnesota and Wisconsin are saturated so any additional rainfall will rapidly run off into area waterways. After sunset Wednesday, the overall weather pattern will change. Rain will still be possible over next weekend but amounts will be much lighter than what has been seen over the past 10 days. Mississippi River... The new forecasts for the Mississippi river still show rises occurring all the way through October 16th. However, the new forecasts show a slight delay of 6 to 12 hours compared to the morning forecasts. Delays like this can be expected due to slight changes in how runoff from the rain moves into the river system and in the overall timing of the routed flow moving downstream. With more heavy rain expected across Minnesota and Wisconsin, crests on the Mississippi river will occur October 17th through the 24th. Confidence remains high that moderate to major flooding will be seen from LD 14 at Le Claire, IA down through Gregory Landing, MO. North of LD 14, minor to moderate flooding is expected. Iowa Tributary rivers... Routed water is already moving downstream through the basins. With the addition of heavy rainfall through sunset Wednesday, confidence is high that moderate to major flooding will continue along the Cedar, English, Iowa, North Skunk, Skunk, and Wapsipinicon rivers. The evening forecasts have lowered the crests considerably along the Cedar river and to a lesser extent on the Iowa river. Such changes show the sensitivity of the model to predicted rainfall, saturated ground, and the overall timing of routed flow moving downstream. From Columbus Junction down to the mouth of the Iowa river, the Cedar river will be providing a majority of routed flow that will result in moderate to major flooding. At Iowa City, runoff from creeks and streams below Coralville from the next round of heavy rain and increased releases from Coralville dam will push the Iowa river close to 23 feet by the weekend. With heavier rainfall expected in central Iowa, major flooding will continue on the North Skunk river with moderate flooding on the Skunk river. The current forecasts are based on predicted rainfall and routed flow moving downstream. Crest forecasts for the North Skunk river have changed very little while a delay and lowering of the crest has occurred on the Skunk river. Pecatonica and Rock rivers... Heavy rainfall of 1 to 1.5 inches is expected in the Pecatonica and Rock river basins through sunset Wednesday. Thus the forecasts are based on a combination of predicted rainfall and routed flow moving through the river system. Crest forecasts have changed very little along the Pecatonica and Rock rivers from this morning. Confidence remains high that moderate flooding will be seen on the Pecatonica river and major flooding from Joslin to the Mississippi. As the Mississippi continues to rise, the rate of fall on the Rock river is likely to slow down and thus prolong the flooding. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...Flash Flood Watch from 1 AM CDT Wednesday through Wednesday afternoon for Clinton-Jackson-Scott. Flash Flood Watch through Wednesday afternoon for Benton- Buchanan-Cedar-Delaware-Des Moines-Dubuque-Henry IA-Iowa- Jefferson-Johnson-Jones-Keokuk-Lee-Linn-Louisa-Muscatine- Van Buren-Washington. IL...Flash Flood Watch from 1 AM CDT Wednesday through Wednesday afternoon for Bureau-Carroll-Hancock-Henderson-Henry IL-Jo Daviess-McDonough-Mercer-Putnam-Rock Island-Stephenson- Warren-Whiteside. MO...Flash Flood Watch through Wednesday afternoon for Clark-Scotland. && $$ SYNOPSIS...12 SHORT TERM...12 LONG TERM...Sheets AVIATION...Uttech HYDROLOGY...08