Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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516 FXUS63 KDVN 300529 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 1229 AM CDT Sun Jun 30 2024 .KEY MESSAGES... - Pleasant weather into Monday. - Showers and storms return Monday night through Tuesday with the threat for heavy rain, and some severe weather potential Tuesday PM/evening conditional upon sufficient instability. - Independence Day forecast looks wet. - Moderate to Major flooding is expected on several area rivers. Crests could be delayed or altered with any heavier rainfall, depending on where it occurs Tuesday through Friday. && .SHORT TERM /THROUGH MONDAY/... Issued at 230 PM CDT Sat Jun 29 2024 Give the AC a break! Surface analysis at 18z places an initial cold front along a line roughly from Chicago, Illinois southwest to an area of low pressure near Wichita, Kansas. A secondary cold front extends from low pressure over eastern Lake Superior through central Wisconsin and northeast Iowa. It`s this latter front that brings a refreshing airmass, denoted by cooler temperatures in the 60s/70s and a marked lowering of dew points into the 40s/50s on gusty NW winds. This front will sweep across the area through late afternoon ushering in the pleasant airmass that will stick around into early next week, as high pressure builds across the western Great Lakes through 12z Monday. Lows tonight are expected to be mainly in the 50s, with a few upper 40s not out of the question in the northern counties pending the extent of decoupling in the boundary layer. Widespread highs in the 70s is expected for Sunday, around 10 to 15 degrees below normal. Monday AM lows will be cool once again, and could even be close to records in a few spots. The combination of 850 hPa temperatures of 10-12C (50-54F), light easterly winds and mainly clear skies suggest lows near to 3-5 degrees below the progged 850 hPa temperatures, or in the upper 40s to mid 50s generally. Please refer to the Climate section below for record low information for Monday at the main climate sites. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Issued at 230 PM CDT Sat Jun 29 2024 On Monday the high pressure system over the Great Lakes will gradually pull away. Strengthening southerly flow surface to 850 hPa will usher in a return of warmer and moist air into the region. This along with ejecting lead shortwaves ahead of Northern Rockies/Great Basin trough will lead to ramping shower and storm chances Monday night and Tuesday, with the higher PoPs (60-80%) favored mainly north and west of the Quad Cities. More widespread coverage of showers and storms is expected for Tuesday night into early Wednesday, as stronger synoptic forcing aided by a shortwave aloft and the right entrance region of a 100-120 kt 250 hPa jet steak overspread the Upper Midwest while at the surface a cold front moves through. The primary concern by Tuesday/Tuesday night looks to be heavy rain. 00z NAEFS and ENS PWATs climb to 1.75 to around 2 inches by 00z Wednesday, which is 2 to 3 standard deviations above climatology and is approaches the 99.5 percentile or is near max of their respective climatologies. NBM 4.2 probabilities support widespread 0.5 inch to 1 inch from 12z Tuesday to 12z Wednesday, especially across the northwest 2/3rds of the service area. However, given the convective nature and magnitude of the synoptic ascent doubling the PWAT would give a general idea of the higher limit, which in this case with PWATs around 2 inches would yield potentially higher amounts of 4 inches. With rivers rising will be watching this heavy rain potential closely, as this could delay or change crest forecasts depending on where it occurs. In addition, the significant moisture advection (IVT) and a southwesterly LLJ of 40 kt could contribute to backbuilding and an elongated MCS and a risk of flash flooding. Severe weather potential may exist by Tuesday PM/evening, as deep layer shear 0-6km increases to 40-50+ kts aided by the approaching shortwave trough. Models try to build in the instability during this time, especially west of the Mississippi River with MLCAPE increasing to 1000- 2000+ j/kg. However, if rain/clouds persist for much of Tuesday that could limit instability or keep the primary instability axis further west, similar to what we saw occur yesterday. So at this time it`s looking like a more conditional severe weather threat for Tuesday PM/eve, possible upon sufficient destabilization. Stay tuned! Behind the cold front high pressure looks to bring a brief dry and quiet period midweek, with the emphasis on brief as already the next system is slated to drop down into the Northern Rockies and Northern Plains by 12z Thursday. This shortwave looks to evolve into a closed low that traverses the Upper Midwest and western Great Lakes Thursday night through Friday night. This will support a return of shower and storm chances during this time, as the surface boundary is drawn northward. For those keeping a close eye on the weather for 4th of July festivities unfortunately it`s looking potentially wet, and while PoPs are likely (55-70%) it won`t rain all of the time. Nonetheless, many of us may have to rely on Mother Nature to provide the fireworks. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1228 AM CDT Sun Jun 30 2024 VFR conditions expected through the period. No sig wx impacts to aviation expected. && .HYDROLOGY... Issued at 1143 AM CDT Sat Jun 29 2024 No significant changes for the tributary rivers from this morning`s new forecasts. The crest on the Cedar River has gone through Cedar Rapids and should reach Conesville by Monday morning. The Iowa River forecast has come in a little lower, but minor flooding is still forecast at Wapello and Oakville. The Rock River continues to fall and have just cancelled the flood warning at Joslin. On the mainstem Mississippi, the new forecasts have resulted in flood category changes for Dubuque, Camanche, and Le Claire LD14 to Major flood and Keokuk LD19 and Gregory Landing to Moderate flood. Overall, rises are still expected through the next 7 days and beyond for most sites. Broad crests are beginning to show up in the last day of the forecast for Dubuque LD11 downstream to Bellevue LD12. However, with additional rain expected Monday night through Tuesday, these crests may be delayed or change depending on where the rain falls. && .CLIMATE... Issued at 145 PM CDT Sat Jun 29 2024 Record low temperatures for July 1 Burlington......51 in 1918 Cedar Rapids....43 in 1924 Dubuque.........47 in 1995 Moline..........48 in 1988 && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...McClure LONG TERM...McClure AVIATION...Gibbs HYDROLOGY...Gross CLIMATE...McClure