Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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437 FXUS63 KDVN 301949 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 249 PM CDT Sun Jun 30 2024 .KEY MESSAGES... - Cool tonight (near record lows for some?), and one more pleasant day on Monday. - Thunderstorms return to the area Monday night into Wednesday morning. These storms will likely lead to heavy rain as humidity increases. There is a chance for strong to severe storms Tuesday PM. - Independence Day forecast looks wet with potential thunderstorms. - 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 240 PM CDT Sun Jun 30 2024 It`s not hard to be distracted by the weather today, between Hurricane Beryl (which has undergone rapid intensification over the past 24 hours into an extremely dangerous Cat 4 -- the earliest Cat 4 on record in the Atlantic Basin), and the absolutely stunning day in progress across our region (temps 10-15+ degrees below normal highs for the date and near 70 to the mid 70s, compliments of northerly flow off an anomalously cool airmass across the Upper Midwest and western Great Lakes)! High pressure will shift from the Upper Midwest to western Great Lakes by 12z Monday, and will continue to provide spectacular weather to the region. Tonight, cool conditions are expected. Portions of far NE Iowa and NW Illinois in closer proximity to the centroid of the surface high are expected to be the coolest, as near calm to light easterly winds and mainly clear skies allow temperatures to fall into the upper 40s to around 50 (approaching/reaching dew points at peak heating this afternoon). This may allow for some patchy radiational fog in river valleys and other low lying areas, as these readings would be near or just below crossover temps. Elsewhere, lows will likely be in the lower to mid 50s with more of an light ESE component to the wind and eventually some pockets of mid/high cloudiness. These lows generally in the upper 40s to mid 50s may be near records in a few locations. More information on record lows for July 1st for our main climate sites is listed in the Climate section below. Monday we`ll see an increase in mid/high cloudiness, as warm advection commences in the wake of departing high pressure. Winds will increase from the ESE 10-20+ mph, but the trajectory will be from Great Lakes through Ohio Valley ridge and thus drier keeping it very comfortable. Some WAA precipitation may work toward the western counties in our service area in the afternoon, but a deep reservoir of dry air surface through 800 hPa will limit PoPs below mention, as more likely just sprinkles if anything. Much of the warm advection will be aloft and this coupled with some cloudiness at times should net result in similar highs from those of today (Sunday) near 70 to the mid 70s. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Issued at 240 PM CDT Sun Jun 30 2024 Strengthening southerly flow surface to 850 hPa will continue to usher in a return of warmer and more moist air into the region. This along with ejecting lead shortwaves ahead of a Northern Rockies/Great Basin trough will lead to 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 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 for this period remains heavy rain and flash flooding. 00z NAEFS and ENS continue to support PWATs climbing to 1.75 to around 2 inches by 00z Wednesday, which is 2 to 3 standard deviations above climatology and approaches the 99.5 percentile or is near max of their respective climatologies. Ensemble guidance shows high probabilities of at least 1 inch from Tuesday evening through Wednesday AM, 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 around 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. This flash flood threat looks to be highest especially across east central and northeast Iowa into northwest Illinois, where rainfall in the past week has accumulated 125-200+ percent of normal and soils are saturated. 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. Initial supercell potential will exist before upscale to a line of storms would be favored with a wind threat, provided sufficient destabilization occurs. As previous shift mentioned, one thing to watch for is any potential OFBs from Tuesday AM convection, which could serve as focii for redevelopment and an earlier severe/flash flood threat Tuesday PM, otherwise Tuesday evening/night would be most favored. If rain/clouds persist for much of Tuesday that could limit instability or keep the primary instability axis further west. Bottom line, extent of instability and initial placement and timing of the surface convergence will play a key role in how far east/south the severe threat reaches. A brief respite in the wet weather is expected Wednesday AM/PM, but the emphasis is on brief as the surface boundary looks to have a play on the area perhaps as early as late Wednesday night/early Thursday AM with convection potential increasing (30-60%) south of I-80. Then, the shower and storm potential increases over the rest of the area on the 4th of July into Thursday evening, as a vigorous shortwave trough evolves into a closed low while traversing near the international border to the north. Ensembles point to PWAT values of 2+ inches pooling near and south of the boundary supporting a heavy rain threat. The frontal location will be critical to where this heavy rain threat eventually sets up, and will bear watching in the coming days given the ongoing river flooding and saturated soils in some areas. Probably still a ways off to cancel fireworks, but it does look likely to have storms around and most of us may have to rely on Mother Nature to provide the fireworks. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1135 AM CDT Sun Jun 30 2024 VFR conditions expected through the period. Scattered diurnal cumulus with bases of 3000-4000 ft AGL will continue to lift and dissipate by sunset. Winds near 10 kt from N/NE will become near calm to light easterly tonight, as a surface high pressure ridge shifts into the western Great Lakes by 12z Mon. Some shallow fog is possible in river valleys and other low lying areas from DBQ to MLI and into NW Illinois, but confidence on occurrence and impacts at either terminal is too low for mention at this time. On Monday, increasing mid/high cloudiness is expected. SE winds will increase to 10-15 kt by mid to late morning, with occasional higher gusts possible at CID. && .HYDROLOGY... Issued at 1135 AM CDT Sun Jun 30 2024 New forecasts this morning for the tributary rivers have come in slightly lower for the Cedar River at Conesville, Iowa River at Wapello, and the Wapsipinicon River near De Witt. However, no changes to the expected flood category were made. The crest on the Cedar River has gone through Cedar Bluff and should reach Conesville by Monday morning. A return to an active weather pattern will bring a heavy rain risk Monday night through Wednesday that may result in renewed rises on many tributary rivers. Those with interests along the tribs should monitor future forecasts, especially Monday evening when the bulk of the 1-3 inch rainfall will be incorporated into the river model. On the mainstem Mississippi, no change to the expected flood categories with the new forecasts this morning. Broad crests are now shown from Dubuque to Fulton LD13 late in the 7 day forecast. A widespread heavy rain event (1-3" amounts across much of eastern IA into southern WI) is anticipated in the Monday evening through Wednesday time frame which may have an impact on expected rises and delay the crest downstream. Residents and interested individuals/businesses should monitor future forecasts for any changes to the river rises. && .CLIMATE... Issued at 145 PM CDT Sun Jun 30 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...McClure HYDROLOGY...Gross CLIMATE...McClure