Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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676 FXUS63 KDVN 261133 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 633 AM CDT Sun May 26 2024 .KEY MESSAGES... - Active weather today, with widespread showers and thunderstorms early this morning - We should largely dry out by this afternoon, but can`t rule out isolated to scattered strong to severe storms across our north and east - A change in the flow pattern aloft is expected to bring a period of quiet weather for much of the coming week && .SHORT TERM /THROUGH MONDAY/... Issued at 231 AM CDT Sun May 26 2024 Convection is beginning to ramp up across central Iowa as of 2 AM this morning, ahead of an approaching mid-level shortwave that will translate across the area this morning. Ahead of the shortwave is a prominent 45 to 55 kt low-level jet, as evidenced on the DSM and MLI VAD wind profiler data. Most-unstable CAPE values of around 500 to 1500 J/kg per the HREF ensemble mean and steep mid-level lapse rates should support the threat for large hail. Soundings indicate a low- level thermal inversion, so this convection should become more elevated, so locally strong winds will be secondary threat, but can`t rule it out entirely with the LLJ and deep-layer shear of around 30 to 40 knots. We are pretty confident in this convection ramping up and moving from west to east this morning. More heavy rainfall is possible with this morning`s activity, given Pwat values around 1.3 to 1.6. IVT per the ENS ensembles are over 97 percent of climatology by 7 AM this morning, so water vapor transport will be supportive of heavy rainfall. NBM probabilities of 1" of rain for today`s precipitation are around 50 to 70 percent for a large portion of the region, so ongoing river flooding will only be exacerbated with this rainfall. Confidence in showers and storms this afternoon is a bit more uncertain, as the mid-level shortwave trough and the attendant surface low crosses the area. There remains some uncertainty on the track of the low, with the GEFS and ENS ensemble low tracks showing some slightly different paths, with the GEFS tracks just to the south of the region, while the ENS paths are more right on top of us. The LLJ will have shunted off to the northeast, so flow will be relatively weak, but with higher dew point air lifting northward today and surface-based CAPE on the order of 1000 to 2000 J/kg, we can`t rule out more thunderstorms this afternoon, some of which could be strong to severe, too. The main warm frontal boundary and instability gradient appears to remain to our south, and the CAMs depict a strong signal for severe convection down that way, but a secondary mid-level shortwave appears to graze our northern and eastern areas, so we will need to keep an eye on at least some isolated to scattered severe storms this afternoon. The bulk of the large-scale forcing will move off to the east after sunset through tonight, with the departure of the mid-level shortwave trough. We have a dry forecast for this evening, save for any lingering showers and storms from the afternoon`s convection. Otherwise, we should have a quiet night, with lows in the 50s. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Issued at 231 AM CDT Sun May 26 2024 The long-term period will start off Monday with yet another chance of showers and an isolated storm moving in from the northwest ahead of an approaching mid-level shortwave that will dive southeast from the Dakotas. Mixed-layer CAPE appears to be pretty meager, with values progged around 500 to 1000 J/kg, so some thunderstorms can`t be ruled out, but with dew points only in the 50s, severe weather is not expected. We will have another brief bout of rain chances on Tuesday as yet another mid-level shortwave dives southeast over the region. For Wednesday through Friday, we are looking at something we haven`t had in a while: an extended stretch of dry and quiet conditions! Guidance is progging a long-wave ridge over the western CONUS and a surface high pressure settling across the western Great Lakes region for much of next week. Temperatures look to be seasonal, with highs in the 70s for most locations, and lows in the 50s. Another chance of showers and storms might move in for Saturday, but there are some timing differences among the guidance at this time. && .AVIATION /12Z TAFS THROUGH 12Z MONDAY/... Issued at 633 AM CDT Sun May 26 2024 Widespread showers with some embedded thunderstorms continue across the area. It appears that the coverage of thunderstorms is a bit lower than what many of the high-res models were suggesting, which has helped to limit the MVFR to IFR conditions. The ongoing precipitation will gradually come to an end over the next 3 to 5 hours after TAF issuance, but models are suggesting that ceilings will lower to MVFR/IFR this morning, with some gradual improvement this afternoon. We are likely not done with showers and storms though, as a front sweeps through the area this afternoon and evening. Coverage of this PM activity remains a bit uncertain, so we will use PROB30 groups to highlight the most likely timing. As the front moves through, winds will quickly turn more northwesterly this afternoon. && .HYDROLOGY... Issued at 850 PM CDT Sat May 25 2024 Flood Warnings continue for many of the tributaries in Eastern Iowa for flooding ranging from minor to major. A Flood Warning is in effect for the Mississippi River from Keithsburg downstream to Burlington for minor flooding, while a Flood Watch remains in effect for Gregory Landing for the potential for minor flooding. Some locations will experience flooding for the next several days and even to a week from now. Please refer to the latest Flood Statements and Flood Warnings for details. A storm system is expected to bring numerous showers and thunderstorms to much of the area later tonight through Sunday evening. Widespread 3/4 to 1 inch of rain is likely with some spots possibly receiving around 1.50 inches in any stronger storms. This may cause higher river levels than currently forecast at some locations if this amount of rain materializes. After this system passes off to our east by Sunday night no significant rain is expected for much of next week. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...Schultz LONG TERM...Schultz AVIATION...Schultz HYDROLOGY...Haase