Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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693 FXUS63 KDVN 031049 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 549 AM CDT Mon Jun 3 2024 ...Updated for 12z Aviation... .KEY MESSAGES... - Active summer-like pattern early this week with warm/muggy conditions and multiple chances of showers and storms. Strong to a few severe storms possible this afternoon/evening, and again Tuesday PM/evening. - Mainly dry mid week into the weekend with pleasant temperatures and lower humidity. && .SHORT TERM /THROUGH TONIGHT/... Issued at 320 AM CDT Sun Jun 2 2024 Water vapor imagery early this morning depicts an active zonal flow pattern from the Northern Rockies through the Upper Midwest, with several embedded low amplitude shortwaves aiding convection across parts of KS/NE/NW IA/MN within a large plume of rich moisture advection with PWATs over 1-1.5 inches. The feature of most interest for our area is a convectively enhanced vort max or MCV apparent in radar and satellite over eastern Nebraska. Guidance generally lifts this across Iowa and into southern Wisconsin/far northern Illinois by this evening. As it approaches, increasing isentropic ascent with a veering nocturnal LLJ should foster some spotty elevated convection mainly across west/northwest sections of the service area this morning through midday. Some small hail can`t be ruled out should any storms occur given modest mid level lapse rates (7+c/km). As this MCV makes inroads this afternoon into early evening, increasing ascent into a largely uncapped, moderately unstable airmass (MLCAPE 1500-2000+ j/kg) will support scattered storm development across the area. Deep layer shear is not overly strong (generally less than 30 kts), but nonetheless given the moderate instability will lead to at least some severe weather potential. Primary concern will be gusty/damaging winds or wet microbursts with any congealing cold pools or organization of multicell clusters. Proxy soundings suggest potential for around 1000+ j/kg of DCAPE. Isolated large hail would be possible as well early on in pulse type environment. A tornado can`t also be totally ruled out with any boundary-storm interaction in the presence of gusty southerly inflow today 20+ mph today along with manageable LCLs aided by increasing surface dew points into the upper 60s to around 70. SPC has placed a Slight Risk or level 2 of 5 from around the Quad Cities north/east where the better ascent is generally suggested, and a Marginal Risk or level 1 of 5 surrounding that with the back edge near a Dubuque to Iowa City line. In addition to the severe weather potential, there is also the potential for locally heavy rain as PWATs climb to around 1.5 inches or above the 90th percentile for KDVN sounding climatology for the date. Given this and progged slow meso-beta convective elements will have to keep an eye out for localized flash flooding possibly. Outside of the convection today, the other focus will be the very warm and summery feel today. Convective trends could put a bit of a wrinkle in the high temperature forecast for some areas, but overall anticipate sufficient solar insolation with the gusty southerly winds to boost highs into the 80s. If more sunshine and less convective influence occurs then thermal parameters are potentially there to support some upper 80s. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 320 AM CDT Sun Jun 2 2024 Heading into mid to late week the guidance continues to support a pattern change with an eventual deepening northern stream trough shifting into the eastern CONUS. An initial shortwave driving this pattern change will evolve eastward across the Northern Rockies and along the International border with ND/MN Tuesday into Wednesday. This will drive a strong cold front through the area Tuesday night bringing the potential for strong storms in the presence of above normal warmth and anomalously high moisture (PWATs over 1.5 to near 1.8 inches above 90th percentile for KDVN sounding climatology and near record). The deterministic ECMWF has stayed fairly consistent over the past several nights painting in the QPF the look of a mature MCS developing to our northwest on Tuesday, and then propagating E/SE into the reservoir of instability and deeper moisture across the region Tuesday night. This would most certainly harbor some wind potential given ramping deep layer shear. However, there is a lot of uncertainty as well and this is largely attributed to the potential that showers and storms could be around parts of the area for much of the day on Tuesday, which if occurs could limit instability and temper subsequent strength of any convection Tuesday night with the cold front. As of right now given the uncertainty SPC has placed a Marginal Risk or level 1 of 5 for western areas, which has the best potential for seeing a line of storms prior to nightfall. Otherwise, much uncertainty exists with the extent of severe weather potential Tuesday night further east toward the Mississippi River and eastward. As mentioned, the anomalously high moisture content will support heavy rain and guidance is depicting this signal with areas of 1-2 inch amounts, especially west of the Mississippi River. The cold front passing Tuesday night will begin the process of ushering in a cooler airmass, which will be reinforced by an upper trough evolving over the Great Lakes and eastern CONUS by late in the week and heading into next weekend. This is likely to result in mainly dry conditions, and below normal temperatures with pleasant days (highs mainly in the 70s) and cool nights (lows in the 50s to possibly a few 40s). && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 535 AM CDT Mon Jun 3 2024 At least scattered coverage of showers and storms is expected at times through this evening, with the timing/location somewhat of a challenge. Spotty showers have developed early this morning west of the Mississippi River ahead of an approaching upper disturbance from Nebraska. We are likely to see additional spotty showers and possibly a couple of storms through midday. Have opted to leave out mention for this activity due to the rather sparse coverage and subsequent low confidence on occurrence at a terminal, but will continue to monitor trends and amend if needed. Otherwise, this afternoon into evening is favored for additional development of showers and storms although the extent is a bit unclear. It would appear as though KCID and KDBQ have the higher probabilities, but some of the recent CAM guidance including the NAMNest and HRRR models would lend support to extending those higher probabilities further south to include at least KMLI but largely predicated on outflow boundary propagation. Overall, confidence to upgrade over PROB30 mention is low at this time but expect refinement and possibly some increase in mention in later updates as mesoscale trends become better defined. Aside from any convection or attendant outflow resulting in variable winds and potentially stronger gusts, winds will be predominantly from a southerly direction throughout at around 10 kts, but will occasionally gust to near 20 kts today. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...McClure LONG TERM...McClure AVIATION...McClure