Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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878 FXUS63 KDVN 041801 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 101 PM CDT Tue Jun 4 2024 .KEY MESSAGES... - The severe potential this afternoon and tonight is dependent upon the amount of heating that occurs during the daytime due to persistent cloud cover. Damaging winds looks to be the primary risk with hail a secondary risk. - Localized flash flooding is a concern for today and tonight due to the potential for high rainfall rates, especially in urban areas. - A pattern change will keep temperatures at or below normal late this week and into next week. && .SHORT TERM /THROUGH TONIGHT/... Issued at 311 AM CDT Tue Jun 4 2024 Upper level disturbance (likely the remnants of an MCV) along the KS/MO border move into eastern Iowa during the late morning and afternoon. Forcing is initially weak through sunrise. However, the overall general lift supplied by the MCV and weak southerly flow aloft may be enough to generate isolated showers through mid-morning. Considerable mid and high level cloud cover will cut down on the overall daytime heating across the area. However the lift generated by the decaying MCV as it moves into eastern Iowa by late morning will initiate diurnal convection across the area. This convection will be scattered with areal coverage ranging from 30-50 percent. However, localized areas of higher coverage (55-70 percent) are possible if storm mergers occur and small discrete lines develop. The overall severe risk today is conditional, that is it is dependent upon how much differential heating occurs during the day. The overall marginal risk from SPC looks reasonable. The primary risk looks to be damaging winds with the potential for precipitation loading in the downdrafts. While hail cannot be completely ruled out, high freezing levels may limit the hail to marginal severe size (1 inch). A bigger concern today is the potential for localized flash flooding. Moisture levels in the atmosphere are very high (1.6 to 1.8 inches) which is near or exceeding the climatological max for June 4th. Storm movement will not be overly fast (25 mph) so high rainfall rates of 1-2 inches per hour or higher could easily result in flash flooding, especially in urban areas. Tonight the strong cold front will sweep through the area. A broken line of showers and thunderstorms is likely along the front. Forcing from the front may result in isolated severe storms with primary risk being damaging winds. Areas west of the Mississippi would be favored for any severe storms as the intensity of storms along the front will be decreasing as it moves east. Storms along the front will be moving just a bit faster (30 mph) than the afternoon storms. However, in spite of the slighly faster movement, localized flash flooding is possible due to the very high atmospheric moisture ahead of the front. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Issued at 311 AM CDT Tue Jun 4 2024 Wednesday and Wednesday night Assessment...Medium confidence Early Wednesday morning there may or may not be some lingering showers in the far east and northeast areas. Any rain present will exit the area by mid-morning leaving the remainder of the morning dry. A secondary cold front and an attendant upper level disturbance will move through the area during the late afternoon and evening hours. Forcing from the front and upper level disturbance should be enough to generate isolated showers and possibly a few thunderstorms. Overall coverage will be low at 20-25 percent. Most locations will only see an increase in clouds along with a wind shift during the frontal passage. Thursday through Friday night Assessment...high confidence of dry conditions Northwest flow aloft will be well established by late week with high pressure moving through the Midwest. Temperatures should be slightly below normal. Saturday Assessment...low to medium confidence for rain chances All models show a weak upper level disturbance moving through in the flow aloft. The question, given northwest flow, is will there be enough moisture present to produce any precipitation. Most deterministic model runs indicate dry conditions. However, there are some ensemble members from the respective models that do generate some light precipitation. The model consensus of the deterministic and ensembles generates low coverage pops (20 percent) during the day Saturday. Thus the overall message is that most of the area will remain dry on Saturday. There is much higher confidence that temperatures will be slightly below normal. Saturday night through Monday Assessment...medium to high confidence The model consensus has dry conditions for the area along with temperatures slightly below normal. There will be weak disturbances in the flow aloft moving through the area. If there is sufficient moisture available, one cannot fully rule out some rogue diurnal showers occurring. If this scenario does occur, coverage would be low (20 percent at best). && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1247 PM CDT Tue Jun 4 2024 A disturbance is forecast to lift across eastern Iowa TAF sites this afternoon prior to 00 UTC with scattered showers and isolated storms. The confidence is low on coverage so used VCSH at all TAF sites for mainly the 20 to 24 UTC timeframe. A second disturbance and cold front will move across the area tonight with a line of weakening showers and thunderstorms moving across the area. MVFR visibilities are possible in the strongest showers and storms tonight. Winds behind the cold front will switch to the west. Showers will end by 12 UTC with skies clearing and VFR conditions prevailing. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...08 LONG TERM...08 AVIATION...Cousins