Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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462 FXUS63 KDVN 300516 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 1216 AM CDT Tue Apr 30 2024 ...Updated for 06z Aviation... .KEY MESSAGES... - Active forecast remains through the long term, with near daily chances for precipitation beginning Tuesday night. - Temperatures will remain above normal through midweek, trending towards normal for the end of the week. - River flooding is now on the falling limb on most tributary rivers that were over flood stage. && .SHORT TERM /THROUGH WEDNESDAY/... Issued at 202 PM CDT Mon Apr 29 2024 Cold cyclonic flow continues around low pressure, resulting in a blustery, cloudy, cold day with occasional showers...but that`s not here, and as we approach May, it`s less likely to be us again until Fall. Our area is on the southern periphery of this cyclonic flow, with mainly scattered cumulus based around 4000 ft, and gusty winds of 15 to 25 mph. With the exception of our far northwestern counties, today probably qualifies as a nice spring day, albeit a bit on the fresh/breezy side. Tonight, after a day of dry advection, we`re set to lose any remaining clouds in the north by mid evening, and with dewpoints already falling to the 40s today, we`re set for temperatures to fall tonight, near 40 north to near 50 south. Winds will quickly decrease this evening, turning light and variable by 9 PM. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Issued at 202 PM CDT Mon Apr 29 2024 Tuesday, a day of warm advection is expected, with mostly sunny skies and a slow increase in moisture given that the Plains are currently shut off from the GOM. By afternoon, dew point values in the lower to mid 50s are expected, which seems plausible, but far lower than some CAMs that have 60+ Tds in place by evening. This is important, as those models are rather aggressive on spreading a strong line of storms through our area Tuesday evening. What actually seems more likely, is a split. As the main dynamics aloft are better with the short wave to the north, convection may hold north of the area into southeast MN and northern Iowa through the evening, while other more robust storms in western Iowa and Nebraska dive / develop southward towards the moist axis/MUCAPE which would take them into Missouri, only brushing our area. Thus, we end up with the NBM pops of 70-90% being too high. I`ve lowered these by about 10% and still feel I`m being too bullish, but with the areas north and west being supported by this scenario, I`ll keep them in the high chance to likely there. Farther east, capping pops in 30- 40 will be enough to allow this to miss that area. QPF has been lowered by more than 50% from earlier WPC forecasts for this period. Following a dry Wednesday morning, the upper pattern becomes active again with moist warm advection by afternoon and evening, with chance to likely pops spreading back in. A developing warm front to our south along with low pressure forming in the Plains will make this a much more likely threat for widespread rainfall. After that system, we will start to see a potent wave deepen over the Rockies mid-late week. We will see a few leading impulses pass through the area, leading to persistent showers/storms for the remainder of the week. This will be a wet period, with the potential to see quite a bit of rain. With recent rains and more forecast, some rises along area rivers are expected. The parent wave developing is the one that has our attention though. Although, there is plenty of uncertainty with this, as well as major timing differences amongst guidance. Although, all long term guidance shows this system. If this wave deepens enough and we get that negative tilt upon arrival, this will bring the potential for strong to severe storms late in the week. Although, it is too soon to say for sure. WPC is highlighting our area in the risk for Excessive Rainfall from midweek through the end of the week, as they are currently forecasting between 1-3+ inches of rain by the week`s end for some. Thus, flash flooding will be possible, as well as rises along area rivers. So, just be mindful and stay up to date on our forecasts! && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 1210 AM CDT Tue Apr 30 2024 VFR conditions are expected through much of the period. Ideal radiational cooling with light winds and clear skies could lead to patchy shallow fog after 09z through 12z, but confidence is too low for any mention. As the high departs Tuesday AM winds will turn southerly and become gusty at 15-25 kt by afternoon ahead of a low pressure system approaching the Upper Midwest. Elevated warm advection could lead to a few high based showers developing into portions of eastern Iowa by mid to late afternoon, but probability appears too low for PROB30 mention at this time. Otherwise, a line of storms is expected to develop to our west this afternoon ahead of a cold front and move into eastern Iowa this evening, while gradually weakening. Before doing so, there is the potential for gusty winds and hail to accompany the storms, particularly at KCID and KBRL which appear to have the better chances for storms. && .HYDROLOGY... Issued at 1006 AM CDT Mon Apr 29 2024 The flood warning in effect for the Skunk River at Augusta has been cancelled this morning, as the river crested just below action stage overnight and continues to fall this morning. Elsewhere, flood warnings continue for Wayland (Fox River) and Colmar (La Moine River). The former will drop below flood stage this afternoon, while the later remains on track to see moderate flooding through Wednesday as routed flow from overnight rains work through the basin. Heavy rains remain possible later this week again as forecast by WPC. The timing of this rain would fall just past the crest on most active tributary rivers. Keep a general awareness of rivers in the week ahead, as this wet pattern continues to evolve. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...Uttech LONG TERM...Ervin AVIATION...McClure HYDROLOGY...Speck