Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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655 FXUS63 KDVN 210700 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 200 AM CDT Sat Sep 21 2024 .KEY MESSAGES... - Highs in the mid 80s to near 90, or 8 to 15 degrees above normal, are expected again today, which will be the last of this heat. - Marginal Risk for severe storms late this afternoon into the evening for the far NW CWA. - Damp and much cooler for Sunday and Monday with highs in the mid 60s to lower 70s, which is slightly below normal. - Dry conditions are expected to prevail Tuesday through Thursday with high temperatures in the low to mid 70s. && .SHORT TERM /THROUGH TONIGHT/... Issued at 158 AM CDT Sat Sep 21 2024 Today will be the last of the stretch of summer-like warmth in this stretch, as a cold front approaches the area tonight. In the mean time, a complicated forecast is in store today, with a wide spread in short term model guidance surrounding convective placement and timing. There were several 00z CAMS suggesting that the convection well to our south would expand northeastward into our south 1/2 early this morning. This trend has yet to begin, with southern storms tracking east/southeast as of 1 AM. In addition, there is a low level dry pocket from northeast Missouri through our CWA, thus any rain processes will need to be elevated through the morning today. As mentioned in the evening update AFD, there are a handful of CAMS suggesting afternoon strong storm development today. However, looking at members that favor this, they all have dew points in the 68 to 72 range along the Mississippi River by early afternoon, with temperatures in the upper 80s to lower 90s. This same area is currently much drier, with dew points in the 55 to 60 range. Thus, the surface based storm threat is probably over forecast by those more aggressive models this past evening, and we prefer a timing more focused on the frontal movement, during the evening hours, and that should favor a multicell environment rather than supercell. SPC has continued to show a marginal, level 1 of 5, risk in our northwestern CWA, once again more focused on the cold frontal timing tonight. Storms this afternoon( if they occur) and tonight, are forecast to have 1500 to 2500 MUCAPE prior to the development of storms, with some potentail DCAPE available as well. This should favor strong downdrafts with stronger/tall cores, and potentially some large hail, through mid level lapse rates are not particularly steep (6- 6.5). The overall QPF maximum has now shifted south of our CWA in the mean guidance with amounts now generally 0.25 to 1 inch, but there remains some CAMS showing swathes of 1-2 inches for our area. These amounts could delay some harvesting, but otherwise would be seen as beneficial rainfall. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 158 AM CDT Sat Sep 21 2024 Sunday, an upper wave will move through the area, with little to no available surface CAPE, thus, rain or showers/weak storms are expected to be rather widespread, with moderate amounts under 1 inch possible. The increasing northeast wind, and cold advection will keep our temperatures steady in the 60s to low 70s Sunday, and mainly in the 60s for Monday. The upper trof will influence our area into Tuesday, with some shower chances continuing in the southern CWA. As dry air arrives, the overnight lows will drop to the upper 40s to lower 50s, making for chilly mornings that reflect the upcoming fall season. Slow moderation is forecast by late week, along with a slight chance for rainfall. Late week highs remain forecast in the 70s, and lows in the 50s. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1211 AM CDT Sat Sep 21 2024 VFR weather will continue into this upcoming morning, but it should be noted, there is a low chance (20%) that some high based thunderstorms may form over southeast Iowa and northeast Missouri through 15Z today. The bulk of Saturday will be dry with warm VFR conditions, followed by a thunderstorm chance arriving in the evening hours. There remains rather low confidence on placement an timing at this time, so a prob30 for storms is included at all sites from 00Z to 06Z Sunday/22nd. Any thunderstorm would bring IFR conditions for a brief time, and possibly gusty winds over 35kts. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...Ervin LONG TERM...Ervin AVIATION...Ervin