Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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843 FXUS63 KDVN 221057 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 457 AM CST Fri Nov 22 2024 ...Updated for 12z Aviation... .KEY MESSAGES... - Brief bout of above normal warmth on Sunday. - The first of two rounds of cold air arrives Monday. - Unsettled weather leading up to Thanksgiving with low confidence on forecast details. - Turning much colder (70-80% chance) post-Thanksgiving, while potentially staying unsettled. && .SHORT TERM /THROUGH SATURDAY NIGHT/... Issued at 307 AM CST Fri Nov 22 2024 Low pressure will continue to merge with a low off the New England Coast today, leaving cyclonic flow lingering across the region. Satellite/observational data shows a lot of lower clouds/stratus upstream across the Upper Midwest into southern Canada early this morning. The 00z RAOB from Minneapolis (MPX) shows a large subsidence inversion trapping these lower clouds. Mid level ridging/subsidence across the Plains into portions of the Upper Midwest will build into the region tonight. In doing so this subsidence should further strengthen a low level inversion overhead, similar to what was observed at MPX last night. Bottom line, confidence is high that we`ll see the cloud cover stick around into tonight. We are likely to see a few breaks, but overall more in the way of cloudiness is expected. This should limit highs areawide to the upper 30s to mid 40s. Some patches of drizzle will remain possible this morning across portions of NW Illinois with the saturated low levels, as some weak lift lingers with the passage of mid level shortwave energy. A lingering pressure gradient will foster continued gusty winds today tapering off by late afternoon through evening, as ridging builds closer. NBM 90th percentile wind gusts are in the range of 25 to 35 mph today giving an idea of our max gust potential. So, breezy or brisk but not nearly as windy as Thursday. Later tonight into Saturday, as the flow turns neutral to slightly anticyclonic with the ridge approaching I would anticipate a decrease in the lower clouds. Typically this time of year it`s tough to clear at night barring a strong synoptic system, and so my feeling while some partial clearing is possible especially far west/south, many of us will likely hang onto the clouds and it may not be until during the day on Saturday for the lower clouds to finally skedaddle. As a result of favoring predominantly clouds tonight, I favored toward the 90th percentile of NBM lows giving a range of some upper 20s where any partial clearing occurs (again would be favored far west and south should it happen), to the lower to middle 30s elsewhere. Saturday highs, with the idea of seeing a bit more in the way of breaks or sunshine by afternoon, has highs a skosh warmer from the mid 40s to around 50 with much lighter wind. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Issued at 307 AM CST Fri Nov 22 2024 Late in the weekend into the start of the new work week, the models generally depict a shortwave trough traversing the northern tier of states within predominantly zonal flow aloft. At the surface, we`ll see gusty southerly return flow develop on Sunday ahead of a developing low pressure to our west. This warm advection will help push highs into the 50s areawide, with a few lower 60s possible south of I-80. Moisture is mostly pacific in origin with limited/shallow low level moisture with a veering LLJ and main IVT transport focused into the Ohio Valley. Any precipitation Sunday night into Monday would appear to be very light and possibly just drizzle with the shallow low level saturation. We may have to watch for our far northern service area on Monday to potentially get brushed by wrap-around precipitation /light snow/ from a Great Lakes low. This low will help dislodge a chunk of cold air and settle in southward across the region Monday heading into midweek, with temperatures dropping below normal with a period of gustiness as the cold air arrives Monday into Monday night. Forecast uncertainty increases greatly mid to late next week, or around the Thanksgiving holiday due largely in part to an active split jet stream. Cluster analysis show big differences with the track and strength of a shortwave trough moving west to east across the CONUS midweek, as one cluster is much more pronounced with this southern stream wave as it ejects from the Rockies toward the Ohio Valley while other clusters are much weaker with one placing more energy in the northern stream. Given the timing of around the Thanksgiving holiday we`ll definitely be monitoring the forecast over the next few days with this system, which is actually remnant energy from the anomalously deep low situated off the Pacific Northwest coast early this morning. This could bring some impactful weather to portions of the region, so be sure to stay tuned! While there is great uncertainty on precipitation chances and timing/location mid to late next week, what is fairly certain is an even colder airmass settling into the region around Thanksgiving and through the following weekend, as the deterministic and ensemble guidance support a chunk of arctic air moving into the Midwest. This is due to an eventual N/NW flow pattern resulting from a blocking ridge developing over the North Pacific and Alaska, which could keep the much colder conditions around through early December. For more on this colder weather see the Climate section below. && .AVIATION /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 452 AM CST Fri Nov 22 2024 Cyclonic flow will maintain stratus today with some breaks at times. Partial clearing is possible tonight near CID and BRL, as ridging begins to build into the region. Confidence in any persistent clearing is low, and overall MVFR ceilings are likely to prevail for much of the time today into tonight. Winds will become gusty at times today to 15-25 kt from the N/NW, then become light tonight while eventually turning more westerly as high pressure approaches. && .CLIMATE... Issued at 307 AM CST Fri Nov 22 2024 A broad area of low pressure in the mid/upper levels of the atmosphere is forecast to dominate much of the CONUS starting around Thanksgiving and continuing through next weekend. This will be accompanied by the most significant cold air outbreak of the season thus far. The Climate Prediction Center (CPC) 8 to 14 day (November 29 - December 5) temperature outlook has the probabilities for below normal temperatures at 70-80 percent across the Midwest. For context, normal highs during this timeframe are in the upper 30s and lower 40s, while normal lows are in the lower to middle 20s. The CPC 8-14 day precipitation outlook is for near to below normal precipitation. Suffice it to say should any precipitation occur it would likely be frozen. So, we`ll be monitoring this forecast closely for the holiday and especially the post- holiday weekend travel for any impactful weather. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...McClure LONG TERM...McClure AVIATION...McClure CLIMATE...McClure