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Displaying AFOS PIL: AFDDMX Received: 2018-05-17 08:56 UTC
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147 FXUS63 KDMX 170856 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 356 AM CDT Thu May 17 2018 .SHORT TERM.../Today through Tonight/ Issued at 354 AM CDT Thu May 17 2018 Bottom Line up Front... Today looks to be close to a carbon copy of yesterday more or less, with sunshine and warm temperatures into the mid 80s expected across Iowa. 08z GOES-R Water vapor imagery clearly picking up on compact shortwave spinning near the Kansas City area. Meanwhile, there is broad anticyclonic flow over the Great Lakes region, and a broad, weak area of cyclonic flow over the southeastern CONUS. These latter two features are effectively hindering the departure of this shortwave. GOES-R "Upper-level" Water vapor imagery clearly picking up on high-level clouds covering most of Iowa that are tied into this shortwave. For the rest of today, agree with models in keeping ci/cs over Iowa most of today, especially southern Iowa. 850mb temperatures are around 2C warmer than yesterday, so have generally went with persistence plus a few degrees for max temps today. Though we mix to above 800mb, fcst soundings show winds aloft are not much above 10 kts in the low levels, so expect another day of light winds. Quiet weather expected into Friday. .LONG TERM.../Friday through Wednesday/ Issued at 354 AM CDT Thu May 17 2018 Bottom Line up Front... Shower and thunderstorm potential continues for this upcoming weekend. Models have slowed progression of system, so Saturday is trending to be drier for longer into the day, and Sunday may feature increased precipitation chances into the afternoon hours. Temperatures will likely be above normal for the next 7 days... at least. This Weekend... 08z Water vapor imagery picking up on well-defined, closed upper low propagating southeastward along the California/Nevada border. 500mb height analysis shows longwave trough dropping all the way through the SW conus, reaching down towards Baja California. Models in decent agreement with propagating this broad trough/closed low northeastward towards the Midwest, placing the upper low near northeastern Colorado by 12z Sat. The overall consensus trend has certainly been to slow the progression of this system. Through 12z Sat, confidence increasing in dry forecast as lack of significant forcing mechanism should keep atmos capped. After 12z Sat, model evolution discrepancies begin to crop up... Confidence in forecast from around 12z Sat-12z Mon has diminished since yesterday as model-to-model agreement is not great. the 00z GFS has established itself as the slowest model... keeping the closed low in eastern Nebraska at 12z Sun, and propagating it into western Wisconsin by 12z Mon. The 00z ECMWF and the 00z UKMET are much faster with the progression of this low, not only opening it up sooner, but placing it into western Iowa by 12z Sun and well into the Great Lakes region by 12z Mon. The 00z GFS and the 00z ECMWF both initialize well. Other models, such as the 00z NAM, are more or less in the middle. Ultimately, have stuck with a 00z model consensus blend for the moment as struggling where to find opportunity to add value to determine if the GFS or the ECMWF track should be favored. GFS seems to be more of an outlier overall with the strength of the low, so a slight nudge away from it may be prudent. With going forecast, best moisture does not arrive in Iowa until around 00z Sun - 06z Sun timeframe. Moisture amounts certainly decreased from what they were progged to be 24 hours ago. 850-300mb wind analysis picking up on anticyclonic flow directly over Louisiana at 12z Sat... effectively shutting off the Gulf of Mexico for notable moisture transport to Iowa. 00z GFS, the strongest model with the low now struggles to even get a 30kt LLJ into Iowa... continuing with the theme of being a stark difference from 24 hours ago. Ultimately, potential for heavy rainfall has surely taken a hit. If the GFS solution wins out, will have to watch for severe weather potential during peak heating Sunday. Boundary associated with baroclinic zone may be over central to southern Iowa somewhere, serving as a focusing mechanism for convection. With so much uncertainty in track, confidence low enough to where it is not worth getting into potential mesoscale details for Sunday. Monday and beyond... Eventually this system pushes east of the DMX CWA. Long-range models attempt to establish what appears to be a rex block over the western US. Correctly placed is a thermal ridge that builds across the Great Plains to the Canada/US border. Models break down this rex block by Wednesday... but it would seem plausible to hold it into Thursday/Friday. When this rex block breaks down, it would seem plausible the thermal ridge would crash over Iowa... likely around the end of next week/into next weekend. When that happens, near-record highs in the 90s are coming to Iowa. Precipitation- wise, though not likely, highly scattered peak- heating convective showers may be possible during peak heating. && .AVIATION.../For the 06Z TAFS through 06Z Thursday night/ Issued at 1144 PM CDT Wed May 16 2018 Widespread VFR conditions across all sites for this period with few clouds and unrestricted visibilities. Winds increase slightly for Thursday afternoon, from the east and southeast. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Kotenberg LONG TERM...Kotenberg AVIATION...Hagenhoff