875 FXUS63 KDMX 180537 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 1137 PM CST Sun Nov 17 2019 ...Aviation Update... .DISCUSSION.../Tonight through Sunday/ Issued at 325 PM CST Sun Nov 17 2019 ...Light precip possible Monday, with no hazardous conditions expected... ...Widespread precipitation likely on Wednesday PM-Thu AM... ...Generally near-normal temperatures expected through this week... Light precipitation possible Monday... Key Points: Light precipitation may move from west to east throughout Monday morning and afternoon. Intensity should be very light, with generally no accumulation expected. With daytime temperatures above-freezing, this should be more in the form of rain or drizzle. No hazardous impacts are expected. Scientific Discussion: 20z GOES-R water vapor imagery is picking up on a weak impulse ejecting off the Rockies along the US/Canada border over Montana. Models are converging on this feature and generally have it propagating towards Iowa, crossing into the western portion of the state near 12z Mon, and pushing east of the state by around 00z Tue. There is some kinematic support and support through 750mb to 700mb frontogenetical forcing. But the moisture profile from sub-850mb highlights a fair amount of dry air. SFC dewpoint depressions may be running around 10 degrees. Ultimately, getting much precip beyond drizzle/light rain will be difficult. Widespread precipitation expected Wed PM-Thu AM... Key Points: Confidence is becoming high in precipitation moving across Iowa during this timeframe. On Wednesday, temperatures for this event should be well into the 40s and 50s, so this will be a rainfall event. There is a chance of isolated thunder during later Wednesday evening. As of now, rainfall amounts may be near the half- inch range, so this will be more towards the moderate end of the spectrum for this time of year. By Thursday morning, temperatures will drop to near freezing, so there could be a light rain/snow mix with any lingering precipitation. As of this time, it appears intensity should be light by Thursday morning, meaning any noteworthy snow accumulation appears unlikely. By late Thursday morning, this system should be east of our area. Scientific discussion: Models have been converging on a system that features decent westward tilt with height ejecting off the Rockies and pushing through Iowa during this timeframe. Interestingly, the GFS solution is the one the long-range models have been trending towards. The GFS solution has been trending slower/further NW and stronger. Kinematics are very impressive with this system. Will be watching how 06z Thu 850mb LLJ placement evolves over next few days. As of now, heaviest precip looks to be in northern/NE Missouri... but if this shifts slower and northwest, some of this heavier precip could make it into southern Iowa. So, have boosted precip chances... with expectation that future shifts may continue boosting trend. With strong WAA/PVA ahead of this system, a signal for elevated instability exists. Thus, have interjected thunder into the forecast. The severe weather threat is effectively nil at this time. Generally near-normal temperatures expected through this week... Key points: Normal highs for this time of year are around the mid 40s. Highs for Wednesday look to be well-above normal in the 50s... and even 60s in southern Iowa. There certainly is a good chance the Des Moines metro may reach 60 on Wednesday. Behind this system, temperatures should fall back to the 40s as there is not any "extreme" cold air projected to make it to Iowa. && .AVIATION.../For the 06Z TAFS through 06Z Monday night/ Issued at 1123 PM CST Sun Nov 17 2019 Non VFR conditions continue to prevail at all TAF sites as of the beginning of the 06z TAF period. Main concerns through the overnight/period continue to be the low, predominantly MVFR, stratus. KFOD/KDSM likely to see some stratus clearing between 06z to 07z, though most high resolution guidance stalls the clearing in the neighborhood of both sites overnight. Considering the persistent eastward clearing, which has been quicker and more aggressive than much of the guidance this evening, have introduced prevailing VFR conditions at KDSM by and after 07z, but may need to be monitored. Elsewhere, have generally hung onto MVFR stratus until mid-morning, then VFR prevailing as winds also turn southerly. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...Kotenberg AVIATION...Curtis