139 FXUS63 KDMX 102339 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 637 PM CDT Wed Oct 10 2018 .SHORT TERM.../Tonight through Thursday/ Issued at 300 PM CDT Wed Oct 10 2018 Confidence: High Main challenges will be wind and temperatures...along with some residual precipitation mainly this afternoon and early evening. Major storm now exiting the state early today. 13z surface analysis shows low near LaCrosse, Wisconsin with several trailing cold fronts and troughs. Central pressure near 1000mb at 16z. At H850 a 138dm closed low is rotating northeast of Iowa this morning with cold air funneling in behind the system. A rather cold Canadian High pressure system over central Canada sports -10 to -15C temperatures at H850 with a nose of cold air already streaming south into the Northern Plains this morning. Across the Dakotas south to central Nebraska, light snow has been reported, mixed or all light snow at times already today. Surface winds over the region are now northwest with gusts to 25 mph at times. By tonight the system is expected to continue lifting northeast into Upper Michigan taking the attendant deformation axis and light precipitation along with it. Some light precipitation will still be possible over northern Iowa through 00z, otherwise clouds with a few breaks from time to time will hold on through the balance of tonight...with some clearing expected by 12z Thursday as high pressure builds into the state. Temperatures at H850 will be quite cold by 12z Thursday with -6C over the northwest to about 2C in the southeast. Normally this would lead to temperatures in the 20s for much of the region, but with subsidence, some clouds and continued mixing expected for much of the night, lows are likely to remain in the lower to mid 30s. Thursday will feature continued cold air advection with some clouds increasing over the west just after sunset. Winds will mix to near 30 mph again during the day. Afternoon H850 temperatures will remain near -3.5C over the northwest to near 0C in the southeast. Highs will struggle to reach the lower 40s north to the lower 50s in the south. .LONG TERM.../Thursday night through Wednesday/ Issued at 300 PM CDT Wed Oct 10 2018 Confidence: Medium to High Upstream wave forecast to track near the state with weak isentropic lift expected as some south flow returns across the H850 boundary from Thursday into Friday. Models differ on the track and extent of the precipitation over our area. Current GFS has been trending similarly with previous GFS model runs...while the Euro has also shown run to run consistency. The NAM is also trending more south similar to the GFS. The outlier right now is the Euro model which is suggesting a somewhat more northerly track with higher qpf extending over the south half of the forecast area. Thickness values in the Euro model supports a rain/snow mix or brief period of snow while the GFS/NAM both support only rainfall. Will go with the Euro for placement as GFS is now coming around to the more consistent Euro solution. Friday should see any mix changing over to light rain before ending. Lows Thursday night over the north are expected to drop below freezing. Winds will be near the point when frost is a possibility and we may need headlines for frost over the northeast third of the forecast area. In the south lows are anticipated to remain in the mid 30s...and though frost may occur, it will be less likely due to cloud cover and the tendency for temperatures to hold up for a bit longer and some chances for precipitation. As the weak upper level system tracks out of the region by Friday evening, high pressure will briefly allow for clearing and a period of light winds. With fast moving flow continuing into the weekend, a return to southerly flow will occur Saturday morning as a northern stream shortwave tracks across southern Canada. Temperatures will briefly recover to the mid to upper 50s Saturday before another strong cold front pushes through the region Saturday night. It is likely that some shower activity will accompany the boundary as it moves through during the evening hours. Both the GFS/Euro model show a secondary shortwave dropping south into Minnesota behind the Friday system. This wave will also be accompanied by a cold front with another push of Canadian air into Iowa and the Great Lakes. H850 temperatures are expected to fall again into Sunday/Sunday night with another period when lows will drop below the freezing mark. At this time there is some uncertainty regarding the expected cloud cover and temperature profile over the region Sunday night into Monday morning. The GFS is already bringing weak warm air advection into the region by 06z Monday, while the Euro is bringing clouds and light precipitation from a southern stream wave into the region. Both models suggest that it could be cold enough for a hard freeze, but clouds and a potential return to slightly warmer air may keep temperatures just warm enough to avoid a hard freeze. The remainder of the period will feature one additional strong upper level system tracking southeast out of Canada with a warm/cold air advection couplet tracking over the region. Tuesday should be briefly warmer and Wednesday colder as the system passes to the east. Both the GFS/Euro show a warming trend following the midweek system as the upper level pattern begins to relax and become generally more zonal. The deep H500 trough that continues over us now is expected to translate into eastern Canada and a ridge begins to build over the western CONUS. && .AVIATION.../For the 00Z TAFS through 00Z Thursday evening/ Issued at 637 PM CDT Wed Oct 10 2018 MVFR cigs will remain in place through at least 12Z before beginning to improve. Strong west to northwest wind will keep sustained winds between 15 and 20 kts with gusts to 30kts at times. Sprinkles are also developing and may impact however minor...all but KOTM. VFR conditions will first occur over southern TAF sites then gradually work northward. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...REV LONG TERM...REV AVIATION...FAB