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Displaying AFOS PIL: AFDDMX Received: 2018-01-17 23:25 UTC
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524 FXUS63 KDMX 172325 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 525 PM CST Wed Jan 17 2018 .SHORT TERM.../Tonight through Thursday/ Issued at 332 PM CST Wed Jan 17 2018 Fairly straight forward in the shorter term with dry atmosphere in place across the Midwest. Therefore little in the way of clouds or precipitation is expected through Thursday. Main issues are with temperatures with building thermal ridge across the Plains and into Iowa. Already have seen a vast improvement in temperatures today with strong southwest surface flow aiding warm advection through the state. This will persist overnight into Thursday with the expanding warm air across the region. Despite the clear skies, modest surface flow should help to buoy temperatures tonight with readings only dropping into the teens in most locations. The decent southwest flow and sunshine on Thursday should add another 10 to 15 degrees to highs which would likely have been more had not the snow cover been in place. .LONG TERM.../Thursday night through Wednesday/ Issued at 332 PM CST Wed Jan 17 2018 Longer term focus will be on the system expected to pass through the region late this weekend into early next week. System is currently in the eastern Pacific and is forecast to come onshore early Saturday before beginning to strengthen over the intermountain west. Cyclogenesis will occur along the Front Range of Colorado Saturday into early Sunday before the low advects to the northeast on Sunday into Monday. Timing differences are still apparent between the Euro and GFS with the GFS remaining more progressive although their actual tracks are quite similar. In advance of the system, thermal ridging across the state on Friday and good southwest surface flow will lead to temperatures well above normal. Even Saturday will see above normal readings although a bit more muted with increased cloud cover, weak and meandering surface flow as a surface boundary settles into the state. This boundary will begin to intensify on Saturday night into Sunday with the ongoing cyclogenesis and increasing surface flow. Soundings have an increases depth of near surface moisture on Saturday night and likely to see drizzle/very light rain develop late that night. Seems plausible that fog will may become an issue with increasing dew points advecting over relatively cool ground. This will persist into Sunday morning as mid and upper levels stay relatively dry. However, deeper forcing will arrive later Sunday into Sunday night with lift increasing rapidly. The uncertainty here lies in the speed differences between the models as opposed to placement. GFS would sweep the surface low across the state by Monday morning with Euro just entering the southwest. The slower evolution seems more plausible given the historic more gradual progression of southwest US systems, however will not totally discount the GFS. In either case, much of central Iowa will remain liquid precipitation with the warm sector into the southeast half of the forecast area. There may be some thunder late Sunday afternoon into the evening across the southeast given weak elevated instability. Otherwise, the southeast will see the dry slot move overhead with the passage of the surface low effectively cutting of precipitation until potential wrap around later Monday. Across the northwest, colder air will be deeper and snow is favored precipitation type for most of this event near Estherville. Some significant snowfall totals are not out of the question in the far north to northwest where strong forcing produces a good amount of QPF/Snow. In addition, northwest winds should be quite robust producing blowing and drifting snow as well. Headlines may be needed in a few more cycles should current forecast output remain in place. Lingering precipitation is expected later Monday into Monday evening with a broad area of wrap around/deformation precipitation across much of central Iowa. Temperatures will be much colder as well with strong cold advection on the backside of the system. && .AVIATION.../For the 00Z TAFS through 00Z Thursday evening/ Issued at 524 PM CST Wed Jan 17 2018 VFR conditions will persist through the period. Breezy southwest winds will diminish this evening and may become breezy again by Thursday afternoon. Steep low level inversion will create local LLWS. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Cogil LONG TERM...Cogil AVIATION...Donavon