547 FXUS63 KARX 070736 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 230 AM CDT Sun Oct 7 2018 .SHORT TERM...(Today through Wednesday) Issued at 230 AM CDT Sun Oct 7 2018 No change in the expected wet pattern the region will be lodged under through Wednesday. The various models all remain in lockstep with carving out a trough over the west coast/desert southwest over the next couple days while amplifying a ridge over the east coast. This places the Upper Mississippi River valley under a fairly active upper level flow while also locking in a northwest-southeast running sfc boundary. The 300 mb jet will aid through the period with a broad area of persistent upper level divergence serving to enhance the low level thermodynamics/mid level shortwaves. With a steady supply of relatively mild/moist air from the low level jet/850 mb moisture transport as fuel, periods of rain are a given. It's not matter of if you will get wet, but when and how much. Bits of upper level and low level warm air advection will produce a smattering of showers today, which should become more widespread tonight as a warm front approaches from the south and the low level jet impinges on it. The higher precipitation chances then shift more west/northwest for Mon/Tue as the warm front sets up as a trough from northwest WI trough southern IA. The southwest trough is progged to lift northeast across the plains Tue, shifting across the local area tue night/wed. The stronger wave will enhance the forcing with the models showing more banding and qpf from the resulting pcpn. There will be some thunder chances over the next few days, although meager instability, cap and cloud concerns will work to keep any strong/severe threat in check - at least for the next couple days. late Tue showing some interest, esp in the NAM with MUCAPE around 500 j/kg overlapping with 30-35 kts of 0-3km shear. Cap could break down by 00z, although storms more likely on and behind the sfc front. Think any severe threat is pretty small at this time, but a few stronger storms can't be ruled out. Mostly though, the concern through Wed is for heavy rain and the possibility (probability?) of flooding. More on those chances in the hydrology section below. .LONG TERM...(Thursday through Saturday) Issued at 230 AM CDT Sun Oct 7 2018 With the passage of the Wed system, the GFS and EC point to a change in the upper level pattern - shifting from southerly to more of a northwest flow. Models favoring a general dry forecast for most of the local area, but a couple shortwave troughs are on the docket to drop across the upper mississippi river valley - one Thu night/Fri morning and the other Sat/Sat night. These systems will be competing with a sfc high in the south, and potentially some saturation issues associated with the high. The upshot for the moment is keeping most pcpn chances across northern portions of the region, and generally light in amounts. Will let consensus solution detail the chances. Temperatures are going to tumble for the later half of the week with a shot of cold air post the wed system, and then another shot (potentially colder) for Sunday. Highs in the 40s/50s are likely, and freezing temps look possible Fri morning. If you haven't had a killing frost/freeze yet, it might come by the weekend. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) Issued at 1022 PM CDT Sat Oct 6 2018 Stratus holding firm across the area as expected, with mainly MVFR ceilings likely to remain intact overnight and really right on through the next 24 hours. Should see ceilings gradually lower into Sunday afternoon as moisture starts to increase, with widespread IFR and even LIFR conditions developing later in the afternoon and evening as a large shield of rain overspreads the area. Winds will be from a north to northeasterly direction overnight, shifting due east through the day and into Sunday evening at 5-15 knots, strongest of course at RST. && .HYDROLOGY... Issued at 230 AM CDT Sun Oct 7 2018 Summer-ish airmass with pws from 1.5-1.75 inches and warm cloud depths around 3.5 kft at times favorable for heavy rain, efficient rain producers - especially for early October. Nearly stationary sfc front with steady influx of mid level shortwave and upper level jet support will provide ample lift for rain - which could repeat at some, if not many locations. Grounds are saturated across parts of the forecast area in the south. Those that aren't could become that way from the expected rainfall over the next few days. River and stream rises can be anticipated, and flooding possible to likely. Depending on where the rain falls and amounts, the threat for widespread flash flooding could also be on the rise by Tue/Wed. The EC and NAM suggest upwards of 4 to 5 inches by 12z Wed from northwest WI into western IA. A very consistent signal from the EC. The GFS is not as robust with some of its forcing and its qpf is lower as a result. Its also shifted more west through 12z Wed. Leaning toward the wetter solution for now. Flash Flood Watches will probably needed at sometime over the next few days, although areal layout is uncertain. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...Rieck LONG TERM....Rieck AVIATION...Lawrence HYDROLOGY....Rieck