813 FXUS63 KARX 091910 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 210 PM CDT Tue Oct 9 2018 .SHORT TERM...(This evening through Wednesday night) Issued at 210 PM CDT Tue Oct 9 2018 Water vapor satellite this afternoon shows the trough over the Rockies deepening with an upper level low forming over southern Colorado. The low will continue to deepen and become closed over the Dakotas tonight and remained closed as it moves northeast across Minnesota Wednesday. As the low moves northeast, a strong short wave trough will move over the region and is expected to produce strong pv advection in the 500-300 mb layer as moves across late tonight into Wednesday morning. The surface front currently extends from southwest Iowa into northern Wisconsin and will not move much tonight and then get pushed east of the area Wednesday. The short wave trough will push a surface low along the front that is expected to move across the area overnight and Wednesday morning. As these features approach the area, the low level jet will crank up ahead of the surface low and should be focused on the area this evening before becoming focused farther to the north overnight. As the nose of the low level jet works into the area, should see showers and some storms rapidly redevelop over the area late this afternoon into the evening. The latest set of hi-res meso scale models then suggest there could be a break from the late evening into the early overnight until the surface low and short wave start influencing the area with more activity expected to form along the front and then work east through the late overnight into Wednesday morning. All the activity should then taper off from southwest to northeast late Wednesday afternoon through the evening with just some lingering precipitation chances into Wednesday night across the far north in the cyclonic rap around flow. With the front bisecting the area this afternoon, the areas east of it are warming up with temperatures well into the 70s. Dew points in the warm sector are in the middle to upper 60s yielding ML CAPE values of 500-1000 J/Kg over northeast Iowa into southwest Wisconsin. The 09.17Z RAP holds this CAPE in place in the warm sector through the evening with just a slight decrease expected from the loss of daytime heating. Plenty of shear will be in place with 30 to 40 knots in the 0-3 km layer and up to 30 knots in the 0-1 km layer. This continues to suggest a severe potential through the evening hours with damaging winds the main threat. There will also be a tornado threat if any storms can remain discrete and latch onto a boundary to maximize the turning in the low level wind field. .LONG TERM...(Wednesday night through Tuesday) Issued at 210 PM CDT Tue Oct 9 2018 Once this system moves past the area, much cooler air will spill in behind it. The entire area looks to have low temperatures below freezing Thursday night and headlines will be needed to highlight the end of the growing season. The next chance of precipitation will be from Saturday night into Monday as the western long wave trough finally looks like it will become progressive and should be moving east across the central part of the country. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 1207 PM CDT Tue Oct 9 2018 Not expecting much overall change in conditions through Wednesday morning. The nearly stationary front extended from central Iowa into north-central Wisconsin and based on analysis looks to be very close to KLSE. Even if the front does temporarily shift through KLSE, the biggest impact would be to bring the winds around to the east/southeast but speeds would still remain under 10 knots. If the front does go through, ceilings at KLSE could pop up to MVFR for a while. Confidence too low to include in the forecast at this time. As the surface low moves into Iowa, enough increase in forcing for some storms to develop along the frontal boundary and will continue to include a VCTS for both airports from late afternoon through much of the night. With the increase in the low level jet ahead of the low tonight there could be enough speed difference for some low level wind shear but did not include as wind shear is implied with the inclusion of thunder. && .HYDROLOGY... Issued at 210 PM CDT Tue Oct 9 2018 No changes will be made to the ongoing flood watch. Conditions remain favorable for more heavy rain through the overnight. As mentioned above, the low level moisture transport will strengthen and become focused on the area this evening before focusing farther north overnight. Precipitable water values in the warm sector will remain in the 1.75 to 2 inch range with warm cloud depths around 3.5 km. With the repeated rounds of showers and storms tonight into Wednesday morning, another 1 to 2 inches can be expected to fall on grounds that are already saturated. Rivers and streams will continue to rise with numerous river flood warnings already issued and more expected to be issued tonight and Wednesday. See the latest river flood warnings and statements for specific river information or consult our hydrology web page at water.weather.gov/ahps2/index.php?wfo=ARX. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...Flood Watch through Wednesday morning for WIZ017-029-032>034- 041>044-053>055-061. MN...Flood Watch through Wednesday morning for MNZ079-086>088-094>096. IA...Flood Watch through Wednesday morning for IAZ008>011-018-019-029- 030. && $$ SHORT TERM...04 LONG TERM...04 AVIATION...04 HYDROLOGY...04