419 FXUS63 KARX 091706 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 1206 PM CDT Tue Oct 9 2018 .SHORT TERM...(Today and tonight) Issued at 325 AM CDT Tue Oct 9 2018 Water vapor imagery early today continued to show amplified meridional flow across the area with strong ridging centered off the Mid-Atlantic coast. Deep southerly flow continues to advect a steady stream of anomalous moisture into the area with precipitable water anomalies remaining 2 to 3 standard deviations above average for this time of year. A surface boundary stretches from KS northeast towards the UP of Michigan. This morning a few shortwave troughs and associated low-level moisture transport within the frontal zone will continue to provide support for showers and isolated storms lifting northeast across the area, with the focus from north-central IA through north-central WI. The frontal boundary will not move much through tonight with the synoptic flow regime relatively unchanged. Another shortwave trough and slug of stronger moisture transport will arrive later this afternoon and this evening with more widespread showers and storms returning. This will be the favored time period for additional heavier rains. See the hydro section below for more details. With portions of northeast IA through southwest WI in the warm sector and the RAP/NAM showing up to 1000 to 2000 J/kg of MLCAPE around 40 kts of 0-3 km shear and increasing 0-1 km shear this evening as the low-level jet increases, certainly will have to watch for potential severe storms in this area late afternoon into the evening. Damaging winds and possibly an isolated tornado are the main threats. With the front draped across the area today, highs will range from near 60 over parts of SE MN into NC WI to the upper 70s in SW WI. .LONG TERM...(Wednesday through Monday) Issued at 325 AM CDT Tue Oct 9 2018 Guidance is a tad slower in lifting the main upper wave and surface low across the Upper Mississippi Valley on Wednesday, consequently keeping rain chances going into the day with some storms possible ahead of the front. By evening, the cold front will have cleared the area with the low moving towards Lake Superior. This should finally put an end to most of the rain over the area. Strong cold advection will take hold behind the front Wednesday into Wednesday night as 850 mb temps plummet from 12-15C 12Z Wed to around -5C by early Thursday. A period of strong, gusty northwest winds are expected with the surge of cold advection Wed afternoon/evening with temps falling into the 30s by Thursday morning. A few showers could linger over northern WI Wed night as the low pulls away. Thursday will be a brisk, chilly day with some lingering low stratocu, gusty northwest winds, and highs stuck in the 40s. Gradual clearing is expected as surface high pressure builds in from the west. Thursday night continues to look like a cold night with the surface high approaching. Lows should fall into the 20s to low 30s over the area. There will be, however, some increase in mid/high clouds overnight ahead of another upper trough approaching from the northwest. With the surface high sliding across the area on Friday, expect another dry and chilly day, despite the upper trough passage. Dry conditions with shortwave ridging are expected for at least most of Saturday ahead of an upper trough that will approach by late in the weekend into early next week. The trough passage will be accompanied by some precip chances late Saturday into Monday, although models differ on the evolution of the upper trough and surface reflection. Some snow could even mix in by Sunday night. Cooler than average temps will persist through early next week with highs in the 40s to low 50s. && .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 325 AM CDT Tue Oct 9 2018 Conditions will remain favorable for locally heavy rainfall into Wednesday with anomalous moisture (pwats near or above 1.5 inches) for early October and several upper impulses riding along a relatively stationary boundary draped across the area. Additional rainfall of 1 to 3 inches is possible through Wednesday, with locally higher amounts. The highest amounts are favored from parts of northeast IA through southeast MN and northwest WI, with the heaviest rains expected late this afternoon into tonight. The combined effects of rainfall over the past few days and the expected rainfall will lead to rising river levels with minor to moderate flooding possible on some area rivers over the coming days. While the greatest impacts look to be on rivers and streams, some urban flooding or localized flash flooding could develop this evening, especially if thunderstorms repeat over the same area. A Flood Watch has been expanded to include the entire area through tonight. A trend towards drier weather is expect beginning later Wednesday as a cold front moves through. && .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...JM LONG TERM...JM AVIATION...04 HYDROLOGY...JM