Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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065 FXUS63 KARX 300335 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 1035 PM CDT Wed May 29 2024 .KEY MESSAGES... - A recurrence of valley fog is favored tonight into early Thursday morning. - Periodic Showers and Storms from Friday into Wednesday. Maybe some stronger storms from Tuesday into Wednesday. && .DISCUSSION... Issued at 213 PM CDT Wed May 29 2024 Fog tonight into early Thursday morning: After Wednesday morning saw fog develop in many of the forecast area`s river valleys and the cranberry bog area, a repeat is favored tonight. Fog seems to comport well with the overall pattern, where surface high looks to become centered over NE WI as an upper wave, located over eastern Ontario, exits over MI, leading to very light winds at the surface. With skies expected to be clear, excellent radiational cooling should result in fog. Potential failure mode may be winds a bit too strong at the top of the boundary layer and the light northeasterly winds this afternoon bringing in enough drier air to overcome the abundant surface moisture that is present due to the well above normal rainfall over the past few weeks. Friday through Monday Night: Periodic Showers and Storms A longwave ridge will move east of the area on Thursday night. As this occurs, a shortwave trough will move east through the area on Friday and Friday night. 0-1 km mixed-layer CAPES ahead of this trough are only up to 250 J/kg. 0-3 km shear remains in the 20 to 35 knot range and the 3-6 km shear is generally less than 15 knots. Due to this, not expecting to see any severe weather. For the remainder of this period, the 500 mb flow will become zonal. Embedded shortwave troughs in the flow pattern will bring periodic showers and storms. One will move through area on Saturday night and another one from Sunday afternoon into Sunday night. While the 0-3 km mixed-layer CAPES climb up to 1000 J/kg, the 0-6 km shear remains weak, so not anticipating organized severe weather with either these systems. Tuesday into Wednesday: Maybe Some Stronger Storms A much stronger shortwave trough will move through the region. While the 0-3 km mixed-layer CAPES climb up to 1000 J/kg, the 0-6 km shear remains weak. From looking at just these parameters, it does not look that favorable for severe weather. However, some of the ensemble members are showing that this this system will be potentially negative tilted and this would enhance the 0-3 km and 0-6 km shear. In addition, the Colorado State machine learning has up to a 15% chance of severe weather, so this system bears watching. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1035 PM CDT Wed May 29 2024 Main taf concern is fog development in river valleys tonight. With light winds...clear skies and an inversion developing tonight...fog will possibly form in the river valleys after 09z Thursday. However...winds do increase near the inversion over 10 knots and the region is slightly drier near the surface compared to the last couple of nights/evenings. This will inhibit fog development in river valleys. At this time...have kept patchy fog in river valley and MVFR visibility condition at LSE taf site. Otherwise...surface ridge will dominate the area and VFR conditions will prevail. Southerly wind speeds will increase to 10 to 15 knots late Thursday morning at both taf sites. Then...wind speeds are expected to diminish near 10 knots or less after sunset Thursday evening. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Boyne/Ferguson AVIATION...DTJ