Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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056 FXUS63 KARX 111015 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 515 AM CDT Tue Jun 11 2024 .KEY MESSAGES... - Will there be enough recovery this afternoon and early evening for some isolated strong to severe storms to develop? If the atmosphere is able to recover, the main threats would be damaging winds and hail up to 1-inch in diameter. - Still some uncertainty of how long discreet supercells will last prior to becoming line/lines of storms. The discreet storms will be capable of producing tornadoes, large hail, and damaging winds. As cold pools coalesce, these storms will evolve into line/lines with damaging winds becoming the primary threat. - From Fathers Day weekend into early next week, still uncertainty on the position of a strong 500 mb ridge. This impacts the tracks of mesoscale convective complexes and temperatures. && .DISCUSSION... Issued at 332 AM CDT Tue Jun 11 2024 Through early this evening... A convectively induced shortwave trough will move east through the area this morning and early afternoon. There is little CAPE across the area during this time period, so just looking at some showers for this time period. From mid-afternoon into early this afternoon, a cold front will be moving east through the area. Still plenty of uncertainty on whether the atmosphere will be able to recover enough for showers and thunderstorms to develop. The 11.00z LREF has up to a 30% chance of surface-based CAPES reaching 500 J/kg and less than a 10% chance of the surface-based CAPES reaching 1000 J/kg. The high-resolution FV3 and 4 km NAM have the most robust storms and greatest coverage. Meanwhile, HRRR and RAP only have isolated showers and storms. If there is enough recovery in CAPES in the afternoon, soundings would suggest that there could be some damaging wind gusts and hail approaching 1-inch in diameter. Wednesday and Wednesday night... The models continue to show that a 60-80 knot mid-level jet moving along the US and Canadian border during the afternoon and evening. The CAMs are differing on timing issues and what areas will be impacted by strong to severe storms. Overall, they are in decent agreement that the convection will initially start out as discreet supercells over western Minnesota and then they evolve into line or lines of storms. The discreet supercells will be capable of producing tornadoes, large hail (possibly in the excess of 2-inch in diameter) and damaging winds. The main question is how fast will it take for the supercell cold pools to coalesce and evolve into line/lines. Both the NAM and GFS show strengthening winds below 3 km. This results in helicities in the 200 to 400 range along and west of the Mississippi River. However, there is also concern that there may be some convective feedback in these models and this might be causing these winds to be too high. Once the storms develop into lines, the primary threat will likely turn more into a wind threat. The latest CAMS are suggesting that the showers and storms will be moving south of the area by early evening, so concerned that the rain chances are too high for overnight Wednesday night and Thursday morning. Fathers Day Weekend... The 500 mb ridge will be building north and moving east at the same time. Still some uncertainty on how far north this front will build. This impacts the tracks of a couple of mesoscale convective complexes and the potential high temperatures. If this ridge does not build as far north as expected, high temperatures would be in the 70s and lower 80s. If the ridge builds further north, high temperatures would range from the mid-80s to lower 90s. Early Next Week... The strong 500 mb ridge will be centered somewhere from the Mid-Atlantic to the southern Great Lakes. There continues to be some uncertainty on the western periphery of the 700 mb capping. This will impact the track of a series of mesoscale convective complexes and temperatures. && .AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/... Issued at 515 AM CDT Tue Jun 11 2024 CIGS: band of mid level BKN-OVC VFR cigs (approx 5 kft) set to slide across the area this morning, associated with -shra. Should scatter out toward 18z with the potential for a brief period of bkn cigs as a cold front moves in from the west late afternoon (could dip into MVFR). Nighttime hours look SKC. WX/vsby: -shra for a few hours this morning powered by a warm air advection. Amounts minimal. Eastward moving cold front could spark isold/sct -tsra for the mid/late afternoon hours. A lot of uncertainties with whether enough instability can build to help fire off storms and CAMS models aren`t clear on what to expect, between themselves and within. Will hold the PROB30 at KRST for now. Expect some refinement here as we move into the afternoon. Widespread TSRA with vsby and wind impacts likely Wed afternoon and evening. WINDS: southerly and picking up this morning. Some gusts into the lower 20 kts. Will swing westerly with passage of cold front later in the day, but become light and more south/southeast by mid to late evening. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Boyne AVIATION.....Rieck