Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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186 FXUS63 KARX 130721 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 221 AM CDT Thu Jun 13 2024 .KEY MESSAGES... - Isolated to scattered strong/severe storms are still possible early this morning. Any additional strong and severe storms this afternoon look to be south of the area. - Severe weather chances look less for this weekend, but still could see some localized flooding. - Above-normal temperatures expected for next week. However, the temperature anomalies are uncertain. In addition, shower and storm chances are also uncertain. These uncertainties are due to questions on the western extent of the 500 mb ridge and strength of the cap. && .MESOSCALE... Issued at 221 AM CDT Thu Jun 13 2024 As a shortwave trough moves southeast through the area early this morning, 850 mb moisture convergence along and ahead of this trough will keep showers and storms going through dawn. With DCAPE of a 1000 to 1500 J/kg, we will have to watch for the potential damaging winds. However, as this convection moves southeast, the low-level CIN will be increasing into the 400 to 500 J/kg range along and south of Interstate 90. This will limit the damaging wind threat. The effective shear will remain in the 25 to 35 knot range north of Interstate 90 and from 35 to 50 knots across the remainder of the area, so may have to watch for some isolated to scattered supercells between 3 AM and 6 AM south of Interstate 90. Hail would be the primary threat. As the 850 mb moisture transport shifts off to the east toward dawn, the showers and storms will quickly come to the end across the area. && .DISCUSSION... Issued at 221 AM CDT Thu Jun 13 2024 Today... Another 700-500 mb shortwave trough and surface cold front will move through the area today. Between 8 AM and 10 AM, a band of showers and scattered storms will begin to move into the areas north of Interstate 90 between 8 AM and 10 AM. While the deep shear is favorable for supercells, the instability remains weak generally less than 500 J/kg for much of the area. However, there are some CAMs suggesting anywhere from 500 to 1500 J/kg in our far southern areas. This might result in a few strong in these counties, but overall the better severe weather chances look to be south of our area. The CONSShort precipitation chances looks too low, so used the CAMs to raise the precipitation chances up into the categorical range. This made sense considering the good agreement in timing and location of their precipitation. Father`s Day Weekend... The models continue to show that a 500 mb ridge will build northward and then move east of the region. As this occurs, a warm front will lift northward into the region. On Saturday and Saturday night, the better shear and instability remains to the southwest of the area. As a result, it looks like the severe weather chances have dramatically lessened for this time period. The warm front will move north across much of the area on Sunday. As this occurs, temperatures will warm well into the mid- and upper 80s. There may be even some lower 90s. Due to differences in the low level dew points, there continues to be some differences in the 0-1 km mixed-layer CAPEs. The GFS has CAPEs between 1000 and 3000 J/kg. Meanwhile, the ECMWF is in the 1000 to 2000 J/kg range. The GFS has a weaker 500 mb ridge and this results in a cold front dropping south into the region on Sunday night. If this does indeed occur, the strongest 0-6 km shear remains post frontal, so organized severe weather chances look to be low. Meanwhile, the ECMWF and Canadian has a stronger ridge and capping over the region, so there are questions on whether any showers and storms will even develop. With a mean precipitable water value around 1.5 inches and warm cloud layer depths climbing to around 4 km, any showers and storms that do happen to develop will be efficient rain producers. This could result in some localized flooding. Monday through Wednesday... There continues to be uncertainty on the location of the eastern U.S. 500 mb ridge. Both the ECMWF and Canadian have their ridge further west into the Upper Mississippi River Valley. This results in well-above normal temperatures (mid-80s to mid-90s) and dry. Meanwhile, the GFS is further east with the ridge and this results in temperatures more in the 80s with periodic showers and storms. Some of these could be strong to severe. In addition, with warm cloud layer depths of around 4 km and and precipitable water values of 1.5 to 2 inches, there will be the potential for localized flooding. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1149 PM CDT Wed Jun 12 2024 The potential for thunderstorms at LSE/RST overnight remain the main concern over the next TAF cycle. Confidence has decreased in occurrence over the past several hours given latest trends in observations and short term guidance. Have therefore altered prevailing mentions of TS to TEMPO groups and adjusted timing. Otherwise, abundant low level moisture, particularly if storms occur, suggest fog at LSE may occur around sunrise Thursday. Given low confidence, have elected to only include an MVFR mention at this time. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ MESOSCALE...Boyne/Skow DISCUSSION...Boyne AVIATION...Ferguson