Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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663 FXUS63 KARX 070342 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 1042 PM CDT Thu Jun 6 2024 .KEY MESSAGES... - Hit and miss showers and winds diminishing this evening. - Dry and breezy with seasonable temperatures for Friday. - Below normal temperatures persist into this weekend, temperatures warm up next week. - Showers, possibly a storm (15-25% chance), this weekend will bring rainfall amounts of up to 1/3" overnight Friday and into Saturday. && .DISCUSSION... Issued at 248 PM CDT Thu Jun 6 2024 Overview: Water vapor satellite imagery, 500mb heights, and lightning showed an area of closed low pressure over Ontario, Canada with the troughing extending southeastward through eastern Great Lakes and Ohio River Valley. Convection was mostly confined to the Gulf States, however a line of storms was noted on the east side of the Western U.S. ridge over parts of Kansas. Hit and miss showers and winds diminishing this evening. Dry and breezy with seasonable temperatures for Friday: At 18Z...surface high pressure was located over the Rockies with surface low pressure over Ontario. The local area was under northwest flow aloft with the thermal 850mb trough moving through WI. Temperatures aloft to the west were already moderating. Deeper moisture in the low-to mid levels of the atmosphere is pushing south and east with the thermal trough. With heating today clouds continue to form and should see some hit and miss showers increase with the heating in the 60s to lower 70s. The most recent WSR-88D mosaic had the showers north of I94. This should continue to be the area where spotty showers occur with a few sprinkles possible farther west. There are some hints that an area showers could re- develop this evening with weak warm air advection aloft. There is an uptick in the 900mb winds going from 28 to 30kts to 30 to 40kts. For now have some sprinkles mentioned, but left out measurable precipitation. A wind advisory is in effect until 6pm. Several sites in southeast MN and northeast IA had sustained winds around 30mph. Gusts mostly 35 to 50 mph. Farther north and with increased cloud cover, with was still breezy to windy, but more intermittent. The winds should decouple this evening as they become less mixed and uni-directional. The ridge builds in more for Friday with temperatures in the 60s to mid 70s. Fewer clouds, but it does look like northwest winds will be on the increase. The winds aloft are not as strong. The winds are actually stronger in the morning over Wisconsin and drop off, but it should not be as windy, but should still see gusts 20 to 30kts. Friday Night - Sunday: Cool with Showers, Maybe a Storm A fairly persistent upper-level pattern will continue into the weekend with a parked upper-level trough situated to our west allowing for predominantly northwest upper-level flow to remain in place across the region. Friday night and into Saturday will feature a piece of shortwave energy that will progress northwest of the region in the aforementioned northwest flow regime. Consequently, associated lift with the wave will help to instigate broader coverage of convective development (mainly showers) across much of the region overnight Friday and into Saturday. Currently, a ribbon of weak instability (up to around 500-750 J/kg as shown in the 06.15z RAP) is advected into portions of our region, primarily across northeast Iowa on Saturday morning. However with quite a bit of spread amongst guidance how thermodynamic profiles will manifest, confidence is still on the lower side for if any storms will result. Regardless, this shortwave could bring some rainfall totals of up to 1/3" or so, primarily north of I-90. This is further suggested in the 06.12z GEFS/EC ensemble which has high probabilities for over 0.1" (60-90% chance). Otherwise, Saturday and Sunday will trend below normal for temperatures with 06.00z grand ensemble (GEFS/EC ensemble/Canadian ensemble) showing the vast majority of ensemble members (almost 100%) keeping temperatures below the daily average high of roughly 80 degrees at La Crosse for both Saturday and Sunday, with median high temperatures in the upper 60s to middle 70s across the local area for the weekend. Additional showers are possible (15-25% chance) into Sunday as well with cyclonic flow and weak instability still in place. Next Week: Mild Beginning with a Warming Trend, Some Rain Chances As we start next week, temperatures will remain mild relative to average as the aforementioned broad upper-level trough begins to slide further east. While this occurs, deterministic guidance hints at a possible secondary smaller scale trough that sneaks into the region early Tuesday. Currently, deterministic and probabilistic guidance is all over the place with this system as the deterministic 06.12z GFS develops a very strong upper-level trough into the region. This is contrasted heavily by the 06.12z EC which has a much weaker shortwave. Consequently, the 06.12z GEFS/EC ensemble have probabilities for measurable precipitation that reflect this (40-60% chance), suggesting that there is large disagreement between various ensemble members. As a result, hard to totally buy into any rain chances early next week but will keep chance (roughly 30%) mention for precipitation chances for Tuesday. Regardless on the impact of this trough to our region, guidance suggests that the large scale ridge further west will push into our region but flatten as it progresses beginning in the middle of the week. Consequently, temperatures will begin warming by the middle of next week with increasing confidence (60-90% chance in the 06.12z GEFS) in highs reaching 80 during the second half of next week. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1040 PM CDT Thu Jun 6 2024 VFR expected across the local forecast area from southeast Minnesota, northeast Iowa, and western into central Wisconsin. Increased winds through Friday, albeit not as strong as Thursday. Subsequent flight impacts and precipitation overnight Friday into Saturday morning. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Naylor/Zapotocny AVIATION...JAR