Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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418 FXUS63 KARX 030231 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 931 PM CDT Thu May 2 2024 .KEY MESSAGES... - Fog(locally dense?) probabilities have increased for Friday morning in northeast Iowa with fresh rainfall, wet soils, clearing skies, and winds dropping off as high pressure builds in. - Another round of showers late Friday night into Saturday. Rainfall amounts of up to a half of an inch possible. - Active weather pattern develops for next week. Periodic showers and storm chances through the period. Severe potential will depend on timing of each individual systems. && .UPDATE... Issued at 930 PM CDT Thu May 2 2024 Have increased the morning fog coverage over northeast Iowa for morning. This area has had fresh rainfall today, soils remain moist, GOES satellite showing clearing skies shortly moving in, and high pressure at the surface anchored over Iowa will provide diminishing winds. As the ridge builds in, dewpoints will fall some with dry air advection, however, with dewpoint depressions already a few degrees, that will only work to prolong the fog formation to later tonight. By morning, some locally dense fog could be possible. NBM hourly probabilities for fog support this forecast move as well with an increasing run-to-run trend. Fog should disipate rapidly in the morning. && .DISCUSSION... Issued at 219 PM CDT Thu May 2 2024 Today through Friday: Rain will continue to move through the area and into central Wisconsin. Compared to previous forecasts, model guidance continues to push the greater instability to our southeast, into eastern Iowa, northern Illinois, and far southern Wisconsin. As a result, this will be the area where thunderstorms develop. Scattered showers will be possible this afternoon, with northeastern Iowa and southwestern Wisconsin being the areas that have the greatest potential to see these showers. With these showers, there is a small chance (10 to 20%) of thunder. All rain chances are expected to diminish by midnight in our area. Low clouds will continue to be in the area through the overnight hours. Skies will gradually clear up and by Friday mid-morning, clear skies are expected across the area. Southerly flow will return for Friday out ahead of the next shortwave trough that will bring us more rain late Friday night into Saturday. Friday night through Saturday Next concern is shower/storm chances late Friday night/Saturday across the forecast area. Another impulse embedded in the southwesterly flow aloft will track into the Upper Great Lakes Region late Friday night/Saturday. The 02.12z GFS/NAM show decent QG forcing/vertical motion in association with the impulse. This will spread precipitation over the forecast area late Friday night into Saturday. Thunderstorm chances continue to diminish...as latest bufkit soundings and GFS/NAM indicate very little or if any 0-6km Most Unstable CAPE...less than 100 j/kg. With the limited instability have removed mention of thunder for Saturday and the forecast area should see all showers/rain. Shortwave ridge builds into the Northern Plains/Upper Great Lakes region Sunday. Subsidence underneath ridge should allow for dry weather and temperatures will be near normal with highs in the middle 60s to around 70. Sunday night through Thursday Main forecast concerns from Sunday night through Thursday are shower/storm chances mainly from Monday evening through Thursday. Shortwave ridge over the region Sunday night into Monday breaks down Monday evening. Upper level closed low slowly moves over the Northern Plains States and pieces of energy rotating around the closed upper level low are expected to track over the forecast area Monday night into Thursday. Latest ensembles/deterministic models suggest there are differences in timing of the pieces of energy moving over the Upper Mississippi River Valley...especially the first piece of energy Monday afternoon. This will have impacts on any potential severe storms or when the convection moves into the forecast area. Temperatures will remain near or slightly above normal through the forecast period...with highs in the middle to upper 60 to middle 70s. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 652 PM CDT Thu May 2 2024 Current satellite imagery this evening shows cloud cover over much of the region with MVFR ceilings remaining across the local area. Clearing can be seen expanding gradually eastward across portions of southwest Minnesota and northwest Iowa and is expected to continue through the evening/night bringing a return to VFR for the local area. While there has been a hint that some patchy fog could development for a short time this remains of lower confidence (vis probs MVFR 20-40%, IFR 15-25%). Will continue to monitor conditions for now and make any adjustments if needed. Otherwise, clearer skies and light winds remain for the daytime tomorrow. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ UPDATE...Baumgardt DISCUSSION...DTJ AVIATION...EMS