Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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063 FXUS63 KARX 150355 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 1055 PM CDT Sat Sep 14 2024 .KEY MESSAGES... - Summer warmth through much of the new week with highs in the low to mid 80s. - Most locations will stay dry into Wed with increasing chances from west to east moving into next weekend. && .DISCUSSION... Issued at 140 PM CDT Sat Sep 14 2024 OVERVIEW: models remain in lockstep with reestablishing the upper level ridge across the upper mississippi river valley as we move into the new work week. This holds through the better part of the work week despite a west coast longwave trough periodically tossing shortwaves at the ridge`s western flank. The GFS and EC suggest another trough, this one dropping out of western Canada, will finally kick the ridge axis east moving through next weekend. Upshot to this pattern is persistent summery warmth with mostly nil to low end rain chances until next weekend. PCPN: north-south running piece of upper level energy will continue to fire scattered/areas of showers into the evening, mostly north of I-94 and diminishing into the overnight. RAP/HRRR soundings continue to suggest weak instability will build for the afternoon/early evening hours - so a thunderstorm or two remains a possibility. Some of the short/medium range guidance continues to suggest that a very weak ripple or two could still rotate north/northwest of what is left of Francine for Sun/Mon - producing a smattering of light qpf here and there. Not as much saturation to play with though, per bufkit soundings and time/height x-sections. NBM keeps pops around 10% with a smattering of 20% here and there. For now, will lean into a "dry" forecast. Even if a few sprinkles are realized Sunday, most locations will be missed. Moving into the new work week, the ridge should provide at least a few dry days for the region. Recent deterministic runs of the EC and GFS then suggest mostly western parts of the forecast area could start seeing low end rain chances by Wed - as both models spin bits of shortwave energy out of a west coast trough. However, the bulk of both models` ensemble members suggest they area will stay dry. In addition, the grand ensemble model blend holds measurable rain chances from 10 to 30% mostly along/west of the Mississippi river starting late Wed night. Only by the weekend do these chances start to increase as a trough from western Canada pushes the ridge axis east. The NBM still looks a bit aggressive with how far east and how soon its spreads rain chances over the forecast area...and think there is likely a better shot for most locations to stay dry until the weekend. For now will continue to side with the NBM for chances. TEMPS: the models` enthusiasm for the continued warmth has grown over the past few days. Probabilities for 80+ degree days in the grand ensemble of models have moved to 70-100% into next Friday. Looking at the EPS and GEFS ensembles, they also show increasing consensus for the warmth with little variation between individual members - as little as 10 degrees between 10 and 90% outcomes. Low to mid 80s looks like a safe bet given the trends with some of the area`s warmer locations likely topping out in the upper 80s to near 90 on a few days. After a relatively humid weekend, drier air will return with the ridge dropping sfc tds from the mid to upper 60s to the upper 50s to around 60 for the work week. So while the heat cranks up a few notches, the humidity will be lower. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1055 PM CDT Sat Sep 14 2024 Current nighttime satellite imagery shows some mid-high level clouds continuing to move across the region, with ceilings forecast to remain VFR through the period. There remains some lingering moisture from earlier rainfall, so will need to continue to monitor the potential for patchy fog development where clouds can clear out and winds remain light. Confidence was not high enough to include restrictions at the TAF sites for now, but short term adjustments may be needed. Some guidance still suggests the potential for an afternoon shower or storm, but confidence and chances (10-15%) remain much too low to mention at this time. Otherwise, light winds remain generally southeast to south through the period. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Rieck AVIATION...EMS