Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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048 FXUS63 KARX 201751 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 1251 PM CDT Sat Jul 20 2024 .KEY MESSAGES... - Slight precipitation and storm potential for some today, highest confidence along western and northern periphery. - Similar conditions through new week: diurnally induced storm potential with a low possibility for anything severe. && .DISCUSSION... Issued at 230 AM CDT Sat Jul 20 2024 The dry conditions come to a close for some today, eventually. The trough seen on WV imagery early this morning with weakening energy struggle to eradicate and saturate the dry air in place. Have gone with a slightly drier forecast as a result. Rain & Storm Chances Today: Initial saturation along our western periphery this morning is associated with a surface low well to the southwest. With the trajectory of this low, expect precipitation potential to remain along our western periphery through this evening. Subsequent precipitation chances early this afternoon sag south from northern Wisconsin as the upper level trough traverses the Upper Mississippi River Valley; dragging a back door cold front with it. While mid to upper level lapse rates steepen from the upper level low, a low to mid level temperature inversion and lack of forcing limits overall confidence and coverage in precipitation and storms. Southwest extent of precipitation potential will be main forecast challenge albeit overall limited impact. Any storms that do form will remain isolated and short lived with little to no shear to work with; pulsing up and down with heavy rain as a primary hazard. Through The New Week: The upper level low lingers through the new week, sending perturbations around its periphery, perpetuating daytime precipitation and storm chances locally. Long range ensembles (GEFS/EPS/GEPS) all exhibit associated waves of 0.01"+ 100% probabilities through the week. Coincidental timing of these meager perturbations and peak diurnal heating will dictate best storm potential. Investigating individual members, most contain some semblance of SBCABE during the first half of the week concurrent with diurnal heating before eroding it for the second half. Long term (ECMWF/GFS) soundings show minimal concurrent shear, limiting any confidence for severe potential. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1243 PM CDT Sat Jul 20 2024 Strong signal in both deterministic and probabilistic models for fog - perhaps LIFR - continues. That said, still a possiblity that high clouds help prevent fog from forming, so have elected to keep things MVFR tonight into early Sunday morning with this update. As for TS possibilities, this is looking increasingly unlikely during this TAF period, so have left out all mentions of precip. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...JAR AVIATION...Ferguson