Area Forecast Discussion
Issued by NWS La Crosse, WI

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071 FXUS63 KARX 191900 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 200 PM CDT Mon Apr 19 2021 .SHORT TERM...(This evening through Tuesday) Issued at 200 PM CDT Mon Apr 19 2021 Quite the change today from the weekend with a return to well below average temps in the wake of last night`s strong frontal passage. An intense shortwave trough seen in water vapor imagery continues to rotate across the northern Great Lakes with plenty of post-frontal cold advection stratocu and even some rain/snow showers across the region this afternoon. Temps were mainly in the 30s and low 40s early this afternoon...closer to average lows at this time of year. An unseasonably cool airmass will persist across the region through Tuesday with upper troughing residing across the Upper Midwest. Diurnally enhanced cu will likely gradually dissipate tonight although some increase in mid/high cloud cover will occur from the southwest ahead of a shortwave trough rotating through the broader trough. The main story locally will be the cold temps with lows falling into the 20s over most of the area tonight. The airmass remains quite chilly on Tuesday with 925 mb temps hovering a few degrees below 0C. Highs will remain mostly in the 40s with diurnal cu developing thanks to cold mid-level temps/steep lapse rates with cyclonic flow aloft. Moisture depth looks to be lacking, but a few showers are possible in this environment. There will also be continued mid/high cloud cover across portions of the region associated with the wave passing to the south, but precip with this system is expected to remain south. .LONG TERM...(Tuesday night through Monday) Issued at 200 PM CDT Mon Apr 19 2021 Not much change will occur in the overall pattern through mid-week with an upper level trough and associated cool pool of air residing over the area. With the dry, cool airmass beneath expansive high pressure, lows Tuesday/Wednesday nights should again fall into the 20s, with highs Wednesday in the 40s. Continued steep lapse rates/cold temps aloft in conjunction with a shortwave trough passage could induce a few diurnal showers on Wednesday, but soundings show a fairly dry profile. The trough will finally be dislodged by Thursday as progressive shortwave ridging spread across the area with temps recovering back into the 50s. There is reasonable model consensus for a few progressive shortwave troughs to pass across the region Friday into Saturday. However, confidence in timing and coverage of precip is relatively low given uncertainty in the shortwave placement and models indicating little amplification/interaction of the troughs at this point. GEFS/EPS members show variation in precip amounts, but most ensemble members indicate 0.1 to 0.2" or less for rain, so it`s not looking like a significant rainfall. Behind this system, model guidance supports at least some degree of ridge building into early next week across the central US as a trough crashes ashore across the Pacific Northwest. This would suggest warming temps into early next week, but EPS members show very large spread in temps, so confidence all in all remains tempered. Overall, dry/seasonably cool weather is expected to dominate mid/late week through the weekend. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1145 AM CDT Mon Apr 19 2021 Cold/cyclonic flow was producing widespread (VFR) stratocumulus over the area along with an isolated rain or snow shower. Plan on this cloud cover to scatter out tonight with scattered to broken altocumulus (VFR) cloud expected tonight into Tuesday morning. Otherwise, look for the gusty northwest winds to taper off this evening, but then picking up again Tuesday after sunrise. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...JM LONG TERM...JM AVIATION...DAS

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