Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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574 FXUS63 KARX 122340 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 640 PM CDT Sun May 12 2024 .KEY MESSAGES... - Scattered showers/storms into the evening with rain chances shifting south of I-90 Monday. Gusty winds, lightning and small hail possible through this evening. - Air quality alerts for MN/Parts of WI through Monday Morning. Extensions may be needed. - Seasonable temps with the next better chance for widespread rain Wednesday night into Thursday && .DISCUSSION... Issued at 255 PM CDT Sun May 12 2024 Overview: Showers and thunderstorms have developed this afternoon with heating with increasing 850mb moisture and warm air/theta-e advection. The HRRR seemed to pick up on these showers/storms over northeast Iowa the best. We did have a gust to 50mph near New Hampton and some small hail. The SPC had SBCAPE around 1500J/kg and very steep low level lapse rates of 9-10deg. C/km. Downdraft CAPE was 900-1100J/kg...and inverted-v soundings favor gusty winds. The effective shear has decreased from earlier today over southwest WI and is generally 25kts or less. Water vapor satellite imagery, 500mb heights, and lightning show a trough over CO/western Plain and also over the Ontario. Lightning was noted between the two systems from northern WI into parts of southern MN along the cold front and the area across northern Iowa The surface cold front at 19Z was moving through the Twin Cities. Scattered showers/storms into the evening with pcpn chances shifting south of I-90 Monday (15-85% higher toward DBQ): The storm system over the Plains does phase somewhat with the northern stream wave, however the cold front does push through areas north of I90, then slow down. We`ll see the scattered showers and thunderstorms continue per the CAMs with a southern area and an area along the cold front, generally pushing south I 90 by 03-04Z with a weakening trend there, but continuing across parts of eastern IA and southwest WI. Smoke/Air Quality Alerts Smoke from wildfires in Canada continue to affect parts of the area today. The HRRR Smoke forecast calls for the near surface smoke/integrated smoke to continue to push south with the cold front into southeast MN/much of central WI and into northern IA through Noon Monday. As a result, both MN and WI have issued air quality alerts through Monday morning. We`ll continue to monitor conditions for extensions Monday. Extended: Tuesday through Wednesday we should generally be in-between weather systems with seasonable temperatures in the 60s to lower 70s. The next full latitude trough will move through Wednesday night into Thursday night. It appears to deepens as it exits the area with increasing areal coverage of precipitation, taking the higher rainfall amounts to the east. Per the European/GFS/Canadian ensembles, the probability for 0.25" for the 24hrs ending 7am Friday is 20 to 50% with the higher probabilities toward far southern WI. We have a better chance of seeing a wetting rain (0.10"), 50 to 70%. Friday should generally be dry unless the storm system slows down and precipitation chances linger across the far southern portion of the forecast area. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 641 PM CDT Sun May 12 2024 Southwest winds will shift to northwest winds during the evening and overnight periods as a cold front continues to move through the region. Scattered showers and thunderstorms are expected to continue through the the evening. A brief break from the rain during the overnight before rain chances return, primarily for portions of northeast Iowa and southern Wisconsin, Monday mid- morning. VFR conditions are expected for the rest of the day today before smoke moves into the area beginning after midnight. This smoke is expected to reduce visibilities into the MVFR flight category. The smoke will gradually dissipate through the afternoon on Monday. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...Air Quality Alert until noon CDT Monday for MNZ079-086>088- 094>096. IA...None. && $$ DISCUSSION...Rieck/Zapotocny AVIATION...Cecava