FXUS63 KGRB 210555 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1255 AM CDT Sat Mar 21 2026 Forecast discussion for routine afternoon forecast issuance .KEY MESSAGES... - Snowmelt will cause increased flows and rising levels on rivers and streams. Several rivers may reach bankfull or even minor flood stage beginning this weekend. - Areas of fog and low clouds expected this morning. A 20 percent chance of rain or freezing rain near the Upper Michigan border. - Rain (30-50% chance) tonight into Sunday morning. Rain may briefly mix with snow or sleet before ending, but little or no accumulation is expected. - Well above normal temperatures expected today, especially in central Wisconsin, where highs could reach well into the 60s and possibly 70 (20-40% chance). Mild readings into the 50s are also anticipated next Tuesday and Thursday. - A wintry mix of precipitation possible during the middle of next week, especially Wednesday into Thursday. && .DISCUSSION... Issued at 1255 AM CDT Sat Mar 21 2026 Some patchy fog and stratus will impact the region this morning with light winds and low-level moisture from melting snow. Once the fog dissipates, there will be a small (10-30%) chance for rain or freezing rain this morning in response to isentropic lift in a moisture starved air mass. Today will likely be the warmest day of the week as an approaching low pressure system from the Northern Plains brings a warm front and associated surge of very mild air into the forecast area. This warmth will primarily be felt in central Wisconsin, where there is a 60-80% chance of highs greater than 65 degrees and a 20-40% chance of highs hitting 70 degrees across the far southwest corner of the region. Farther north and east, a combination of low clouds (north of the warm front) and SE-S winds off Lake Michigan will keep readings in the 40s and 50s. As the low shifts east, a cold front will sweep through the forecast area during the late afternoon/evening. Models show strong mid-level FGEN forcing with this system, which should bring a band of light rain through the area tonight into early Sunday. This band should sag southeast with time, with the lagging influx of colder air only leading to a brief period of mixed precipitation (mainly sleet/snow) on the northwest periphery of the precipitation band. Therefore, not expecting much (if any) snow accumulation. Most of the precipitation should be gone by Sunday afternoon. High pressure will then provide mainly dry weather and more seasonable temperatures from Sunday afternoon through Monday night. Another clipper system will move through during the middle of next week. This system looks fairly similar to this weekend's system, with potential for a light mix of rain/snow, especially Wednesday into Thursday. Mild days occur ahead of the clipper on Tuesday, and within a dry slot on Thursday, with potential for 50s both days. && .AVIATION...for 06Z TAF Issuance Issued at 903 PM CDT Fri Mar 20 2026 VFR conditions prevailed across the forecast area this evening. Mostly clear skies, decoupling winds, and ample low-level moisture from melting snow will then result in a window for fog development late this evening and overnight, potentially dropping vsbys into IFR or LIFR territory. However, opted not to include any TEMPO groups, as it is still uncertain whether or not this will materialize as fog or low stratus. Slight chances for rain or freezing rain then arrive from the north toward the end of the TAF period, though this should remain north of RHI. Winds will gradually veer to south/southwesterly throughout the day on Saturday, picking up slightly Saturday afternoon. Gusts between 15 and 20 knots will be possible. LLWs may become a concern late Saturday morning and afternoon as 850 mb winds ramp up. && .HYDROLOGY... Issued at 1255 AM CDT Sat Mar 21 2026 As temperatures warm across the region, the snowmelt will result in increasing flows and rising river levels. Some rivers could reach bankfull or even minor flood stage starting this weekend. The lack of a prolonged significant warmup points to a more gradual rise in area rivers as opposed to widespread rapid rise flooding. That being said, the flooding situation will be monitored closely given how much water is locked up in the current snowpack across the region. Modeled snowpack temperature from the NOHRSC site points to widespread ripening of the snowpack (and higher susceptibility of melting/runoff) over the area today. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kurimski AVIATION.......Goodin HYDROLOGY......Kurimski