FXUS63 KGRB 150850 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 350 AM CDT Tue Jul 15 2025 Forecast discussion for routine morning forecast issuance .KEY MESSAGES... - Isolated showers and storms this morning in far northern WI. Followed by scattered storms across northern WI late this afternoon into tonight. Severe storms are possible far north- central WI during the late afternoon/evening with a marginal to slight risk for severe weather. Heavy rain also a risk. - Staying active with showers and a chance of storms Wednesday through Wednesday evening. Marginal to slight risk of severe storms and heavy rainfall in central and east-central WI. Lingering scattered showers on Thursday, then dry for the end of the week. - Very warm and humid through Wednesday. Heat index values peaking in the lower to middle 90s today. Cooler and less humid late this week. && .DISCUSSION... Issued at 348 AM CDT Tue Jul 15 2025 Short Term...Today...Tonight...and Wednesday Dry conditions along with warm and moist air will prevail across the area early this morning. There will be a couple of opportunities for showers and thunderstorms today, with the first possible later this morning across north-central Wisconsin as a weak mid level shortwave tracks through the northern Great Lakes region. This activity is already firing up across northwest Wisconsin. This activity is not expected to be severe and should shift northeast late in the morning into the early afternoon. The outflow boundary from this system along with an upstream cold front will be the impetus for additional activity later this afternoon across northwest Wisconsin as it tracks east through north-central Wisconsin late this afternoon and into the early evening. This activity is generally expected to weaken as it tracks through the area; however, if this activity can track through the area early enough there will be enough instability and shear for strong to severe storms. SBCAPEs are expected to be 1500 to 2000 J/kg along with 30 knots of bulk shear. This would be enough to produce damaging winds and large hail if storms roll through early enough before instability and shear wane or the system weakens. Heavy rain will also accompany any thunderstorms across north-central Wisconsin this afternoon as PWAT values hover around 150 percent of normal. Another hot and humid day will be on tap today as highs range from around 90 across central and east-central Wisconsin with middle to upper 80s across north-central Wisconsin. The warm temperatures and high dew points will push heat index values into the lower to middle 90s across much of the area this afternoon. The cold front lingers across north-central Wisconsin tonight, with precipitation chances uncertain. It appears the best chance would be across north-central Wisconsin tonight, with some models indicating precipitation along the front may wipe out with only some light rain or possibly mostly dry conditions could occur. Given the model uncertainties will keep rain chances limited to the north. Rain chances increase on Wednesday as a shortwave tracks through the western Great Lakes, which will push the stalled out cold front through the region. Although the best potential for severe weather on Wednesday appears to be across southern Wisconsin, SBCAPEs do soar to 1500 to 2000 J/kg across southern portions of the region along with 30-40 knots of bulk shear. This could bring strong to severe storms across central and east-central Wisconsin if it can track through the area early enough before the cold front pushes south. CAMs models indicate the southern 2 tiers of counties will be most at risk for severe weather Wednesday afternoon. Heavy rain will again be possible as PWATs will be 125 to 150 percent of normal for this time of year. Temperatures on Wednesday will vary greatly due to the cold front, with highs ranging from around 60 across the far north, to the lower to middle 80s across the southern 2 tiers of counties. Long Term...Wednesday Night Through Monday Lingering activity Wednesday evening as a surface front, mid-level short wave, and upper jet continue to track across Wisconsin. Instability still as high as 1500 J/kg at 00Z/Thu, and pwats as high was 1.75 inches; however, both of these parameters quickly wave as the sun sets and drier air filters in from the northwest behind the front. A couple hours of isolated strong/severe storms with strong winds and heavy rain are possible Wednesday evening, following by a few lingering non-severe storms or rain showers the rest of the night. Surface high pressure will lead to dry weather for the rest of Thursday and Friday. Temperatures will be cooler/less humid with the arrival of cooler and drier air behind the front. Highs on Thursday will be in the low 70s, and in the mid 70s on Friday. Weak disturbances will create on and off chances for showers and thunderstorms from Saturday into early next week. Right now, the most likely days for any precip are Saturday afternoon and evening, and late Monday into Tuesday, but confidence in the specifics is low. It is too early to determine any severe potential this far out, but as previously mentioned, the higher instability is currently progged much farther south and west. Temperatures from Saturday into early next week will be near normal. && .AVIATION...for 06Z TAF Issuance Issued at 1038 PM CDT Mon Jul 14 2025 Mid-level clouds and a few sprinkles will be exiting far northern WI at TAF issuance, and should stay north of RHI. There is some potential for minor vsby restrictions due to fog overnight, with models suggesting patchy fog from central into far northeast WI, so will only mention TEMPO groups with MVFR vsbys at AUW/CWA for now. Would not be shocked if patchy fog develops over a larger area, as surface RHs are 80-100% in many locations. A weak frontal boundary will lift back to the north overnight, with SCT-BKN stratocumulus pushing into northern WI. SCT cumulus clouds may redevelop elsewhere due to the heating of the day on Tuesday. A line of thunderstorms is expected to reach NC WI Tuesday evening, so have added showers and a TEMPO group for storms at RHI. The line is expected to weaken as it pushes southeast, so only added a mention of showers at AUW/CWA for the last couple hours of the TAF period. MVFR conditions should overspread NC WI as the showers and storms move through, and IFR ceilings may develop later in the evening, mainly north of RHI. Light S-SW winds expected overnight, then becoming gusty during the day on Tuesday. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kurimski/KLJ AVIATION.......Kieckbusch