


Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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530 FXUS63 KGRB 102129 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 429 PM CDT Thu Jul 10 2025 Forecast discussion for routine afternoon forecast issuance .KEY MESSAGES... - Showers and thunderstorms are possible at times from this afternoon through Saturday. Heavy downpours are possible within any thunderstorms. A few strong to severe storms will also be possible on Saturday. - Next round of active weather arrives during the middle of next week. && .DISCUSSION... Issued at 428 PM CDT Thu Jul 10 2025 A mid-level shortwave over eastern MN/western WI producing scattered showers and thunderstorms is progged to make eastward progress through this evening before weakening with time overnight. This will allow the scattered showers and thunderstorms to move into portions of central, north-central, and east-central WI this afternoon through this evening. The potential for strong or severe storms is low, but PWATs will be nearing 2 inches leaving the potential for heavy downpours within any thunderstorm. Later this evening, the weakening of the shortwave and loss of daytime heating will cause the coverage to decrease or remain mainly across southern WI. Meanwhile, another shortwave will be on its tail that is progged to phase/overcome the leading shortwave overnight. However, the evolution of this second shortwave has much uncertainty revolving around it. Models are still not in agreement with the timing, placement, or intensity of the shortwave/precip axis for Friday, but there is decent agreement Friday morning will be dry under some cloud cover. Overall, there appears to be a southern trend with the shortwave/precip axis for Friday afternoon and evening, but there are still indications that portions of eastern WI could see some of the main precip swath. If the latter is correct, these areas would be more likely to see higher rainfall totals (1-2+ inches), especially with a juicy atmosphere in place (PWATs around 2 inches). Otherwise, if the more southern solution occurs, much of the forecast area could see much lower rainfall amounts (less than 0.75 inches) for Friday/Friday night. Given the low confidence and much uncertainty, the potential for strong or severe storms has also decreased. Additional showers and thunderstorms are possible on Saturday with the main upper-level trough and leading surface cold front sweeping across the region. The severe potential Saturday afternoon and evening will depend on what happens Friday afternoon/night and how much cloud cover sticks around. Cannot rule it out at the moment given a tongue of 1000-2000 J/kg of MUCAPE ahead of the cold front, deep layer shear around 35-40 kts, and steeper mid-level lapse rates. SPC has included almost the entire forecast area in a Marginal Risk for severe storms, which reflects these features. The remainder of the weekend will be dry, but there are subtle indications of a weak boundary sweeping across the area on Monday, which could bring light rain and a chance of thunderstorms. A higher chance for widespread showers and thunderstorms is shaping up for midweek with an upper-level trough moving across the northern CONUS. && .AVIATION...for 18Z TAF Issuance Issued at 104 PM CDT Thu Jul 10 2025 A scattered cu field, with cloud bases between 2000 and 4500 ft AGL, has developed this afternoon under widespread high clouds. Mid-level clouds will gradually shift into the region from the southwest this afternoon but should stay confined to the central WI TAF sites. A few showers and perhaps some thunder may accompany the mid-level clouds this afternoon into this evening for CWA/AUW, therefore decided to keep a PROB30 group for TSRA. The shower activity should end late this evening. Some clearing may occur in portions of central and north-central WI overnight, which may allow for patchy fog development late tonight/early Friday morning. Decided to include a TEMPO group at CWA/AUW/RHI for the MVFR vsbys and potential IFR cigs. MVFR cigs are anticipated to spread eastward Friday morning with the potential for additional shower activity. Due to uncertainty in where and when this shower activity will occur, decided to include PROB30 groups for only CWA/AUW with this TAF issuance. Additional PROB30 or TEMPO groups may need to be added for the east-central WI TAF sites with the next TAF issuance. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kruk AVIATION.......Kruk