![National Oceanic and Atmospheric Administration](/build/images/header/noaa.d87e0251.png)
![National Weather Service](/build/images/header/nws.4e6585d8.png)
![United States Department of Commerce](/build/images/header/doc.b38ba91a.png)
Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
075 FXUS63 KGRB 131134 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 634 AM CDT Tue Aug 13 2024 Updated aviation portion for 12Z TAF issuance .KEY MESSAGES... - Isolated showers and storms (15% to 30% chance) will be possible this afternoon and early this evening. Severe thunderstorms are not expected. - Showers and some thunderstorms are forecast at times on (60 to 80% chance) Thursday into Friday. While the severe potential remains low, favorable conditions will exist for heavy rainfall and localized urban and low-land flooding. - Conditions hazardous to small craft possible on Lake Michigan Thursday and Thursday night. && .DISCUSSION... Issued at 347 AM CDT Tue Aug 13 2024 Short Term...Today...Tonight...and Wednesday Shower/Storm Chances & Cloud Trends: A dry start to the day is on tap today with plenty of sunshine, with only a few patches of fog/clouds across parts of the area. Then as temps climb, look for a cumulus field to develop in the mid to late morning. Instability will build to 500-1000 J/kg by early afternoon. A weak, nearly stationary boundary, along with lake/bay breeze boundaries and steepening lapse rates will combine with the instability to produce isolated to possibly scattered sprinkles/showers and a few storms mainly this afternoon and early evening. Little to no upper forcing, along with some dry air, a weak cap above 10,000 feet and surface high pressure to overcome, so think coverage will be limited. Weak shear under 20 kts will lead to slow moving showers/storms that could drop some locally heavy rain if/where the activity develops (PWATs around an inch). The stronger showers/storms could produce some brief gusty winds as well (with inverted-V soundings promoting evaporative cooling). The outflow could also produce additional boundaries for other storms to develop along. Any lingering shower/storm will end in the early evening as instability wanes and temps cool. Mostly clear skies are expected tonight, with clouds increasing from the west Wednesday afternoon. The weak boundary/lake breeze could touch off a shower near the MI border, but signs are not as strong as today, so will keep a dry forecast. Fog/Smoke/Temperatures: Light winds and mostly clear skies will lead to some patchy fog early this morning and again late tonight into early Wednesday. Any fog will burn off near/shortly after sunrise. A thin layer of smoke will remain across parts of the western Great Lakes at times through mid-week. No impacts are expected at/near the surface as the thicker smoke looks to stay west of the area. Temps look to be a little above normal today into Wednesday. Highs each day will be from around 80 degrees to the mid 80s, with slightly cooler readings near the shores of Lake Michigan. Lows will be a little chilly (in the low 50s) in the cold spots across north- central WI, with mainly upper 50s and lower 60s elsewhere. Long Term...Wednesday Night Through Monday Focus in this part of the forecast mainly revolves around the heavy rainfall potential during the Thursday and Thursday night timeframe. Thereafter, the upper level flow will transition to northwest which will keep the higher end instability off to the south and west. Wednesday night through Friday...Warm advection will be increasing across the state ahead of shortwave energy moving east across the northern Plains and northern Mississippi Valley. Saturation will primarily be above 10kft during the evening, but increasing ascent further down the column and within increasing warm advection will lead to deep saturation moving in overnight with rain chances arriving after midnight. Low pressure will then move across the region on Thursday and Thursday night. Precipitable water values will be increasing to around 1.8-1.9 inches across the region. Forecast soundings indicate thunderstorm potential will be elevated in nature given the cool boundary layer under ample cloud cover and precipitation. Up to 1000 j/kg will be possible over central to east-central Wisconsin by late Thursday afternoon into Thursday evening that could result in isolated strong storms, but the severe risk appears low. A higher risk appears to be heavy rainfall given some elevated instability and slowing storm motion to under 10 kts by late in the evening. Rainfall amounts of 1-2 inches appears possible over primarily central to east-central WI by the end of Thursday night. Some light showers will likely continue on Friday beneath the upper trough. Given the recent dry weather and longer duration rainfall, the risk of flash flooding appears low, and mainly confined to urban areas. Rest of the forecast...The upper trough will be spinning over the northern Great Lakes on Saturday, which could prolong the shower activity over far northeast WI. Behind this system, northwest flow takes over and the weather looks relatively quiet until the middle of next week. && .AVIATION...for 12Z TAF Issuance Issued at 633 AM CDT Tue Aug 13 2024 Patchy ground fog will lift/burn off early this morning, giving way to mostly sunny skies. Look for daytime cumulus to develop later this morning and continue into the afternoon. Some of these could produce some sprinkles, showers and possibly a storm. Coverage looks too spotty to include in any one TAF at this time, but with the high cloud bases expected (5,000-10,000 feet), only the strongest activity would be able to reduce conditions to MVFR. Otherwise, VFR conditions are expected. Patchy ground fog will be possible again late tonight into early Wednesday. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Bersch/MPC AVIATION.......Bersch