Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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533 FXUS63 KGRB 091141 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 641 AM CDT Tue Jul 9 2024 Updated aviation portion for 12Z TAF issuance .KEY MESSAGES... - Small chances (30% or less) for showers and storms will continue today through Thursday. The severe weather threat remains very low. Locally heavy rainfall will be possible. - Some rivers, creeks, and streams across east-central Wisconsin will continue to run above bankfull due to recent rainfall. - A warmer/drier period looks to be in store toward the end of the week and into the weekend. Heat index values in the 90s are expected for much of the area. && .DISCUSSION... Issued at 350 AM CDT Tue Jul 9 2024 Short Term...Today...Tonight...and Wednesday The chances for showers/storms and fog chances/trends are the main focus today into Wednesday. Shower/Storm & Cloud Trends: Dry conditions are expected this morning, then as daytime instability builds, expect a few showers to develop across far northeast WI, especially near the MI border where the greatest surface convergence will exist (lake/bay breezes). Some weak upper support thanks to a RRQ of an upper jet and weak shortwave, but capping around 700mb, SBCAPEs of only 500-1000 J/kg and deep- layer shear of 10 to 20 kts will hold back any storm that can form. This activity could slowly meander south into the Fox Valley later in the day, but any activity will wane this evening as instability/convergence weakens. After the low clouds and fog burn off, some sun is expected across central and northern WI this morning, then look for daytime cu to develop in the later morning and afternoon along with some higher clouds spreading in. Further south/east, the cloud shield from the remnants of Beryl will limit sunshine, especially this afternoon. This cloud shield looks to stick around into Wednesday morning as well, especially over eastern WI, with additional daytime cu expected later in the day. Have increased cloud cover over much of the area on Wednesday. While the majority of the precip from the remnants of Beryl will stay to our east, parts of far east central WI could get clipped by some light rain. In addition, a weak trough/shortwave will push across the region, bringing the chance of a few pop-up showers/storms in the late morning and afternoon, though the better coverage looks to be to our southwest. Weak shear and limited instability will again the storms in check, but heavy downpours will be possible in any shower/storm. Fog / Wind / Temps: Light winds and clear skies, along with recent rainfall, has allowed for fog to develop across parts of the area early this morning. Nighttime microphysics satellite showing the most widespread fog (locally dense) across north central WI. The fog will continue early this morning, possibly expanding a little south/east toward sunset, then will burn off/lift by mid-morning. Fog potential tonight will be a little tricky as clouds associated with the remnants of Beryl will likely limit fog potential. But will include fog across north central WI, where skies are expected to remain mostly clear for at least part of the night and enough low level moisture from recent rains will remain in place. Temps look to remain near or slightly above normal with highs mainly between 75-85 degrees. Lows tonight will drop into the 50s across north-central WI, and hold in the 60s across the Fox Valley. A touch of humidity will remain in place across central and eastern WI, with dewpoints mainly in the 60s. Some dewpoints in the 50s will bring less humid conditions to much of the Northwoods. Long Term...Wednesday Night Through Monday Dry conditions will end the work week before much hotter conditions arrive for the weekend. The heat and humidity will prime the area for a couple rounds of active weather starting over the weekend into early next week. The only interruption to a dry end of the work week will be a brief chance for a few stray showers Thursday afternoon. Any showers will rely heavily on weak surface instability (SBCAPE around 500-1000 J/kg) as upper forcing will be lacking during this time. Ultimately, would expect some developing afternoon cumulus with a few showers possible if the better dewpoints and warmth do build into the area, but even then would expect most of the area to be dry. High pressure begins to build in Thursday night into Friday, which will keep us dry until the weekend. Southerly flow will ramp up Friday night, bringing a surge of very warm and humid air into the region for the weekend through early next week. High temperatures in the middle to upper 80s are expected by Saturday, with a few 90s mixed in for both Sunday and Monday. This will push heat indices into the middle 90s so make sure to plan for the heat if you are outdoors this weekend. While the surface flow brings in much warmer temperatures, upper flow will bring a series of fast moving shortwaves Saturday through Monday. This will make for several potential rounds of active weather, with the best bet being during the afternoon when diurnal instability is at its maximum. && .AVIATION...for 12Z TAF Issuance Issued at 641 AM CDT Tue Jul 9 2024 Ground fog, thickest across north central WI, will lift and/or mix out through ~13z. Otherwise, look for VFR conditions today. A cloud shield associated with the remnants of Beryl will spread high clouds across much of the area, thickest across the Fox Valley and lake shore. Some daytime cu are also expected. An isolated shower or storm will be possible this afternoon or early evening, but chances too low (20% or lower) that it will impact a TAF site. Any shower/storm will dissipate late this afternoon or evening. Ground fog will be possible again late tonight and early Wednesday morning across mainly north central WI (RHI). Some light showers or sprinkles may approach MTW Wednesday morning as well. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Bersch/Uhlmann AVIATION.......Bersch