Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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915 FXUS63 KGRB 071734 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1234 PM CDT Fri Jun 7 2024 Updated aviation portion for 18Z TAF issuance .KEY MESSAGES... - Breezy west to northwest winds are expected today, with gusts to 25-35 mph. Conditions hazardous to small craft are expected today due to the gusty winds. - Showers are expected overnight into Saturday morning, with a slight chance of thunderstorms Saturday afternoon, mainly across northern Wisconsin. && .DISCUSSION... Issued at 420 AM CDT Fri Jun 7 2024 Short Term...Today...Tonight...and Saturday We dry out today but remain on the breezy side. Light rain spreads back across the region overnight into Saturday. Main forecast concerns are timing precip chances, assessing thunder chances on Saturday and how gusty winds will get today (especially near Lake Michigan). Shower/Thunder Chances & Clouds: Other than a stray sprinkle early this morning, look for dry conditions today. A mix of clear skies and clouds will start the day, with most of the clouds in northern and eastern WI, with some clearing in central WI. We will remain in cyclonic flow with enough moisture remaining in the lower levels to get some daytime cu, especially were it is sunny for a time in the morning. Clouds will increase and thicken from the west tonight as a shortwave trough and frontal boundary approaches from MN. These features, along with an area of deep layer moisture, will spread an area of mainly light rain across the area overnight (mainly central and north-central WI) and into Saturday morning (area-wide). Most of the rain will exit late Saturday morning or early afternoon. Rain amounts look to be in the 0.10-0.40" range for most locations, so there will be no flooding concerns. As for thunder chances, looks like the clouds/rain arrive early enough to really limit instability during most of the day (under 100 J/kg MUCAPE expected) so will remove the thunder mention for most of the area. Exception may be over the far north where models show a ribbon on slightly higher instability (along with 30-50 kts of bulk shear) that may be be enough to touch off a storm right along the front. Better instability builds behind the boundary as some sun is expected to provide surface heating. This could touch off a few spotty showers (or storm?) late in the day, but some concerns how much moisture would be left over to produce any significant activity. Severe weather is not expected. Winds: Soundings look pretty similar to yesterday, showing 25-30 kt winds around 2000 ft to mix down to the surface. This should produce gusts to 30 mph across the area, with a few gusts to 35 mph possible. Winds will diminish later this afternoon as winds aloft decrease and the better mixing fades. Less breezy conditions arrive for Saturday with gusts mainly under 20 mph. Temps: With a similar set up to yesterday, followed the best performing guidance (BCONSALL/BCCONSRAW/NBM) for this afternoon which has highs climbing into the upper 60s to middle 70s. This is supported by 925mb temps climbing to between 13-17C. Lows tonight will drop into the upper 40s to middle 50s. Clouds and rain will hold temps down for part of the day on Saturday, but as the precip exits in the afternoon and winds downslope, still think we can get into the mid and upper 60s to possibly near 70. Did lower temps near the lake shore as they will be see the rain exit last and have an onshore winds for part of the day. Long Term...Saturday Night Through Thursday Main focus from this forecast period revolves around precipitation trends for Sunday and early next week. Temperatures will be slightly below normal for Sunday through early next week, with potential warming by midweek next week. Saturday night through Sunday...Besides some lingering light chances for showers and storms Saturday evening across the north following a cold frontal passage from earlier in the day, dry conditions are expected for Saturday night. A shortwave dropping over the western Great Lakes and CAA may allow for light diurnally driven showers to develop on Sunday. However, forecast soundings indicate limited moisture in the column, leading to isolated coverage. Thunder chances will be very low given a lack in instability and steep mid-level lapse rates. Rest of the extended...High pressure and upper-level ridging look to build over the Upper Mississippi Valley for Monday, however, there is a new wrench being thrown into the mix of solutions. Some solutions indicate the ridge will not occur, rather a closed low would drop southeast across the Northern Plains to the Midwest on Monday. While this signal has been present in some ensemble clusters over the past couple of runs, the spread was quite high. The latest ensemble clusters still show a signal for the ridge to occur, but there are now more members agreeing with the closed low solution, in addition to the deterministic GFS and UKMET. If the ridge occurs on Monday, the next chance for precip would be sometime Tuesday/Tuesday night. But, if the ridge doesn`t occur, portions of the forecast area may see precip on Monday and be dry for Tuesday. Until details become clearer, forecast confidence is not high for any period for the remainder of the long term. && .AVIATION...for 18Z TAF Issuance Issued at 1234 PM CDT Fri Jun 7 2024 VFR cumulus clouds from 4K-5K ft expected this afternoon before dissipating late afternoon/early evening. Mid and high clouds are forecast to quickly overspread the region this evening into the overnight period as a frontal boundary and shortwave trough approach from the west. Chance of showers to reach central WI toward daybreak with cigs/vsbys lowering into the MVFR category. These MVFR conditions would then spread east into eastern WI Saturday morning, along with the rain showers. Cigs could briefly dip to IFR under any of the heavier showers in the morning. Some improvement is expected Saturday afternoon with cigs returning to VFR. Depending on amount of clearing, a few showers/storms could pop up mainly over northern WI in the afternoon. West/northwest winds will gust to 30 kts through early afternoon, then diminish later this afternoon. && .MARINE... Issued at 420 AM CDT Fri Jun 7 2024 A similar synoptic set today as yesterday. Several sites had gusts near/over small craft criteria yesterday, while others struggled. There still is some uncertainly regarding how much mixing will occur as you get near/in the cooler waters, especially with no showers to help bring down the gustier winds. But with soundings showing 25-30 kts of wind mixing down from 1000 ft, would expect some gusts to around 25 kts, mainly near the shores of the bay and Lake Michigan. A Small Craft Advisory has been issued from 7am to 6pm. Less breezy conditions arrive this evening into Saturday. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Bersch/Kruk AVIATION.......Kallas MARINE.........Bersch