Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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062 FXUS63 KGRB 081159 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 659 AM CDT Sat Jun 8 2024 Updated aviation portion for 12Z TAF issuance .KEY MESSAGES... - Widespread showers are expected this morning, ending from west to east late this morning and early this afternoon. Under 0.25" of rain for most spots. - There is a slight chance of thunderstorms this afternoon, mainly across northern Wisconsin. Severe weather is not expected. Another slight chance of thunderstorms is forecast Tuesday evening. - Below normal temperatures are forecast through early next week, with a possible warm up at the latter half of the week. && .DISCUSSION... Issued at 422 AM CDT Sat Jun 8 2024 Short Term...Today...Tonight...and Sunday Main forecast concerns will be timing the arrival/exit of the precip today, if/where any showers/storms can develop this afternoon/evening and if any lingering showers impact the north on Sunday. Shower/Storm Trends: Area of light showers and sprinkles early this morning will transition into a more widespread area of showers through the morning (with some lulls/breaks expected), as better moisture arrives ahead of an approaching frontal boundary and shortwave trough. Some thunder has been observed upstream with very limited instability (100-200 J/kg) and a little pocket of steeper mid- level lapse rates, but models all have this instability waning in the early morning hours, so will keep thunder out of the of the forecast this morning. Models have come into decent agreement, bringing the back edge of the rain across eastern WI between 18-20z. Rain totals look to be under 0.25" for most spots. For this afternoon, instability is forecast to build to between 100-400 J/kg, highest north of Hwy 29, behind the steadier area of rain. Bulk shear looks to be in the 30-50 kt range, highest over northern WI, so chances for a few storms is warranted. Weak surface convergence is expected as the boundary drops across the area, triggering isolated showers and storms. Better convergence and higher chances for storms looks to be in the U.P., but have increased chances over far northeast WI and Door Co. as this appears to be the area with the highest chance activity in our area. NAMNest showing a thin line of showers extending all the way back into central WI, but convergence/moisture concerns will limit this potential. Severe weather is not expected, but the inverted-V shown on model soundings could lead to a few higher wind gusts. Luckily, the 40+ kt winds are over 15,000 ft. A lingering shower or two may push across parts of central and northern WI in the evening as another weak shortwave drop into the state, but this activity should wane as instability fades. On Sunday, showers will be possible mainly over northern WI as another weak shortwave drops across the state and temps cool aloft. Models showing pretty much no instability over northern WI so will not include any thunder mention. Temps: Below normal high temps are expected this weekend. Clouds and rain will hold temps down this morning, but partial clearing later in the day will allow a period where temps can climb back into the upper 60s and low 70s for most locations. Lows tonight look to fall into the 40s and low 50s. Highs on Sunday will struggle to get into the 60s over the far north as a push of CAA arrives. Further south, the CAA should be just delayed enough to allow highs to climb into the mid 60s to low 70s. Long Term...Sunday Night Through Friday Main focus from this forecast period revolves around precipitation trends from midweek through the end of next week. Shortwave energy will be departing the region Sunday night and make way for a ridge of high pressure Monday into Monday night. Dry conditions and slightly below normal highs (ranging from the middle 60s to low 70s) under mostly sunny skies will be the result. The ridge of high pressure will depart on Tuesday and bring the next chance for showers and storms from a trailing shortwave trough and surface cold front. The precip should exit the region by Wednesday morning. The best forcing will coincide with the cold front, which looks to track across the forecast area Tuesday evening/late evening, when instability is quickly decreasing. Therefore, do not anticipate any severe storms, but there will still be a low chance for general thunderstorms. Following this shortwave trough, a brief lull in precip is anticipated Wednesday from a surface ridge, before the next chance for showers and thunderstorms arrives from another shortwave. Model guidance is not in agreement with the timing of this shortwave and has it moving through the area sometime between Wednesday night and Thursday night. Forecast confidence will remain low with this shortwave and the rest of the extended until the shortwave timing window becomes clearer over the next couple of days. && .AVIATION...for 12Z TAF Issuance Issued at 657 AM CDT Sat Jun 8 2024 Light rain will continue to spread across the area this morning, ending from west to east in the late morning and afternoon. VFR conditions will lower to MVFR for a time as the heavier/steadier rain pushes through. VFR conditions will return this afternoon into tonight. Isolated showers and possibly a storm is possible this afternoon and evening, especially across northern WI. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Bersch/Kruk AVIATION.......Bersch