Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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182 FXUS63 KGRB 040340 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1040 PM CDT Mon Jun 3 2024 Updated aviation portion for 06Z TAF issuance .KEY MESSAGES... - Showers and thunderstorms late this afternoon into this evening. Isolated severe storms are possible mainly south of Highway 10. Gusty winds, small hail and torrential downpours will be the main threats. - Locally heavy rainfall is possible late this afternoon into tonight with isolated amounts of 1 to 2 inches. This may lead to minor flooding in urban and low-lying areas. - More strong storms are possible late Tuesday into Tuesday night. Gusty winds, small hail, and heavy rain will be the primary hazards. - Conditions hazardous to small craft will be possible at times from Wednesday through Saturday. && .DISCUSSION... Issued at 332 PM CDT Mon Jun 3 2024 Short Term...Tonight and Tuesday Several concerns to focus on from potentially strong storms into this evening, locally heavy rainfall that may lead to minor flooding and timing of next precipitation event Tuesday afternoon. The 19Z MSAS surface analysis showed one area of low pressure over the MN Arrowhead with a warm front extended southeast through Lake Superior. A second area of low pressure was over southeast SD with a second warm front extended southeast through central IA. Finally, a cold front connected the two areas of low pressure. Radar mosaic indicated one band of thunderstorms across eastern WI with more storms developing over western/southern WI, eastern IA and northern IL. Ongoing showers and thunderstorms will continue this evening (more so over eastern WI) as a remnant MCV moves northeast across southern WI and interacts with moderate instability (MLCAPES 1000- 1500 J/KG). Shear is rather weak (25-35 knots) and focused more over southern WI. A few of these storms could become locally strong with gusty winds and small hail, but the bigger threat could be heavy rain with PW values around 1.5 inches and the potential for training cells to create a minor flood situation, especially in urban or low-lying areas. Have held off on any flood watches since we have only received one report of one inch rain totals so far today. Once the MCV exits the area, the weather should calm down but with lingering low-level moisture in place, low clouds and fog are expected overnight. Min temperatures to be in the upper 50s near Lake MI, around 60 degrees north and middle 60s south. The start of Tuesday looks relatively quiet with a lack of trigger evident. Attention turns to the Upper MS Valley where a cold front and mid-level shortwave trough to be co-located. Instability will be on the rise across WI through the day and expect the next round of showers and thunderstorms to push toward/into central WI late in the afternoon. MUCAPES could surpass 2K J/KG, however shear is practically non-existent (< 20 knots), thus pulse-type storms are expected with a minimal threat of severe. Heavy rain threat will continue with dew points in the 60s and PW values still around 1.5 inches. It will feel like summer on Tuesday as max temperatures reach the lower to middle 70s near Lake MI, upper 70s to lower 80s inland and humid conditions to exist. Long Term...Tuesday Night Through Monday A cold front will sweep through the area Tuesday night into Wednesday morning, bringing showers and thunderstorms along with the possibility for moderate to heavy rain. The best chance for heavier rain will be Tuesday evening across central Wisconsin; however, there are some indications some moderate rain could make its way to the east late Tuesday night into Wednesday morning. Some storms Tuesday evening could be strong to severe as MUCAPEs rise to 1000 to 2000 J/kg; however, bulk shear values will only be around 20 knots. The main threat for any severe weather would be damaging winds, as wet bulb zero heights will be 10k ft along with fairly narrow CAPE profiles in the hail growth zone. The area of concern is mainly central and portions of north-central Wisconsin as the storms will move through before the instability diminishes later in the evening and overnight. Once this cold front pushes east of the area, the weather will be dominated by cooler weather and periods of light showers and a few thunderstorms through the weekend. The main driver of the weather during this period will be a closed upper low situated across south-central Canada that will spin off other closed lows that will track southeast from southern Canada through the Great Lakes region at times. The first of these lows to spin off will occur later Wednesday into Wednesday night and slowly track towards the eastern Great Lakes by the end of the week. The second low to spin off will be on the heels of the previous one, as it spins off during the weekend towards the Great Lakes and eventually establishes itself across southeastern Canada early next week. Meanwhile, the original low will continue to meander across southern Canada and spin off shortwaves that will track through the Great Lakes when the spin off lows aren`t affecting the region. What this boils down to is these mid level lows and shortwaves will bring several periods of light rain showers and isolated thunderstorms at times from late this week through the weekend and into early next week. There will also be dry periods at times, especially at night and in the morning when instability will be at its lowest. Holistically, the forecast looks more dry than wet during this period with the periods of rain difficult to pinpoint given the light nature of the precipitation and weak forcing. Temperatures will start out above normal for Wednesday, then fall to around normal for this time of year through early next week. && .AVIATION...for 06Z TAF Issuance Issued at 1039 PM CDT Mon Jun 3 2024 Conditions will gradually begin to dry out tonight as showers/storms exit to the east. However, lingering low-level moisture and relatively light winds should allow for some low clouds and fog to stick around north and west of the Fox Valley, with cigs and vsbys dropping down into the MVFR to IFR range. Locally LIFR conditions will be possible across central to north-central Wisconsin. Tuesday is expected to start out mostly dry with IFR and MVFR cigs gradually lifting to VFR across the region by mid-afternoon. GRB, ATW, and MTW may briefly meet the LLWS threshold early Tuesday morning as 925 to 850 mb winds increase in the wake of a shallow, transient shortwave. A cold front is then expected to arrive late Tuesday, bringing additional chances for showers and thunderstorms to the forecast area Tuesday evening. MVFR to IFR cigs are expected to return from west to east during this time. Some thunder may be possible at the end of the TAF period, although opted not to include due to low confidence given timing and a stabilizing effect from a lake breeze. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kallas/Kurimski AVIATION.......Goodin