Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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850 FXUS63 KGRB 111140 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 640 AM CDT Tue Jun 11 2024 Updated aviation portion for 12Z TAF issuance .KEY MESSAGES... - Showers and a few thunderstorms expected, especially this afternoon and evening. No severe weather is anticipated. - There is a Slight/Marginal Risk of severe thunderstorms late Wednesday afternoon and Wednesday night. One or more complexes of storms could impact the region, but confidence is low where the complexes would have the biggest impact. - Warm Wednesday and Thursday, then cooler Friday and Saturday before temperatures turn well above normal late in the weekend into the middle of next week. - Gusty west to northwest winds are expected on Thursday which could create hazardous conditions for small craft. A Small Craft Advisory may be needed which could linger into early Thursday evening. && .DISCUSSION... Issued at 406 AM CDT Tue Jun 11 2024 Short Term...Today...Tonight...and Wednesday Precipitation trends today into tonight, and potential for strong thunderstorms late Wednesday afternoon, will be the main forecast concerns. High pressure was departing eastern WI as a cold front moved from the eastern Dakotas into western MN. A band of light rain was moving through MN, ahead of the cold front, and in association with a short-wave trough. This morning will start off with some sunshine, as high clouds gradually increase. Models generally agree that light showers will reach NC/C WI late this morning, but the best chance of measurable rain should occur as a more potent short-wave trough and a 30-35 knot low-level jet move through during the late afternoon and evening. This wave will have better moisture to work with, as PWATs increase to 1.0-1.3 inches. It will also have a little bit of instability, with mid-level lapse rates of 6.5 to 7 C/km, and H8 LI`s of 0 to -2 C. Will carry high end chance to low-end likely pops during the more favorable period, along with a slight chance of embedded thunderstorms. These showers should taper off from west to east during the early to mid evening. Dry conditions should prevail overnight, and for most of the day on Wednesday. Late in the day, a developing 35-45 knot low-level jet will develop over the western half of the forecast area, and could generate a few strong storms in a moist (PWATs increasing to 1.5 inches) and marginally unstable (CAPE 750-1250 j/kg) air mass. However, the best instability is expected to develop to our west (closer to the approaching cold front), and models are suggesting that storms may split north and south of the forecast area Wednesday evening, with the stronger complex possibly clipping central WI. High temperatures will be dependent on the extent of clouds and precipitation today, but there should be enough sunshine for a quick recovery this morning, and there likely be breaks in the rain. Will forecast highs from the middle 60s to the lower 70s. Partial clearing late tonight should allow lows to drop into the 50s regionwide, though some upper 40s may occur in the typical cold spots. Patchy fog may also occur, but will hold off on any mention at this time. On Wednesday, plenty of sunshine is expected through much of the day, with increasing S-SW winds and WAA helping to boost highs into the upper 70s to middle 80s, but a little cooler lakeside. Long Term...Wednesday Night Through Monday Zonal pattern at 500mb expected through much of the work week, then building 500mb heights suggest above normal temperatures early next week. This is a typical summer time pattern which will mean for periodic chances of thunderstorms into early next week. The first chance of thunderstorms arrives Wednesday evening. The Storm Prediction Center Day 2 Outlook has a Marginal Risk across much of the area, with the only exception across our western counties where there is a Slight Risk. Looking at some of the severe parameters indicated most unstable cape values around 1,000 J/KG and 0-6 km shear values around 35 knots. The problem tonight is where to focus the strongest convection. The ECMWF model was significantly different with the focus for the strongest convection across the far northern counties. However, the GFS- Canadian-NAM was focusing strong or severe storms across southeast Minnesota and west-central Wisconsin and then dives the complex south/southeast with our western counties being clipped by the strongest storms. Have trended the highest chances of rain across the north and across central Wisconsin with the lowest chances towards Door County. Most of the shower and storm activity should come to an end overnight, with a few lingering showers possible into Thursday morning. One thing to watch is convection is expected to fire again Thursday afternoon across northern Minnesota. Will need to watch to see if any of this activity would sneak into the far north Thursday evening. High pressure builds into the area Friday and lingers across the region into Saturday morning. Lowered minimum temperatures across the north with the slower arrival of the rain on Saturday. The weekend will be interesting as there could be the potential for several rounds of showers and thunderstorms. The showers and storms should arrive sometime Saturday afternoon and continue Saturday night into Sunday morning. Could not rule out some stronger storms with this round. For Sunday, confidence is lower on the high temperatures as the area will be drying out from the first round of storms. There have been events where temperatures struggle to climb to forecast values due to how quick the rain and ends and how quick the clouds break up. More uncertainty exists Sunday afternoon as the ECMWF is more robust with convection breaking across the area. The Canadian and GFS model were not as bullish in the QPF totals which support the previous convection may have not allowed the atmosphere to destabilize as much. With all the uncertainties in the forecast at this point, there are a lot of uncertainties in the frontal position for Monday which would impact precipitation chances and the expected high temperatures. && .AVIATION...for 12Z TAF Issuance Issued at 631 AM CDT Tue Jun 11 2024 An approaching cold front and upper level disturbance will bring increasing clouds this morning, and a band of showers to the region in the afternoon and early evening. Flight conditions should generally remain VFR in eastern WI, but will drop to MVFR and perhaps even IFR in north central and far NE WI later this afternoon and evening. There will be a small chance of storms, but confidence is not high enough to include in the TAFs at this time. Showers will exit the region from west to east this evening, followed by at least partial clearing and a return to VFR conditions overnight. Winds will become southerly today, with gusts to 15 to 20 kts in the late morning and afternoon. Later tonight, winds will switch to the SW or WSW, but will be quite light. && .GRB WATCHES/WARNINGS/ADVISORIES... Frost Advisory until 7 AM CDT this morning for WIZ005-010>013- 018. && $$ DISCUSSION.....Kieckbusch/Eckberg AVIATION.......Kieckbusch