748 FXUS63 KGRB 141152 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 652 AM CDT Fri Jun 14 2019 Updated aviation portion for 12Z TAF issuance .SHORT TERM...Today...Tonight...and Saturday Issued at 437 AM CDT Fri Jun 14 2019 Unsettled/cooler weather pattern expected through much of the short- term forecast. The main focus will be on timing/amounts of precipitation along with the strong/severe thunderstorm potential this afternoon. Gusty south to southwest winds to 30 to 40 mph will also be an issue this afternoon along with dangerous swimming conditions. Today: A trough is expected to lift to or near the U.P. border through late this morning before shifting slowly southward during the late afternoon as a cold front. The isentropic upglide on warm air advection and added moisture advection along the trough, will lead to increased chances for showers and thunderstorms across largely the north-half of the area. Additional forcing will likely come from northeast WI being at the nose of a 40kt-50kt LLJ. This will help to increase low-level convergence and force the moisture to lift across the area as well. Overall, instability looks to be fairly limited across the area through much of the morning; however, models are trending toward increasing instability and perhaps a bit thicker CAPE across portions of mainly north-central WI ahead of the cold front this afternoon. The better instability will likely remain west of the area, over far NW Wisconsin and Minnesota; however, some of the models are painting out around 500-1000J/kg of cape over the north- central portions of the area. Models are actually showing closer to 30 knots or so of 0-3km shear, which could lead to some organization in any storms that form. The main concern would be hail and damaging winds; however, increased helicity in the vicinity of the frontal boundary would support at least an isolated chance of a tornado across the north-central this afternoon/evening. This of course hinges largely on if the forecast instability values can be realized with widespread rainfall/cloud cover across the area. At this point, the Storm Prediction Center has place much of the north half of the area under a Marginal Risk for severe storms this afternoon. Heavy rain will likely be another potential this afternoon as the front sags southward. PWATs are expected to jump to around 1 to 1.5 inches across the area, which is about 1.5 times the normal for this time of year. Generally looking at around an additional half inch to an inch for the north half of the area today. In addition to the rainfall potential, south winds may gust as high as 30 to 40 mph at times this afternoon as winds just above the surface are expected to be around 45 to 55 mph. Some of this may mix down, especially during the afternoon hours with the best chance of this occurring over east-central and far northeast WI, where the stronger core of low-level winds are located. This will lead to an increased swim risk along Lake Michigan today into tonight. Farther north and west, the amount of mixing will also be limited by the potential for widespread rainfall. High temperatures will likely warm into the 60s over the north half with some low 70s possible over the south half. Tonight: The aforementioned cold front is expected to continue moving southward from the U.P. border around 00Z/15 to and through much of the rest of northeast WI by 12Z/15. Widespread rainfall is expected along the front and post-frontal as this happens. This would lead to widespread rainfall oriented west to east with the front steadily moving southward through the overnight hours. West to east flow in the vicinity of the southward progressing front could lead to increased rainfall totals across portions of central/east-central WI, especially if any training occurs. Not overly confident in the heaviest rainfall totals that some of the hi-res models are painting out as the front may shift south a bit quicker that guidance suggests. It is worth mentioning that a heavier rain band may set up, but exact placement is less certain. This may lead to totals approaching or exceeding an inch tonight for some locations. Otherwise, most places will end up seeing up to an inch. The additional rainfall on top of the widespread 0.5 inch to 1.5 inches that fell over the past few days, may lead to increasing river levels and possibly some minor flooding potential. In fact, WPC has placed central and east-central portions of the area under a slight risk for excessive rainfall, while the rest of the area is under a marginal. Overnight lows will be in the upper 40s to upper 50s, warmest south. Saturday: The cold front will remain fairly close to the southern portions of the area through the morning hours, which will keep at least a chance of rain showers across the area. Otherwise, the rain will likely taper off across the north half of the area as some drier air works in from the north. North to northeast winds may become gusty during the day Saturday on the back side of the cold front. Some gusts to 20 mph will also be possible, especially along the bay where funneling occurs. High temperatures will likely be in the 60s to low 70s. The better chance of seeing low 70s will be along the U.P. border where more sunshine may sneak out. .LONG TERM...Saturday Night Through Thursday Issued at 437 AM CDT Fri Jun 14 2019 Zonal flow at 500mb expected through the period. Weak disturbances moving through the mean flow will bring a chance of showers and perhaps a few thunderstorms at times during the period. For Saturday night, the cold front is expected to drop well south of the forecast area. Much of north-central and far northeast Wisconsin will be dry. Only the Canadian and ECMWF have some light rainfall amounts across the forecast area. Showers and storms are expected across western Wisconsin and Minnesota. This cluster of showers and storms are expected to move into portions of central and north-central Wisconsin towards 12z Sunday, then move across the area during the day Sunday. Only showers are expected across the area. The precipitation will taper off to drizzle or end Sunday night. The forecast becomes much more uncertain as the models differ on the timing and location of the next round of rain moving across the northern United States. The GFS/Canadian models would suggest dry conditions on Monday, while the ECMWF has rain moving back into north-central and central Wisconsin Monday afternoon. This uncertainty continues Tuesday as the Canadian/GFS are dry while the ECMWF depicts rainfall during the day. Little changes made to the forecast Wednesday and Thursday. Temperatures will start out below normal, then return closer to normal by the middle of next week. && .AVIATION...for 12Z TAF Issuance Issued at 652 AM CDT Fri Jun 14 2019 A warm front/ trough will lift northward through the area this morning, bringing widespread showers and possibly a few thunderstorms. This will allow ceilings to lower, possibly reaching MVFR criteria at times. Any heavier rain would have the potential for reducing visibilities to around 5 sm at times. Additional showers and storms will likely redevelop this afternoon into tonight along a cold front dropping in from the north. A low-level jet will bring a chance of LLWS to the region this morning, as southwest winds aloft increase to around 50 knots. During the afternoon, some of these gusty winds may mix down to the surface at or around 30kts, before diminishing in the evening and overnight hours. && .GRB WATCHES/WARNINGS/ADVISORIES... Beach Hazards Statement from 1 PM CDT this afternoon through late tonight for WIZ022-040-050. && $$ SHORT TERM.....Cooley LONG TERM......Eckberg AVIATION.......Cooley